Cited by 266Bacterial Genetics and BiotechnologyBacterial biofilms and quorum sensingEscherichia coli research studies

Indole production by the tryptophanase TnaA in escherichia coli is determined by the amount of exogenous tryptophan

Li, Gang, Young, Kevin D.·2013·Microbiology

Abstract

The signalling molecule indole occurs in significant amounts in the mammalian intestinal tract and regulates diverse microbial processes, including bacterial motility, biofilm formation, antibiotic resistance and host cell invasion. In Escherichia coli, the enzyme tryptophanase (TnaA) produces indole from tryptophan, but it is not clear what determines how much indole E. coli can produce and excrete, making it difficult to interpret experiments that investigate the biological effects of indole at high concentrations. Here, we report that the final yield of indole depends directly, and perhaps solely, on the amount of exogenous tryptophan. When supplied with a range of tryptophan concentrations, E. coli converted this amino acid into an equal amount of indole, up to almost 5 mM, an amount well within the range of the highest concentrations so far examined for their physiological effects. Indole production relied heavily on the tryptophan-specific transporter TnaB, even though the alternative transporters AroP and Mtr could import sufficient tryptophan to induce tnaA expression. This TnaB requirement proceeded via tryptophan transport and was not caused by activation of TnaA itself. Bacterial growth was unaffected by the presence of TnaA in the absence of exogenous tryptophan, suggesting that the enzyme does not hydrolyse significant quantities of the internal anabolic amino acid pool. The results imply that E. coli synthesizes TnaA and TnaB mainly, or solely, for the purpose of converting exogenous tryptophan into indole, under conditions and for signalling purposes that remain to be fully elucidated.

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Crossref · 10.1099/mic.0.064139-0

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Authors
Li, G., & Young, K. D.
Affiliations
University of Arkansas for Medical Sciences (US)
Venue
Microbiology
Published
2013-02-01
Volume
159
Issue
Pt_2
Pages
402-410
ISSN
  • 1350-0872 (ISSN-L)
  • 1465-2080
OpenAlex
W2157113460
Cited by
266
References
59
Citations by year
2026: 22 · 2025: 20 · 2024: 34 · 2023: 22 · 2022: 28 · 2021: 27 · 2020: 26 · 2019: 19 · 2018: 20 · 2017: 8 · 2016: 11 · 2015: 12 · 2014: 15 · 2013: 2
FWCI
8.82
Type
journal article
Language
en
Open access
closed
Locations
  • Microbiology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Bacterial Genetics and Biotechnology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Bacterial biofilms and quorum sensing
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Endocrinology › Escherichia coli research studies
Keywords
indole production, Escherichia coli, tryptophan, tryptophan transport, bacterial quorum sensing, bacterial growth
MeSH terms
Escherichia coli, Indoles, Tryptophan, Tryptophanase, Gene Expression Regulation, Bacterial, Gene Expression Regulation, Enzymologic, Amino Acid Transport Systems, Escherichia coli Proteins

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