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

Abstract

Two halophilic moderately acidophilic archaeal strains, MH1-136-2 T and MH1-370-1 were isolated from commercial salt samples made from seawater in Japan and Indonesia, respectively. Cells of the two strains were pleomorphic and Gram-stain-negative. Strain MH1-136-2 T was pink pigmented, while MH1-370-1 was orange-red pigmented. Strain MH1-136-2 T was able to grow at 9-30 % (w/v) NaCl (with optimum, 21 % NaCl, w/v) at pH 4.5-6.2 (optimum, pH 5.2-5.5) and at 18-55 6C (optimum, 45 6C). Strain MH1-370-1 was able to grow at 12-30 % (w/v) NaCl (optimum, 18 %, w/v) at pH 4.2-6.0 (optimum, pH 5.2-5.5) and 20-50 6C (optimum, 45 6C). Strain MH1-136-2 T required at least 1 mM Mg 2+ , while MH1-370-1 required at least 10 mM for growth. Both strains reduced nitrate and nitrite under aerobic conditions. The 16S rRNA gene sequences of strains MH1-136-2 T and MH1-370-1 were identical, and the closest relative wasHalarchaeum rubridurum MH1-16-3 T with 98.3 % similarity. The level of DNA-DNA relatedness between these strains was 90.9 % and 92.4 % (reciprocally), while that between MH1-136-2 T and Halarchaeum acidiphilum MH1-52-1 T , Halarchaeum salinum MH1-34-1 T and Halarchaeum rubridurum MH1-16-3 T was 37.7 %, 44.3 % and 41.1 % (each an average), respectively. Based on the phenotypic, genotypic and phylogenetic analyses, it is proposed that the isolates represent a novel species of the genus Halarchaeum, for which the name Halarchaeum nitratireducens sp. nov. is proposed. The type strain is MH1-136-2 T (5JCM 16331 T 5CECT 7573 T ) isolated from solar salt produced in Japan.Members of the family Halobacteriaceae, 143 species accommodated in 40 genera (as of June 2013), are known to grow at neutral to alkaline pH (Oren, 2007). We have, however, demonstrated that moderately acidophilic haloarchaeal strains able to grow at acidic pH 4.5 can be isolated from many solar salt samples (Minegishi et al., 2008) and the most acidophilic strain MH1-52-1 T was classified as Halarchaeum acidiphilum gen. nov., sp. nov. (Minegishi et al., 2010). Subsequently, we proposed Halarchaeum salinum (Yamauchi et al., 2013a) and Halarchaeum rubridurum (Yamauchi et al., 2013b). In this study, we repeated the isolation of acidophilic haloarchaeal strains using medium adjusted to pH 4. 3 , pH adjusted to 4.0 with HCl. The medium was autoclaved for 20 min at 121 uC. After incubation for 2-4 weeks at 37 uC, colonies were picked up and transferred to new plates. A total of 74 strains were purified by repeated streaking, and 16S rRNA gene sequences were determined according to the method of Minegishi et al. (2012). Two strains selected for further study, MH1-136-2 T and MH1-370-1, were isolated from commercial solar salt samples made from seawater in Japan and Indonesia, respectively.Phenotypic tests were performed according to the methods of Minegishi et al. (2010) and Oren et al. (1997). The analyses were conducted using liquid or solidified MH1 medium at 37 u C. Colony morphology was observed on agar medium. Gram-staining was performed according to the ...

Insights into the metabolism, lifestyle and putative evolutionary history of the novel archaeal phylum ‘Diapherotrites’

“…Historically, Archaea were regarded as a collection of extremophiles that could only thrive in extreme habitats, for example, high temperature (Huber et al, 1991;Jannasch et al, 1992;Antoine et al, 1995;Whitaker et al, 2003), high salinity (Oren et al, 1990;Cui et al, 2010;Goh et al, 2011;Inoue et al, 2011), low pH (Edwards et al, 2000;Dopson et al, 2004), strict anaerobic conditions (Mikucki et al, 2003;Sakai et al, 2007) or combinations thereof (Huber et al, 1989;Itoh et al, 1999;Minegishi et al, 2008Minegishi et al, , 2013.…”

Systematics of haloarchaea and biotechnological potential of their hydrolytic enzymes

“…solikamskense (isolated from the foamy products of flotation enrichment of potassium minerals, Russia) [31] and Hla. nitratireducens (isolated from commercial salt, Japan) [32] are other members of this genus.…”

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

“…H. solikamskense (Saralov et al , 2012) was proposed as a novel species of the genus Halarchaeum , with 16S rRNA gene sequence JN227878 (1448 bp), and the name was validly published in 2014 (Saralov et al , 2014). The sequence JN227878 shared 99.9 % similarity with AB372515 of ‘Halophilic archaeon MH1-136-2’, which was later proposed as the type strain of H. nitratireducens (Minegishi et al , 2013). We determined in this study full-length sequences of the 16S rRNA gene and rpoB ′ gene of H. solikamskense DSM 26612 T and also performed DNA–DNA hybridization.…”

“…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).…”