Halarchaeum rubridurum sp. nov., a moderately acidophilic haloarchaeon isolated from commercial sea salt samples

Abstract

Six halo-acidophilic archaeal strains were isolated from four commercial salt samples obtained from seawater in the Philippines, Indonesia (Bali) and Japan (Okinawa) on agar plates at pH 4.5. Cells of the six strains were pleomorphic, and stained Gram-negative. Two strains were pink-red pigmented, while four other strains were orange-pink pigmented. Strain MH1-16-3T was able to grow at 9-30 % (w/v) NaCl [with optimum at 18 % (w/v) NaCl], at pH 4.5-6.8 (optimum, pH 5.5) and at 20-50 6C (optimum, 42 6C). The five other strains grew at slightly different ranges. The six strains required at least 1 mM Mg 2+ for growth. The 16S rRNA gene sequences of the six strains were almost identical, sharing 99.9 (1-2 nt differences) to 100 % similarity. The closest relatives were Halarchaeum acidiphilum MH1-52-1 T and Halarchaeum salinum MH1-34-1 T with 97.7 % similarity. The DNA G+C contents of the six strains were 63.2-63.7 mol%. Levels of DNA-DNA relatedness amongst the six strains were 79-86 %, while those between MH1-16-3 T and H.acidiphilum MH1-52-1 T and H. salinum MH1-34-1 T were both 43 and 45 % (reciprocally), respectively. Based on the phenotypic, genotypic and phylogenetic analyses, it is proposed that the six isolates represent a novel species of the genus Halarchaeum, for which the name Halarchaeum rubridurum sp. nov. is proposed. The type strain is MH1-16-3 T (5JCM 16108Members of the family Halobacteriaceae (Oren, 2012) are, at the time of writing, accommodated in 138 species of 40 genera. Most strains grow at neutral to slightly alkaline pH, or in media of pH 8.5-11.0. Minegishi et al. (2008) showed that moderately acidophilic haloarchaeal strains could be isolated from solar salt samples, and that most strains grew at a pH range of 4.5-6.0. The most acidophilic of these strains, MH1-52-1, was classified later as representing a novel species of a new genus, Halarchaeum acidiphilum (Minegishi et al., 2010). In a previous study, we repeated the isolation of acidophilic haloarchaeal strains using the same medium used by Minegishi et al. (2008), and proposed a second species of the genus, Halarchaeum salinum, based on three strains (Yamauchi et al., 2013). In the present study, we report the phenotypic and phylogenetic characterization of six halo-acidophilic strains, MH1-16-3 T , , and propose to classify them as representing a novel species of the genus Halarchaeum.Commercial salt samples (0.3 g each) were dissolved in 1 ml sterile 5 % NaCl solution, and one drop each was 3Present address: Graduate School of Interdisciplinary New Science, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585, Japan.Abbreviation: PGP-Me, phosphatidylglycerol phosphate methyl ester; S-TGD-1, sulfated triglycosyl diether-1.The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequence of Halarchaeum rubridurum MH1-16-3

Systematics of haloarchaea and biotechnological potential of their hydrolytic enzymes

“…Hla. rubridurum (isolated from solar salt, Philippines) [29], Hla. salinum (isolated from commercial salt, Indonesia) [30], Hla.…”

Halocalculus aciditolerans gen. nov., sp. nov., an acid-tolerant haloarchaeon isolated from commercial salt

“…The G+C contents of the total DNA of strains MH2-243-1 T , MH2-93-1 and MH2-91-1 determined by the HPLC method of Tamaoka & Komagata (1984) were 68.5, 68.8 and 68.3 mol%, respectively. In contrast, DNA G+C contents of the type strains of species of the genera Halobacterium , Salarchaeum and Halarchaeum are slightly lower [54.5–66.4, 64, 59.3–66.4 mol%, respectively (Gutiérrez et al , 1989; Gruber et al , 2004; Yang et al , 2006; Shimane et al , 2011; Minegishi et al , 2010a, 2013; Yamauchi et al , 2013a, b; Saralov et al , 2012)]. These data again suggested the three strains represent a novel taxon.…”

“…A representative strain, MH1-52-1 T , was classified as a new genus and species, Halarchaeum acidiphilum , the first acidophilic haloarchaeon described (Minegishi et al , 2010a). Subsequently, our group proposed three more species of this genus, Halarchaeum salinum (Yamauchi et al , 2013a), Halarchaeum rubridurum (Yamauchi et al , 2013b) and Halarchaeum nitratireducens (Minegishi et al , 2013), using the medium MH1.…”

Halarchaeum grantii sp. nov., a moderately acidophilic haloarchaeon isolated from a commercial salt sample

“…nov., the first acidophilic haloarchaeon described (Minegishi et al , 2010a). Subsequently, our group proposed three more species of the genus, Halarchaeum salinum (Yamauchi et al , 2013a), Halarchaeum rubridurum (Yamauchi et al , 2013b) and Halarchaeum nitratireducens (Minegishi et al , 2013). Another species, Halarchaeum solikamskense , was proposed by Saralov et al (2012), and the name was validly published (Saralov et al , 2014).…”