Identification and Characterization of Hemolytic Bacillus cereus Isolated from Commercial Ssam-jang
2017
Kim, D.M., The University of Tokyo, Tokyo, Japan | Park, S.K., Soonchunhyang University, Chungnam, Republic of Korea | Oh, K.H., Soonchunhyang University, Chungnam, Republic of Korea
This study was undertaken to identify and characterize hemolytic Bacillus cereus isolated from commercial ssam-jang. The physiological and biochemical properties of isolate were first examined. Using the BIOLOG system, the isolate was identified and assigned to B. cereus MH-2. Phylogenetic tree of MH-2 was plotted based on 16S rRNA sequence comparisons. Hemolytic activity was observed around wells of sheep blood agar plates seeded with MH-2 cultures; the zone of hemolysis gradually increased with increasing incubation time of the cultures. Zymographic analysis estimated the molecular weight of the presumed hemolysis-causing molecule to be about 30 kDa. Survival rates of MH-2 cells decreased with increasing NaCl concentrations in the media. The stress shock proteins (e.g., DnaK and GroEL) induced by NaCl were reduced in proportion to the NaCl concentration and exposure period to B. cereus MH-2. Analysis of SDSPAGE and Western blot revealed that the stress shock proteins, 70-kDa DnaK and 60-kDa GroEL were decreased proportionate to the NaCl concentrations as well as exposure period in exponentially growing cultures. Scanning electron mic-roscopy demonstrated the presence of perforations and irregular rod forms with wrinkled surfaces in cells treated with NaCl.
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