Duport Catherine, Zigha Assia, Rosenfeld Eric, Schmitt Philippe
Université d'Avignon, UMR A408, Sécurité et Qualité des Produits d'Origine Végétale, INRA, Avignon F-84914, France.
J Bacteriol. 2006 Sep;188(18):6640-51. doi: 10.1128/JB.00702-06.
In contrast to Bacillus subtilis, the role of the two-component regulatory system ResDE has not yet been investigated in the facultative anaerobe Bacillus cereus. We examined the role of ResDE in the food-borne pathogen B. cereus F4430/73 by constructing resDE and resE mutants. Growth performances, glucose metabolism, and expression of hemolysin BL (Hbl) and nonhemolytic enterotoxin (Nhe) were analyzed in the three strains under distinct oxygenation and extracellular oxidoreduction potential (ORP) conditions. We show that growth and glucose metabolism were only moderately perturbed in both resDE and resE mutants under aerobiosis, microaerobiosis, and anaerobiosis generated under N(2) atmosphere (initial ORP = +45 mV). The major effects of resDE and resE mutations were observed under low-ORP anaerobic conditions generated under hydrogen atmosphere (iORP = -148 mV). These conditions normally favor enterotoxin production in the wild type. The resE mutation was more deleterious to the cells than the resDE mutation, causing growth limitation and strong deregulation of key catabolic genes. More importantly, the resE mutation abolished the production of enterotoxins under all of the conditions examined. The resDE mutation only decreased enterotoxin expression under anaerobiosis, with a more pronounced effect under low-ORP conditions. Thus, the ResDE system was found to exert major control on both fermentative growth and enterotoxin expression, and it is concluded that the ResDE system of B. cereus should be considered an anaerobic redox regulator. The data presented also provide evidence that the ResDE-dependent regulation of enterotoxins might function at least partially independently of the pleiotropic virulence gene regulator PlcR.
与枯草芽孢杆菌不同，双组分调节系统ResDE在兼性厌氧菌蜡样芽孢杆菌中的作用尚未得到研究。我们通过构建resDE和resE突变体，研究了ResDE在食源性病原体蜡样芽孢杆菌F4430/73中的作用。分析了这三株菌在不同氧合和细胞外氧化还原电位（ORP）条件下的生长性能、葡萄糖代谢以及溶血素BL（Hbl）和非溶血肠毒素（Nhe）的表达。我们发现，在有氧、微需氧以及在N₂气氛下产生的厌氧条件（初始ORP = +45 mV）下，resDE和resE突变体的生长和葡萄糖代谢仅受到适度干扰。resDE和resE突变的主要影响在氢气气氛下产生的低ORP厌氧条件（iORP = -148 mV）下观察到。这些条件通常有利于野生型中肠毒素的产生。resE突变对细胞的损害比resDE突变更大，导致生长受限和关键分解代谢基因的强烈失调。更重要的是，resE突变在所有检测条件下都消除了肠毒素的产生。resDE突变仅在厌氧条件下降低肠毒素表达，在低ORP条件下影响更明显。因此，发现ResDE系统对发酵生长和肠毒素表达都有主要控制作用，得出结论蜡样芽孢杆菌的ResDE系统应被视为一种厌氧氧化还原调节因子。所呈现的数据还提供了证据，表明ResDE依赖的肠毒素调节可能至少部分独立于多效性毒力基因调节因子PlcR发挥作用。
