Community ecology and functional potential of bacteria, archaea, eukarya and viruses in Guerrero Negro microbial mat

Abstract

Background: Guerrero Negro microbial mat is one of the best studied microbial mat ecosystems; however, the vertical functional organization has been less well studied. In this study, the microbial ecology, environmentally relevant adaptations and the potential evolutionary interlinking of the responsible genes between bacterial, archaeal and viral lineages in Guerrero Negro (GN) microbial mat were investigated using metagenomic sequencing across a vertical transect at millimeter scale. Through metagenomics, the current study provides a taxonomic description of the vertical taxonomic organization as well as a functional organization delineated between bacteria, archaea, eukarya and viruses in a GN microbial mat – revealing new insights into the ecology of these communities. Results: The community composition based on the number of unique genes recovered (n) and coverages (c) comprised bacteria (98.06 / 98.71 % n/c), archaea (1.82 / 1.19 % n/c), eukarya (0.07 / 0.07 % n/c) and viruses (0.05 / 0.03 % n/c). The greatest coverages of genes of bacteria and eukarya were detected in first layers, while the highest coverages of genes of archaea and viruses were found in deeper layers. Many genes potentially related to adaptation to the local environment (e.g., UV radiation, multidrug resistance, oxidative stress, and heavy metals) were detected. Those genes were found in bacterial, archaeal and viral lineages totalling 3255, 44, and 1 genes, respectively. We employed phylogenetics in order to investigate the evolutionary histories of genes with similar functional annotations that were taxonomically classified as coming from bacteria, archaea and viruses. Conclusions: A gene-focused analysis of bacteria, archaea, eukarya, and viruses showed a vertical partitioning of the community, both in taxonomic affinity and function. The presence of genes potentially involved in adaptation to environmental conditions may have implications and resilience to stress conditions. Phylogenetic analyses showed an interlinking between domains, where genes taxonomically classified as archaea and viruses formed clades suggesting they were phylogenetically relatively closely related to genes present in bacteria lineages – potentially indicating horizontal gene transfer in GN mat.