Enrichment and isolation of Bacillus beveridgei sp. nov., a facultative anaerobic haloalkaliphile from Mono Lake, California, that respires oxyanions of tellurium, selenium, and arsenic
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Mono Lake sediment slurries incubated with lactate and tellurite [Te(IV)] turned progressively black with time because of the precipitation of elemental tellurium [Te(0)]. An enrichment culture was established from these slurries that demonstrated Te(IV)-dependent growth. The enrichment was purified by picking isolated black colonies from lactate/Te(IV) agar plates, followed by repeated streaking and picking. The isolate, strain MLTeJB, grew in aqueous Te(IV)-medium if provided with a small amount of sterile solid phase material (e.g., agar plug; glass beads). Strain MLTeJB grew at high concentrations of Te(IV) (~8 mM) by oxidizing lactate to acetate plus formate, while reducing Te(IV) to Te(0). Other electron acceptors that were found to sustain growth were tellurate, selenate, selenite, arsenate, nitrate, nitrite, fumarate and oxygen. Notably, growth on arsenate, nitrate, nitrite and fumarate did not result in the accumulation of formate, implying that in these cases lactate was oxidized to acetate plus CO2. Strain MLTeJB is a low G + C Gram positive motile rod with pH, sodium, and temperature growth optima at 8.5–9.0, 0.5–1.5 M, and 40°C, respectively. The epithet Bacillus beveridgei strain MLTeJBT is proposed.
KeywordsAlkaliphile ecology, systematics Anaerobic bacteria Halophile: ecology, biotechnology, phylogeny, genetics, taxonomy, enzymes Isolation and characterization Metal oxidation and reduction Alkaliphiles: systematics, ecology, phylogeny
R. Bansal for 16S rRNA gene cloning and sequencing and J. Patterson for transmission electron microscopy. We are grateful to J. T. Hollibaugh for providing his dataset of other dissolved constituents of this ecosystem and thank S. E. Hoeft for advice in the choice of buffers for the pH experiments and L. G. Miller for technical assistance. This work was funded in part by the USGS and by a grant from the NASA Exobiology Program.
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