Université d'Avignon et des Pays de Vaucluse, UMR408, Sécurité et Qualité des Produits d'Origine Végétale, F-84000 Avignon, France.
Res Microbiol. 2010 Jan-Feb;161(1):30-9. doi: 10.1016/j.resmic.2009.11.003. Epub 2009 Nov 26.
We had previously demonstrated that Fnr is required for fermentative growth and oxic production of hemolysin BL (Hbl) and non-hemolytic enterotoxin (Nhe) in the food-borne pathogen Bacillus cereus F4430/73. In the present work, the regulatory impact of Fnr on microaerobic growth and enterotoxin production in response to carbohydrates was examined using glucose, fructose, sucrose or a glucose-fructose mixture as carbon and energy sources. Growth parameters, byproduct spectra and transcription levels of catabolic and enterotoxin genes were analyzed in a strain lacking Fnr in comparison to the parental F4430/73 strain. The results showed that B. cereus prefers glucose to other carbohydrates for microaerobic growth, and that lacking of Fnr less strongly affected the respiro-fermentative catabolism of glucose than fructose and, to a lesser extent than sucrose. In addition, lacking of Fnr strongly decreased expression of hbl and nhe genes, leading to the absence of Hbl and low production of Nhe independently of the carbohydrate used as carbon source. We conclude that Fnr is an important element for carbon source regulation in B. cereus F4430/73 and that the regulation of enterotoxin gene expression in response to carbohydrates may represent one aspect of overall catabolite control mediated by Fnr.
我们之前已经证明，在食源性致病菌蜡样芽胞杆菌 F4430/73 中，Fnr 是发酵生长和需氧产生溶血素 BL（Hbl）和非溶血肠毒素（Nhe）所必需的。在本工作中，使用葡萄糖、果糖、蔗糖或葡萄糖-果糖混合物作为碳源和能源，研究了 Fnr 对微需氧生长和碳水化合物应答肠毒素产生的调节作用。在缺乏 Fnr 的菌株中，与亲本 F4430/73 菌株相比，分析了生长参数、副产物谱和分解代谢及肠毒素基因的转录水平。结果表明，蜡样芽胞杆菌优先使用葡萄糖进行微需氧生长，而缺乏 Fnr 对葡萄糖的呼吸发酵分解代谢的影响比对果糖和蔗糖的影响要小。此外，缺乏 Fnr 会强烈降低 hbl 和 nhe 基因的表达，导致 Hbl 缺失和 Nhe 产量降低，而与所用的碳源无关。我们得出结论，Fnr 是蜡样芽胞杆菌 F4430/73 中碳源调节的重要因素，而碳水化合物应答肠毒素基因表达的调节可能代表 Fnr 介导的整体分解代谢控制的一个方面。
