Taxon-Function Decoupling as an Adaptive Signature of Lake Microbial Metacommunities Under a Chronic Polymetallic Pollution Gradient
Bachar Cheaib, Malo Le Boulch, Pierre-Luc Mercier et Nicolas Derome
Frontiers in Microbiology // 03 May 2018
Abstract: Adaptation of microbial communities to anthropogenic stressors can lead to reductions in microbial diversity and disequilibrium of ecosystem services. Such adaptation can change the molecular signatures of communities with differences in taxonomic and functional composition. Understanding the relationship between taxonomic and functional variation remains a critical issue in microbial ecology. Here, we assessed the taxonomic and functional diversity of a lake metacommunity system along a polymetallic pollution gradient caused by 60 years of chronic exposure to acid mine drainage (AMD). Our results highlight three adaptive signatures. First, a signature of taxon—function decoupling was detected in the microbial communities of moderately and highly polluted lakes. Second, parallel shifts in taxonomic composition occurred between polluted and unpolluted lakes. Third, variation in the abundance of functional modules suggested a gradual deterioration of ecosystem services (i.e., photosynthesis) and secondary metabolism in highly polluted lakes. Overall, changes in the abundance of taxa, function, and more importantly the polymetallic resistance genes such as copA, copB, czcA, cadR, cCusA, were correlated with trace metal content (mainly Cadmium) and acidity. Our findings highlight the impact of polymetallic pollution gradient at the lowest trophic levels.
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Northern ecosystems are facing unprecedented assaults resulting from direct (e.g. industrial activities, such as mining and hydroelectricity) and indirect (global warming) anthropogenic activities, thus amplifying the risk of disturbing essential ecosystem services mediated by microbial communities (nitrogen cycle, primary production) and contaminate the whole food web. Because gut microbiota is critically implicated in modulating the host response to contaminants and toxins, such bio-accumulated contaminants (e.g. iron, mercury, arsenic, lead, cadmium, arsenic and manganese) are expected to have serious consequences on major host functions such as immune response, energetic performance and development. Furthermore, there are enough results suggesting that climate change could alter stages and rates of development of endemic pathogens, modify host resistance, and result in changes in the physiology of host-pathogen interactions. Because microbiota constitutes the first immune barrier by both producing specific antimicrobial compounds and outcompete invasive microbes for host resources, it is crucial to develop a sentinel model for studying skin and gut microbiota resilience when facing allochthonous pathogens in controlled conditions.