Inhibitory effect of NaCl on the production of extracellular proteins by Aeromonas spp.

气单胞菌是引起成人和儿童腹泻的致病菌，在生理条件下能产生活性金属蛋白酶和脂肪酶，但在含3%NaCl的培养基中不能产生。在这项研究中，我们构建了突变株，其中编码LysR型转录因子的基因被删除，并检查LysR的删除是否影响金属蛋白酶的生产。结果表明，LysR型转录因子不参与金属蛋白酶的产生。此外，我们发现脂肪酶基因在含3%NaCl的培养基中也能转录，在含0. 5%NaCl的盐胁迫下，脂肪酶的产量有所下降。结果表明，在含3%NaCl的培养基中产生的脂肪酶略有变性。

Aeromonas, which is a causative agent of diarrhea of adults and children, could not produce active metalloprotease and lipase in the medium containing 3% NaCl, though it could produce them under physiological condition. In this study, we constructed the mutant strain in which the gene encoding LysR type transcriptional factor is deleted and examined whether the deletion of LysR affects the production of metalloprotease. The results show that LysR type transcriptional factor is not involved in production of metalloprotease. Additionally, we found the lipase gene is transcribed in the medium containing 3% NaCl as well as in the medium 0. 5% NaCl, though production of lipase is reduced under salty condition. And we showed that the lipase produced slightly in the medium containing 3% NaCl is denatured.