Toxins, butyric acid, and other short-chain fatty acids are coordinately expressed and down-regulated by cysteine in Clostridium difficile.
It was recently found that a mixture of nine amino acids down-regulate Clostridium difficile toxin production when added to peptone yeast extract (PY) cultures of strain VPI 10463 (S. Karlsson, L. G. Burman, and T. Akerlund, Microbiology 145:1683-1693, 1999). In the present study, seven of these amino acids were found to exhibit a moderate suppression of toxin production, whereas proline and particularly cysteine had the greatest impact, on both reference strains (n = 6) and clinical isolates (n = 28) of C. difficile (>99% suppression by cysteine in the highest toxin-producing strain). Also, cysteine derivatives such as acetylcysteine, glutathione, and cystine effectively down-regulated toxin expression. An impact of both cysteine and cystine but not of thioglycolate on toxin yield indicated that toxin expression was not regulated by the oxidation-reduction potential. Several metabolic pathways, including butyric acid and butanol production, were coinduced with the toxins in PY and down-regulated by cysteine. The enzyme 3-hydroxybutyryl coenzyme A dehydrogenase, a key enzyme in solventogenesis in Clostridium acetobutylicum, was among the most up-regulated proteins during high toxin production. The addition of butyric acid to various growth media induced toxin production, whereas the addition of butanol had the opposite effect. The results indicate a coupling between specific metabolic processes and toxin expression in C. difficile and that certain amino acids can alter these pathways coordinately. We speculate that down-regulation of toxin production by the administration of such amino acids to the colon may become a novel approach to prophylaxis and therapy for C. difficile-associated diarrhea.
Karlsson
S
S
Department of Bacteriology, Swedish Institute for Infectious Disease Control, S-171 82, Solna.
Lindberg
A
A
Norin
E
E
Burman
L G
LG
Akerlund
T
T
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001427:Bacterial Toxins / Q000096:biosynthesis*; D000440:Butanols / Q000494:pharmacology; D020148:Butyric Acid / Q000378:metabolism; D016360:Clostridioides difficile / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D003470:Culture Media; D003545:Cysteine / Q000494:pharmacology*; D015536:Down-Regulation; D004761:Enterocolitis, Pseudomembranous / Q000382:microbiology; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D000440:Butanols; D003470:Culture Media; D005232:Fatty Acids, Volatile; D020148:Butyric Acid; D010088:Oxidoreductases; D003545:Cysteine