Aranyak Goswami
Posters-Accepted Abstracts: Biol Syst Open Access
The genus of Bacillus is known for the metabolic diversity, ecological ubiquity, clinical significance and commercial potential of its members. Co-existence of three conspicuous genome features an explicit Purine Asymmetry (PAS), extremely high Strand bias in Gene Distribution (SGD) and the presence of PolC (DNA polymerase III, α subunit) has differentiated Bacillus and some other members of Firmicutes, Fusobacteria and Tenericutes from the rest of the bacterial world. The primary objective of the present study was to examine whether these features, especially PAS, could impart any influence on protein evolution in these organisms and the genus of Bacillus has been selected as a case study. Analysis of various protein features in 21 Bacillus species of varied metabolic, pathogenic and ecological traits has revealed that all Bacillus species except the Serespiring Bacillus selenitireducens, display distinct strand-specific biases in amino acid usage. This strand asymmetry is often reflected also in the pI profiles or surface charge distribution of Bacillus proteins with prevalence of acidic and basic residues in the leading and lagging strand proteins respectively. The dinucleotide relative abundance signatures of Bacillus genomes are however not affected by PAS. Distinct lineage-specific and/or niche-specific trends also prevail in the gene and protein features of the members of this genus. Divergence in synonymous codon usage patterns between two strands of replication is quite apparent in the cereus group but not in the non-cereus group of Bacillus. Higher occurrences of Cys or Asp in halophilic/ alkaliphilc members or abundance of basic residues in thermo-tolerant species corroborate earlier reports on hypersaline and thermal adaptation of bacteria. The study, therefore suggests that protein evolution in Bacillus may be an outcome of a perfect harmony between three distinct factors, purine asymmetry, taxonomic heritage and niche specialization.
