Analysis of Maturation pathway protein toxin of Enteric Bacteria and Studies of Prevention of Diarrhea

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The studies on maturation pathway of enterotoxin and protease of Aeromonas and heat-stable enterotoxin of enterotoxigenic Escherichia coil were performed in this study. The diarrheagenic toxin of Aeromonas has rapacity to lyse erythrocytes, therefore, another name the toxin is hemolysin. The culture filtrates of A. sobria and A. hydrophila exhibit hemolytic activity, because the hemolysin is produced into the solution. However, the filtrate of A. caviae does not exhibit However, A. caviae caused diarrhea in humans. We examined the production of diarrheagenic toxin of A. caviae. It has been shown that A. caviae synthesis the hemolysin and release it into outside of the cells, however, the hemolysin is broken by the proteases produced by A. caviae. Therefore, the culture filtrate of A. caviae does not exhibit hemolytic activity. In intestinal lumen and agar medium, these hemolysins produced by A. caviae can bind the appropriate cells and express the activity before these hemolysins are broken by proteases. Another finding of this research project is that production of serineprotease and metallo protease of A. sobria is inhibited by salt (sodium chloride) in the medium. hi the medium containing sodium chloride at the ratio of more than 2%, the production of these proteases is significantly repressed. The studies on the mechanism of the repression showed that the repressions of production of serineprotease and metallo pro ease are derived from inhibitions of maturation pathway and of transcriptional stage of each toxin, respectively. In the study about Escherichia coil, the structure of TolC which is involved in the translocation of ST(heat-stable enterotoxin) across the outer membrane was examined. To examined, we constructed the chimeric TolC which is consisted of E. coli TolC and Vibrio parahaemolyticus TolC. The result shows that the region covering 198th -214th of E. coli TolC plays an important role in the transport of ST.