The sigma factor RpoN (σ54) is involved in osmotolerance in Listeria monocytogenes
The sigma factor RpoN (σ54) is involved in osmotolerance in Listeria monocytogenes
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DOI：
10.1111/j.1574-6968.2006.00405.x
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发表时间：
2006-10-01
影响因子：
2.1
通讯作者：
Igimi, Shizunobu
中科院分区：
文献类型：
--
作者：
Okada, Yumiko;Okada, Nobuhiko;Igimi, Shizunobu
单核细胞增生李斯特菌能够在高渗透压的条件下生长。我们构建了一个缺失突变体的rpoN，编码替代西格玛因子RpoN，并分析其对渗透胁迫的反应。在含有4%NaCl和1mM甜菜碱的基本培养基中，突变体显示出与亲本菌株EGD相似的生长。在含有4%NaCl和1M肉毒碱的相同培养基中，突变体的生长速率大大降低，当在600 nm处的光密度（OD 600）在生长起始点为0.15时。然而，当培养物在0.025的OD 600开始生长时，突变体的生长与EGD的生长相似。该突变体的甜菜碱转运蛋白基因betL和gbuB以及肉毒碱转运蛋白基因opuCA的表达被诱导至与EGD相似的水平，并且其肉毒碱摄取速率与EGD相似。这些结果表明，从rpoN突变体的生长缺陷是由opuCA的转录调控或肉毒碱摄取减少，但可能是由更大量的肉毒碱被需要在基本培养基中的突变体的生长时，NaCl是存在的。
Listeria monocytogenes is able to grow under conditions of high osmolarity. We constructed a deletion mutant of rpoN, encoding the alternative sigma factor RpoN, and analyzed its response to osmotic stress. In a minimal medium with 4% NaCl and 1 mM betaine, the mutant showed a similar growth to that of the parental strain, EGD. In the same medium with 4% NaCl and 1 M carnitine, the growth rate of the mutant was greatly reduced, when the optical density at 600 nm (OD600) at the starting point of growth, was 0.15. However, when growth of the culture was started at an OD600 of 0.025, the growth of the mutant was similar to that of EGD. The mutant's expression of two betaine transporter genes, betL and gbuB, and the carnitine transporter gene opuCA, was osmotically induced at a level similar to EGD, and its rate of carnitine uptake was similar to that of EGD. These results suggest that the growth defect from the rpoN mutant is caused not by the transcriptional regulation of opuCA or by a decrease in carnitine uptake, but possibly by larger amounts of carnitine being needed for growth of the mutant in minimal medium when NaCl is present.