In silico comparative genomic analysis of arsenic resistance operons in bacterial representatives associated with Urmia and Van lakes

Arsenic contamination poses major ecological and health risks, and
microorganisms play key roles in arsenic cycling and detoxification. This
study presents a comparative in silico analysis of arsenic resistance
operons in representative bacterial genomes associated with two extreme
ecosystems, Urmia Hypersaline Lake (Iran) and Van Soda Lake (Türkiye). Six
representative genomes were selected based on 16S rRNA gene sequence
homology, and their operons were characterised. Both canonical and
noncanonical arrangements were identified, reflecting lineage-specific
adaptations and horizontal gene transfer. The predicted promoters and
terminators indicate regulatory diversity among the operons. Phylogenetic
analysis of 16S rRNA gene sequences from 17 isolates showed low nucleotide
diversity, whereas functional genes displayed high polymorphism. Haplotype
diversity was the greatest for arsR (Hd = 0.960), followed by arsB and
arsC (Hd = 0.933 each). Population differentiation analysis showed a
significant divergence of arsR between Urmia and Van isolates (F_ST =
0.759), highlighting its role in local adaptation to arsenic-rich
environments. These findings suggest a dual strategy for microbial
adaptation, maintaining conserved core operons while incorporating diverse
accessory genes to broaden detoxification potential. This study provides
insights into microbial survival strategies in extreme saline and soda
lakes and offers a genomic framework for future functional investigations.