Culture-independent molecular phylogenetic analysis of microbial communities living at saturating levels of magnesium sulfate

Abstract

Athalassohaline epsomite lakes in the northwestern plains of North America contain high concentrations of magnesium sulfate (MgSO4). Hot Lake located outside of Oroville, WA is one such lake in which the MgSO4 precipitates as epsomite (MgSO4-7H2O). Natural environments containing high concentrations of MgSO4 are rare and there has been little previous microbiological analysis of the communities that dwell in Hot Lake or of any analogous epsomite-rich environment. It was unclear whether the microbial communities inhabiting this distinctive environment were archaea, novel bacteria endemic to epsomite environments, bacteria commonly associated with hyperhaline environments, or typical forest soil bacteria which have adapted strategies for survival under conditions of osmotic-stress. This study utilized culture-independent and culture-dependent techniques to analyze the microbial diversity of Hot Lake. The culture-dependent campaign resulted in nearly 100 isolates which were isolated on 10% NaCl or 2 M MgSO4 agar plates. The clone library was dominated by Gram-positive clades, specifically sequences related to uncultured actinobacteria. Sequences related to sulfur-reducing Deltaproteobacteria were also abundant in the culture-independent library. Conversely, the isolate collection produced a near even split between Gram-negative and Gram-positive clades. Halomonas, Idiomarina, Marinobacter, Marinococcus, Nesterenkonia, Nocardiopsis and Planococcus were the most abundant genera found. This research was supported by NASA ROSES Planetary Protection (PPR), Kansas NASA EPSCoR, NIH NCRR NIGMS KINBRE, and NSF GK-12.