Study on signal transduction and involvement of protein synthesis machinery in the production of Bacilhus subtilis proteass

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Microorganisms in nature show various modes of life style. Bacillus subtilis is a soil bacterium that encounters severe environmental stresses such as nutritional deficiency, desiccation, drastic temperature changes and so on. The bacterium, however, carries various means to cope with these unfavorable situations. Against nutritional deficiency, for example, it secretes proteases and degradative enzymes to digest high molecular weight proteins or carbohydrates that happen to be present around the cell, and takes up the hydrolyzed products for nutrition. The machinery that serves to sense the environment is thought to be the two-component regulatory system in which the sensor kinase detect environmental cues and phosphorylates the cognate regulator, which then activates the target genes.We have studied a signal transduction system involving a two-component system, DegS-DegU, which regulates the production of extracellular degradative enzymes. For the investigation of cellular processes … More in general, the most useful approach will be to use genetic means. For the DegS-DegU system, however, many genetic approaches have already been applied, and therefore the possibility to obtain new findings seemed to be low. We tried, therefore, to find chemical agents that might affect the signal transduction involving DegS-DegU. As a result, antibiotics such as lincomycin and erythromycin that are known to inhibit protein biosynthesis through affecting the ribosomal function were found to prevent the expression of the alkaline protease gene, aprE, the target of the DegS-DegU system. In this study we tried to identify the target of the antibiotics through which the DegS-DegU transmits a signal to induce the expression of aprE. We found that lincomycin inhibits RelA-dependent ppGpp synthesis. Furthermore, the expression of aprE was greatly reduced in relA-deficient cell. These results indicate that lincomycin prevents aprE expression by inhibiting ppGpp synthesis. This is the first report that an antibiotic inhibits signal transduction.We also applied microarray analysis on B. subtilis two-component systems that carry a helix-tum-helix motif in the regulator, and found that networks are formed among several of the systems. Less