Description of Nocardioides jiangsuensis sp. nov., and Proposal for Reclassification of the Genus Marmoricola as Nocardioides

A Gram-staining-positive, non-motile, aerobic, spherical actinobacterium, designated WL0053^T, was isolated from the coastal sediment of Nantong City, Jiangsu Province, China. The 16S rRNA gene sequence of strain WL0053^T exhibited the highest similarities to Nocardioides mesophilus MSL-22^T (98.0%), N. massiliensis GD12^T (97.8%), Marmoricola bigeumensis MSL-05^T (97.6%), and N. jensenii DSM 20641^T (97.3%). The polyphasic taxonomic approach was used for the identification of strain WL0053^T. This strain formed white, round, and smooth colonies and grew in the presence of 0-18% (w/v) NaCl (optimum, 0-4.0%), at pH 6.0-9.0 (optimum, pH 7.0) and at 20-37 °C (optimum, 28 °C). The main cellular fatty acids comprised of C_17:1 ω8c, C_18:1 ω9c, and iso-C_16:0. The genomic DNA G + C content was 71.9%. The predominant quinone was MK-8(H₄), and the major polar lipid consisted of phosphatidylcholine, glycolipid, phosphatidylethanolamine, and two unidentified phospholipids. Phylogenetic trees of 16S rRNA gene and bac120 gene set indicted that strain WL0053^T was closely related to the species N. iriomotensis and N. mesophilus, while these two species clustered in a separate clade together with M. caldifontis YIM 730233^T in the bac120 tree. Combined with the analysis of average nucleotide identity (ANI), average amino acid identity (AAI), and digital DNA-DNA hybridization (dDDH), it can be considered that the strain WL0053^T is a new member of the genus Nocardioides and is proposed to be named as Nocardioides jiangsuensis sp. nov.. The type strain is WL0053^T (=MCCC 1K05897^T=JCM 34671^T=GDMCC 4.192^T). Furthermore, based on the fact that the genera Nocardioides and Marmoricola both appeared polyphyletic with no significant difference on phenotypic and chemotaxonomic traits, we proposed to reclassify the genus Marmoricola as Nocardioides.

Marmoricola caldifontis sp. nov., a novel actinobacterium isolated from a hot spring

A Gram-staining-positive, aerobic, non-motile, non-spore-forming and coccoid-shaped actinobacterial strain, designated YIM 730233^T, was isolated from a sediment sample, collected from a hot spring in Tibet, China. Colonies were brownish, circular, smooth and convex. Strain YIM 730233^T was able to grow in the temperature range of 20-50 °C, pH 6.5-8.0 and in the presence of up to 1.0 % (w/v) NaCl. A comparison of the 16S rRNA gene sequence of strain YIM 730233^T with sequences of type strains of most closely related species of Marmoricola showed highest sequence similarities to Marmoricola bigeumensis MSL-05^T (98.3%) and Marmoricola pocheonensis Gsoil 818^T (98.1%). The draft genome of strain YIM 730233^T had a size of 4 806 234 bp with a DNA G+C content of 72.1 mol%. The major fatty acids (>10 %) of strain YIM 730233^T mainly consisted of iso-C_16 : 0, anteiso-C_17 : 0 and C_18 : 1 ω9c, typical of the genus Marmoricola. Strain YIM 730233^T had LL-2,6-diaminopimelic acid as the diagnostic diamino acid in the cell wall. The predominant isoprenoid quinone was MK-8(H₄). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, unidentified phospholipids and an unidentified lipid. DNA-DNA hybridizations between strain YIM 730233^T and type strains of Marmoricola bigeumensis MSL-05^T and Marmoricola pocheonensis Gsoil 818^T resulted in similarity values of 21 and 19% respectively. Based on DNA-DNA hybridization results, together with the differentiating biochemical and chemotaxonomic features, showed that strain YIM 730233^T represents a novel Marmoricola species, for which the name Marmoricola caldifontis sp. nov. (type strain YIM 730233^T=KCTC 49192^T=CGMCC 4.7521^T), is proposed.

Marmoricola mangrovicus sp. nov., an endophytic actinobacterium isolated from Kandelia candel

A Gram-stain-positive, aerobic, motile, non-spore-forming and rod-shaped actinobacterium, designated strain 4Q3S-7^T, was isolated from a piece of surface-sterilized bark of Kandelia candel collected at the Cotai Ecological Zone in Macao, China. Colonies were yellowish white, circular, smooth and convex. The 16S rRNA gene sequence of strain 4Q3S-7^T exhibited highest similarities to Marmoricola ginsengisoli Gsoil 097^T (97.6 %), Marmoricola solisilvae KIS18-7^T (97.6 %) and Marmoricola pocheonensis Gsoil 818^T (97.3 %). Phylogenetic analysis showed that strain 4Q3S-7^T clustered with species of the genus Marmoricola and was clearly affiliated to the genus Marmoricola. Genomic analyses, including average nucleotide identity and DNA-DNA hybridization, clearly separated strain 4Q3S-7^T from M. ginsengisoli Gsoil 097^T, M. solisilvae KIS18-7^T and M. pocheonensis Gsoil 818^T with values below the thresholds for species delineation. Strain 4Q3S-7^T had ll-2,6-diaminopimelic acid as the diagnostic diamino acid in the cell wall. The major fatty acids (>10 % of total fatty acids) were C18 : 0 10-methyl (TBSA), C18 : 1ω9c, iso-C16 : 0 and iso-C16 : 0 2-OH. The predominant menaquinone was MK-8(H4). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol and an unidentified phospholipid. The DNA G+C content of strain 4Q3S-7^T was 72.0 mol% (draft genome sequence). Based on its phylogenetic, phenotypic and chemotaxonomic features, strain 4Q3S-7^T is considered to represent a novel species of the genus Marmoricola, for which the name Marmoricola mangrovicus sp. nov. is proposed. The type strain is 4Q3S-7^T (=KCTC 39790^T=CGMCC 4.7424^T).