Response to chromate challenge by marine Staphylococcus sp. NIOMR8 evaluated by differential protein expression

Liquid Chromatography-Mass Spectrometry-Quadrupole Time of Flight (LC/MS QToF) protein profiling of marine-derived Staphyloccous gallinarum NIOMR8 was carried out to evaluate proteins conferring chromate (Cr⁶⁺) resistance and possible metabolic pathways that were altered as a result. Expressional (up or down-regulation) responses to varying Cr⁶⁺ (0, 50, 100, 150, and 200 µg mL^- 1) concentrations varied, with as many as 346 proteins identified. Most number of proteins-their numbers in parentheses-were up-regulated when grown in medium with 50 µg mL^- 1 (162) and, down-regulated in medium with 100 (281) or 200 µg mL^- 1 Cr⁶⁺ (280). Among these, eight proteins were commonly up-regulated, while 58 were commonly down-regulated across all conditions of Cr⁶⁺. Expression of protein moieties in metabolic pathways like translation (38), transcription (14), replication (18) and repair (4), metabolism of carbohydrates (26), amino acids (27), nucleotides (17), and membrane transport (21) was evidenced. Up-regulation patterns suggest that reduction of molecular oxygen (5), DNA repair (4) and peptide misfolding (7) were the potential protective mechanisms employed to counter Cr⁶⁺ stress. Additionally, proteins associated with biofilm and cell wall biogenesis highlight their hypothetical involvement in toxicity tolerance. Results also indicate that at higher concentrations of Cr⁶⁺, down-regulation of functional proteins impedes normal cellular functions.