The motile, predominantly square-shaped, red archaeon strain 801030/1T, isolated from a brine pool in the Sinai peninsula (Egypt), was characterized taxonomically. On the basis of its polar lipid composition, the nucleotide sequences of its two 16S rRNA genes, the DNA G+C content (60·1 mol%) and in growth characteristics, the isolate could be assigned to the genus Haloarcula. However, phylogenetic analysis of the two 16S rRNA genes detected in this organism and low DNA-DNA hybridization values with related Haloarcula species showed that strain 801030/1T is sufficiently different from the recognized Haloarcula species to warrant its designation as a new species. A new species, Haloarcula quadrata, is therefore proposed, with strain 801030/1T (= DSM 11927T) as the type strain.
Two novel hyperthermophilic, rod-shaped crenarchaeotes were isolated from an acidic hot spring in the Philippines. Cells were mostly straight or slightly curved rods 0·4-0·7 μm in width. Bent cells, branched cells, and cells bearing globular bodies were commonly observed. The isolates were heterotrophs and grew anaerobically and microaerobically. The addition of archaeal cell extract or a vitamin mixture to the medium significantly stimulated growth. The isolates grew over a temperature range of 60-92 °C, and optimally around 85 °C and grew over a pH range of 2·3-6·4, and optimally at pH 3·7-4·2. The isolates utilized glycogen, gelatin, beef extract, peptone, tryptone and yeast extract as carbon sources. They required sulfur, thiosulfate or sulfate as electron acceptors. The lipids mainly consisted of various cyclized glycerolbisdiphytanyl-glycerol tetraethers. The G+C content of the genomic DNAs was 43 mol%. The 16S rDNA contained two small introns. The comparison of the 16S rDNA exon sequences revealed that they represented an independent lineage in the family Thermoproteaceae. The two strains were included in a single species because of high levels of DNA-DNA relatedness. From these results, Caldivirga maquilingensis gen. nov., sp. nov. is proposed in the family Thermoproteaceae to accommodate these isolates. The type strain of C. maquilingensis is strain IC-167T (= JCM 10307T =MCC-UPLB 1200T = ANMR 0178T).