Strand-biased gene distribution, purine assymetry and environmental factors influence protein evolution in Bacillus.

A strong purine asymmetry, along with strand-biased gene distribution and the presence of PolC, prevails in Bacillus and some other members of Firmicutes, Fusobacteria and Tenericutes. The analysis of protein features in 21 Bacillus species of diverse metabolic, virulence and ecological traits revealed that purine asymmetry in conjunction with lineage/niche specific constraints significantly influences protein evolution in Bacillus. All Bacillus species, except for Se-respiring Bacillus selenitireducens, display distinct strand-specific biases in amino acid usage, which may affect the isoelectric point or surface charge distribution of proteins with prevalence of acidic and basic residues in the leading and lagging strand proteins, respectively.