Yamakawa K, Karasawa T, Ohta T, Hayashi H, Nakamura S
Department of Bacteriology, School of Medicine, Kanazawa University, Ishikawa, Japan.
J Med Microbiol. 1998 Sep;47(9):767-71. doi: 10.1099/00222615-47-9-767.
Production of toxins A and B by Clostridium difficile is enhanced in a defined medium with biotin-limited conditions. In the present study compounds inhibitory to enhanced toxin production by a C. difficile strain were examined. Increases in biotin concentration from 0.05 nM to 50 nM accelerated growth and inhibited enhanced toxin production. Asparagine, glutamic acid and glutamine (10 mM) showed an effect on growth and toxin production similar to that of biotin. Lysine (10 mM) suppressed growth and inhibited toxin production. Addition of these toxin-inhibitory compounds within an incubation period of 2 days inhibited the enhanced toxin production, but later addition showed only slight inhibition of toxin production. Amino acids contained in the defined medium under the biotin-limited conditions were actively utilised in the presence of the three toxin-inhibitory amino acids, but in the presence of lysine, amino-acid utilisation was suppressed. Different mechanisms of action of these toxin-inhibitory molecules, which may be divided into excess biotin, asparagine-glutamic acid-glutamine group, and lysine, are discussed.
艰难梭菌在生物素受限条件下的特定培养基中，毒素A和B的产生会增强。在本研究中，检测了对艰难梭菌菌株增强毒素产生具有抑制作用的化合物。生物素浓度从0.05 nM增加到50 nM会加速生长并抑制增强的毒素产生。天冬酰胺、谷氨酸和谷氨酰胺（10 mM）对生长和毒素产生的影响与生物素类似。赖氨酸（10 mM）抑制生长并抑制毒素产生。在2天的孵育期内添加这些毒素抑制化合物可抑制增强的毒素产生，但较晚添加时仅显示出对毒素产生的轻微抑制。在三种毒素抑制性氨基酸存在的情况下，生物素受限条件下特定培养基中所含的氨基酸会被积极利用，但在赖氨酸存在的情况下，氨基酸的利用受到抑制。讨论了这些毒素抑制分子的不同作用机制，它们可分为过量生物素、天冬酰胺 - 谷氨酸 - 谷氨酰胺组和赖氨酸。
