The impact of DNA methylation in Alphaproteobacteria.

Alphaproteobacteria include bacteria with very different modes of life, from free-living to host-associated and pathogenic bacteria. Their genomes vary in size and organization from single circular chromosomes to multipartite genomes and are often methylated by one or more adenine or cytosine methyltransferases (MTases). These include MTases that are part of restriction/modification systems and so-called orphan MTases. The development of novel technologies accelerated the analysis of methylomes and revealed the existence of epigenetic patterns in several Alphaproteobacteria. This review describes the known functions of DNA methylation in Alphaproteobacteria and also discusses its potential drawbacks through the accidental deamination of methylated cytosines. Particular emphasis is given to the strong connection between the cell cycle-regulated orphan MTase CcrM and the complex network that controls gene expression and cell cycle progression in Alphaproteobacteria.