Soil and sediment microbial community structure and diversity are shaped by ecological gradients in a hypersaline lake ecosystem

Abstract The study of hypersaline ecosystems has yielded numerous novel organisms and contributed substantially to our understanding of extreme environments. Yet, with the exception of a few well-characterized sites, most remain unstudied. One such system is La Sal del Rey, a naturally occurring hypersaline lake located in southern Texas, USA. Soils and sediments from La Sal del Rey were surveyed in an attempt to characterize the structure, composition, and diversity of their microbial communities. Samples were collected at 8 points along a transect that originated in a vegetated upland, included exposed lakebed sediments, and continued toward the water’s edge, capturing a wide range of microenvironments and multiple physical and chemical gradients. Community qPCR was used in combination with pyrosequencing, 16S rRNA gene cloning and Sanger sequencing, and multivariate statistics to characterize the lake’s soil and sediment microbial communities and identify the relationships they share with their environment. La Sal del Rey’s microbial communities were highly diverse, harbored a wide variety of taxa, contained many unclassified Bacteria and Archaea, and were closely tied to site water content. Bacteria were numerically dominant in these communities, and among them, three phyla -- the Proteobacteria, Bacteroidetes, and Firmicutes –accounted for the majority of taxa detected. The depth of sampling achieved with pyrosequencing resulted in the detection of taxa that have not been described in hypersaline sediments before and provided coverage of the transect communities that allowed us to detect differences among them and describe their relationships with the surrounding environment. The results of this study build upon the growing literature dedicated to hypersaline environments and provide new information regarding a previously undescribed ecosystem.