Microbial biogeography

From Wikipedia, the free encyclopedia

Microbial biogeography is a subset of biogeography, a field that concerns the distribution of organisms across space and time.^[1] Although biogeography traditionally focused on plants and larger animals, recent studies have broadened this field to include distribution patterns of microorganisms. This extension of biogeography to smaller scales—known as "microbial biogeography"—is enabled by ongoing advances in genetic technologies.

The aim of microbial biogeography is to reveal where microorganisms live, at what abundance, and why. Microbial biogeography can therefore provide insight into the underlying mechanisms that generate and hinder biodiversity.^[2] Microbial biogeography also enables predictions of where certain organisms can survive and how they respond to changing environments, making it applicable to several other fields such as climate change research.

History

Schewiakoff (1893) theorized about the cosmopolitan habitat of free-living protozoans.^[3] In 1934, Lourens Baas Becking, based on his own research in California's salt lakes, as well as work by others on salt lakes worldwide,^[4] concluded that "everything is everywhere, but the environment selects".^[5] Baas Becking attributed the first half of this hypothesis to his colleague Martinus Beijerinck (1913).^[6][7]

Baas Becking hypothesis of cosmopolitan microbial distribution would later be challenged by other works.^{[8][9][10][11]}

Microbial vs macro-organism biogeography

The biogeography of macro-organisms (i.e., plants and animals that can be seen with the naked eye) has been studied since the eighteenth century. For macro-organisms, biogeographical patterns (i.e., which organism assemblages appear in specific places and times) appear to arise from both past and current environments. For example, polar bears live in the Arctic but not the Antarctic, while the reverse is true for penguins; although both polar bears and penguins have adapted to cold climates over many generations (the result of past environments), the distance and warmer climates between the north and south poles prevent these species from spreading to the opposite hemisphere (the result of current environments). This demonstrates the biogeographical pattern known as "isolation with geographic distance" by which the limited ability of a species to physically disperse across space (rather than any selective genetic reasons) restricts the geographical range over which it can be found.

The biogeography of microorganisms (i.e., organisms that cannot be seen with the naked eye, such as fungi and bacteria) is an emerging field enabled by ongoing advancements in genetic technologies, in particular cheaper DNA sequencing with higher throughput that now allows analysis of global datasets on microbial biology at the molecular level. When scientists began studying microbial biogeography, they anticipated a lack of biogeographic patterns due to the high dispersibility and large population sizes of microbes, which were expected to ultimately render geographical distance irrelevant. Indeed, in microbial ecology the oft-repeated saying by Lourens Baas Becking that “everything is everywhere, but the environment selects” has come to mean that as long as the environment is ecologically appropriate, geological barriers are irrelevant.^[12] However, recent studies show clear evidence for biogeographical patterns in microbial life, which challenge this common interpretation: the existence of microbial biogeographic patterns disputes the idea that “everything is everywhere” while also supporting the idea that environmental selection includes geography as well as historical events that can leave lasting signatures on microbial communities.^[2]

Microbial biogeographic patterns are often similar to those of macro-organisms. Microbes generally follow well-known patterns such as the distance decay relationship, the abundance-range relationship, and Rapoport's rule.^[13][14] This is surprising given the many disparities between microorganisms and macro-organisms, in particular their size (micrometers vs. meters), time between generations (minutes vs. years), and dispersibility (global vs. local). However, important differences between the biogeographical patterns of microorganism and macro-organism do exist, and likely result from differences in their underlying biogeographic processes (e.g., drift, dispersal, selection, and mutation). For example, dispersal is an important biogeographical process for both microbes and larger organisms, but small microbes can disperse across much greater ranges and at much greater speeds by traveling through the atmosphere (for larger animals dispersal is much more constrained due to their size).^[2] As a result, many microbial species can be found in both northern and southern hemispheres, while larger animals are typically found only at one pole rather than both.^[15]

Distinct patterns

Reversed latitudinal diversity gradient

Larger organisms tend to exhibit latitudinal gradients in species diversity, with larger biodiversity existing in the tropics and decreasing toward more temperate polar regions. In contrast, a study on indoor fungal communities^[14] found microbial biodiversity to be significantly higher in temperate zones than in the tropics. Interestingly, the same study found that drastically different buildings exhibited the same indoor fungal composition in any given location, where similarity increased with proximity. Thus despite human efforts to control indoor climates, outside environments appear to be the strongest determinant of indoor fungal composition.

Bipolar latitude distributions

Certain microbial populations exist in opposite hemispheres and at complementary latitudes. These ‘bipolar’ (or ‘antitropical’) distributions are much rarer in macro-organisms; although macro-organisms exhibit latitude gradients, ‘isolation by geographic distance’ prevents bipolar distributions (e.g., polar bears are not found at both poles). In contrast, a study on marine surface bacteria^[15] showed not only a latitude gradient, but also complementarity distributions with similar populations at both poles, suggesting no "isolation by geographic distance". This is likely due to differences in the underlying biogeographic process, dispersal, as microbes tend to disperse at high rates and far distances by traveling through the atmosphere.

Seasonal variations

Microbial diversity can exhibit striking seasonal patterns at a single geographical location. This is largely due to dormancy, a microbial feature not seen in larger animals that allows microbial community composition to fluctuate in relative abundance of persistent species (rather than actual species present). This is known as the "seed-bank hypothesis"^[16] and has implications for our understanding of ecological resilience and thresholds to change.^[17]

Applications

Directed panspermia

Panspermia suggests that life can be distributed throughout outer space via comets, asteroids, and meteoroids. Panspermia assumes that life can survive the harsh space environment, which features vacuum conditions, intense radiation, extreme temperatures, and a dearth of available nutrients. Many microorganisms are able to evade such stressors by forming spores or entering a state of low-metabolic dormancy.^[18] Studies in microbial biogeography have even shown that the ability of microbes to enter and successfully emerge from dormancy when their respective environmental conditions are favorable contributes to the high levels of microbial biodiversity observed in almost all ecosystems.^[19] Thus microbial biogeography can be applied to panspermia as it predicts that microbes are able to protect themselves from the harsh space environment, know to emerge when conditions are safe, and also take advantage of their dormancy capability to enhance biodiversity wherever they may land.

Directed panspermia is the deliberate transport of microorganisms to colonize another planet. If aiming to colonize an Earth-like environment, microbial biogeography can inform decisions on the biological payload of such a mission. In particular, microbes exhibit latitudinal ranges according to Rapoport's rule, which states that organisms living at lower latitudes (near the equator) are found within smaller latitude ranges than those living at higher latitudes (near the poles). Thus the ideal biological payload would include widespread, higher-latitude microorganisms that can tolerate of a wider range of climates. This is not necessarily the obvious choice, as these widespread organisms are also rare in microbial communities and tend to be weaker competitors when faced with endemic organisms. Still, they can survive in a range of climates and thus would be ideal for inhabiting otherwise lifeless Earth-like planets with uncertain environmental conditions. Extremophiles, although tough enough to withstand the space environment, may not be ideal for directed panspermia as any given extremophile species requires a very specific climate to survive. However, if the target was closer to Earth, such as a planet or moon in our Solar System, it may be possible to select a specific extremophile species for the well-defined target environment.

Microbial ecology

From Wikipedia, the free encyclopedia

The great plate count anomaly. Counts of cells obtained via cultivation are orders of magnitude lower than those directly observed under the microscope. This is because microbiologists are able to cultivate only a minority of naturally occurring microbes using current laboratory techniques, depending on the environment.^[1]

Microbial ecology (or environmental microbiology) is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life—Eukaryota, Archaea, and Bacteria—as well as viruses.^[2]

Microorganisms, by their omnipresence, impact the entire biosphere. Microbial life plays a primary role in regulating biogeochemical systems in virtually all of our planet's environments, including some of the most extreme, from frozen environments and acidic lakes, to hydrothermal vents at the bottom of deepest oceans, and some of the most familiar, such as the human small intestine.^[3][4] As a consequence of the quantitative magnitude of microbial life (Whitman and coworkers calculated 5.0×10³⁰ cells, eight orders of magnitude greater than the number of stars in the observable universe^[5][6]) microbes, by virtue of their biomass alone, constitute a significant carbon sink.^[7] Aside from carbon fixation, microorganisms' key collective metabolic processes (including nitrogen fixation, methane metabolism, and sulfur metabolism) control global biogeochemical cycling.^[8] The immensity of microorganisms' production is such that, even in the total absence of eukaryotic life, these processes would likely continue unchanged.^[9]

History

While microbes have been studied since the seventeenth-century, this research was from a primarily physiological perspective rather than an ecological one.^[10] For instance, Louis Pasteur and his disciples were interested in the problem of microbial distribution both on land and in the ocean.^[11] Martinus Beijerinck invented the enrichment culture, a fundamental method of studying microbes from the environment. He is often incorrectly credited with framing the microbial biogeographic idea that "everything is everywhere, but, the environment selects", which was stated by Lourens Baas Becking.^[12] Sergei Winogradsky was one of the first researchers to attempt to understand microorganisms outside of the medical context—making him among the first students of microbial ecology and environmental microbiology—discovering chemosynthesis, and developing the Winogradsky column in the process.^[13]:644

Beijerinck and Windogradsky, however, were focused on the physiology of microorganisms, not the microbial habitat or their ecological interactions.^[10] Modern microbial ecology was launched by Robert Hungate and coworkers, who investigated the rumen ecosystem. The study of the rumen required Hungate to develop techniques for culturing anaerobic microbes, and he also pioneered a quantitative approach to the study of microbes and their ecological activities that differentiated the relative contributions of species and catabolic pathways.^[10]

Roles

Microorganisms are the backbone of all ecosystems, but even more so in the zones where photosynthesis is unable to take place because of the absence of light. In such zones, chemosynthetic microbes provide energy and carbon to the other organisms.

Other microbes are decomposers, with the ability to recycle nutrients from other organisms' waste products. These microbes play a vital role in biogeochemical cycles.^[14] The nitrogen cycle, the phosphorus cycle, the sulphur cycle and the carbon cycle all depend on microorganisms in one way or another. For example, the nitrogen gas which makes up 78% of the earth's atmosphere is unavailable to most organisms, until it is converted to a biologically available form by the microbial process of nitrogen fixation.

Due to the high level of horizontal gene transfer among microbial communities,^[15] microbial ecology is also of importance to studies of evolution.^[16]

Symbiosis

Microbes, especially bacteria, often engage in symbiotic relationships (either positive or negative) with other microorganisms or larger organisms. Although physically small, symbiotic relationships amongst microbes are significant in eukaryotic processes and their evolution.^[17][18] The types of symbiotic relationship that microbes participate in include mutualism, commensalism, parasitism,^[19] and amensalism,^[20] and these relationships affect the ecosystem in many ways.

Mutualism

Mutualism in microbial ecology is a relationship between microbial species and between microbial species and humans that allow for both sides to benefit.^[21] One such example would be syntrophy, also known as cross-feeding,^[20] which is clearly shown in Methanobacterium omelianskii. Although initially thought of as one microbial species, this system is actually two species - an S organism and Methabacterium bryantii. The S organism provides the bacterium with the H₂, which the bacterium needs in order to grow and produce methane.^[17][22] The reaction used by the S organism for the production of H₂ is endergonic (and so thermodynamically unfavored) however, when coupled to the reaction used by Methabacterium bryantii in its production of methane, the overall reaction becomes exergonic.^[17]  Thus the two organisms are in a mutualistic relationship which allows them to grow and thrive in an environment, deadly for either species alone. Lichen is an example of a symbiotic organism.^[22]

Amensalism

Amensalism (also commonly known as antagonism) is a type of symbiotic relationship where one species/organism is harmed while the other remains unaffected.^[21] One example of such a relationship that takes place in microbial ecology is between the microbial species Lactobacillus casei and Pseudomonas taetrolens.^[23] When co-existing in an environment, Pseudomonas taetrolens shows inhibited growth and decreased production of lactobionic acid (its main product) most likely due to the byproducts created by Lactobacillus casei during its production of lactic acid.^[24] However, Lactobacillus casei shows no difference in its behaviour, and such this relationship can be defined as amensalism.

Microbial resource management

Biotechnology may be used alongside microbial ecology to address a number of environmental and economic challenges. For example, molecular techniques such as community fingerprinting can be used to track changes in microbial communities over time or assess their biodiversity. Managing the carbon cycle to sequester carbon dioxide and prevent excess methanogenesis is important in mitigating global warming, and the prospects of bioenergy are being expanded by the development of microbial fuel cells. Microbial resource management advocates a more progressive attitude towards disease, whereby biological control agents are favoured over attempts at eradication. Fluxes in microbial communities has to be better characterized for this field's potential to be realised.^[25] In addition, there are also clinical implications, as marine microbial symbioses are a valuable source of existing and novel antimicrobial agents, and thus offer another line of inquiry in the evolutionary arms race of antibiotic resistance, a pressing concern for researchers.^[26]

In built environment and human interaction

Microbes exist in all areas, including homes, offices, commercial centers, and hospitals. In 2016, the journal Microbiome published a collection of various works studying the microbial ecology of the built environment.^[27]

A 2006 study of pathogenic bacteria in hospitals found that their ability to survive varied by the type, with some surviving for only a few days while others survived for months.^[28]

The lifespan of microbes in the home varies similarly. Generally bacteria and viruses require a wet environment with a humidity of over 10 percent.^[29] E. coli can survive for a few hours to a day.^[29] Bacteria which form spores can survive longer, with Staphylococcus aureus surviving potentially for weeks or, in the case of Bacillus anthracis, years.^[29]

In the home, pets can be carriers of bacteria; for example, reptiles are commonly carriers of salmonella.^[30]

S. aureus is particularly common, and asymptomatically colonizes about 30% of the human population;^[31] attempts to decolonize carriers have met with limited success^[32] and generally involve mupirocin nasally and chlorhexidine washing, potentially along with vancomycin and cotrimoxazole to address intestinal and urinary tract infections.^[33]

Antimicrobials

Some metals, particularly copper and silver, have antimicrobial properties. Using antimicrobial copper-alloy touch surfaces is a technique which has begun to be used in the 21st century to prevent transmission of bacteria.^[34] Silver nanoparticles have also begun to be incorporated into building surfaces and fabrics, although concerns have been raised about the potential side-effects of the tiny particles on human health.

Green nanotechnology

From Wikipedia, the free encyclopedia

Green nanotechnology refers to the use of nanotechnology to enhance the environmental sustainability of processes producing negative externalities. It also refers to the use of the products of nanotechnology to enhance sustainability. It includes making green nano-products and using nano-products in support of sustainability.

Green nanotechnology has been described as the development of clean technologies, "to minimize potential environmental and human health risks associated with the manufacture and use of nanotechnology products, and to encourage replacement of existing products with new nano-products that are more environmentally friendly throughout their lifecycle."^[1]

Goals

Green nanotechnology has two goals: producing nanomaterials and products without harming the environment or human health, and producing nano-products that provide solutions to environmental problems. It uses existing principles of green chemistry and green engineering^[2] to make nanomaterials and nano-products without toxic ingredients, at low temperatures using less energy and renewable inputs wherever possible, and using lifecycle thinking in all design and engineering stages.

In addition to making nanomaterials and products with less impact to the environment, green nanotechnology also means using nanotechnology to make current manufacturing processes for non-nano materials and products more environmentally friendly. For example, nanoscale membranes can help separate desired chemical reaction products from waste materials. Nanoscale catalysts can make chemical reactions more efficient and less wasteful. Sensors at the nanoscale can form a part of process control systems, working with nano-enabled information systems. Using alternative energy systems, made possible by nanotechnology, is another way to "green" manufacturing processes.

The second goal of green nanotechnology involves developing products that benefit the environment either directly or indirectly. Nanomaterials or products directly can clean hazardous waste sites, desalinate water, treat pollutants, or sense and monitor environmental pollutants. Indirectly, lightweight nanocomposites for automobiles and other means of transportation could save fuel and reduce materials used for production; nanotechnology-enabled fuel cells and light-emitting diodes (LEDs) could reduce pollution from energy generation and help conserve fossil fuels; self-cleaning nanoscale surface coatings could reduce or eliminate many cleaning chemicals used in regular maintenance routines;^[3] and enhanced battery life could lead to less material use and less waste. Green Nanotechnology takes a broad systems view of nanomaterials and products, ensuring that unforeseen consequences are minimized and that impacts are anticipated throughout the full life cycle.^[4]

Current research

Solar cells

Research is underway to use nanomaterials for purposes including more efficient solar cells, practical fuel cells, and environmentally friendly batteries. The most advanced nanotechnology projects related to energy are: storage, conversion, manufacturing improvements by reducing materials and process rates, energy saving (by better thermal insulation for example), and enhanced renewable energy sources.
One major project that is being worked on is the development of nanotechnology in solar cells.^[5] Solar cells are more efficient as they get tinier and solar energy is a renewable resource. The price per watt of solar energy is lower than one dollar.

Research is ongoing to use nanowires and other nanostructured materials with the hope of to create cheaper and more efficient solar cells than are possible with conventional planar silicon solar cells.^[6][7] Another example is the use of fuel cells powered by hydrogen, potentially using a catalyst consisting of carbon supported noble metal particles with diameters of 1–5 nm. Materials with small nanosized pores may be suitable for hydrogen storage. Nanotechnology may also find applications in batteries, where the use of nanomaterials may enable batteries with higher energy content or supercapacitors with a higher rate of recharging.^{[citation needed]}

Nanotechnology is already used to provide improved performance coatings for photovoltaic (PV) and solar thermal panels. Hydrophobic and self-cleaning properties combine to create more efficient solar panels, especially during inclement weather. PV covered with nanotechnology coatings are said to stay cleaner for longer to ensure maximum energy efficiency is maintained.^[8]

Nanoremediation and water treatment

Nanotechnology offers the potential of novel nanomaterials for the treatment of surface water, groundwater, wastewater, and other environmental materials contaminated by toxic metal ions, organic and inorganic solutes, and microorganisms. Due to their unique activity toward recalcitrant contaminants, many nanomaterials are under active research and development for use in the treatment of water and contaminated sites.^[9][10]

The present market of nanotech-based technologies applied in water treatment consists of reverse osmosis(RO), nanofiltration, ultrafiltration membranes. Indeed, among emerging products one can name nanofiber filters, carbon nanotubes and various nanoparticles.^[11] Nanotechnology is expected to deal more efficiently with contaminants which convectional water treatment systems struggle to treat, including bacteria, viruses and heavy metals. This efficiency generally stems from the very high specific surface area of nanomaterials which increases dissolution, reactivity and sorption of contaminants.^[12][13]

Environmental remediation

Nanoremediation is the use of nanoparticles for environmental remediation.^[14][15] Nanoremediation has been most widely used for groundwater treatment, with additional extensive research in wastewater treatment.^{[16][17][18][19]} Nanoremediation has also been tested for soil and sediment cleanup.^[20] Even more preliminary research is exploring the use of nanoparticles to remove toxic materials from gases.^[21]

Some nanoremediation methods, particularly the use of nano zerovalent iron for groundwater cleanup, have been deployed at full-scale cleanup sites.^[15] Nanoremediation is an emerging industry; by 2009, nanoremediation technologies had been documented in at least 44 cleanup sites around the world, predominantly in the United States.^[16][22][23] During nanoremediation, a nanoparticle agent must be brought into contact with the target contaminant under conditions that allow a detoxifying or immobilizing reaction. This process typically involves a pump-and-treat process or in situ application. Other methods remain in research phases.

Scientists have been researching the capabilities of buckminsterfullerene in controlling pollution, as it may be able to control certain chemical reactions. Buckminsterfullerene has been demonstrated as having the ability of inducing the protection of reactive oxygen species and causing lipid peroxidation. This material may allow for hydrogen fuel to be more accessible to consumers.

Water cleaning technology

In 2017 the RingwooditE Co Ltd was formed in order to explore Thermonuclear Trap Technology (TTT) for the purpose of cleaning all sources of water from pollution and toxic contents. This patented nanotechnology uses a high pressure and temperature chamber to separate isotopes that should by nature not be in drinking water to pure drinking water, as to the by the WHO´s established classification. This method has been developed by among others, by professor Vladimir Afanasiew, at the Moscow Nuclear Institution. This technology is targeted to clean Sea, river, lake and landfill waste waters. It even removes radioactive isotopes from the sea water, after Nuclear Power Stations catastrophes and cooling water plant towers. By this technology pharmaca rests are being removed as well as narcotics and tranquilizers. Bottom layers and sides at lake and rivers can be returned, after being cleaned. Machinery used for this purpose are much similar to those of deep sea mining. Removed waste items are being sorted by the process, and can be re used as raw material for other industrial production.

Water filtration

Nanofiltration is a relatively recent membrane filtration process used most often with low total dissolved solids water such as surface water and fresh groundwater, with the purpose of softening (polyvalent cation removal) and removal of disinfection by-product precursors such as natural organic matter and synthetic organic matter.^[24][25] Nanofiltration is also becoming more widely used in food processing applications such as dairy, for simultaneous concentration and partial (monovalent ion) demineralisation.

Nanofiltration is a membrane filtration based method that uses nanometer sized cylindrical through-pores that pass through the membrane at a 90°. Nanofiltration membranes have pore sizes from 1-10 Angstrom, smaller than that used in microfiltration and ultrafiltration, but just larger than that in reverse osmosis. Membranes used are predominantly created from polymer thin films. Materials that are commonly used include polyethylene terephthalate or metals such as aluminum.^[26] Pore dimensions are controlled by pH, temperature and time during development with pore densities ranging from 1 to 106 pores per cm². Membranes made from polyethylene terephthalate and other similar materials, are referred to as "track-etch" membranes, named after the way the pores on the membranes are made.^[27] "Tracking" involves bombarding the polymer thin film with high energy particles. This results in making tracks that are chemically developed into the membrane, or "etched" into the membrane, which are the pores. Membranes created from metal such as alumina membranes, are made by electrochemically growing a thin layer of aluminum oxide from aluminum metal in an acidic medium.

Some water-treatment devices incorporating nanotechnology are already on the market, with more in development. Low-cost nanostructured separation membranes methods have been shown to be effective in producing potable water in a recent study.^[28]

Nanotech to disinfect water

Nanotechnology provides an alternative solution to clean germs in water, a problem that has been getting worse due to the population explosion, growing need for clean water and emergence of additional pollutants. One of the alternatives offered is antimicrobial nanotechnology stated that several nanomaterials showed strong antimicrobial properties through diverse mechanisms, such as photocatalytic production of reactive oxygen species that damage cell components and viruses.^[29]

Cleaning up oil spills

The U.S. Environmental Protection Agency (EPA) documents more than ten thousand oil spills per year. Conventionally, biological, dispersing, and gelling agents are deployed to remedy oil spills. Although, these methods have been used for decades, none of these techniques can retrieve the irreplaceable lost oil. However, nanowires can not only swiftly clean up oil spills but also recover as much oil as possible. These nanowires form a mesh that absorbs up to twenty times its weight in hydrophobic liquids while rejecting water with its water repelling coating. Since the potassium manganese oxide is very stable even at high temperatures, the oil can be boiled off the nanowires and both the oil and the nanowires can then be reused.^[30]

In 2005, Hurricane Katrina damaged or destroyed more than thirty oil platforms and nine refineries. The Interface Science Corporation successfully launched a new oil remediation and recovery application, which used the water repelling nanowires to clean up the oil spilled by the damaged oil platforms and refineries.^[31]

Removing plastics from oceans

One innovation of green nanotechnology that is currently under development are nanomachines modeled after a bacteria bioengineered to consume plastics, Ideonella sakaiensis. These nano-machines are able to decompose plastics dozens of times faster than the bioengineered bacteria not only because of their increased surface area but also because of the fact that the energy released from decomposing the plastic is used to fuel the nano-machines.^[32]

Air pollution control

In addition to water treatment and environmental remediation, nanotechnology is currently improving air quality. Nanoparticles can be engineered to catalyze, or hasten, the reaction to transform environmentally pernicious gases into harmless ones. For example, many industrial factories that produce large amounts harmful gases employ a type of nanofiber catalyst made of magnesium oxide (Mg₂O) to purify dangerous organic substances in the smoke. Although chemical catalysts already exist in the gaseous vapors from cars, nanotechnology has a greater chance of reacting with the harmful substances in the vapors. This greater probability comes from the fact that nanotechnology can interact with more particles because of its greater surface area.^[33]

Additionally, research is currently being conducted to find out if nanoparticles can be engineered to separate car exhaust from methane or carbon dioxide,^[33] which has been known to damage the Earth's ozone layer. In fact, John Zhu, a professor at the University of Queensland, is exploring the creation of a carbon nanotube(CNT) which can trap greenhouse gases hundreds of times more efficiently than current methods can.^[34]

Nanotechnology for sensors

Perpetual exposure to heavy metal pollution and particulate matter will lead to health concerns such as lung cancer, heart conditions, and even motor neuron diseases. However, humanity's ability to shield themselves from these health problems can be improved by accurate and swift nanocontact-sensors able to detect pollutants at the atomic level. These nanocontact sensors do not require much energy to detect metal ions or radioactive elements. Additionally, they can be made in automatic mode so that they can be readably used at any given moment. Additionally, these nanocontact sensors are energy and cost effective since they are composed with conventional microelectronic manufacturing equipment using electrochemical techniques.^[30]

Some examples of nano-based monitoring include:

1. Functionalized nanoparticles able to form anionic oxidants bonding thereby allowing the detection of carcinogenic substances at very low concentrations.^[33]
2. Polymer nanospheres have been developed to measure organic contaminates in very low concentrations
3. "Peptide nanoelectrodes have been employed based on the concept of thermocouple. In a 'nano-distance separation gap, a peptide molecule is placed to form a molecular junction. When a specific metal ion is bound to the gap; the electrical current will result conductance in a unique value. Hence the metal ion will be easily detected."^[34]
4. Composite electrodes, a mixture of nanotubes and copper, have been created to detect substances such as organophosphorus pesticides, carbohydrates and other woods pathogenic substances in low concentrations.

Concerns

Although green nanotechnology poses many advantages over traditional methods, there is still much debate about the concerns brought about by nanotechnology. For example, since the nanoparticles are small enough to be absorbed into skin and/or inhaled, countries are mandating that additional research revolving around the impact of nanotechnology on organisms be heavily studied. In fact, the field of eco-nanotoxicology was founded solely to study the effect of nanotechnology on earth and all of its organisms. At the moment, scientists are unsure of what will happen when nanoparticles seep into soil and water, but organizations, such as NanoImpactNet, have set out to study these effects.^[33]

Gaia philosophy

From Wikipedia, the free encyclopedia

Gaia philosophy (named after Gaia, Greek goddess of the Earth) is a broadly inclusive term for related concepts that living organisms on a planet will affect the nature of their environment in order to make the environment more suitable for life. This set of theories holds that all organisms on a life-giving planet regulate the biosphere in such a way as to promote its habitability. Gaia concept draws a connection between the survivability of a species (hence its evolutionary course) and its usefulness to the survival of other species.

While there were a number of precursors to Gaia theory, the first scientific form of this idea was proposed as the Gaia hypothesis by James Lovelock, a UK chemist, in 1970. The Gaia hypothesis deals with the concept of Biological homeostasis, and claims the resident life forms of a host planet coupled with their environment have acted and act like a single, self-regulating system. This system includes the near-surface rocks, the soil, and the atmosphere. Today many scientists consider such ideas to be unsupported by, or at odds with, the available evidence (see recent criticism). These theories are however significant in green politics.

Predecessors to the Gaia theory

There are some mystical, scientific and religious predecessors to the Gaia philosophy, which had a Gaia-like conceptual basis. Many religious mythologies had a view of Earth as being a whole that is greater than the sum of its parts (e.g. some Native American religions and various forms of shamanism).

Lewis Thomas believed that Earth should be viewed as a single cell; he derived this view from Johannes Kepler's view of Earth as a single round organism.

Isaac Newton wrote of the earth, "Thus this Earth resembles a great animall or rather inanimate vegetable, draws in æthereall breath for its dayly refreshment & vitall ferment & transpires again with gross exhalations, And according to the condition of all other things living ought to have its times of beginning youth old age & perishing."^[1]

Pierre Teilhard de Chardin, a paleontologist and geologist, believed that evolution unfolded from cell to organism to planet to solar system and ultimately the whole universe, as we humans see it from our limited perspective. Teilhard later influenced Thomas Berry and many Catholic humanist thinkers of the 20th century.

Buckminster Fuller is generally credited with making the idea respectable in Western scientific circles in the 20th century. Building to some degree on his observations and artifacts, e.g. the Dymaxion map of the Earth he created, others began to ask if there was a way to make the Gaia theory scientifically sound.

Oberon Zell-Ravenheart in 1970 in an article in Green Egg Magazine, independently articulated the Gaia Thesis.^[2]

None of these ideas are considered scientific hypotheses; by definition a scientific hypothesis must make testable predictions. As the above claims are not testable, they are outside the bounds of current science.

These are conjectures and perhaps can only be considered as social and maybe political philosophy; they may have implications for theology, or thealogy as Zell-Ravenheart and Isaac Bonewits put it.

Range of views

According to James Kirchner there is a spectrum of Gaia hypotheses, ranging from the undeniable to radical. At one end is the undeniable statement that the organisms on the Earth have radically altered its composition. A stronger position is that the Earth's biosphere effectively acts as if it is a self-organizing system which works in such a way as to keep its systems in some kind of equilibrium that is conducive to life. Today many scientists consider that such a view (and any stronger views) are unlikely to be correct.^{[3][4][5][6][7]} An even stronger claim is that all lifeforms are part of a single planetary being, called Gaia. In this view, the atmosphere, the seas, the terrestrial crust would be the result of interventions carried out by Gaia, through the coevolving diversity of living organisms.

The most extreme form of Gaia theory is that the entire Earth is a single unified organism with a highly intelligent mind that arose as an emergent property of the whole biosphere. In this view, the Earth's biosphere is consciously manipulating the climate in order to make conditions more conducive to life. Scientists contend that there is no evidence at all to support this last point of view, and it has come about because many people do not understand the concept of homeostasis. Many non-scientists instinctively and incorrectly see homeostasis as a process that requires conscious control.

The more speculative versions of Gaia, including versions in which it is believed that the Earth is actually conscious, sentient, and highly intelligent, are usually considered outside the bounds of what is usually considered science.

Gaia in biology and science

Buckminster Fuller has been credited as the first to incorporate scientific ideas into a Gaia theory, which he did with his Dymaxion map of the Earth.
The first scientifically rigorous theory was the Gaia hypothesis by James Lovelock, a UK chemist.

A variant of this hypothesis was developed by Lynn Margulis, a microbiologist, in 1979. Her version is sometimes called the "Gaia Theory" (note uppercase-T). Her model is more limited in scope than the one that Lovelock proposed.

Whether this sort of system is present on Earth is still open to debate. Some relatively simple homeostatic mechanisms are generally accepted. For example, when atmospheric carbon dioxide levels rise, plants are able to grow better and thus remove more carbon dioxide from the atmosphere. Other biological effects and feedbacks exist,^[7] but the extent to which these mechanisms have stabilized and modified the Earth's overall climate is largely not known.

The Gaia hypothesis is sometimes viewed from significantly different philosophical perspectives. Some environmentalists view it as an almost conscious process, in which the Earth's ecosystem is literally viewed as a single unified organism. Some evolutionary biologists, on the other hand, view it as an undirected emergent property of the ecosystem: as each individual species pursues its own self-interest, their combined actions tend to have counterbalancing effects on environmental change. Proponents of this view sometimes point to examples of life's actions in the past that have resulted in dramatic change rather than stable equilibrium, such as the conversion of the Earth's atmosphere from a reducing environment to an oxygen-rich one.

Depending on how strongly the case is stated, the hypothesis conflicts with mainstream neo-Darwinism. Most biologists would accept Daisyworld-style homeostasis as possible, but would certainly not accept the idea that this equates to the whole biosphere acting as one organism.

A very small number of scientists, and a much larger number of environmental activists, claim that Earth's biosphere is consciously manipulating the climate in order to make conditions more conducive to life. Scientists contend that there is no evidence to support this belief.

Gaia in the social sciences

A social science view of Gaia theory is the role of humans as a keystone species who may be able to accomplish global homeostasis. Whilst a few social scientists who draw inspiration from 'organic' views of society have embraced Gaia philosophy as a way to explain the human-nature interconnections, most professional social scientists are more involved in reflecting upon the way Gaia philosophy is used and engaged with within sub-sections of society. Alan Marshall, in the Department of Social Sciences at Mahidol University, for example, reflects upon the way Gaia philosophy has been used and advocated by environmentalists, spiritualists, managers, economists, and scientists and engineers (see The Unity of Nature, 2002, Imperial College Press: London and Singapore). Social Scientists themselves in the 1960s gave up on systems ideas of society since they were interpreted as supporting conservatism and traditionalism.

Gaia in politics

Some radical political environmentalists who accept some form of the Gaia theory call themselves Gaians. They actively seek to restore the Earth's homeostasis — whenever they see it out of balance, e.g. to prevent manmade climate change, primate extinction, or rainforest loss. In effect, they seek to cooperate to become the "system consciously manipulating to make conditions more conducive to life". Such activity defines the homeostasis, but for leverage it relies on deep investigation of the homeorhetic balances, if only to find places to intervene in a system which is changing in undesirable ways.

Tony Bondhus brings up the point in his book, Society of Conceivia, that if Gaia is alive, then societies are living things as well. This suggests that our understanding of Gaia can be used to create a better society and to design a better political system.

Other intellectuals in the environmental movement, like Edward Goldsmith, have used Gaia in the completely opposite way; to stake a claim about how Gaia's focus on natural balance and resistance and resilience, should be emulated to design a conservative political system (as explored in Alan Marshall's 2002 book The Unity of Nature, (Imperial College Press: London).

Gaians do not passively ask "what is going on", but rather, "what to do next", e.g. in terraforming or climate engineering or even on a small scale, such as gardening. Changes can be planned, agreed upon by many people, being very deliberate, as in urban ecology and especially industrial ecology.

Gaians argue that it is a human duty to act as such - committing themselves in particular to the Precautionary Principle. Such views began to influence the Green Parties, Greenpeace, and a few more radical wings of the environmental movement such as the Gaia Liberation Front and the Earth Liberation Front. These views dominate some such groups, e.g. the Bioneers. Some refer to this political activity as a separate and radical branch of the ecology movement, one that takes the axioms of the science of ecology in general, and Gaia theory in particular, and raises them to a kind of theory of personal conduct or moral code.

Gaia in religion

The ecologist and theologian Anne Primavesi is the author of two books dealing with the Gaia hypothesis and theology.^[8]

Rosemary Radford Ruether, the American feminist scholar and theologian, wrote a book called "Gaia and God: An Ecofeminist Theology of Earth Healing".

A book edited by Allan Hunt Badiner called Dharma Gaia explores the ground where Buddhism and ecology meet through writings by the Dalai Lama, Gary Snyder, Thich Nhat Hanh, Allen Ginsberg, Joanna Macy, Robert Aitken, and 25 other Buddhists and ecologists.^[9]

Many new age authors have written books which mix New Age teachings with Gaia philosophy. This is known as New Age Gaian. Often referred to as Gaianism, or the Gaian Religion, this spiritual aspect of the philosophy is very broad and inclusive, making it adaptable to other religions: Taoism, Neo-Paganism, Pantheism, Judeo-Christian Religions, and many others.

Semantic debate

The question of "what is an organism", and at what scale is it rational to speak about organisms vs. biospheres, gives rise to a semantic debate. We are all ecologies in the sense that our (human) bodies contain gut bacteria, parasite species, etc., and to them our body is not organism but rather more of a microclimate or biome. Applying that thinking to whole planets:

The argument is that these symbiotic organisms, being unable to survive apart from each other and their climate and local conditions, form an organism in their own right, under a wider conception of the term organism than is conventionally used. It is a matter for often heated debate whether this is a valid usage of the term, but ultimately it appears to be a semantic dispute. In this sense of the word organism, it is argued under the theory that the entire biomass of the Earth is a single organism (as Johannes Kepler thought).

Unfortunately, many supporters of the various Gaia theories do not state exactly where they sit on this spectrum; this makes discussion and criticism difficult.

Much effort on behalf of those analyzing the theory currently is an attempt to clarify what these different hypotheses are, and whether they are proposals to 'test' or 'manipulate' outcomes. Both Lovelock's and Margulis's understanding of Gaia are considered scientific hypotheses, and like all scientific theories are constantly put to the test.

More speculative versions of Gaia, including all versions in which it is held that the Earth is actually conscious, are currently held to be outside the bounds of science, and are not supported by either Lovelock or Margulis.

Gaian reproduction

One of the most problematic issues with referring to Gaia as an organism is its apparent failure to meet the biological criterion of being able to reproduce. Richard Dawkins has asserted that the planet is not the offspring of any parents and is unable to reproduce.^[10]

Daisyworld

From Wikipedia, the free encyclopedia

Plots from a standard black & white DaisyWorld simulation.

Daisyworld, a computer simulation, is a hypothetical world orbiting a star whose radiant energy is slowly increasing or decreasing. It is meant to mimic important elements of the Earth-Sun system, and was introduced by James Lovelock and Andrew Watson in a paper published in 1983^[1] to illustrate the plausibility of the Gaia hypothesis. In the original 1983 version, Daisyworld is seeded with two varieties of daisy as its only life forms: black daisies and white daisies. White petaled daisies reflect light, while black petaled daisies absorb light. The simulation tracks the two daisy populations and the surface temperature of Daisyworld as the sun's rays grow more powerful. The surface temperature of Daisyworld remains almost constant over a broad range of solar output.

Mathematical model to sustain the Gaia hypothesis

The purpose of the model is to demonstrate that feedback mechanisms can evolve from the actions or activities of self-interested organisms, rather than through classic group selection mechanisms.^[2] Daisyworld examines the energy budget of a planet populated by two different types of plants, black daisies and white daisies. The colour of the daisies influences the albedo of the planet such that black daisies absorb light and warm the planet, while white daisies reflect light and cool the planet. Competition between the daisies (based on temperature-effects on growth rates) leads to a balance of populations that tends to favour a planetary temperature close to the optimum for daisy growth.

Lovelock and Watson demonstrated the stability of Daisyworld by making its sun evolve along the main sequence, taking it from low to high solar constant. This perturbation of Daisyworld's receipt of solar radiation caused the balance of daisies to gradually shift from black to white but the planetary temperature was always regulated back to this optimum (except at the extreme ends of solar evolution). This situation is very different from the corresponding abiotic world, where temperature is unregulated and rises linearly with solar output.

Later versions of Daisyworld introduced a range of grey daisies, as well as populations of grazers and predators, and found that these further increased the stability of the homeostasis^{[citation needed]}. More recently, other research, modeling the real biochemical cycles of Earth, and using various types of organisms (e.g. photosynthesisers, decomposers, herbivores and primary and secondary carnivores) has also been shown to produce Daisyworld-like regulation and stability, which helps to explain planetary biological diversity.^{[citation needed]}

This enables nutrient recycling within a regulatory framework derived by natural selection amongst species, where one being's harmful waste becomes low energy food for members of another guild. This research on the Redfield ratio of nitrogen to phosphorus shows that local biotic processes can regulate global systems (See Keith Downing & Peter Zvirinsky, The Simulated Evolution of Biochemical Guilds: Reconciling Gaia Theory with Natural Selection).

Original 1983 simulation synopsis

Play media

A short video about the DaisyWorld model and its implications for real world earth science.

At the beginning of the simulation, the sun's rays are weak and Daisyworld is too cold to support any life. Its surface is barren, and gray. As the luminosity of the sun's rays increases, germination of black daisies becomes possible. Because black daisies absorb more of the sun's radiant energy, they are able to increase their individual temperatures to healthy levels on the still cool surface of Daisyworld. As a result, they thrive and the population soon grows large enough to increase the average surface temperature of Daisyworld.

As the surface heats up, it becomes more habitable for white daisies, whose competing population grows to rival the black daisy population. As the two populations reach equilibrium, so too does the surface temperature of Daisyworld, which settles on a value most comfortable for both populations.

In this first phase of the simulation we see that black daisies have warmed Daisyworld so that it is habitable over a wider range of solar luminosity than would have been possible on a barren, gray planet. This allowed growth of the white daisy population, and the two populations of daisies are now working together to regulate the surface temperature.

The second phase of the simulation documents what happens as the sun's luminosity continues to increase, heating the surface of Daisyworld beyond a comfortable range for the daisies. This temperature increase causes white daisies, who are better able to stay cool because of their high albedo or ability to reflect sunlight, to gain a selective advantage over the black daisies. White daisies begin replacing black daisies, which has a cooling effect on Daisyworld. The result is that Daisyworld's surface temperature remains habitable - in fact almost constant - even as the luminosity of the sun continues to increase.

In the third phase of the simulation, the sun's rays have grown so powerful that soon even the white daisies can no longer survive. At a certain luminosity their population crashes, and the barren, gray surface of Daisyworld, no longer able to reflect the sun's rays, rapidly heats up.

At this point in the simulation solar luminosity is programmed to decline, retracing its original path to its initial value. Even as it declines to levels that previously supported vast populations of daisies in the third phase, no daisies are able to grow because the surface of barren, gray Daisyworld is still far too hot. Eventually, the sun's rays decrease in power to a more comfortable level which allows white daisies to grow, who begin cooling the planet.

Relevance to Earth

Because Daisyworld is so simplistic, having for example, no atmosphere, no animals, only one species of plant life, and only the most basic population growth and death models, it should not be directly compared to Earth. This was stated very clearly by the original authors. Even so, it provided a number of useful predictions of how Earth's biosphere may respond to, for example, human interference. Later adaptations of Daisyworld (discussed below), which added many layers of complexity, still showed the same basic trends of the original model.

One prediction of the simulation is that the biosphere works to regulate the climate, making it habitable over a wide range of solar luminosity. Many examples of these regulatory systems have been found on Earth.

Modifications to the original simulation

Daisyworld was designed to refute the idea that there was something inherently mystical about the Gaia hypothesis that Earth's surface displays homeostatic and homeorhetic properties similar to those of a living organism. Specifically, thermoregulation was addressed. The Gaia hypothesis had attracted a substantial amount of criticism from scientists such as Richard Dawkins,^[3] who argued that planet-level thermoregulation was impossible without planetary natural selection, which might involve evidence of dead planets that did not thermoregulate. Dr. W. Ford Doolittle^[4] rejected the notion of planetary regulation because it seemed to require a "secret consensus" among organisms, thus some sort of inexplicable purpose on a planetary scale. Incidentally, neither of these neoDarwinians made a close examination of the wide-ranging evidence presented in Lovelock's books that was suggestive of planetary regulation, dismissing the theory based on what they saw as its incompatibility with the latest views on the processes by which evolution works. Lovelock's model countered the criticism that some "secret consensus" would be required for planetary regulation by showing how in this model thermoregulation of the planet, beneficial to the two species, arises naturally.^[5]

Later criticism of Daisyworld itself centers around the fact that although it is often used as an analogy for Earth, the original simulations leaves out many important details of the true Earth system. For example, the system requires an ad-hoc death rate (γ) to sustain homeostasis, and it does not take into account the difference between species-level phenomena and individual level phenomena. Detractors of the simulation believed inclusion of these details would cause it to become unstable, and therefore, false. Many of these issues are addressed in a more recent paper by Timothy Lenton and James Lovelock in 2001.^[6] In this paper it is shown that inclusion of these factors actually improves Daisyworld's ability to regulate its climate.

Biodiversity and stability of ecosystems

The importance of the large number of species in an ecosystem, led to two sets of views about the role played by biodiversity in the stability of ecosystems in Gaia theory. In one school of thought labelled the "species redundancy" hypothesis, proposed by Australian ecologist Brian Walker, most species are seen as having little contribution overall in the stability, comparable to the passengers in an aeroplane who play little role in its successful flight. The hypothesis leads to the conclusion that only a few key species are necessary for a healthy ecosystem. The "rivet-popper" hypothesis put forth by Paul R. Ehrlich and his wife Anne H. Ehrlich, compares each species forming part of an ecosystem as a rivet on the aeroplane (represented by the ecosystem). The progressive loss of species mirrors the progressive loss of rivets from the plane, weakening it till it is no longer sustainable and crashes.^[7]

Later extensions of the Daisyworld simulation which included rabbits, foxes and other species, led to a surprising finding that the larger the number of species, the greater the improving effects on the entire planet (i.e., the temperature regulation was improved). It also showed that the system was robust and stable even when perturbed. Daisyworld simulations where environmental changes were stable gradually became less diverse over time; in contrast gentle perturbations led to bursts of species richness. These findings lent support to the idea that biodiversity is valuable.^[8]

This finding was supported by an eleven-year-old study of the factors species composition, dynamics and diversity in successional and native grasslands in Minnesota by David Tilman and John A. Downing wherein they discovered that "primary productivity in more diverse plant communities is more resistant to, and recovers more fully from, a major drought". They go on to add "Our results support the diversity stability hypothesis but not the alternative hypothesis that most species are functionally redundant".^[7][9]