The microbial community in an alkaline saline sediment of a former maar lake bed

Abstract

The “Hoya del Rincon de Parangueo (HRP)” is a maar that contained a perennial alkaline lake that drained in the 1980s so that a sediment with high pH and extreme salinity remained. The aim of this work was to determine how the bacterial and archaeal community was controlled by these extreme conditions. Sediment samples were collected from the 0–20-cm layer along a crater-wide transect. Physicochemical characteristics and the archaeal and bacterial community were determined by analysis of the 16S rRNA through Illumina sequencing. The sediment samples had a pH 10 and an electrolytic conductivity (EC) that ranged from 29.8 to 74.4 dS m−1. Three archaeal and 37 bacterial phyla were detected with Euryarchaeota (relative abundance 62.7 ± 17.6%) dominating the Archaea, and Proteobacteria (28.2 ± 10.7%) and Actinobacteria (21.1 ± 6.4%) the Bacteria. The most abundant archaeal genus was Candidatus Nitrososphaera while Euzebya, Halomonas, KSA1 and Planctomycetes dominated the bacterial gene. Thaumarchaeota were enriched in sediment samples with a higher Pb content and Euryarchaeota in sediment with a higher Mg content, while Crenarchaeota and Candidatus Nitrososphaera were enriched in sediment with a higher sand, total N and organic C content. Proteobacteria were enriched in sediment with a higher organic C and total N, Si and sand content, while Bacteroidetes and Planctomycetes in sediment with a higher water holding capacity and clay and Mg content. Members of KSA1 and Euzebya were enriched in sediment with a lower EC, organic C and total N content. Although a large number of bacterial and archaeal groups were correlated significantly with a range of sediment characteristics, the sediment characteristics explained the variation of only two bacterial groups > 50% (TM6 and Desulfonatronospira) using the machine learning tool randomForest and none of the archaeal groups. Archaeal and bacterial functional guilds were dominated by ammonium oxidation and nitrite reduction. Although the different sediment samples were dominated often by similar bacterial and archaeal groups, the measured sediment characteristics explained little of the variation found between the sampling points. The high bacterial and archaeal diversity indicated that the site might be a source of unclassified species and phylotypes with specific metabolic capacities involved in the N and S cycles.