Background: Several bacteria tolerate chromate with this attribute important in bacteria intended
for biotechnological applications on chromate clean-up. Marine bacteria are beginning to show
promise in this field due to their range and novelty. However, the general mechanisms of chromate tolerance
employed by marine bacteria remain unknown.
Objective: To understand differential protein expression of a marine Staphylcoccus sp. in terms of response
to hexavalent chromium stress.
Method: In this study, protein extracted from Staphylococcus xylosus grown in varying chromate
(Cr (VI)) conditions (50, 100, 150 and 200 µg mL-1 Cr (VI)) was subject to spectral counting strategy
where unlabelled protein samples were analyzed separately using the same protocol as each other, and
the relative protein quantification was established by comparing the number of MS/MS spectra identified
for each protein.
Results: A total of 613 proteins detected in S. xylosus were differentially expressed when grown in varying
Cr (VI) conditions and were grouped functionally. Response in medium with 50 µg mL-1 Cr (VI) was
not very different from that of the control (no Cr). Whereas, in medium with 200 µg mL-1 Cr (VI), the
ability of S. xylosus to cope with Cr stress seemed to be reduced as the number of upregulated stress tolerant
proteins (4) was less than those observed in medium with 150 µg mL-1 (15) or 100 µg mL-1 Cr (VI)
(16). Up-regulation patterns showed that superoxide removal, directed DNA repair and proteins involved
in peptide mis-folding were mechanisms employed by S. xylosus for surviving Cr induced stress in medium
with 100 and 150 µg mL-1 Cr (VI).
Conclusion: These findings have important implications for understanding mechanisms of chromate tolerance,
which provides new information of how a marine Staphylococcus deals with chromate toxicity.