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The genetic factors that allow gut symbiotic bacteria to occupy intestinal niches remain poorly understood.
Lee et al. 2022 Journal of Microbiology 60(2) 215-223
Following the experimental evolution of Aeromonas veronii in gnotobiotic zebrafish, we identify bacterial traits that promote host colonization.
Robinson et al. 2021 Cell Host & Microbe 29:
Several independently developed high-immigration isolates carried mutations in a gene we named proline diguanylate cyclase enzyme (SpdE) sensor, based on structural, biochemical, and phenotypic evidence that SpdE encodes an amino acid-sensing diguanylate cyclase.
Robinson et al. 2021 Cell Host & Microbe 29:
Bacterial colonization and SpdE-dependent motility were regulated by the resident microbiota, as bacterial collagenolytic activity can liberate SpdE ligands from the host, thus increasing bacterial motility and enhancing host transmission.
Robinson et al. 2021 Cell Host & Microbe 29:
SpdE recognizes free proline and, to a lesser extent, valine and isoleucine, leading to decreased production of intracellular c-di-GMP, a second messenger that controls bacterial motility. Indeed, the binding of SpdE to amino acids increased bacterial motility and colonization of the host. Hosts serve as sources of SpdE-detected amino acids, with concentrations varying depending on the microbial colonization status. Our work shows that bacteria use chemically regulated motility, or chemokinesis, to detect signals emitted by the host that trigger active migration into the host.
Robinson et al. 2021 Cell Host & Microbe 29:
Intestinal domination has been defined as gut colonization with a predominating bacterial taxon representing at least 30% relative abundance
The Stomach and small intestine have relatively few organisms because of the acidic environment, the presence of bile and pancreatic juice, and the effects of peristalsis that limit stable colonisation
For bacterial species to coexist, each member must utilize some critical resources better than any other coexisting species. The abundance of these critical resources determines the abundance of the microbe occupying the corresponding nutrient niches.
The co-existence of more than 100 bacterial species suggests that the colonic habitat comprises more than 100 discrete nutrient niches