Year: 2022

SEVERAL EVENTS. "Although the rates of gene gain, loss, and duplication greatly differ across the bacterial diversity, in the most dynamic groups, several gene gains and losses occur during the time the genome accumulates, on average, one nucleotide substitution per gene." https://lnkd.in/dSemZpD View in LinkedIn

LOSSES BEAT MUTATIONS. "Strikingly, the most common process of genome dynamics is actually loss of genes: for most (although not all) groups of microbes, evolutionary reconstructions indicate a twofold to threefold excess of losses over gains per nucleotide substitution." https://lnkd.in/dSemZpD View in LinkedIn

LOSSES OFFSET BY MASSIVE GAINS. "In the long term, excess of gene losses obviously would lead to genome degradation and eventually extinction, and indeed such is the fate of many groups of microbes, in particular parasites and symbionts. In general, however, the gradual gene loss appears to be offset by episodic, massive gene gain that might accompany the emergence of major groups of prokaryotes." https://lnkd.in/dSemZpD View in LinkedIn

GIANT GENE GAINS. "The same reconstructions indicate that in all analyzed groups of microbes, the rate of gene gain exceeds the gene duplication rate by at least an order of magnitude. The primary source of gene gain is HGT, which accordingly is the principal route of evolutionary innovation in bacteria and archaea." (HGT = horizontal gene transfer). https://lnkd.in/dSemZpD View in LinkedIn

BUGS DEFY DARWINIAN EVOLUTION. "Taken together, the reconstructions of the dynamics of microbial genome evolution show that, in the microbial world, evolution primarily occurs not via the classic Darwinian process adopted by the Modern Synthesis of Evolutionary Biology, i.e. gradual accumulation of numerous, “infinitesimally small” changes (mutations), but rather by much bigger, at least gene-sized, leaps." https://lnkd.in/dSemZpD View in LinkedIn

DIFFERENT MECHANISM. "In a sharp contrast to eukaryotes, in bacteria and archaea, the dominant feature of genome evolution is not gene duplication but rather evolution by extensive gene loss and gene gain via HGT." (HGT = horizontal gene transfer). https://lnkd.in/dSemZpD View in LinkedIn

DEPENDENT ON HGT. "Can microbes evolve without substantial HGT, simply via the competition of clonal populations? Apparently not, as population genetic modeling indicates that this evolutionary regime is unsustainable in the long term." (HGT = horizontal gene transfer). https://lnkd.in/dSemZpD View in LinkedIn

ASEXUAL DEAD END. "Clonal populations typically deteriorate due to the action of the evolutionary mechanism known as Muller’s ratchet, i.e. gradual loss of fitness and eventual extinction caused by accumulation of slightly deleterious mutations via genetic drift." https://lnkd.in/dSemZpD View in LinkedIn

LAW OF THE RATCHET. "Demise caused by Muller’s ratchet appears to be the typical fate of bacteria that are confined to intracellular parasitism or symbiosis, although the ratchet can be slowed down by lowering the mutation rate." https://lnkd.in/dSemZpD View in LinkedIn

OFFSETTING THE RATCHET. "The only route of actual escape from Muller’s ratchet appears to be gene acquisition via HGT resulting in either displacement of a mutated gene by a functional copy or gain of new genes that offsets the deleterious effects of accumulating mutations." (HGT = horizontal gene transfer). https://lnkd.in/dSemZpD View in LinkedIn