Viral eukaryogenesis has been controversial for several reasons.
For one, it is sometimes argued that the posited evidence for the viral
origins of the nucleus can be conversely used to suggest the nuclear origins of some viruses. Secondly, this hypothesis has further inflamed the longstanding debate over whether viruses are livingorganisms.
Hypothesis
The
viral eukaryogenesis hypothesis posits that eukaryotes are composed of
three ancestral elements: a viral component that became the modern
nucleus; a prokaryotic cell (an archaeon according to the eocyte hypothesis) which donated the cytoplasm and cell membrane of modern cells; and another prokaryotic cell (here bacterium) that, by endocytosis, became the modern mitochondrion or chloroplast.
In 2006, researchers suggested that the transition from RNA to DNA genomes first occurred in the viral world. A DNA-based virus may have provided storage for an ancient host that
had previously used RNA to store its genetic information (such host is
called ribocell or ribocyte). Viruses may initially have adopted DNA as a way to resist RNA-degradingenzymes in the host cells. Hence, the contribution from such a new component may have been as significant as the contribution from chloroplasts or mitochondria. Following this hypothesis, archaea, bacteria, and eukaryotes each obtained their DNA informational system from a different virus. In the original paper, it was also an RNA cell at the origin of eukaryotes, but eventually more complex, featuring RNA processing.
Although this is in contrast to nowadays' more probable eocyte
hypothesis, viruses seem to have contributed to the origin of all three
domains of life ('out of virus hypothesis'). It has also been suggested
that telomerase and telomeres, key aspects of eukaryotic cell replication, have viral origins. Further, the viral origins of the modern eukaryotic nucleus may have relied on multiple infections of archaeal cells carrying bacterial mitochondrial precursors with lysogenic viruses.
The viral eukaryogenesis hypothesis depicts a model of eukaryotic evolution in which a virus, similar to a modern pox virus, evolved into a nucleus via gene acquisition from existing bacterial and archaeal species. The lysogenic virus then became the information storage center for the cell, while the cell retained its capacities for gene translation
and general function despite the viral genome's entry. Similarly, the
bacterial species involved in this eukaryogenesis retained its capacity
to produce energy in the form of ATP while also passing much of its genetic information into this new virus-nucleus organelle. It is hypothesized that the modern cell cycle, whereby mitosis, meiosis, and sex occur in all eukaryotes, evolved
because of the balances struck by viruses, which characteristically
follow a pattern of tradeoff between infecting as many hosts as possible
and killing an individual host through viral proliferation.
Hypothetically, viral replication cycles may mirror those of plasmids and viral lysogens.
However, this theory is controversial, and additional experimentation
involving archaeal viruses is necessary, as they are probably the most
evolutionarily similar to modern eukaryotic nuclei.
The viral eukaryogenesis hypothesis points to the cell cycle of eukaryotes, particularly sex and meiosis, as evidence. Little is known about the origins of DNA or reproduction in prokaryotic
or eukaryotic cells. It is thus possible that viruses were involved in
the creation of Earth's first cells. The eukaryotic nucleus contains linear DNA with specialized end
sequences, like that of viruses (and in contrast to bacterial genomes,
which have a circular topology); it uses mRNA capping, and separates transcription from translation. Eukaryotic nuclei are also capable of cytoplasmic replication. Some large viruses have their own DNA-directed RNA polymerase. Transfers of "infectious" nuclei have been documented in many parasiticred algae.
Recent supporting evidence includes the discovery that upon the infection of a bacterialcell, the giant bacteriophage201 Φ2-1 (of the genus Phikzvirus)
assembles a nucleus-like structure around the region of genome
replication and uncouples transcription and translation, and synthesized
mRNA is then transported into the cytoplasm where it undergoes
translation. The same researchers also found that this same phage encodes a eukaryotic homologue to tubulin (PhuZ) that plays the role of positioning the viral factory in the center of the cell during genome replication. The PhuZ
spindle shares several unique properties with eukaryotic spindles:
dynamic instability, bipolar filament arrays, and centrally positioning
DNA.
Analogous to the phage nucleus is the viroplasm, also known as a "virus factory" and "virus inclusion". Viroplasms are inclusion bodies wrapped in lipid membranes and aggregates of viral proteins, and they serve as sites for viral replication and assembly. The viroplasm may serve to protect the viral genome from host cell defense mechanisms, and it also contains viral polymerases for mRNA transcription and DNA
replication and repair, separating these processes from the cytoplasm,
much like the cell nucleus. Expression of this structure is prevalent
among most members of the phylum nucleocytoviricota, notably the nucleocytoplasmic large DNA viruses (NCLDVs).
Central dogma proteins
Phylogenetic
analysis determined that the presence of certain eukaryotic proteins in
nucleocytoviricota – particularly, ones responsible for DNA replication
and repair, mRNA transcription, and mRNA capping – may have preceded
the evolution of the last eukaryotic common ancestor,
suggesting the evolution of these proteins in eukaryotes and
nucleocytoviruses may have been a result of horizontal gene transfer
between ancient nucleocytoviruses and proto-eukaryotes or Asgard archaea. The eukaryotic DNA polymerasePol δ, for example, was found to be phylogenetically nested within the clade of nucleocytovirus, mirusvirus, and herpesvirus DNA polymerases, with medusavirus polymerases being the closest relative to the Pol δ clade; Pol α and Pol ε, on the other hand, are more closely related to archaeal PolB DNA polymerases, with Pol ε being derived from Asgard Pol ε. Similarly, the phylogenetic study suggests that eukaryotic and viral RNA polymerases (RNAPs) are deeply related – with RNAP I and RNAP III being basally branching to this viral/eukaryotic RNAP II
clade, and are themselves being derived from or are closely related to
archaeal RNA polymerases. The evolution of these proteins may have been
rapid, and may have resulted from interactions between these viruses and
proto-eukaryotes.
Further, many classes of NCLDVs such as mimiviruses
have the apparatus to produce m7G capped mRNA and contain homologues of
the eukaryotic cap-binding protein eIF4E. Those supporting viral
eukaryogenesis also point to the lack of these features in archaea, and
so believe that a sizable gap separates the archaeal groups most related
to the eukaryotes and the eukaryotes themselves in terms of the
nucleus. In light of these and other discoveries, Bell modified his
original thesis to suggest that the viral ancestor of the nucleus was an
NCLDV-like archaeal virus rather than a pox-like virus. Another piece of supporting evidence is that the m7G capping apparatus (involved in uncoupling of transcription from translation) is present in both Eukarya and Mimiviridae but not in Lokiarchaeota that are considered the nearest archaeal relatives of Eukarya according to the Eocyte hypothesis (also supported by the phylogenetic analysis of the m7G capping pathway).
Implications
Several precepts in the theory are possible. For instance, a helical virus with a bilipidenvelope bears a distinct resemblance to a highly simplified cellular nucleus
(i.e., a DNA chromosome encapsulated within a lipid membrane). In
theory, a large DNA virus could take control of a bacterial or archaeal
cell. Instead of replicating and destroying the host cell,
it would remain within the cell, thus overcoming the tradeoff dilemma
typically faced by viruses. With the virus in control of the host cell's
molecular machinery, it would effectively become a functional nucleus.
Through the processes of mitosis and cytokinesis, the virus would thus recruit the entire cell as a symbiont—a new way to survive and proliferate.
Protestantism is the largest grouping of Christians in the United States, with its combined denominations collectively comprising about 43% of the country's population (or 141 million people) in 2019. Other estimates suggest that 48.5% of the U.S. population (or 157 million people) is Protestant. Simultaneously, this corresponds to around 20% of the world's total Protestant population. The U.S. contains the largest Protestant population of any country in the world. Baptists comprise about one-third of American Protestants. The Southern Baptist Convention
is the largest single Protestant denomination in the U.S., comprising
one-tenth of American Protestants. Twelve of the original Thirteen Colonies were Protestant, with only Maryland having a sizable Catholic population due to Lord Baltimore's religious tolerance.
The country's history is often traced back to the Pilgrim Fathers whose Brownist beliefs motivated their move from England to the New World. These English Dissenters, who also happened to be Puritans—and therefore Calvinists—, were first to settle in what was to become the Plymouth Colony. America's Calvinist
heritage is often underlined by various experts, researchers and
authors, prompting some to declare that the United States was "founded
on Calvinism", while also underlining its exceptional foundation as a
Protestant majority nation. American Protestantism has been diverse from the very beginning with large numbers of early immigrants being Anglican, various Reformed, Lutheran, and Anabaptist. In the next centuries, it diversified even more with the Great Awakenings throughout the country.
Protestants are divided into many different denominations, which are generally classified as either "mainline" or "evangelical", although some may not fit easily into either category. Some historically African-American denominations are also classified as Black churches.
Protestantism had undergone an unprecedented development on American
soil, diversifying into multiple branches, denominations, several
interdenominational and related movements, as well as many other
developments. All have since expanded on a worldwide scale mainly
through missionary work.
Statistics
The
map above shows plurality religious denomination by state as of 2014.
In 43 out of the 50 states, Protestantism took a plurality of the
state's population. Protestantism
70–79%
60–69%
50–59%
40–49%
30–39%
Catholicism
40–49%
30–39%
Mormonism
50–59%
Unaffiliated
30–39%
Protestants in the United States by tradition according to the Pew Research Center (2014)
Baptists are the largest Protestant grouping in the United States accounting for one-third of all American Protestants.
Baptist churches were organized, starting in 1814, as the Triennial Convention. In 1845, most southern congregations split, founding the Southern Baptist Convention, which is now the largest Protestant denomination in the U.S., with 13.2 million members as of 2023. The Triennial Convention was reorganized into what is now American Baptist Churches USA and includes 1.1 million members and 5,057 congregations.
Baptists have been present in the part of North America that is now the United States since the early 17th century. Both Roger Williams and John Clarke, his compatriot in working for religious freedom, are credited with founding the Baptist faith in North America. In 1639, Williams established a Baptist church in Providence, Rhode Island (First Baptist Church in America) and Clarke began a Baptist church in Newport, Rhode Island (First Baptist Church in Newport).
According to a Baptist historian who has researched the matter, "There
is much debate over the centuries as to whether the Providence or
Newport church deserved the place of 'first' Baptist congregation in
America. Exact records for both congregations are lacking."
The first ministers were recruited from Northern Ireland. While several Presbyterian churches had been established by the late
1600s, they were not yet organized into presbyteries and synods until
the early 1700s.
With 2.7 million members, the Evangelical Lutheran Church in America (ELCA) is the largest American Lutheran denomination, followed by the Lutheran Church–Missouri Synod (LCMS) with 1.7 million members, and the Wisconsin Evangelical Lutheran Synod (WELS) with 344,000 members. The differences between the Evangelical Lutheran Church in America
(ELCA) and the Lutheran Church–Missouri Synod (LCMS) largely arise from
historical and cultural factors, although some are theological in
character. The ELCA tends to be more involved in ecumenical endeavors
than the LCMS.
When Lutherans came to North America,
they started church bodies that reflected, to some degree, the churches
left behind. Many maintained their immigrant languages until the early
20th century. They sought pastors from the "old country" until patterns
for the education of clergy could be developed in America. Eventually, seminaries
and church colleges were established in many places to serve the
Lutheran churches in North America and, initially, especially to prepare
pastors to serve congregations.
The LCMS sprang from German immigrants fleeing the forced Prussian Union,
who settled in the St. Louis area and has a continuous history since it
was established in 1847. The LCMS is the second largest Lutheran church
body in North America (1.7 million). It identifies itself as a church
with an emphasis on biblical doctrine and faithful adherence to the
historic Lutheran confessions. Insistence by some LCMS leaders on a
strict reading of all passages of Scripture led to a rupture in the
mid-1970s, which in turn resulted in the formation of the Association of
Evangelical Lutheran Churches, now part of the ELCA.
Although its strongly conservative views on theology and ethics might seem to make the LCMS politically compatible with other Evangelicals
in the U.S., the LCMS as an organization largely eschews political
activity, partly out of its strict understanding of the Lutheran
distinction between the Two Kingdoms.
It does, however, encourage its members to be politically active, and
LCMS members are often involved in political organizations such as
Lutherans for Life.
The earliest predecessor synod of the Evangelical Lutheran Church
in America was constituted on August 25, 1748, in Philadelphia. It was
known as the Ministerium of Pennsylvania
and Adjacent States. The ELCA is the product of a series of mergers and
represents the largest (3.0 million members) Lutheran church body in
North America. The ELCA was created in 1988 by the uniting of the
2.85-million-member Lutheran Church in America, 2.25-million-member American Lutheran Church, and the 100,000-member Association of Evangelical Lutheran Churches.
The ALC and LCA had come into being in the early 1960s, as a result of
mergers of eight smaller ethnically based Lutheran bodies.
Pentecostalism is a renewalist religious movement within
Protestantism, that places special emphasis on a direct personal
experience of God through the baptism of the Holy Spirit. The term Pentecostal is derived from Pentecost, a Greek term describing the Jewish Feast of Weeks. For Christians, this event commemorates the descent of the Holy Spirit
and Pentecostals tend to see their movement as reflecting the same kind
of spiritual power, worship styles and teachings that were found in the
early church.
Pentecostalism is an umbrella term that includes a wide range of
different theological and organizational perspectives. As a result,
there is no single central organization or church that directs the
movement. Most Pentecostals consider themselves to be part of broader
Christian groups; for example, most Pentecostals identify as
Protestants. Many embrace the term Evangelical, while others prefer Restorationist. Pentecostalism is theologically and historically close to the Charismatic Movement, as it significantly influenced that movement; some Pentecostals use the two terms interchangeably.
In typical usage, the term mainline is contrasted with evangelical.
The distinction between the two can be due as much to sociopolitical
attitude as to theological doctrine, although doctrinal differences may
exist as well. Theologically conservative critics accuse the mainline
churches of "the substitution of leftist social action for Christian
evangelizing, and the disappearance of biblical theology", and maintain
that "All the Mainline churches have become essentially the same church:
their histories, their theologies, and even much of their practice lost
to a uniform vision of social progress."
The Association of Religion Data Archives (ARDA) counts 26,344,933 members of mainline churches versus 39,930,869 members of evangelical Protestant churches. There is evidence of a shift in membership from mainline denominations to evangelical churches.
Mainline Protestant Christian denominations are those Protestant
denominations that were brought to the United States by its historic
immigrant groups; for this reason they are sometimes referred to as
heritage churches. The largest are the Episcopal (English), Presbyterian (Scottish),
Methodist (English and Welsh), and Lutheran (German and Scandinavian)
churches.
Many mainline denominations teach that the Bible is God's word in
function, but tend to be open to new ideas and societal changes. They have been increasingly open to the ordination of women. Mainline churches tend to belong to organizations such as the National Council of Churches and World Council of Churches.
Evangelicalism is a Protestant Christian movement in which adherents consider its key characteristics to be a belief in the need for personal conversion (or being "born again"), some expression of the gospel in effort, a high regard for Biblical authority and an emphasis on the death and resurrection of Jesus. David Bebbington has termed these four distinctive aspects "conversionism",
"activism", "biblicism", and "crucicentrism", saying, "Together they
form a quadrilateral of priorities that is the basis of Evangelicalism."
Note that the term "evangelical" does not equal Christian fundamentalism,
although the latter is sometimes regarded simply as the most
theologically conservative subset of the former. The major differences
largely hinge upon views of how to regard and approach scripture
("Theology of Scripture"), as well as construing its broader world-view
implications. While most conservative evangelicals believe the label has
broadened too much beyond its more limiting traditional distinctives,
this trend is nonetheless strong enough to create significant ambiguity
in the term. As a result, the dichotomy between "evangelical" vs. "mainline"
denominations is increasingly complex (particularly with such
innovations as the "emergent church" movement).
The contemporary North American usage of the term is influenced
by the evangelical/fundamentalist controversy of the early 20th century.
Evangelicalism may sometimes be perceived as the middle ground between
the theological liberalism of the mainline denominations and the cultural separatism of fundamentalist Christianity. Evangelicalism has therefore been described as "the third of the
leading strands in American Protestantism, straddl[ing] the divide
between fundamentalists and liberals." While the North American perception is important to understand the
usage of the term, it by no means dominates a wider global view, where
the fundamentalist debate was not so influential.
Evangelicals held the view that the modernist and liberal parties
in the Protestant churches had surrendered their heritage as
evangelicals by accommodating the views and values of the world. At the same time, they criticized their fellow fundamentalists for their separatism and their rejection of the Social Gospel
as it had been developed by Protestant activists of the previous
century. They charged the modernists with having lost their identity as
evangelicals and the fundamentalists with having lost the Christ-like
heart of evangelicalism. They argued that the Gospel needed to be
reasserted to distinguish it from the innovations of the liberals and
the fundamentalists.
They sought allies in denominational churches and liturgical
traditions, disregarding views of eschatology and other
"non-essentials," and joined also with Trinitarian varieties of
Pentecostalism. They believed that in doing so, they were simply
re-acquainting Protestantism with its own recent tradition. The
movement's aim at the outset was to reclaim the evangelical heritage in
their respective churches, not to begin something new; and for this
reason, following their separation from fundamentalists, the same
movement has been better known merely as "Evangelicalism." By the end of
the 20th century, this was the most influential development in American
Protestant Christianity.
According to Scientific Elite: Nobel Laureates in the United States by Harriet Zuckerman, a review of American Nobel prizes winners awarded between 1901 and 1972, 72% of American Nobel Prize laureates have identified from Protestant background. Overall, 84.2% of all the Nobel Prizes awarded to Americans in Chemistry, 60% in Medicine, and 58.6% in Physics between 1901 and 1972 were won by Protestants.
