Journal article
Multiple factors contribute to bimodal toxin gene expression in Clostridioides (Clostridium) difficile
Molecular microbiology, Vol.110(4), pp.533-549
11/2018
DOI: 10.1111/mmi.14107
PMCID: PMC6446242
PMID: 30125399
Abstract
Clostridioides
(formerly
Clostridium
)
difficile
produces two major toxins, TcdA and TcdB, upon entry into stationary phase. Transcription of
tcdA
and
tcdB
requires the specialized sigma factor, σ
TcdR
, which also directs RNA Polymerase to transcribe
tcdR
itself. We fused a gene for a red fluorescent protein to the
tcdA
promoter to study toxin gene expression at the level of individual
C. difficile
cells. Surprisingly, only a subset of cells became red fluorescent upon entry into stationary phase. Breaking the positive feedback loop that controls σ
TcdR
production by engineering cells to express
tcdR
from a tetracycline-inducible promoter resulted in uniform fluorescence across the population. Experiments with two regulators of
tcdR
expression, σ
D
and CodY, revealed neither is required for bimodal toxin gene expression. However, σ
D
biased cells towards the Toxin-ON state, while CodY biased cells towards the Toxin-OFF state. Finally, toxin gene expression was observed in sporulating cells. We conclude that (i) toxin production is regulated by a bistable switch governed by σ
TcdR
, which only accumulates to high enough levels to trigger toxin gene expression in a subset of cells, and (ii) toxin production and sporulation are not mutually exclusive developmental programs.
Clostridioides difficile
, the leading cause of antibiotic-associated diarrhea, produces toxins that inactivate host Rho GTPases. We used a fluorescent reporter to visualize toxin gene expression in
C. difficile
within individual cells. Our findings imply toxin production is an example of bistability governed by cell-to-cell variation in the levels of the sigma factor TcdR, which is directly required for transcription of the toxin genes. TcdR levels are in turn controlled by several metabolic and genetic inputs.
Details
- Title: Subtitle
- Multiple factors contribute to bimodal toxin gene expression in Clostridioides (Clostridium) difficile
- Creators
- Eric M Ransom - Graduate Program in Genetics, University of Iowa, Iowa City, IA 52242Gabriela M Kaus - Graduate Program in Genetics, University of Iowa, Iowa City, IA 52242Phuong M Tran - Graduate Program in Genetics, University of Iowa, Iowa City, IA 52242Craig D Ellermeier - Graduate Program in Genetics, University of Iowa, Iowa City, IA 52242David S Weiss - Graduate Program in Genetics, University of Iowa, Iowa City, IA 52242
- Resource Type
- Journal article
- Publication Details
- Molecular microbiology, Vol.110(4), pp.533-549
- DOI
- 10.1111/mmi.14107
- PMID
- 30125399
- PMCID
- PMC6446242
- NLM abbreviation
- Mol Microbiol
- ISSN
- 0950-382X
- eISSN
- 1365-2958
- Grant note
- name: Public Health Service, award: R21 AI121576; name: National Institutes for Allergy and Infectious Disease; name: Carver College of Medicine, Holden Comprehensive Cancer Center; name: Iowa City Veteran's Administration Medical Center
- Language
- English
- Date published
- 11/2018
- Academic Unit
- Microbiology and Immunology
- Record Identifier
- 9984002395502771
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