Thermophilic Magnetotactic Bacteria from Mickey Hot Springs, an Arsenic-Rich Hydrothermal System in Oregon

Abstract

Magnetotactic bacteria (MTB) thrive in aquatic sediments all over the world, but their complete role(s) in their geobiological habit as well as their significance in the fossil record remains unresolved. We were able to collect, enrich, and purify MTB from Mickey Hot Springs, a unique arsenic-rich hot spring system located in the Alvord Desert of southeastern Oregon. Populations of MTB were present in water and surface sediment samples in a geothermal spring at temperature 47 °C, pH of 8.0, and 0.96 mg/L arsenic. Using 16S rDNA analysis, the organism was found to belong to the phylum Nitrospirae. Cells had rod to vibrioid morphology, a single flagellum and single magnetosome chain as determined by scanning transmission electron microscopy (STEM). The magnetosomes contained bullet-shaped crystals of magnetite (Fe3O4) approximately 84 nm long and 39 nm wide. This is the first instance of MTB collected from an arsenic-rich, moderately thermophilic environment. The discovery of MTB at this site extends the limits of habitats for these bacteria and provides a proxy for the search for magnetofossils in the rock record.