Whether inhabiting soil, fresh water, or marine ecosystems, bacteria are constantly facing the threat of numerous and effective predators such as protists, nematodes, or phages. To defend against such predation, bacteria have evolved a number of strategies, including getting larger in size, moving faster, producing defensive secondary metabolites, and forming biofilms. Because of its anthropocentric appeal, one strategy stands out—keeping a locked armory of genetic weapons. The strategy involves breaking open the armory when confronted by perils—activating the genes that were locked mostly to save the cost of expressing them when not needed.
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