title: Effect of isoleucine on toxin production by Clostridium difficile in a defined medium.
abstract: Supplementation of a carbohydrate-free minimal medium with a high level (100 mM) of histidine, methionine, valine, isoleucine, proline and leucine, in particular isoleucine, markedly increased toxin production by Clostridium difficile VPI 10463. The effect of isoleucine was further examined. Increasing the concentration of isoleucine from 20 to 100 mM remarkably increased toxin production, while bacterial growth decreased gradually. Amino acid analysis of the culture revealed that, at 100 mM isoleucine, consumption of isoleucine was remarkably increased. During the incubation period when toxin titers increased markedly but bacterial growth was declining, isoleucine, leucine and cysteine were taken up preferentially and alanine and cystathionine, which were not found at 1 mM isoleucine, were produced in large quantities. These findings suggest that isoleucine may play an important role in toxin production by C. difficile and that alanine and cystathionine production may be co-regulated with the toxin production in the absence of fermentable carbohydrates.
authors.affiliation: Department of Bacteriology, School of Medicine, Kanazawa University, Japan.
authors.forename: D
authors.initials: D
authors.lastname: Ikeda
authors.forename: T
authors.initials: T
authors.lastname: Karasawa
authors.forename: K
authors.initials: K
authors.lastname: Yamakawa
authors.forename: R
authors.initials: R
authors.lastname: Tanaka
authors.forename: M
authors.initials: M
authors.lastname: Namiki
authors.forename: S
authors.initials: S
authors.lastname: Nakamura
mesh_terms: D000596:Amino Acids; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000096:biosynthesis*; D016360:Clostridioides difficile / Q000187:drug effects / Q000378:metabolism*; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004768:Enterotoxins / Q000096:biosynthesis*; D007532:Isoleucine / Q000378:metabolism* / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003470:Culture Media; D004768:Enterotoxins; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile; D007532:Isoleucine