Divergence in gene regulation contributes to sympatric speciation of Shewanella baltica strains.

This study investigated genomic composition of two Shewanella baltica clades previously identified through multi-locus sequencing typing and recovered from the redox transition zone in the central Baltic Sea. Comparative genomic analysis revealed significantly higher inter- than intra-clade genomic dissimilarity, and that a subset of genes present in Clade A were associated with potential adaptation to respiration of sulfur compounds present in the redox-transition zone. Transcriptomic divergence between two representative strains of Clades A and D, OS185 and OS195, was also characterized and revealed marked regulatory differences. We found that both transcriptional divergence of shared genes and expression of strain-specific genes lead to differences in regulatory patterns between strains that correlate with environmental redox niches. For instance, under anoxic conditions of respiratory nitrate ammonification, OS185 - the strain isolated from nitrate-rich environment, upregulated nearly twice the number of shared genes compared to OS195 - the strain isolated from H2S-containing anoxic environment. Conversely, OS195 showed stronger induction of strain-specific genes, especially those associated with sulfur compound respiration, under thiosulfate-reducing conditions. A positive association between the level of transcriptional divergence and sequence divergence for shared genes was also noted. Our results provide further support for the hypothesis that genomic changes impactin...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research