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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 [9] and have spread to inhabit a variety of different habitats including hydrothermal vents, glacial rocks, and other organisms.
Phylogenetic tree linking all major groups of living organisms, namely the Bacteria, Archaea, and Eukarya, as proposed by Woese et al 1990, [1] with the last universal common ancestor (LUCA) shown at the root
These are endotoxins, which come from broken bacterial cells, and exotoxins, which are produced by bacteria and released into the environment. [231] The bacterium Clostridium botulinum for example, produces a powerful exotoxin that cause respiratory paralysis, and Salmonellae produce an endotoxin that causes gastroenteritis. [ 231 ]
Some findings suggest Europeans could have carried the nonvenereal tropical bacteria home, where the organisms may have mutated into a more deadly form in the different conditions and low immunity of the population of Europe. [53] Syphilis was a major killer in Europe during the Renaissance. [54]
Last universal common ancestor (LUCA): [34] [35] split between bacteria and archaea. [36] Bacteria develop primitive photosynthesis, which at first did not produce oxygen. [37] These organisms exploit a proton gradient to generate adenosine triphosphate (ATP), a mechanism used by virtually all subsequent organisms. [38] [39] [40] 3000 Ma
Cholera (caused by Vibrio cholerae bacteria) and bubonic plague, or the Black Death (caused by the bacterium Yersinia pestis) are some of the most famous examples of how devastating a pandemic can be.
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
Early micro-fossils may have come from a hot world of gases such as methane, ammonia, carbon dioxide, and hydrogen sulfide, toxic to much current life. [230] Analysis of the tree of life places thermophilic and hyperthermophilic bacteria and archaea closest to the root, suggesting that life may have evolved in a hot environment. [231]