Abstract
Nine pure cultures of neutrophilic haloaloarchaea capable of anaerobic growth by carbohydrate-dependent sulfur respiration were isolated from hypersaline lakes in southwestern Siberia and southern Russia. According to phylogenomic analysis the isolates were closely related to each other and formed a new species within the genus Halapricum (family Haloarculaceae). They have three types of catabolism: fermentative, resulting in H2 formation; anaerobic respiration using sulfur compounds as e-acceptors and aerobic respiration. Apart from elemental sulfur, all isolates can also use three different sulfoxides as acceptors and the type strain also grows with thiosulfate, reducing it partially to sulfide and sulfite. All strains utilized sugars and glycerol as the e-donors and C source for anaerobic growth and some can also grow with alpha-glucans, such as starch and dextrins. The major respiratory menaquinones are MK-8:8 and MK-8:7, but 5–19% consists of “thermoplasmata” quinones (MMK-8:8 and MMK-8:7), whose occurrence in haloarchaea is unprecedented. On the basis of their unique physiological properties and results of phylogenomic analysis, the isolates are suggested to be classified into a novel species Halapricum desulfuricans sp. nov. (type strain HSR12-2T = JCM 34032T = UNIQEM U1001T).
Highlights
Nine pure cultures of neutrophilic haloaloarchaea capable of anaerobic growth by carbohydratedependent sulfur respiration were isolated from hypersaline lakes in southwestern Siberia and southern Russia
On the basis of their unique physiological properties and results of phylogenomic analysis, the isolates are suggested to be classified into a novel species Halapricum desulfuricans sp. nov
Our previous research into anaerobic haloarchaea growing by sulfur respiration resulted in the discovery of two functional groups in this novel ecotype of extremely halophilic archaea, including obligately anaerobic acetate- and formate-utilizing genera Halanaeroarchaeum and Halodesulfurarchaeum [1,2,3,4,5]
Summary
Our previous research into anaerobic haloarchaea growing by sulfur respiration resulted in the discovery of two functional groups in this novel ecotype of extremely halophilic archaea, including obligately anaerobic acetate- and formate-utilizing genera Halanaeroarchaeum and Halodesulfurarchaeum [1,2,3,4,5]. To be self-sufficient, this new functional system of sulfur-respiring haloarchaea lacked one metabolic group, namely primary anaerobes, which would decompose carbohydrates and provide electron donors for the aforementioned subgroups. Such organisms have recently been discovered and their metabolism characterized [6]. We provide a formal taxonomic description of these organisms as Halapricum desulfuricans sp. nov
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