R. Hemamalini, Rajeshwari Sinha and Sunil Kumar Khare* Pages 318 - 325 ( 8 )
Background: Halophiles, which thrive under saline/hypersaline habitats and retain their structural and functional integrity under high salt conditions, present an interesting model system for understanding their global proteome under different salinity.
Objective: The present work compares the intracellular proteome profiles of two moderately halophilic Gram positive Bacillus sp. EMB9 and Gram negative Marinobacter sp. EMB5 in different salt concentrations.
Method: Moderately halophilic bacterial cells were incubated in the presence of varying NaCl concentration and their growth profile monitored. Their responses towards the altered saline environment were further evaluated using a trizole-based protein extraction followed by 2D gel electrophoresis. The change in protein spot intensities between the control and treated samples was analyzed using the Image Master Platinum 7.0 software and was a measure of the protein expression levels.
Results: Notable global changes in the intracellular bacterial proteome were observed when grown under optimal (5%, w/v) and low NaCl concentrations. Protein expression levels decreased by 21% and 32% under low salinity in case of Bacillus sp. EMB9 and Marinobacter sp. EMB5 respectively. Of the total number of 235 protein spots detected in case of Bacillus sp. EMB9, 91 were commonly expressed, 12 new protein spots were observed while 41 proteins spots were completely suppressed. In case of Marinobacter strain, 83 total protein spots were detected, of which 20 were commonly expressed, 36 new protein spots appeared and expression of 27 protein spots was suppressed under low salinity. The role of suppressed proteins could be specific to the presence of higher salinity, and associated with the regulation of saline/environmental stress. Proteins exclusively expressed in low salinity may be responsible for survival at low salt concentration.
Conclusion: The study provides preliminary understanding on the protein diversity in moderately halophilic Gram positive and negative bacteria under varying salinity. The work is deemed to add to the knowhow of osmoadaptive strategies in moderately halophilic bacteria.
Moderate halophile, proteome, saline-stress, osmoadaptation, haloadaptation, salt concentration.
Enzyme and Microbial Biochemistry Laboratory, Department of Chemistry, Indian Institute of Technology Delhi, New Delhi, Enzyme and Microbial Biochemistry Laboratory, Department of Chemistry, Indian Institute of Technology Delhi, New Delhi, Enzyme and Microbial Biochemistry Laboratory, Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016