Gut Health and Food Safety, Quadram Institute, Norwich, UK.
Sci Rep. 2018 May 4;8(1):7060. doi: 10.1038/s41598-018-25411-x.
Clostridium botulinum is an anaerobic spore forming bacterium that produces the potent botulinum neurotoxin that causes a severe and fatal neuro-paralytic disease of humans and animals (botulism). C. botulinum Group II is a psychrotrophic saccharolytic bacterium that forms spores of moderate heat resistance and is a particular hazard in minimally heated chilled foods. Spore germination is a fundamental process that allows the spore to transition to a vegetative cell and typically involves a germinant receptor (GR) that responds to environmental signals. Analysis of C. botulinum Group II genomes shows they contain a single GR cluster (gerX3b), and an additional single gerA subunit (gerXAO). Spores of C. botulinum Group II strain Eklund 17B germinated in response to the addition of L-alanine, but did not germinate following the addition of exogenous Ca-DPA. Insertional inactivation experiments in this strain unexpectedly revealed that the orphan GR GerXAO is essential for L-alanine stimulated germination. GerX3bA and GerX3bC affected the germination rate but were unable to induce germination in the absence of GerXAO. No role could be identified for GerX3bB. This is the first study to identify the functional germination receptor of C. botulinum Group II.
肉毒梭菌是一种厌氧孢子形成细菌，可产生强效的肉毒神经毒素，导致人类和动物严重且致命的神经麻痹性疾病（肉毒中毒）。C 型肉毒梭菌 II 组是一种嗜冷型糖化细菌，形成耐热性中等的孢子，是轻微加热冷却食品中的一个特殊危害。孢子萌发是一个基本过程，使孢子过渡到营养细胞，通常涉及到对环境信号做出响应的发芽受体（GR）。对 C 型肉毒梭菌 II 组基因组的分析表明，它们含有单个 GR 簇（gerX3b），以及单个额外的 gerA 亚基（gerXAO）。C 型肉毒梭菌 II 组菌株 Eklund 17B 的孢子在添加 L-丙氨酸后可萌发，但在添加外源 Ca-DPA 后不萌发。在该菌株中进行的插入失活实验出人意料地表明，孤儿 GR GerXAO 对 L-丙氨酸刺激的萌发是必需的。GerX3bA 和 GerX3bC 影响萌发率，但在没有 GerXAO 的情况下无法诱导萌发。无法确定 GerX3bB 的作用。这是首次鉴定 C 型肉毒梭菌 II 组的功能性萌发受体的研究。
