Ecophysiology of “ Halarsenatibacter silvermanii ” Strain SLAS-1 ^T , gen. nov., sp. nov., a Facultative Chemoautotrophic Arsenate Respirer from Salt-Saturated Searles Lake, California

Abstract

Searles Lake occupies a closed basin harboring salt-saturated, alkaline brines that have exceptionally high concentrations of arsenic oxyanions. Strain SLAS-1T was previously isolated from Searles Lake (R. S. Oremland, T. R. Kulp, J. Switzer Blum, S. E. Hoeft, S. Baesman, L. G. Miller, and J. F. Stolz, Science 308:1305-1308, 2005). We now describe this extremophile with regard to its substrate affinities, its unusual mode of motility, sequenced arrABD gene cluster, cell envelope lipids, and its phylogenetic alignment within the order Halanaerobacteriales, assigning it the name “Halarsenatibacter silvermanii” strain SLAS-1T. We also report on the substrate dynamics of an anaerobic enrichment culture obtained from Searles Lake that grows under conditions of salt saturation and whose members include a novel sulfate reducer of the order Desulfovibriales, the archaeon Halorhabdus utahensis, as well as a close homolog of strain SLAS-1T.

Desulfuribacillus alkaliarsenatis gen. nov. sp. nov., a deep-lineage, obligately anaerobic, dissimilatory sulfur and arsenate-reducing, haloalkaliphilic representative of the order Bacillales from soda lakes

“…The dual capacity to grow by dissimilatory respiration of sulfur and arsenate in a haloalkaliphilic organism has only been reported once before for extremely halophilic and alkaliphilic representative of the order Halanaerobiales , Halarsenatibacter silvermanii , isolated from the hypersaline alkaline Searles Lake (Switzer Blum et al 2009). …”

Desulfohalophilus alkaliarsenatis gen. nov., sp. nov., an extremely halophilic sulfate- and arsenate-respiring bacterium from Searles Lake, California

“…The question of the origin of the sulfide detected in Searles Lake is ecologically relevant because both strain SLSR-1 and H. silvermanii also have the ability to oxidize sulfide using either arsenate or nitrate as the oxidant (Table 2; Oremland et al 2005; Switzer Blum et al 2009). …”

Functional microbiology of soda lakes

“…At hypersaline conditions, microbial sulfur reduction seems to be restricted to prokaryotes utilizing the 'salt-in' osmotic strategy, that is, to bacterial members of the Halanaerobiales and to haloalkaliphilic archaea. The examples of Halanaerobiales are Halarsenatibacter silversmanii, an extremely halophilic alkaliphile using lactate as e À -donor and sulfur and arsenate as e À -acceptors [78], and Natroniella sulfidigena, an extreme natronophile utilizing acetate, H 2 and formate as e À -donors for sulfur/polysulfidedependent respiration [79]. Recently, we have also discovered two different groups of facultatively anaerobic alkaliphilic haloarchaea growing by polysulfide respiration with formate, H 2 and VFA (but not acetate) as e À -donors in hypersaline soda lakes [unpublished results].…”