Stress induces sex in bacteria

Bacterial sex (transformation) also appears to be an adaptation to stress. For instance, transformation occurs near the end of logarithmic growth, when amino acids become limiting in Bacillus subtilis, or in Haemophilus influenzae when cells are grown to the end of logarithmic phase. In Streptococcus mutans and other streptococci, transformation is associated with high cell density and biofilm formation. In Streptococcus pneumoniae, transformation is induced by the DNA damaging agent mitomycin C. These, and other, examples indicate that bacterial transformation, like eukaryote meiosis in protists, is an adaptation to stressful conditions. This observation suggests that the natural selection pressures maintaining meiosis in protists are similar to the selective pressures maintaining bacterial transformation. This similarity further indicates continuity, rather than a gap, in the evolution of sex from bacteria to eukaryotes.