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Assessing the Viability of a Synthetic Bacterial Consortium on the In Vitro Gut Host-microbe Interface
Published on: July 4, 2018
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Bacterial colonization factors control specificity and stability of the gut microbiota
S Melanie Lee1, Gregory P Donaldson, Zbigniew Mikulski
1Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, USA.
Nature
|August 20, 2013
Summary
The commensal colonization factors (CCF) system allows Bacteroides bacteria to specifically colonize the mammalian gut. This system helps bacteria attach to the colonic surface and maintain long-term colonization, even after disruptions.
Area of Science:
- Microbiology
- Gastroenterology
- Host-Microbe Interactions
Background:
- Mammalian gut microbiomes are crucial for health, with Bacteroides being a dominant genus.
- Mechanisms by which symbiotic bacteria stably colonize the gastrointestinal tract remain poorly understood.
- Species-specific colonization resistance is observed in the gut microbiome.
Purpose of the Study:
- To elucidate the molecular mechanisms enabling stable colonization by intestinal Bacteroides species.
- To identify bacterial factors responsible for species-specific, saturable colonization in the mammalian gut.
Main Methods:
- Germ-free mice were used for mono-association experiments to study colonization resistance.
- An in vivo genetic screen was employed to identify bacterial colonization factors.
- Deletion mutants of identified genes were created and tested for colonization defects in mice.
- Microbial biogeography was visualized within the mouse colon using microscopy.
Main Results:
- A novel class of polysaccharide utilization loci, termed commensal colonization factors (ccf), was discovered and conserved among intestinal Bacteroides.
- Deletion of ccf genes in Bacteroides fragilis impaired colonization in mice and reduced horizontal transmission.
- B. fragilis with intact ccf genes penetrated colonic mucus and resided in crypt channels, while ccf mutants showed defective crypt association.
- The CCF system was essential for B. fragilis colonization recovery after disruptions like Citrobacter rodentium infection or antibiotic treatment.
Conclusions:
- Intestinal Bacteroides have evolved species-specific interactions with the host, mediated by the CCF system, for stable and resilient gut colonization.
- The CCF system represents a novel molecular mechanism enabling bacteria to utilize specific host niches, such as colonic crypts, for long-term symbiosis.
- Colonic crypts serve as a reservoir for maintaining bacterial populations, facilitating resilience and long-term colonization.
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