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A single regulatory gene is sufficient to alter bacterial host range
Mark J Mandel1, Michael S Wollenberg, Eric V Stabb
1Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, 1550 Linden Drive, Madison, Wisconsin 53706, USA. mmandel@wisc.edu
Nature
|February 3, 2009
Summary
A single gene, RscS, enables the Vibrio fischeri bacterium to colonize squid. This regulatory gene controls biofilm formation, crucial for bacterial symbiosis and host specificity evolution.
Area of Science:
- Microbiology
- Symbiosis
- Evolutionary Biology
Background:
- Microbial symbioses are vital for animal development, but host specificity mechanisms are poorly understood.
- Bacteria must acquire specific symbiotic partners from the environment each generation.
- Identifying genetic factors governing bacterial host specificity is a key challenge.
Purpose of the Study:
- To investigate the genetic basis of host specificity in the Vibrio fischeri-Euprymna scolopes squid symbiosis.
- To identify specific genes responsible for the efficient colonization of squid by Vibrio fischeri.
- To understand the role of regulatory genes in bacterial host range evolution.
Main Methods:
- Comparative genomics to identify genes present in squid symbionts but absent in fish symbionts.
- Genetic manipulation (heterologous expression) to test gene function.
- Phylogenetic analysis to trace the evolutionary history of identified genes.
- Microscopy and molecular techniques to study biofilm formation and colonization.
Main Results:
- The two-component sensor kinase RscS is essential and sufficient for Vibrio fischeri colonization of Euprymna scolopes squid.
- RscS induces the Syp exopolysaccharide, a biofilm mediator critical for initial squid colonization.
- The rscS gene is present in squid symbionts but absent in fish symbionts, like Vibrio fischeri MJ11.
- Heterologous expression of RscS in strain MJ11 enabled colonization of E. scolopes, similar to natural squid symbionts.
- Phylogenetic analyses indicate rscS played a significant role in the evolution of the squid symbiosis.
Conclusions:
- A single regulatory gene, RscS, can determine the host range of animal-associated bacteria.
- RscS facilitates squid colonization by activating pre-existing bacterial capabilities for host interaction via biofilm formation.
- This finding highlights how regulatory genes, rather than direct host-interacting effectors, can drive the evolution of bacterial host specificity.
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