[Two-dimensional gel electrophoresis analysis of moderately halophilic bacterium Halobacillus dabanensis D-8T under hypoosmotic shock condition].

Halobacillus dabanensis D-8~T was isolated from the saline deposits of Daban lake in Xinjiang of China,and is able to grow in complex medium containing 0.5% to 25% salt.To figure out the survival mechanisms of Gram-positive moderately halophilic bacteria under hypoosmotic shock conditions,two-dimensional gel electrophoresis(2-DE) was carried out to investigate differential protein expression profiles of H.dabanensis D-8~T in response to low osmotic challenge.The 2-D gels were stored as dry gels and their images were taken by ImageScanner and analyzed by Imagemaster~(TM) 2D Platinum software.About 650 protein spots were detected in 2-D gel.Most of proteins were distributed in molecular mass of 17.5～66kDa and the range of isoelectric point 4.0～5.9.A total of 34 protein spots were found to alter their expression after strain D-8~T was subjected to hypoosmotic shock from 20% to 0% salinity for 5 min and 50 min.Among them,the expression of 20 protein spots is up-regulated including 6 new protein spots,while that of 14 protein spots is down-regulated in answer to sudden osmotic down-shift.Protein spots of interest were excised from the gels and digested by trypsin.By means of matrix-assisted laser desorption ionization-time of flight mass spectrometry(MALDI-TOF/MS) and MASCOT search engine,4 up-regulated protein spots were identified with peptide mass fingerprint,and are similar to heat shock protein DanK,rod shape-determining protein,penicillin-binding protein(PBP-1A) and 5-enolpyruvoylshikimate-3-phosphate synthase,respectively.Noticeably,PBP-1A firstly was up-regulated after shock of 5 min but disappeared after shock of 50 min. This indicated that the strain activate a minor mechanism of peptidoglycan synthesis to compensate the major synthesis mechanism for cells survival through a down-shift challenge.In addition,this paper was the first report that heat shock proteins were up-regulated in response to sudden osmotic down-shift.