Ouhib Ouassila, Clavel Thierry, Schmitt Philippe
INRA, UMR A408, Sécurité et Qualité des Produits d'Origine Végétale, Avignon F-84914, France.
Curr Microbiol. 2006 Sep;53(3):222-6. doi: 10.1007/s00284-006-0094-6. Epub 2006 Jun 26.
Enterotoxin production is a key factor in Bacillus cereus food poisoning. Herein, the effect of the growth rate (mu) on B. cereus toxin production when grown on sucrose was studied and the Hemolytic BL enterotoxin (HBL) and nonhemolytic enterotoxin (Nhe) production by B. cereus was compared according to carbohydrate at mu = 0.2 h(-1). The anaerobic growth was carried out on continuous cultures in synthetic medium supplemented with glucose, fructose, sucrose, or an equimolar mixture of glucose and fructose. Concerning the HBL and Nhe enterotoxin production: (1) the highest enterotoxin production has occurred at mu = 0.2 h(-1) when growing on sucrose; (2) HBL production was repressed when glucose was consumed and the presence of fructose (alone or in mixture) cancelled glucose catabolite repression; (3) the consumption of sucrose increased Nhe production, which was not affected by the catabolite repression. Furthermore, analysis of the fermentative metabolism showed that whatever the mu or the carbon source, B. cereus used the mixed acid fermentation to ferment the different carbohydrates. The enterotoxin productions by this strain at mu = 0.2 h(-1) are highly influenced by the carbohydrates that do not involve any fermentative metabolism changes.
产生肠毒素是蜡样芽孢杆菌食物中毒的一个关键因素。在此，研究了生长速率（μ）对蜡样芽孢杆菌在蔗糖上生长时毒素产生的影响，并在μ = 0.2 h⁻¹时，根据碳水化合物比较了蜡样芽孢杆菌溶血素BL肠毒素（HBL）和非溶血肠毒素（Nhe）的产生情况。在补充有葡萄糖、果糖、蔗糖或葡萄糖与果糖等摩尔混合物的合成培养基中进行连续培养，以实现厌氧生长。关于HBL和Nhe肠毒素的产生：（1）在蔗糖上生长时，μ = 0.2 h⁻¹时肠毒素产生量最高；（2）葡萄糖消耗时HBL产生受到抑制，果糖（单独或混合）的存在消除了葡萄糖分解代谢阻遏；（3）蔗糖的消耗增加了Nhe的产生，其不受分解代谢阻遏的影响。此外，发酵代谢分析表明，无论μ或碳源如何，蜡样芽孢杆菌都利用混合酸发酵来发酵不同的碳水化合物。该菌株在μ = 0.2 h⁻¹时的肠毒素产生受到不涉及任何发酵代谢变化的碳水化合物的高度影响。
