The community recovery dynamics of commensal gut microbiota in fish (Fundulus heteroclitus)

Background/Question/Methods

Little is understood about how commensal microbial communities (aka “microbiota”) are affected by external environmental pollution, and even less is known about the dynamics of commensal population recovery after the host is exposed to exogenous toxicants. In this study, we follow the intestinal microbiota of the mummichog (Fundulus heteroclitus) over a period of 6 weeks after removal from a heavily contaminated estuary (Callahan Mine, Brooksville ME). We completed a reciprocal caging experiment where fish were captured from both the contaminated and reference sites and housed in the reciprocal site, in situ. Fish were sampled at 2-week time intervals (n=8 for each time point). We utilized a high-throughput, massively parallel sequencing platform (454 GS FLX+; Roche) to identify the microbiota structure by sequencing 16S amplicons from the intestinal mucosal layer. This will enable detection of uncultureable microbial strains and provide a clearer picture of the diverse microbiota of killifish from both pristine and metal-impacted habitats.

Results/Conclusions

Of the 25 most abundant genera in all samples, 10 genera were shared amongst all fish hosts and time points.  The microbial genera included Acinetobacter, Citrobacter, Enterobacter, Lactococcus, Leuconostoc, Roseobacter, Shewanella, Streptococcus, Vibrio, and Weissella. All of the host fish harbored substantially high abundances (>50%) of lactic acid bacteria (“LAB”, Lactococcus, Leuconostoc, etc). The high abundance of LAB is most notable because, although it is not uncommon for the fish intestinal microbiota to be populated at low abundance by LAB, it was previously believed that LAB were not dominant intestinal microbiota in fish. Some LAB species discovered in killifish intestinal populations have heavy metal binding capabilities, and may be serving as a detoxifying service to Fundulus heteroclitus.