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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Natural competence | 2/2 | https://en.wikipedia.org/wiki/Natural_competence | reference | science, encyclopedia | 2026-05-05T07:16:03.334926+00:00 | kb-cron |
=== Hypothesis of DNA as food === The second hypothesis, DNA as food, relies on the fact that cells that take up DNA inevitably acquire the nucleotides the DNA consists of, and, because nucleotides are needed for DNA and RNA synthesis and are expensive to synthesize, these may make a significant contribution to the cell's energy budget. Some naturally competent bacteria also secrete nucleases into their surroundings, and all bacteria can take up the free nucleotides these nucleases generate from environmental DNA. The energetics of DNA uptake are not understood in any system, so it is difficult to compare the efficiency of nuclease secretion to that of DNA uptake and internal degradation. In principle the cost of nuclease production and the uncertainty of nucleotide recovery must be balanced against the energy needed to synthesize the uptake machinery and to pull DNA in. Other important factors are the likelihoods that nucleases and competent cells will encounter DNA molecules, the relative inefficiencies of nucleotide uptake from the environment and from the periplasm (where one strand is degraded by competent cells), and the advantage of producing ready-to-use nucleotide monophosphates from the other strand in the cytoplasm. Another complicating factor is the self-bias of the DNA uptake systems of species in the family Pasteurellaceae and the genus Neisseria, which could reflect either selection for recombination or for mechanistically efficient uptake.
=== Hypothesis of repair of DNA damage === In bacteria, the problem of DNA damage is most pronounced during periods of stress, particularly oxidative stress, that occur during crowding or starvation conditions. Some bacteria induce competence under such stress conditions, supporting the hypothesis that transformation helps DNA repair. In experimental tests, bacterial cells exposed to agents damaging their DNA, and then undergoing transformation, survived better than cells exposed to DNA damage that did not undergo transformation. In addition, competence to undergo transformation is often inducible by known DNA damaging agents. Thus, a strong short-term selective advantage for natural competence and transformation would be its ability to promote homologous recombinational DNA repair under conditions of stress.
=== Horizontal gene transfer === A long-term advantage may occasionally be conferred by occasional instances of horizontal gene transfer also called lateral gene transfer, (which might result from non-homologous recombination after competence is induced), that could provide for antibiotic resistance or other advantages. Regardless of the nature of selection for competence, the composite nature of bacterial genomes provides abundant evidence that the horizontal gene transfer caused by competence contributes to the genetic diversity that makes evolution possible.
== See also == Transformation (genetics)
== References ==