Based on a comprehensive analyses based of a large variety of bacteria by integrating taxonomic, phylogenetic and metagenomic data it is suggested that a single-gene sweep, that is, the emergence of dnaE2 derived from an early duplication event of the primordial dnaE, followed by a series of niche-specific genomic adaptations, including GC content increase, intensive horizontal gene transfer and constant genome expansion, led to successful bacterial land colonization.
Hao WU et al., ISME Journal 2014, doi: 10.1038/ismej.2013.247