Despite intensive microbiological characterization of soda lake microbial communities, no culturable representatives from the phylum Planctomycetota have been isolated from these haloalkaline habitats. In the context of studying polysaccharide utilization by soda lake microbial communities, we used polysaccharide hyaluronic acid as enrichment substrate at aerobic, moderate haloalkaline conditions (1 M total Na+, pH 9.5). This resulted in a
selective enrichment and isolation in pure culture of a bacterial strain AB-hyl4 belonging to Planctomycetota. The cells are tiny motile cocci growing in large aggregates, with the Gram-negative type of ultrastructure and producing a yellow pigment. This obligate aerobic saccharolytic heterotroph has an extremely narrow growth substrate range including, besides hyaluronic acid, melezitose and glycerol. The membrane lipids consist of phosphatidylcholine and two types of neutral lipids, including hopanoids and monounsaturated C17 and C19 hydrocarbons. Phylogenomic analysis placed the isolate into the family Phycisphaeraceae, class Phycisphaerae, as a new genus-level lineage. Its genome contained a gene encoding a polysaccharide lyase from the PL8 family which is probably responsible for the degradation of hyaluronic acid to a dimer, followed by its transport and hydrolysis into monomers in periplasm and final glycolytic degradation in cytoplasm. On the basis of distinct phenotypic and genomic properties, strain AB-hyl4T (DSM 117794 = UQM 41914) is proposed to be classified as
Natronomicrosphaera hydrolytica gen. nov., sp. nov.

A pure culture of alkaliphilic haloarchaeon strain AArc-ST capable of anaerobic growth by carbohydrate-dependent sulfur respiration was obtained from hypersaline lakes in southwestern Siberia. According to phylogenetic analysis, AArc-ST formed a new genus level branch most related to the genus Natronoarchaeum in the order Halobacteriales. The strain is facultatively anaerobic with strictly respiratory metabolism growing either by anaerobic respiration with elemental sulfur and thiosulfate as the electron acceptors or by aerobic respiration at microoxic conditions. Thiosulfate is reduced partially to sulfide and sulfite. It is a first sulfur-reducing alkaliphilic haloarchaeon utilizing sugars, starch and glycerol as substrates for anaerobic growth. It is extremely halophilic (optimum at 3.5 M total Na+) and obligately alkaliphilic (optimum at pH 9.5). The dominant polar lipids include PG and PGP-Me with the archaeol (C20-C20) or extended archaeol (C20-C25) cores. The dominant respiratory lipoquinone is MK-8:8. On the basis of unique physiological properties and results of phylogenetic analysis, the soda lake isolate is suggested to be classified into a novel genus and species Natranaeroarchaeum sulfidigenes gen. nov., sp. nov. (=JCM 34033T = UNIQEM U1000T). Furthermore, on the bases of phylogenomic reconstruction, a new family Natronoarchaeaceae fam. nov. is proposed within the order Halobacteriales incorporating Natranaeroarchaeum and three related genera: Natronoarchaeum, Salinarchaeum and Halostella.

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).