Presenter(s): Helena Klein − Biology
Faculty Mentor(s): Karen Guillemin, Cathy Robinson
Poster 85
Research Area: Natural/Physical Science
Funding: META Grant
The bacteria that live in our guts, and those of other vertebrates, affect our health in a myriad of ways, from aiding in digestion to training our immune system. However, how bacteria first colonize the gut is little-understood. In particular, environment seems to play an important role in host colonization, especially in aquatic organisms. I proposed investigating environmental adaptation to find novel mechanisms for host colonization. I hypothesized that adaptation of a bacterial symbiont to its host’s environment increases host colonization. I tested this hypothesis via experimental evolution by serially passaging a strain of Aeromonas veronii, a zebrafish gut isolate, in fish-conditioned water to quickly and non-specifically find new genes that could affect host colonization. Surprisingly, I found that while the evolved strains grew to higher population densities in the water than the ancestor, these strains had variable gut colonization fitness. In fact, one strain had significantly reduced gut colonization fitness. Genome sequencing revealed that this strain had mutations affecting motility and Type I secretion system membrane protein genes. I recreated the latter mutation in the wildtype bacterial strain and found that it increased Aeromonas fitness in fish water, however gut colonization was comparable to the wildtype. This suggests that other mutations in the evolved isolate, presumably those in the motility genes, are responsible for the reduced host colonization. Future work will further investigate motility mutations among others. This work contributes to our understanding of host colonization dynamics and can lead to the development of probiotics to improve human health.