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Mice gut microbes influenced by industrial pollution – by Erin Dimech

Here MA student Erin Dimech summarizes a fascinating peer reviewed study looking at how environmental pollution can reverberate throughout an ecosystem, even down to the guts of mice living in those areas.

 

            Anyone who is researching gut microbes can probably share the excitement I feel when a paper comes out that relates the composition of the gut microbiota to larger systems.  These larger systems go beyond the individual organism that the microbes actually reside in. Microbial communities are extremely important for population and ecosystem health.  But it works both ways!  Healthy populations and ecosystems are essential for healthy populations of microbes to flourish and persist.  In a great study by Dr. Joseph D. Coolon and colleagues, titled Microbial ecological response of the intestinal flora of Peromyscus maniculatus and P. Leucopus to heavy metal contamination in Molecular Ecology (2010), the fascinating links between human alteration of the environment and the composition of the gut microbiota are addressed.

            This paper is especially unique because it aims to study the effects of heavy metal contamination on two intertwined microbial communities, soil microbes and gut microbes of the mice that inhabit the area.  The authors chose to conduct their study at the Tri-State Mining District, a large area that spans throughout southeastern Kansas, southwestern Missouri and northeastern Oklahoma.   Hundreds of years of mining in this region has led to severe heavy metal contamination that has had significant effects on human health.  After remediation efforts began in the early 1990’s, negative human health effects have declined, but environmental and wildlife risks still persist.

            Mice were live-trapped from two remediated sites and two reference sites (unpolluted) within the Tri-State Mining District. Soil samples from each site were also collected. In their results, the authors found that mice from remediated sites had lower body mass, shorter hindfeet and were significantly leaner than mice on reference sites. Although mice (specifically P. maniculatus) were found at a higher abundance in remediated sites, their body condition was poor. This may suggest that remediated sites are still posing negative health consequences for resident wildlife. While no significant differences were found in diversity indices of the gut microbiota between mice at the two sites, assemblages of gut microbial species did differ in response to contamination. This means that there were different community structures of gut microbes present in the intestines of the mice between remediated and reference sites.  Species or groups of gut microbes differed in their abundance between the two sites.   This finding was also true for communities of soil microbes.

            The authors make some interesting conclusions from their findings.  First, differences in the abundance of certain species of gut microbes between the two sites could possibly be leading to negative health consequences. Specifically, the decrease of Ruminoccaceae in mice from remediated sites could be contributing to their decreased fitness.  Second, niche voids left by bacteria that could not survive under increased levels of heavy metal contamination may have allowed more resistant bacteria to establish and persist. The exact health implications of these types of changes are still unknown.  Although the diversity of gut and soil microbial communities between remediated and reference sites was not significantly different, replacement of species in these systems may occur and cause cascading affects on the host organism, the habitat and the entire ecosystem.

            Although it is a well-known fact that natural systems can be severely affected by heavy metal contamination and other human alterations, the world of microbial communities remains as an underexplored aspect of these changes.  The authors of this paper conclude with diligence, that ecosystem integrity does not only extend to individual and community level responses, but to the ecology of microflora communities as well. 

Reference:

Coolon, J. D., Jones, K. L., Narayanan, S., & Wisely, S. M. (2010). Microbial ecological response of the intestinal flora of Peromyscus maniculatus and P. leucopus to heavy metal contamination. Molecular ecology, 19(s1), 67-80.

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