Clauwers Charlien, Lood Cédric, Van den Bergh Bram, van Noort Vera, Michiels Chris W
Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium.
Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium.
Sci Rep. 2017 Nov 13;7(1):15426. doi: 10.1038/s41598-017-15839-y.
Clostridium botulinum is an anaerobic sporeforming bacterium that is notorious for producing a potent neurotoxin. Spores of C. botulinum can survive mild food processing treatments and subsequently germinate, multiply, produce toxin and cause botulism. Control of spore germination and outgrowth is therefore essential for the safety of mildly processed foods. However, little is known about the process of spore germination in group II C. botulinum (gIICb), which are a major concern in chilled foods because they are psychrotrophic. The classical model of spore germination states that germination is triggered by the binding of a germinant molecule to a cognate germinant receptor. Remarkably, unlike many other sporeformers, gIICb has only one predicted canonical germinant receptor although it responds to multiple germinants. Therefore, we deleted the gerBAC locus that encodes this germinant receptor to determine its role in germination. Surprisingly, the deletion did not affect germination by any of the nutrient germinants, nor by the non-nutrient dodecylamine. We conclude that one or more other, so far unidentified, germinant receptors must be responsible for nutrient induced germination in gIICb. Furthermore, the gerBAC locus was strongly conserved with intact open reading frames in 159 gIICb genomes, suggesting that it has nevertheless an important function.
肉毒梭菌是一种厌氧的产芽孢细菌，以产生强效神经毒素而臭名昭著。肉毒梭菌的芽孢能够在温和的食品加工处理中存活，随后发芽、繁殖、产生毒素并导致肉毒中毒。因此，控制芽孢的发芽和生长对于轻度加工食品的安全至关重要。然而，对于II组肉毒梭菌（gIICb）的芽孢发芽过程知之甚少，gIICb是冷藏食品中的主要关注点，因为它们是嗜冷菌。经典的芽孢发芽模型表明，发芽是由发芽分子与同源发芽受体的结合触发的。值得注意的是，与许多其他产芽孢菌不同，gIICb虽然对多种发芽剂有反应，但只有一个预测的典型发芽受体。因此，我们删除了编码这种发芽受体的gerBAC基因座，以确定其在发芽中的作用。令人惊讶的是，这种缺失并不影响任何营养发芽剂或非营养十二烷基胺诱导的发芽。我们得出结论，一种或多种迄今尚未鉴定的其他发芽受体必定负责gIICb中营养诱导的发芽。此外，gerBAC基因座在159个gIICb基因组中具有完整的开放阅读框，且高度保守，这表明它仍然具有重要功能。
