Differential protein expression in a marine-derived Staphylococcus sp. NIOSBK35 in response to arsenic(III)

Peptide mass fingerprinting of Gram-positive marine-derived Staphylococcus cohnii #NIOSBK35 gave us an insight into the proteins involved in conferring arsenic resistance as well as the probable metabolic pathways affected under metal stress. Analysis of the protein profiles obtained from LC/MS QToF (Liquid Chromatography-Mass Spectrometry-Quadrupole Time of Flight) resulted in the identification of 689 proteins. Further grouping of these proteins based on the arsenic concentration (0, 250, 500 and 850 ppm) and the time points (6, 9, 12, 18, 24 and 36 h) in growth phase showed that a total of 13 proteins were up-regulated, while 178 proteins were down-regulated across all the concentrations and time points. Arsenic specific proteins like arsenical pump-driving ATPase, ArsR family transcriptional regulator and arsenic operon resistance repressor were found to be highly up-regulated throughout all the conditions indicating their possible involvement in the tolerance to arsenic. MBL fold metallo-hydrolase, a known stress protein, was the only protein that was up-regulated at all time points across all arsenic concentrations. Metabolic pathways like translation, carbohydrate metabolism, amino acid metabolism, membrane transport, metabolism of cofactors and vitamins, replication and repair, nucleotide metabolism along with stress proteins and hypothetical proteins were found to be significantly expressed. Our results also suggest that arsenic stress at higher levels is negatively affecting the expression of many normal functional proteins required for cell survival.