Phytohabitans aurantiacus sp. nov., an actinomycete isolated from soil.

A novel actinomycete, designated RD004123T, was isolated from a soil sample collected in Hokkaido, Japan, and its taxonomic position was investigated by a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain RD004123T fell within the cluster of the family Micromonosporaceae but did not form a reliable cluster with any member of the family. The similarity values between strain RD004123T and the type species of 29 genera in the family Micromonosporaceae were 91.7-97.7 %. Meanwhile, phylogenomic analyses indicated that strain RD004123T was closely related to members of the genus Phytohabitans. Strain RD004123T contained both meso-diaminopimelic acid and l-lysine as the diagnostic diamino acids of the peptidoglycan. The predominant isoprenoid quinones were MK-10(H8) and MK-10(H6), and the major fatty acids were anteiso-C17 :  0, iso-C16 :  0, iso-C15 :  0 and C17 :  0. The detected polar lipids were phosphatidylinositol mannosides, phosphatidylinositol, phosphatidylethanolamine and diphosphatidylglycerol. These chemotaxonomic features corresponded to those of the genus Phytohabitans. Meanwhile, the results of genome comparison analyses and phenotypic characterizations distinguished strain RD004123T from the other members of the genus Phytohabitans. Therefore, strain RD004123T should be assigned as representing a novel species of the genus Phytohabitans, for which the name Phytohabitans aurantiacus sp. nov. is proposed. The type strain is RD004123T (=NBRC 114997T=DSM 114330T).

Nocardia sputorum sp. nov., an actinobacterium isolated from clinical specimens in Japan.

Two novel actinobacteria, designated IFM 12276T and IFM 12275, were isolated from clinical specimens in Japan, and their taxonomic positions were investigated using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strains IFM 12276 T and IFM 12275 have completely identical 16S rRNA gene sequences and were closely related to members of the genus Nocardia. The highest 16S rRNA gene sequence similarity was observed to Nocardia beijingensis (99.6 %) and Nocarida sputi (99.6 %), followed by Nocardia niwae (99.3 %) and Nocardia araoensis (99.3 %). The whole-cell hydrolysates of strains IFM 12276T and IFM 12275 contained meso-diaminopimelic acid, arabinose and galactose. The acyl type of muramic acid was N-glycolyl. The predominant isoprenoid quinone was MK-8(H4, ω-cycl.) and the principal polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides. Strains IFM 12276T and IFM 12275 contained mycolic acids that co-migrated with those from the type strain of N. niwae. These chemotaxonomic features corresponded to those of the genus Nocardia. Meanwhile, the differences in some phenotypic characteristics, along with the results of average nucleotide identity and digital DNA-DNA hybridization analyses, indicated that strains IFM 12276 T and IFM 12275 should be distinguished from the recognized species of the genus Nocardia. Therefore, these strains represent a novel species of the genus Nocardia, for which the name Nocardia sputorum sp. nov. is proposed. The type strain is IFM 12276T (=NBRC 115477T=TBRC 17096T).

Lolliginicoccus levis gen. nov., sp. nov., a novel bacterium isolated from the brain of the Chiroteuthis picteti squid, and reclassification of two Hoyosella species as Lolliginicoccus suaedae comb. nov. and Lolliginicoccus lacisalsi comb. nov.

A Gram-stain-positive, non-motile, mesophilic, aerobic, coccus-shaped bacterium, designated strain Y7R2T, was isolated from the brain of a Chiroteuthis picteti squid living in mesopelagic water near Muroto, Kochi, Japan. Phylogenetic analyses based on 16S rRNA gene sequences showed that the strain was most closely related to the genus Hoyosella (96.1 % similarity to the type strain of the type species Hoyosella altamirensis) and formed a separate distinct cluster in a stable, deep-branching lineage with the type strains of Hoyosella suaedae and Hoyosella lacisalsi (98.7-99.5% similarities). The major fatty acids (>10 %) of strain Y7R2T were C17 : 1 ω8c, C15 : 0, C16 : 1 ω6c/C16 : 1 ω7c and C16 : 0, and the isoprenoid quinones were menaquinone-7 (57.8 %) and menaquinone-8 (42.2 %). The principal polar lipids were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylinositol, and the DNA G+C content was 68.0 %. These chemotaxonomic features, with the exception of the fatty acid composition, were similar to those of the phylogenetically clustered species (H. suaedae and H. lacisalsi) but different from those of core Hoyosella species (including H. altamirensis). These results suggested that Y7R2T, H. suaedae and H. lacisalsi strains should be assigned to a novel genus. Furthermore, strain Y7R2T showed low average nucleotide identity values (88.0-88.2 %) and low digital DNA-DNA hybridization values (34.3-34.7 %) to the type strains of H. suaedae and H. lacisalsi. These data indicated that strain Y7R2T should be assigned to a novel genus and species, for which the name Lolliginicoccus levis gen. nov., sp. nov. is proposed. The type strain is Y7R2T (=NBRC 114883T=KCTC 49749T). Accordingly, reclassification of H. suaedae and H. lacisalsi as Lolliginicoccus suaedae comb. nov. (type species) and Lolliginicoccus lacisalsi comb. nov. is also proposed.

Arthrobacter mangrovi sp. nov., an actinobacterium isolated from the rhizosphere of a mangrove.

A novel actinobacterium, designated HIs16-36T, was isolated from the rhizosphere of a mangrove on Ishigaki Island, Okinawa, Japan, and its taxonomic position was investigated using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain HIs16-36T was closely related to the members of the genus Arthrobacter. The highest 16S rRNA gene sequence similarity was observed with Arthrobacter crystallopoietes (98.5 %), followed by Arthrobacter globiformis (97.2 %). The peptidoglycan of strain HIs16-36T was of the A4α type, with lysine as the diagnostic diamino acid. The predominant isoprenoid quinone was MK-9(H2) and the major fatty acids were anteiso-C15 : 0 and iso-C15 : 0. The polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two glycolipids. These chemotaxonomic features corresponded to those of the genus Arthrobacter. Meanwhile, the differences in some phenotypic characteristics, along with the results of average nucleotide identity and digital DNA-DNA hybridization analyses, indicated that strain HIs16-36T should be distinguished from the recognized species of the genus Arthrobacter. Therefore, strain HIs16-36T represents a novel species of the genus Arthrobacter, for which the name Arthrobacter mangrovi sp. nov. is proposed. The type strain is HIs16-36T (=NBRC 112813T=TBRC 15750T).

Organocatalytic activity of granaticin and its involvement in bactericidal function.

We previously discovered that actinorhodin, a benzoisochromanequinone antibiotic produced by Streptomyces coelicolor A3(2), serves as a catalyst facilitating the oxidation of ascorbic acid and cysteine (PNAS 48:17,152, 2014). In the present study, we screened for similar ascorbic acid-oxidizing activity in the culture broth of various Streptomyces spp., and discovered marked activity in the culture broth of Streptomyces vietnamensis. The principle active compound was granaticin, a pigmented antibiotic that is structurally related to actinorhodin. The absence of any metals in the purified granaticin fraction indicated that granaticin was an organocatalyst. Granaticin catalyzed the oxidation of L-ascorbic acid, generating L-dehydroascorbic acid and hydrogen peroxide (H2O2) at a 1:1 stoichiometric ratio, with 15 times higher reactivity than that of actinorhodin at an optimum pH of 7.0. Granaticin also oxidizes sulfhydryl compounds, including L-cysteine and glutathione. Growth inhibitory assays demonstrated that knockout mutants of the catalase gene exhibit high sensitivity to granaticin. The results suggest that the bactericidal activity of granaticin is exerted by the oxidation of sulfhydryl groups of cellular components and the toxicity of H2O2 generated during the oxidation reaction.