Microbacterium humicola sp. nov., Microbacterium terrisoli sp. nov., Paenibacillus pedocola sp. nov., Paenibacillus silviterrae sp. nov., Flavobacterium terrisoli sp. nov., and Aquabacterium humicola sp. nov., isolated from soil

Four Gram-stain-positive and two Gram-stain-negative bacterial strains, designated as W4T, FW7T, TW48T, UW52T, PT-3T, and RJY3T, were isolated from soil samples collected from the Republic of Korea. The 16S rRNA gene sequence analysis showed that strains W4T and FW7T belonged to the genus Microbacterium, strains TW48T and UW52T were affiliated to the genus Paenibacillus, strain PT-3T was related to the genus Flavobacterium, and strain RJY3T was associated with the genus Aquabacterium. The closest phylogenetic taxa to W4T, FW7T, TW48T, UW52T, PT-3T, and RJY3T were Microbacterium bovistercoris NEAU-LLET (97.7 %), Microbacterium protaetiae DFW100M-13T (97.9 %), Paenibacillus auburnensis JJ-7T (99.6 %), Paenibacillus allorhizosphaerae JJ-447T (95.7 %), Flavobacterium buctense T7T (97.1 %), and Aquabacterium terrae S2T (99.5 %), respectively. Average nucleotide identity and digital DNA-DNA hybridization values between the novel strains and related reference type strains were <95.0 % and <70.0 %, respectively. The major cellular fatty acid in strains W4T, FW7T TW48T, and UW52T was antiso-C15 : 0. Similarly, strain PT-3T revealed iso-C15 : 0, iso-C15 : 1 G, iso-C17 : 0 3-OH, and iso-C15 : 0 3-OH as its principal fatty acids. On the other hand, RJY3T exhibited summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c), C16 : 0, summed feature 8 (C18 : 1  ω7c and/or C18 : 1  ω6c), and C12 : 0 as its predominant fatty acids. Overall, the polyphasic taxonomic data indicated that strains W4T, FW7T, TW48T, UW52T, PT-3T, and RJY3T represent novel species within the genera Microbacterium, Paenibacillus, Flavobacterium, and Aquabacterium. Accordingly, we propose the names Microbacterium humicola sp. nov., with the type strain W4T (=KCTC 49888T=NBRC 116001T), Microbacterium terrisoli sp. nov., with the type strain FW7T (=KCTC 49859T=NBRC 116000T), Paenibacillus pedocola sp. nov., with the type strain TW48T (=KCTC 43470T=NBRC 116017T), Paenibacillus silviterrae sp. nov., with the type strain UW52T (=KCTC 43477T=NBRC 116018T), Flavobacterium terrisoli sp. nov., with the type strain PT-3T (=KCTC 92106T=NBRC 116012T), and Aquabacterium humicola sp. nov., with the type strain RJY3T (=KCTC 92105T=NBRC 115831T).

Four new Microbacterium species isolated from seaweeds and reclassification of five Microbacterium species with a proposal of Paramicrobacterium gen. nov. under a genome-based framework of the genus Microbacterium

The taxonomic relationships of 10 strains isolated from seaweeds collected from two beaches in Republic of Korea were studied by sequencing and analyses of 16S rRNA genes and whole genomes. For the construction of a more reliable and robust 16S rRNA gene phylogeny, the authentic and nearly complete 16S rRNA gene sequences of all the Microbacterium type strains were selected through pairwise comparison of the sequences contained in several public databases including the List of Prokaryotic names with Standing in Nomenclature (LPSN). The clustering of the ten study strains into five distinct groups was apparent in this single gene-based phylogenetic tree. In addition, the 16S rRNA gene sequences of a few type strains were shown to be incorrectly listed in LPSN. An overall phylogenomic clustering of the genus Microbacterium was performed with a total of 113 genomes by core genome analysis. As a result, nine major (≥ three type strains) and eight minor (two type strains) clusters were defined mostly at gene support index of 92 and mean intra-cluster OrthoANIu of >80.00%. All of the study strains were assigned to a Microbacterium liquefaciens clade and distributed further into four subclusters in the core genome-based phylogenetic tree. In vitro phenotypic assays for physiological, biochemical, and chemotaxonomic characteristics were also carried out with the ten study strains and seven closely related type strains. Comparison of the overall genomic relatedness indices (OGRI) including OrthoANIu and digital DNA-DNA hybridization supported that the study strains constituted four new species of the genus Microbacterium. In addition, some Microbacterium type strains were reclassified as members of preexisting species. Moreover, some of them were embedded in a new genus of the family Microbacteriaceae based on their distinct separation in the core genome-based phylogenetic tree and amino acid identity matrices. Based on the results here, four new species, namely, Microbacterium aurugineum sp. nov., Microbacterium croceum sp. nov., Microbacterium galbinum sp. nov., and Microbacterium sufflavum sp. nov., are described, along with the proposal of Paramicrobacterium gen. nov. containing five reclassified Microbacterium species from the "Microbacterium agarici clade", with Paramicrobacterium agarici gen. nov., comb. nov. as the type species.

Microbacterium nymphoidis sp. nov. and Microbacterium festucae sp. nov., two novel species with high plant-promoting potential isolated from wetland plants in China

Two novel plant growth-promoting, rod-shaped, Gram-positive and non-motile rhizobacteria, W1NT and W2RT, were isolated from wetland plants Festuca elata and Nymphoides peltatum, respectively, in China. The results of the 16S rRNA sequence alignment analysis showed that they were related to Microbacterium, with the highest similarity to Microbacterium ketosireducens (98.7 %) and Microbacterium laevaniformans (98.5 %) for strain W1NT, and to Microbacterium terricola (98.1 %) and Microbacterium marinum (98.0 %) for strain W2RT. Phylogenetic analyses based on 16S rRNA gene sequences and 92 conserved concatenated proteins suggested that the two strains belong to the genus Microbacterium and were placed in two separate novel phylogenetic clades. The genome sizes of the two strains were 3.2 and 3.7 Mb, and the G+C contents were 71.7 and 68.5 mol%, respectively. The comparative genome results showed that the average nucleotide identity values between W1NT and W2RT and other species ranged from 73.5 to 83.6 %, and the digital DNA-DNA hybridization values ranged from 19.7 to 26.8 %. These two strains show physiological and biochemical features that differ from those of closely related species. Rhamnose, galactose and glucose were present in the characteristic sugar fractions of strains W1NT and W2RT. The peptidoglycan of strains W1NT and W2RT contained the amino acids ornithine, alanine and aspartic acid. C15 : 0 anteiso, C17 : 0 anteiso and C16 : 0 iso were the predominant cellular fatty acids in W1NT and W2RT. Phosphatidylglycerol and diphosphatidylglycerol are major polar lipid components. Strain W1NT not only formed bacterial biofilms but also had the ability to solubilize phosphorus and produce indole-3-acetic acid. Strain W2RT had siderophore-producing and lignin-degrading properties. Based on their genetic and phenotypic characteristics, strains W1NT and W2RT were classified as novel bacteria in the genus Microbacterium and designated as Microbacterium festucae sp. nov. (type strain W1NT=ACCC 61807T=GDMCC 1.2966T=JCM 35339T) and Microbacterium nymphoidis sp. nov. (type strain W2RT=ACCC 61808T=GDMCC 1.2967T=JCM 35340T).

Microbacterium elymi sp. nov., Isolated from the Rhizospheric Soil of Elymus tsukushiensis, a Plant Native to the Dokdo Islands, Republic of Korea

Microbacterium elymi KUDC0405^T was isolated from the rhizosphere of Elymus tsukushiensis from the Dokdo Islands. The KUDC0405^T strain was Gram-stain-positive, non-spore forming, non-motile, and facultatively anaerobic bacteria. Strain KUDC0405^T was a rod-shaped bacterium with size dimensions of 0.3-0.4 × 0.7-0.8 μm. Based on 16S rRNA gene sequences, KUDC0405^T was most closely related to Microbacterium bovistercoris NEAU-LLE^T (97.8%) and Microbacterium pseudoresistens CC-5209^T (97.6%). The dDDH (digital DNA-DNA hybridization) values between KUDC0405^T and M. bovistercoris NEAU-LLE^T and M. pseudoresistens CC-5209^T were below 17.3% and 17.5%, respectively. The ANI (average nucleotide identity) values among strains KUDC0405^T, M. bovistercoris NEAU-LLE^T, and M. pseudoresistens CC-5209^T were 86.6% and 80.7%, respectively. The AAI (average amino acid identity) values were 64.66% and 64.97%, respectively, between KUDC0405^T and its closest related type strains. The genome contained 3,596 CDCs, three rRNAs, 46 tRNAs, and three non-coding RNAs (ncRNAs). The genomic DNA GC content was 70.4%. The polar lipids included diphosphatydilglycerol, glycolipid, phosphatydilglycerol, and unknown phospholipid, and the major fatty acids were anteiso-C_17:0 and iso-C_16:0. Strain KUDC0405^T contained MK-12 as the major menaquinone. Based on genotypic, phylogenetic, and phenotypic properties, strain KUDC0405^T should be considered a novel species within the genus Microbacterium, for which we propose the name M. elymi sp. nov., and the type strain as KUDC0405^T (=KCTC 49411^T, =CGMCC1.18472^T).

Microbacterium chengjingii sp. nov. and Microbacterium fandaimingii sp. nov., isolated from bat faeces of Hipposideros and Rousettus species

Four aerobic, Gram-stain-positive, rod-shaped bacteria (HY60^T, HY54, HY82^T and HY89) were isolated from bat faeces of Hipposideros and Rousettus species collected in PR China. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the four novel strains formed two separate but adjacent subclades close to Microbacterium agarici CGMCC 1.12260^T (97.6-97.7 % similarity), Microbacterium humi JCM 18706^T (97.3-97.5 %) and Microbacterium lindanitolerans JCM 30493^T (97.3-97.4 %). The 16S rRNA gene sequence similarity was 98.3 % between strains HY60^T and HY82^T, and identical within strain pairs HY60^T/HY54 and HY82^T/HY89. The DNA G+C contents of strains HY60^T and HY82^T were 61.9 and 63.3 mol%, respectively. The digital DNA-DNA hybridization and average nucleotide identity values between each novel strain and their closest relatives were all below the 70 % and 95-96 % thresholds for species delimitation, respectively. All four novel strains contained anteiso-C_{15 : 0}, anteiso-C_{17 : 0}, iso-C_{16 : 0} and iso-C_{15 : 0} as the main fatty acids, MK-11 and MK-12 as the major respiratory quinones, and diphosphatidylglycerol, phosphatidylglycerol and one unidentified glycolipid as the predominant polar lipids. The cell-wall peptidoglycan was of B type and contained alanine, glutamate, glycine and ornithine. The acyl type of the muramic acid was glycolyl. The whole-cell sugars were rhamnose and ribose. Based on the foregoing polyphasic analyses, it was concluded that the four uncharacterized strains represented two novel species of the genus Microbacterium, for which the names Microbacterium chengjingii sp. nov. [type strain HY60^T (=CGMCC 1.17468^T=GDMCC 1.1951^T=KACC 22102^T)] and Microbacterium fandaimingii sp. nov. [type strain HY82^T (=CGMCC 1.17469^T=GDMCC 1.1949^T=KACC 22101^T)] are proposed, respectively.

Complete Genome Sequence of Microbacterium sp. Strain SGAir0570, Isolated from Tropical Air Collected in Singapore

Microbacterium sp. strain SGAir0570 was isolated from air samples collected in Singapore. Its genome was assembled using single-molecule real-time sequencing and MiSeq short reads. It has one chromosome with a length of 3.38 Mb and one 59.2-kb plasmid. It contains 3,170 protein-coding genes, 48 tRNAs, and 6 rRNAs.

Microbacterium sp. strain SGAir0570 was isolated from air samples collected in Singapore. Its genome was assembled using single-molecule real-time sequencing and MiSeq short reads. It has one chromosome with a length of 3.38 Mb and one 59.2-kb plasmid. It contains 3,170 protein-coding genes, 48 tRNAs, and 6 rRNAs.

Genome-Based Taxonomic Classification of the Phylum Actinobacteria

The application of phylogenetic taxonomic procedures led to improvements in the classification of bacteria assigned to the phylum Actinobacteria but even so there remains a need to further clarify relationships within a taxon that encompasses organisms of agricultural, biotechnological, clinical, and ecological importance. Classification of the morphologically diverse bacteria belonging to this large phylum based on a limited number of features has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees. Here, draft genome sequences of a large collection of actinobacterial type strains were used to infer phylogenetic trees from genome-scale data using principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families, and genera, as well as many species and a few subspecies were shown to be in need of revision leading to proposals for the recognition of 2 orders, 10 families, and 17 genera, as well as the transfer of over 100 species to other genera. In addition, emended descriptions are given for many species mainly involving the addition of data on genome size and DNA G+C content, the former can be considered to be a valuable taxonomic marker in actinobacterial systematics. Many of the incongruities detected when the results of the present study were compared with existing classifications had been recognized from 16S rRNA gene trees though whole-genome phylogenies proved to be much better resolved. The few significant incongruities found between 16S/23S rRNA and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences. Similarly good congruence was found between the discontinuous distribution of phenotypic properties and taxa delineated in the phylogenetic trees though diverse non-monophyletic taxa appeared to be based on the use of plesiomorphic character states as diagnostic features.

Microbacterium sediminis sp. nov., a psychrotolerant, thermotolerant, halotolerant and alkalitolerant actinomycete isolated from deep-sea sediment

An aerobic, rod-shaped, Gram-positive, oxidase- and catalase-positive bacterial isolate, strain YLB-01T, was characterized using phenotypic and molecular taxonomic methods. 16S rRNA gene sequence analysis revealed that the isolate belonged to the genus Microbacterium and represented an evolutionary lineage that was distinct from recognized species of the genus Microbacterium . The isolate showed <97 % 16S rRNA gene sequence similarity with respect to the type strains of all of the members of the genus Microbacterium with validly published names. Cell-wall hydrolysate from the isolate contained the amino acids ornithine, alanine, glycine homoserine and glutamic acid, and the cell-wall sugars consisted of ribose, glucose and galactose. The main respiratory quinones were MK-8, 9, 10 and 11. The major cellular fatty acids were anteiso-C15 : 0 (38.5 %), anteiso-C17 : 0 (23.1 %) and C16 : 0 (18.9 %). The polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, an unidentified phospholipid and two unidentified glycolipids. The DNA G+C content of strain YLB-01T was 71 mol%. On the basis of the morphological, physiological and chemotaxonomic data and the results of comparative 16S rRNA gene sequence analysis, this isolate represents a novel species of the genus Microbacterium , for which the name Microbacterium sediminis sp. nov. is proposed. The type strain is YLB-01T ( = DSM 23767T = CCTCC AB2010363T = MCCC 1A06153T).

Microbacterium murale sp. nov., isolated from an indoor wall

A Gram-positive rod, designated 01-Gi-001T, was isolated from a wall colonized with moulds. The 16S rRNA gene sequence analysis clearly showed that the isolate belonged to the genus Microbacterium . On the basis of pairwise comparisons of 16S rRNA gene sequences, strain 01-Gi-001T was most closely related to Microbacterium hydrocarbonoxydans DSM 16089T (98.9 % sequence similarity), Microbacterium profundi Shh49T (98.7 %), Microbacterium phyllosphaerae DSM 13468T (98.3 %) and Microbacterium foliorum DSM 12966T (98.1 %). The diagnostic diamino acid of the peptidoglycan was ornithine. The major menaquinones detected were MK-13 and MK-12. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, one unknown phospholipid and one unknown glycolipid. The major fatty acids were anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0, which were in agreement with those reported for other members of the genus Microbacterium . Physiological and biochemical characteristics and DNA–DNA relatedness between strain 01-Gi-001T and the type strains of its closest phylogenetic neighbours showed clear differences. For this reason, strain 01-Gi-001T ( = DSM 22178T = CCM 7640T) is proposed as the type strain of a novel species, Microbacterium murale sp. nov.

Microbacterium amylolyticum sp. nov., isolated from soil from an industrial waste site

A Gram-staining-positive, heterotrophic, aerobic, non-motile, non-endospore-forming, yellow-coloured rod, designated strain N5(T), was isolated from a soil sample collected at an industrial waste site in Noida, on the outskirts of Delhi, India. In phylogenetic analyses based on 16S rRNA gene sequences, strain N5(T) was most closely related to members of established species in the genus Microbacterium (with sequence similarities of approximately 94.0-97.6 %), particularly Microbacterium indicum LMG 23459(T) (97.59 %) and Microbacterium gubbeenense LMG 19263(T) (97.18 %). In DNA-DNA hybridization studies, however, none of the DNA-DNA relatedness values between strain N5(T) and members of the genus Microbacterium exceeded 11.3 %. The genomic DNA G+C content of the novel strain was 68 mol%. The chemotaxonomic characteristics of strain N5(T), which had MK-11 and MK-10 as its major menaquinones and anteiso-C(15 : 0) (45 %), anteiso-C(17 : 0) (37 %), iso-C(16 : 0) (8.5 %) and C(16 : 0) (4.5 %) as its predominant fatty acids, were consistent with classification in the genus Microbacterium. Peptidoglycan in the novel strain, which contained ornithine, alanine, glycine, homoserine, glutamic acid, 3-hydroxyglutamic acid, muramic acid and traces of N-glycolyl residues, was of type B2β. The polar lipid profile of strain N5(T) comprised diphosphatidylglycerol, phosphatidylglycerol and an unknown glycolipid. The novel strain's major cell-wall sugars were glucose and galactose. Based on the phylogenetic, DNA-DNA hybridization, chemotaxonomic and phenotypic data, strain N5(T) represents a novel species within the genus Microbacterium for which the name Microbacterium amylolyticum sp. nov. is proposed; the type strain is N5(T) (= DSM 24221(T) = CCM 7881(T)).

Microbacterium arthrosphaerae sp. nov., isolated from the faeces of the pill millipede Arthrosphaera magna Attems

A Gram-reaction-positive, rod-shaped bacterium, designated strain CC-VM-YT, was isolated from the faeces of the pill millipede Arthrosphaera magna Attems from India and was subsequently studied to determine its taxonomic position. Based on16S rRNA gene sequence similarities, the isolate clearly grouped with members of the genus Microbacterium. On the basis of pairwise comparisons of the 16S rRNA gene sequences, strain CC-VM-YT was most closely related to Microbacterium insulae DS-66T (98 %), Microbacterium hydrocarbonoxydans DSM 160809T (97.8 %) and Microbacterium hominis NBRC 15708T (97.9 %). The peptidoglycan contained the amino acids ornithine (Orn), alanine (Ala), glycine (Gly), homoserine (Hsr) and glutamic acid (Glu) in an approximate molar ratio of 1.0 : 0.8 : 2.2 : 0.8 : 0.3. In addition, substantial amounts of threo-3-hydroxy glutamic acid (Hyg) were detected, which is characteristic of peptidoglycan type B2β. The acyl type of the peptidoglycan was glycolyl. The menaquinones of strain CC-VM-YT were MK-13 (72 %), MK-12 (25 %) and MK-11 (3 %). The polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol, one unknown phospholipid and one unknown glycolipid. The fatty acid profile comprised anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0 as the major fatty acids, which was congruent with fatty acid profiles of other members of the genus Microbacterium. The results of physiological and biochemical tests as well as DNA–DNA hybridizations with the most closely related species, M. insulae, M. hydrocarbonoxydans and M. hominis, revealed clear phenotypic and genotypic differences between strain CC-VM-YT and other members of the genus Microbacterium. Based on these results, strain CC-VM-YT ( = DSM 22421T  = CCM 7681T) represents a new species of the genus Microbacterium, for which the name Microbacterium arthrosphaerae sp. nov. is proposed.

Microbacterium ginsengiterrae sp. nov., a beta-glucosidase-producing bacterium isolated from soil of a ginseng field

Strain DCY37(T) was isolated from a soil sample of a ginseng field in the Republic of Korea and characterized in order to determine its taxonomic position. Cells were Gram-staining-positive, heterotrophic, strictly aerobic, non-motile short rods. 16S rRNA gene sequence analysis revealed that strain DCY37(T) belongs to the genus Microbacterium. According to 16S rRNA gene sequence analysis, it is closely related to Microbacterium aerolatum DSM 14217(T) (98.8 %), Microbacterium hydrocarbonoxydans DSM 16089(T) (98.5 %), Microbacterium natoriense JCM 12611(T) (98.5 %), Microbacterium foliorum (98.4 %) and Microbacterium phyllosphaerae (98.3 %). However, DNA-DNA hybridization studies showed reassociation values of less than 70 % between representative strains and DCY37(T). The DNA G+C content was 64.5&emsp14;mol%. Strain DCY37(T) possessed chemotaxonomic markers that were consistent with classification in the genus Microbacterium, i.e. MK-12 and MK-13 as the major menaquinones and anteiso-C(15 : 0), anteiso-C(17 : 0) and iso-C(16 : 0) as the predominant cellular fatty acids. The major cell wall sugars were ribose, xylose and galactose. The diamino acid in cell-wall hydrolysates of strain DCY37(T) was ornithine and major cell-wall amino acids were alanine, glycine, d-glutamic acid and serine. The major polar lipids were glycolipid, phosphatidylglycerol, diphosphatidylglycerol and unknown aminolipids. Based on these data, DCY37(T) (=KCTC 19526(T) =JCM 15516(T)) should be classified as the type strain of a novel species of the genus Microbacterium, for which the name Microbacterium ginsengiterrae sp. nov. is proposed.