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Escherichia coli GutM4 produces 2,5-diketopiperazines and inhibits human pathogens in vitro
Zhang, Xichun; Du, Junmin; Wang, Yu; Chen, Shuming & Wang, Yingli
Abstract
Background: It has been a very common practice to use probiotics or their metabolites as alternative antimicrobial
strategies for the treatment and prevention of infections as rampant and indiscriminate use of antibiotics causes
the development of antibiotic-resistant pathogens. The objective of this study was to select a potential
antimicrobial probiotic strain of Escherichia coli from the human gastrointestinal tract and investigate the
production of diketopiperazines that contribute to the antimicrobial activity.
Results: E. coli GutM4was isolated from the feces of a healthy adult. E. coli GutM4 showed significant antagonistic
activity against 10 indicator pathogens, and this activity was no less than that of the reference strain E. coli Nissle
1917 against eight of the indicator pathogens. Moreover, E. coli GutM4 produced antagonistic substances
containing trypsin-targeted peptide bonds because the inhibitory effects of E. coli GutM4 supernatant
significantly decreased upon treatment with trypsin. Consistent with the antagonistic activity and peptide
compounds of E. coli GutM4, 14 2,5-diketopiperazines were isolated from the fermented broth of E. coli GutM4,
including 12 cyclo(Pro-Phe), 3 cyclo(Pro-Tyr), and 5 cyclo(4-hydroxyl-Pro-Leu), which are reported to have
antipathogenic activity.
Conclusion: E. coli GutM4 produces 2,5-diketopiperazines that are partly involved in antagonistic action against
human pathogens in vitro.
Keywords
Antibiotics; Antimicrobial; Diketopiperazines; Disease control; Enteropathogenic; Feces; Gastrointestinal tract; Inhibitory; Intestinal microflora; Prevention of infections; Probiotics
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