evolution of bacteria evolution of bacteria the evolution of bacteria has progressed over billions of years since the precambrian time with their first major divergence from the archaeal/eukaryotic lineage roughly 3.2-3.5 billion years ago. this was discovered through gene sequencing of bacterial nucleoids to reconstruct their phylogeny. furthermore, evidence of permineralized microfossils of early prokaryotes was also discovered in the australian apex chert rocks, dating back roughly 3.5 billion years ago during the time period known as the precambrian time. this suggests that an organism in of the phylum thermotogota (formerly thermotogae) was the most recent common ancestor of modern bacteria. colorized scanning electron micrograph showing carbapenem-resistant klebsiella pneumoniae interacting with a human neutrophil. part of a series onevolutionary biologydarwin's finches by john gould index introduction main outline glossary evidence history processes and outcomes population genetics variation diversity mutation natural selection adaptation polymorphism genetic drift gene flow speciation adaptive radiation co-operation coevolution coextinction divergence convergence parallel evolution extinction natural history origin of life common descent history of life timeline of evolution human evolution phylogeny biodiversity biogeography classification evolutionary taxonomy cladistics transitional fossil extinction event history of evolutionary theory overview renaissance before darwin darwin origin of species before synthesis modern synthesis molecular evolution evo-devo current research history of speciation history of paleontology (timeline) fields and applications applications of evolution biosocial criminology ecological genetics evolutionary aesthetics evolutionary anthropology evolutionary computation evolutionary ecology evolutionary economics evolutionary epistemology evolutionary ethics evolutionary game theory evolutionary linguistics evolutionary medicine evolutionary neuroscience evolutionary physiology evolutionary psychology experimental evolution phylogenetics paleontology selective breeding speciation experiments sociobiology island biogeography systematics universal darwinism social implications evolution as fact and theory social effects creation–evolution controversy theistic evolution objections to evolution level of support evolutionary biology portal categoryfurther chemical and isotopic analysis of ancient rock reveals that by the siderian period, roughly 2.45 billion years ago, oxygen had appeared. this indicates that oceanic, photosynthetic cyanobacteria evolved during this period because they were the first microbes to produce oxygen as a byproduct of their metabolic process. therefore, this phylum was thought to have been predominant roughly 2.3 billion years ago. however, some scientists argue they could have lived as early as 2.7 billion years ago, as this was roughly before the time of the great oxygenation event, meaning oxygen levels had time to increase in the atmosphere before it altered the ecosystem during this event. the rise in atmospheric oxygen led to the evolution of pseudomonadota (formerly proteobacteria). today this phylum includes many nitrogen fixing bacteria, pathogens, and free-living microorganisms. this phylum evolved approximately 1.5 billion years ago during the paleoproterozoic era. however, there are still many conflicting theories surrounding the origins of bacteria. even though microfossils of ancient bacteria have been discovered, some scientists argue that the lack of identifiable morphology in these fossils means they can not be utilised to draw conclusions on an accurate evolutionary timeline of bacteria. nevertheless, more recent technological developments means more evidence has been discovered. defining bacteria life timeline−4500 —–—–−4000 —–—–−3500 —–—–−3000 —–—–−2500 —–—–−2000 —–—–−1500 —–—–−1000 —–—–−500 —–—–0 — water single-celled life photosynthesis eukaryotes multicellular life plants arthropods molluscsflowersdinosaurs mammalsbirdsprimateshadeanarcheanproterozoicphanerozoic ←earth formed←earliest water←luca←earliest fossils←lhb meteorites←earliest oxygen←pongola glaciation*←atmospheric oxygen←huronian glaciation*←sexual reproduction←earliest multicellular life←earliest fungi←earliest plants←earliest animals←cryogenian ice age*←ediacaran biota←cambrian explosion←andean glaciation*←earliest tetrapods←karoo ice age*←earliest apes / humans←quaternary ice age*(million years ago)*ice ages bacteria are prokaryotic microorganisms that can either have a bacilli, spirilli, or cocci shape and measure between 0.5-20 micrometers. they were one of the first living cells to evolve and have spread to inhabit a variety of different habitats including hydrothermal vents, glacial rocks, and other organisms. they share characteristics with eukaryotic cells including the cytoplasm, cell membrane, and ribosomes. some unique bacterial features include the cell wall (also found in plants and fungi), flagella (not common for all bacteria), and the nucleoid. bacteria can metabolise in different ways, most commonly by heterotrophic or autotrophic (either photosynthetic or chemosynthetic) processes. bacteria reproduce through binary fission, though they can still share genetic information between individuals either by transduction, transformation, or conjugation. process of bacterial evolution bacteria evolve in a similar process to other organisms. this is through the process of natural selection, whereby beneficial adaptations are passed onto future generations until the trait becomes common within the entire population. however, since bacteria reproduce via binary fission—a form of asexual reproduction—the daughter cell and parent cell are genetically identical. this makes bacteria susceptible to environmental pressures, an issue that is overcome by sharing genetic information via transduction, transformation, or conjugation. this allows for new genetic and physical adaptations to develop, allowing bacteria to adapt to their environment and evolve. furthermore, bacteria can reproduce in as little as 20 minutes, which allows for fast adaptation, meaning new strains of bacteria can evolve quickly. this has become an issue regarding antibiotic resistant bacteria. thermophile bacteria from deep-sea vent. this organism eats sulfur and hydrogen and fixes its own carbon from carbon dioxide. thermotogales thermotogota bacteria are typically thermophilic or hyperthermophilic, gram-negative staining, anaerobic organisms that can live near hydrothermal vents where temperatures can range between 55-95 °c. they are thought to be some of the earliest forms of life. evidence of these organisms has been discovered in the australian apex chert near ancient hydrothermal vents. these rocks date back 3.46 billion years and these fossils are thought to have belonged to early thermophilic bacteria. this is because these organisms do not require oxygen to survive, which was an element that was not present in large quantities in earth's early atmosphere. furthermore, this phylum still has living species such as thermotoga neapolitana, which still largely resemble their ancestral form and still live around these vents, which some scientists have used as evidence to support this theory. more recent evidence has emerged, which suggests that thermotogales evolved roughly between 3.2-3.5 billion years ago. this evidence was collected via gene sequencing of bacterial nucleoids to reconstruct their phylogeny. the first major divergence within the thermotogales phylum was between thermotogaceae and fervidobacteriaceae, however, it is yet to be determined as to when this occurred. the family of thermotogaceae then diverged into the genus thermotoga and the genus pseudothermotoga. the genus thermotoga represents the majority of existing hyperthermophiles and are unique in that they are wrapped in an outer membrane that is referred to as a "toga". some extant thermotoga species include t. neapolitana. thermotogale phylogeny