Species Of Microbacterium Research Articles

Complete genome sequence of Microbacterium sp. che218, an endophyte isolated from Vitis vinifera cv. Chardonnay shoot xylem.

Microbacterium species are bacterial endophytes that live inside plants. We report the complete genome sequence of Microbacterium sp. che218, an endophyte isolated from the shoot xylem of the wine grape Vitis vinifera cv. Chardonnay.

Anthocyanin Accumulation in Grape Berry Skin Promoted by Endophytic Microbacterium sp. che218 Isolated from Wine Grape Shoot Xylem.

Grape berry skin coloration is a key determinant of the commercial value of red wines. Global warming caused by climate change has inhibited anthocyanin biosynthesis in berry skins, leading to poor coloration. Through two-year field experiments, the endophyte che218 isolated from grape shoot xylem promoted anthocyanin accumulation in berry skins. The che218 enhanced anthocyanin biosynthesis in grapevine cultured cells. In the 2022 growing season, applying che218 to grape bunches enhanced anthocyanin accumulation in berry skins on day 20 post-treatment. However, the anthocyanin accumulation enhancing effect of che218 became negligible at harvest. In the 2023 growing season, che218 enhanced anthocyanin accumulation in berry skins on day 15 post-treatment and at harvest (day 30 post-treatment) and also upregulated the transcription of mybA1 and UFGT, two genes that regulate anthocyanin biosynthesis in berry skins. Whole genome sequencing demonstrated that che218 is an unidentified Microbacterium species. However, it remains unknown how che218 is involved in the biosynthesis of anthocyanin in berry skins. This study provides insights into the development of an eco-friendly endophyte-mediated technique for improving grape berry skin coloration, thereby mitigating the effects of global warming on berry skin coloration.

Microbacterium rhizophilus sp. nov., an indole acetic acid-producing actinobacterium isolated from rhizosphere soil.

A novel gram-stain-positive, short rod, aerobic, non-motile and non-spore-forming actinobacterial strain, designated GXG1230T was isolated from the rhizosphere soil of a coastal mangrove forest in Beihai city, Guangxi Zhuang Autonomous Region, PR China. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain GXG1230T was affiliated with the genus Microbacterium. Additionally, it demonstrated a high degree of similarity to Microbacterium paludicola US15T (97.9%) and Microbacterium marinilacus YM11-607T (97.3%). Chemotaxonomic characteristics showed that the whole-cell sugars were glucose, xylose, rhamnose and galactose. Menaquinones MK-11 and MK-12 were detected as respiratory quinones. Lysine was found in the peptidoglycan hydrolysate and the polar lipids were diphosphatidylglycerol, one phospholipid and two unidentified glycolipid. The major fatty acids were anteiso-C15:0, iso-C16:0 and anteiso-C17:0. The strain GXG1230T exhibited a genomic DNA G + C content of 71.7%. Furthermore, the average nucleotide identity values of GXG1230T with the reference strains were 75.4% and 81.9%, respectively, while the digital DNA-DNA hybridization values were 20.1% and 25.0%. Based on physiological, chemotaxonomic and phylogenetic information, strain GXG1230T is considered to represent a novel species of the genus Microbacterium, for which the name Microbacterium rhizophilus sp.nov is proposed, with GXG1230T (= MCCC 1K09302T = KCTC 59252T) as the type strain.

In silico and experimental characterization of a new polyextremophilic subtilisin-like protease from Microbacterium metallidurans and its application as a laundry detergent additive.

Considering the current growing interest in new and improved enzymes for use in a variety of applications, the present study aimed to characterize a novel detergent-stable serine alkaline protease from the extremophilic actinobacterium Microbacterium metallidurans TL13 (MmSP) using a combined in silico and experimental approach. The MmSP showed a close phylogenetic relationship with high molecular weight S8 peptidases of Microbacterium species. Moreover, its physical and chemical parameters computed using Expasy's ProtParam tool revealed that MmSP is hydrophilic, halophilic and thermo-alkali stable. 3D structure modelling and functional prediction of TL13 serine protease resulted in the detection of five characteristic domains: [catalytic subtilase domain, fibronectin (Fn) type-III domain, peptidase inhibitor I9, protease-associated (PA) domain and bacterial Ig-like domain (group 3)], as well as the three amino acid residues [aspartate (D182), histidine (H272) and serine (S604)] in the catalytic subtilase domain. The extremophilic strain TL13 was tested for protease production using agricultural wastes/by-products as carbon substrates. Maximum enzyme activity (390U/gds) was obtained at 8th day fermentation on potato peel medium. Extracellular extract was concentrated and partially purified using ammonium sulfate precipitation methodology (1.58 folds purification fold). The optimal pH, temperature and salinity of MmSP were 9, 60°C and 1M NaCl, respectively. The MmSP protease showed broad pH stability, thermal stability, salt tolerance and detergent compatibility. In order to achieve the maximum stain removal efficacy by the TL 13 serine protease, the operation conditions were optimized using a Box-Behnken Design (BBD) with four variables, namely, time (15-75min), temperature (30-60°C), MmSP enzyme concentration (5-10U/mL) and pH (7-11). The maximum stain removal yield (95 ± 4%) obtained under the optimal enzymatic operation conditions (treatment with 7.5U/mL of MmSP during 30min at 32°C and pH9) was in good agreement with the value predicted by the regression model (98 ± %), which prove the validity of the fitted model. In conclusion, MmSP appears to be a good candidate for industrial applications, particularly in laundry detergent formulations, due to its high hydrophilicity, alkali-halo-stability, detergent compatibility and stain removal efficiency.

Microbacterium algihabitans sp. nov., Microbacterium phycohabitans sp. nov., and Microbacterium galbum sp. nov., isolated from dried beach seaweeds.

Three actinobacterial strains, KSW2-21T, KSW2-29T and KSW4-17T, were isolated from dried seaweeds collected around Gwakji Beach in Jeju, Republic of Korea. Their taxonomic positions were determined based on genomic, physiological and morphological characteristics. The isolates were Gram-positive, aerobic, non-motile, rod-shaped bacteria characterized by the following chemotaxonomic features: ornithine as the cell wall diamino acid, the N-glycolyl type of murein, MK-11 as the predominant menaquinone, polar lipids including diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and four unidentified phospholipids, with anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0 as the the major fatty acids. The 16S rRNA gene phylogeny showed that the novel strains formed three distinct sublines within the genus Microbacterium. Strain KSW4-17T formed a tight cluster with the type strain of Microbacterium hydrothermale, while strains KSW2-21T and KSW2-29T occupied distinct positions between the type strains of M. hydrothermale and Microbacterium testaceum. Strains KSW4-17T and KSW2-29T showed 99.9 % rRNA gene sequence similarity to M. hydrothermale CGMCC 1.12512T, while strain KSW2-21T revealed 99.4 % 16S rRNA gene sequence similarity to the type strains of M. hydrothermale and M. testaceum. The genome sizes and genomic G+C contents of the three isolates ranged from 3.44 to 3.74 Mbp and from 70.3 to 70.8 mol%, respectively. The phylogenomic tree based on 92 core gene sequences exhibited similar topologies to the 16S rRNA gene phylogeny. The comparison of overall genomic relatedness indices, such as average nucleotide indentity and digital DNA-DNA hybridization, supported that the isolates represent three new species of the genus Microbacterium. Based on the results obtained here, Microbacterium algihabitans sp. nov. (type strain, KSW2-21T=KACC 23322T=DSM 116381T), Microbacterium phycohabitans sp. nov. (type strain KSW2-29T=KACC 22350T=NBRC 115221T) and Microbacterium galbum sp. nov. (type strain, KSW4-17T=KACC 23323T=DSM 116383T) are proposed.

Trifolium repens L. recruits root-associated Microbacterium species to adapt to heavy metal stress in an abandoned Pb-Zn mining area

Root-associated microbiota provide great fitness to hosts under environmental stress. However, the underlying microecological mechanisms controlling the interaction between heavy metal-stressed plants and the microbiota are poorly understood. In this study, we screened and isolated representative amplicon sequence variants (strain M4) from rhizosphere soil samples of Trifolium repens L. growing in areas with high concentrations of heavy metals. To investigate the microecological mechanisms by which T. repens adapts to heavy metal stress in abandoned mining areas, we conducted potting experiments, bacterial growth promotion experiments, biofilm formation experiments, and chemotaxis experiments. The results showed that high concentrations of heavy metals significantly altered the rhizosphere bacterial community structure of T. repens and significantly enriched Microbacterium sp. Strain M4 was demonstrated to significantly increased the biomass and root length of T. repens under heavy metal stress. Additionally, L-proline and stigmasterol could promote bacterial growth and biofilm formation and induce chemotaxis for strain M4, suggesting that they are key rhizosphere secretions of T. repens for Microbacterium sp. recruitment. Our results suggested that T. repens adapted the heavy metal stress by reshaping rhizosphere secretions to modify the rhizosphere microbiota.

Microbacterium salsuginis sp. nov., a halotolerant actinobacterium with antimicrobial activity.

A novel Gram-staining-positive actinobacterium with antimicrobial activity, designated CFH 90308T, was isolated from the sediment of a salt lake in Yuncheng, Shanxi, south-western China. The isolate exhibited the highest 16S rRNA gene sequence similarities to Microbacterium yannicii G72T, Microbacterium hominis NBRC 15708T and Microbacterium xylanilyticum S3-ET (98.5, 98.4 and 98.2 %, respectively), and formed a separate clade with M. xylanilyticum S3-ET in phylogenetic trees. The strain grew at 15-40 ºC, pH 6.0-8.0 and could tolerate NaCl up to a concentration of 15 % (w/v). The whole genome of strain CFH 90308T consisted of 4.33 Mbp and the DNA G+C content was 69.6 mol%. The acyl type of the peptidoglycan was glycolyl and the whole-cell sugars were galactose and mannose. The cell-wall peptidoglycan mainly contained alanine, glycine and lysine. The menaquinones of strain CFH 90308T were MK-12, MK-13 and MK-11. Strain CFH 90308T contained anteiso-C15:0, anteiso-C17:0, iso-C16:0 and iso-C15:0 as the predominant fatty acids. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between CFH 90308T and the other species of the genus Microbacterium were found to be low (ANIb <81.3 %, dDDH <25.6 %). The secondary metabolite produced by strain CFH 90308T showed antibacterial activities against Bacillus subtilis, Pseudomonas syringae, Aeromonas hydrophila and methicillin-resistant Staphylococcus aureus. Based on genotypic, phenotypic and chemotaxonomic results, the isolate is considered to represent a novel species of the genus Microbacterium, for which the name Microbacterium salsuginis sp. nov. is proposed. The type strain is CFH 90308T (=DSM 105964T=KCTC 49052T).

Microbacterium horticulturae sp. nov., a novel actinobacterium isolated from flowerpot soil.

Strain CJN36-1NT, a Gram-stain-positive, non-flagellated, strictly aerobic and short rod-shaped bacterium, was isolated from flowerpot soil sampled in the Jeonju region of the Republic of Korea. Based on 16S rRNA gene sequences and the resulting phylogenetic tree, the strain belonged to the genus Microbacterium. Strain CJN36-1NT contained a chromosome of 3.6 Mbp with a G+C content of 68.5 mol%. The strain grew at 10-37 °C (optimally at 28 °C), at pH 5.0-8.0 (optimally at pH 8.0), and in the presence of 0-7 % NaCl (w/v; optimally with 0 % NaCl). Digital DNA-DNA hybridization, average nucleotide identity and average amino acid identity values between strain CJN36-1NT and its closest related species, Microbacterium protaetiae DFW100M-13T, were 82.0, 81.2, and 23.2 %, respectively. We propose naming this novel species Microbacterium horticulturae sp. nov., with CJN36-1NT (=KACC 23027T=NBRC 116065T) as the type strain.

Microbacterium abyssi sp. nov. and Microbacterium limosum sp. nov., two new species of the genus Microbacterium, isolated from deep-sea sediment samples.

Two Gram-positive, non-motile, short rod-shaped actinomycete strains, designated as A18JL241T and Y20T, were isolated from deep-sea sediment samples collected from the Southwest Indian Ocean and Western Pacific Ocean, respectively. Both of the isolates were able to grow within the temperature range of 5-40 °C, NaCl concentration range of 0-7 % (w/v) and at pH 6.0-12.0. The two most abundant cellular fatty acids of both strains were anteiso-C15 : 0 and anteiso-C17 : 0. The major polar lipid contents of the two strains were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and one unidentified glycolipid. These two strains shared common chemotaxonomic features comprising MK-10 and MK-12 as the respiratory quinones. The genomic DNA G+C contents of the two strains were 68.1 and 70.4 mol%, respectively. The 16S rRNA gene phylogeny showed that the novel strains formed two distinct sublines within the genus Microbacterium. Strain A18JL241T was most closely related to the type strain of Microbacterium tenebrionis KCTC 49593T (98.8 % sequence similarity), whereas strain Y20T formed a tight cluster with the type strain of Microbacterium schleiferi NBRC 15075T (99.0 %). The orthologous average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values with the type strains of related Microbacterium species were in the range of 74.1-89.1 % and 19.4-36.9 %, respectively, which were below the recognized thresholds of 95-96 % ANI and 70 % dDDH for species definition. Based on the results obtained here, it can be concluded that strains A18JL241T and Y20T represent two novel species of the genus Microbacterium, for which the names Microbacterium abyssi sp. nov. (type strain A18JL241T=JCM 33956T=MCCC 1A16622T) and Microbacterium limosum sp. nov. (type strain Y20T=JCM 33960T=MCCC 1A16747T) are proposed.

Persistent bacteremia caused by Ralstonia pickettii and Microbacterium: a case report

BackgroundRalstonia pickettii is a low virulent, gram-negative bacillus that is rarely associated with human infections and may cause bacteremia. Microbacterium species are gram-positive coryneforms that are generally considered as a contaminant in Gram staining of blood cultures, especially when the time to positivity is longer than 48 h. Both these bacterial species are emerging opportunistic pathogens that may occasionally cause serious infections and even life-threatening health conditions.Case presentationHere, we report the case of a patient with bacteremia caused by both R. pickettii and Microbacterium. We advocate for providers to order rapid antibiotic susceptibility testing, since our patient’s suffered two kinds of rare pathogens with the opposite of drug sensitivity results to imipenem.ConclusionsOur case present a patient suffered septic shock caused by R. pickettii and Microbacterium. Improving the antibiotic management based on the result of antimicrobial susceptibility tests is the key of successful treatment.

Auxin production and plant growth promotion by Microbacterium albopurpureum sp. nov. from the rhizoplane of leafless Chiloschista parishii Seidenf. orchid.

The strains of the genus Microbacterium, with more than 150 species, inhabit diverse environments; plant-associated bacteria reveal their plant growth-promoting activities due to a number of beneficial characteristics. Through the performance of diverse techniques and methods, including isolation of a novel Microbacterium strain from the aerial roots of leafless epiphytic orchid, Chiloschista parishii Seidenf., its morphological and biochemical characterization, chemotaxonomy, phylogenetic and genome analysis, as well as bioassays and estimation of its auxin production capacity, a novel strain of ET2T is described. Despite that it shared 16S rRNA gene sequence similarity of 99.79% with Microbacterium kunmingense JXJ CY 27-2T, so they formed a monophyletic group on phylogenetic trees, the two strains showed clear divergence of their genome sequences. The average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA-DNA hybridization (dDDH) values of ET2T differed greatly from phylogenetically close JXJ CY 27-2T. Based on the differences being below the threshold for species similarity, together with the unique chemotaxonomic characteristics, strain ET2T represents a novel species of the genus Microbacterium. Several genes, putatively involved in auxin biosynthesis were predicted. This strain revealed obvious plant growth-promoting activities, including diazotrophy and biosynthesis of tryptophan-dependent auxins (indole-3-acetic and indole-3-pyruvic acids). Microbial auxins directly stimulated the rhizogenesis, so that the ET2T-inoculated seeds of wheat, cucumber and garden cress showed evident promotion in their growth and development, both under optimal and under cold stress conditions. Based on phenotypic, chemotypic and genotypic evidences, the strain ET2T belongs to the genus Microbacterium, order Micrococcales, class Actinomycetes, and it represents a novel species, for which the name Microbacterium albopurpureum sp. nov. is proposed, with strain ET2T (VKPM Ac-2212, VKM Ас-2998) as the type strain.

Complete genome sequence of new Microbacterium sp. strain ET2, isolated from roots of leafless orchid.

Whole-genome sequence of ET2 strain, isolated from the roots of leafless orchid, constitutes a single circular chromosome of 3,604,840 bp (69.44% G + C content). BLAST+-based average nucleotide identity (ANIb) and digital DNA-DNA hybridization values indicate that ET2 may be a novel Microbacterium species. Genes putatively involved in plant-microbial interactions were predicted.

Description of Microbacterium dauci sp. nov., a plant growth hormone indoleacetic acid-producing and nitrogen-fixing bacterium isolated from carrot rhizosphere soil.

A plant growth hormone indoleacetic acid-producing strain LX3-4T was isolated from a carrot rhizosphere soil sample collected in Shandong Province, China. It is Gram-stain-positive, non-motile, and has irregular short rod-shaped cells. LX3-4T shared high 16S rRNA gene sequence identity with Microbacterium oleivorans DSM 16091T (99.4%), M. testaceum NBRC 12675T (98.6%), M. marinum DSM 24947T (98.5%), M. resistens NBRC 103078T (98.4%), and M. paraoxydans NBRC 103076T (98.3%). Phylogenetic analysis based on the concatenated gene sequences of 16S rRNA gene, housekeeping genes gryB and rpoB also showed the distinction between strain LX3-4T and other Microbacterium species. Furthermore, analysis of the average nucleotide identities (ANI), the average amino acid identity (AAI), and the digital DNA-DNA hybridization (dDDH) values between strain LX3-4T and its relatives revealed that strain LX3-4T represents a distinct species. The genomic DNA G + C content of the strain is 69.5%. It can grow at 25-37°C (optimum 37°C), pH 5.0-10.0 (optimum pH 6.0-8.0), and the range of NaCl concentration is 0-7% (w/v) (optimum 1-5%). The colonies on agar plates are smooth, translucent, and pale yellow. The main cellular fatty acids of strain LX3-4T are anteiso-C15:0, anteiso-C17:0, and iso-C16:0. The predominant respiratory quinones are MK-12 and MK-11. Diphosphatidylglycerol, phosphatidylglycerol, an unidentified glycolipid, and an unidentified phosphoglycolipid are major polar lipids. The cell-wall sugar of strain LX3-4T is glucose. The cell-wall peptidoglycan contains glycine, alanine, lysine, and glutamic acid. In addition, this strain carries nitrogen fixation genes and can grow in nitrogen-free medium. Based on the polyphasic data, strain LX3-4T represents a novel species of the genus Microbacterium, for which the name Microbacterium dauci sp. nov. is proposed with strain LX3-4T (= CCTCC AB 2023103T = LMG 33159T) designated as the type strain.

Microbacterium aquilitoris sp. nov. and Microbacterium gwkjiense sp. nov., isolated from beach.

Three Gram-reaction-positive bacterial strains, designated KSW-18T, KSW2-22, and KSW4-11T, were isolated from seawater, and two dried seaweed samples collected at Gwakji Beach in Jeju, Republic of Korea, respectively, and their taxonomic positions were examined by a polyphasic approach. The 16S rRNA gene phylogeny showed that strain KSW4-11T was tightly associated with Microbacterium oleivorans NBRC 103075T, while strains KSW-18T and KSW2-22 formed a distinctive subline at the base of a clade including the above two strains. The three isolates showed high sequence similarity with one another (99.7-99.9%; 1-4 nt differences) and Microbacterium oleivorans (99.8-99.9%; 1-3 nt differences). The chemotaxonomic features were typical for the genus Microbacterium; Lysine as the diagnostic diamino acid and N-glycolylated muramic acid of the peptidoglycans, the predominant menaquinones of MK-11, MK-10 and MK-12, the major fatty acids of anteiso-C15:0 and anteiso-C17:0, and the major polar lipids including diphosphatidylglycerol, phosphatidylglycerol, and two or three unidentified glycolipids. In core genome-based phylogenetic tree, strains KSW-18T and KSW2-22 were closely associated with Microbacterium oleivorans NBRC 103075T, while strain KSW4-11T formed a distinctive subline at the base of a clade including the above three strains, in contrast to the 16S rRNA gene tree. Strains KSW-18T and KSW2-22 shared an OrthoANIu of 98.6% and a digital DNA-DNA hybridization of 87.6% with each other, representing that they were strains of a species, while the OrthoANIu and digital DNA-DNA hybridization values between strains KSW-18T and KSW4-11T, and between both of these isolates and all members of the genus Microbacterium were ≤86.5% and ≤30.7%, respectively. The analyses of overall genomic relatedness indices and phenotypic distinctness support that the three isolates represent two new species of the genus Microbacterium. Based on the results obtained here, Microbacterium aquilitoris sp. nov. (type strain KSW-18T = KCTC 49623T = NBRC 115222T) and Microbacterium gwkjiense sp. nov. (type strain KSW4-11T = KACC 23321T = DSM 116380T) are proposed.

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 plantarum sp. nov. and Microbacterium thalli sp. nov., two endophytic metal-resistant bacteria isolated from Sphaeralcea angustifolia (Cav.) G. Don and Prosopis laevigata (Humb. et Bonpl. ex Willd) M.C. Johnston.

Four Gram-positive, aerobic, catalase- and oxidase-negative, rod-shaped, motile endophytic bacterial strains, designated NM3R9T, NE1TT3, NE2TL11 and NE2HP2T, were isolated from the inner tissues (leaf and stem) of Sphaeralcea angustifolia and roots of Prosopis laevigata. They were characterized using a polyphasic approach, which revealed that they represent two novel Microbacterium species. Phylogenetic analysis based on 16S rRNA gene sequencing showed that the species closest to NE2HP2T was Microbacterium arborescens DSM 20754T (99.6 %) and that closest to NM3R9T, NE2TL11 and NE2TT3 was Microbacterium oleivorans NBRC 103075T (97.4 %). The whole-genome average nucleotide identity value between strain NM3R9T and Microbacterium imperiale DSM 20530T was 90.91 %, and that between strain NE2HP2T and M. arborecens DSM 20754T was 91.03 %. Digital DNA-DNA hybridization showed values of less than 70 % with the type strains of related species. The polar lipids present in both strains included diphosphatidylglycerol, phosphatidylglycerol, glycolipids and unidentified lipids, whereas the major fatty acids included anteiso-C15 : 0, anteiso-C17 : 0, iso-C16 : 0 and C16 : 0. Whole-cell sugars included mannose, rhamnose and galactose. Strains NM3R9T and NE2HP2T showed physiological characteristics different from those present in closely related Microbacterium species. According to the taxonomic analysis, both strains belong to two novel species. The name Microbacterium plantarum sp. nov. is proposed for strain NE2HP2T (=LMG 30875T=CCBAU 101117T) and Microbacterium thalli sp. nov. for strains NM3R9T (=LMG 30873T=CCBAU 101116T), NE1TT3 (=CCBAU 101114) and NE2TL11 (=CCBAU 101115).

Comparative Genomic Analysis of Biofilm-Forming Polar Microbacterium sp. Strains PAMC22086 and PAMC21962 Isolated from Extreme Habitats.

The members of Microbacterium isolated from different environments are known to form peptidoglycan. In this study, we compared the biofilm-forming abilities of Microbacterium sp. PAMC22086 (PAMC22086), which was isolated from the soil in the South Shetland Islands and Microbacterium sp. PAMC21962 (PAMC21962), which was isolated from algae in the South Shetland Islands. The analysis of average nucleotide identity and phylogeny of PAMC22086 revealed a 97% similarity to Microbacterium oxydans VIU2A, while PAMC21962 showed a 99.1% similarity to Microbacterium hominis SGAir0570. For the comparative genomic analysis of PAMC22086 and PAMC21962, the genes related to biofilm formation were identified using EggNOG and KEGG pathway databases. The genes possessed by both PAMC22086 and PAMC21962 are cpdA, phnB, rhlC, and glgC, which regulate virulence, biofilm formation, and multicellular structure. Among the genes indirectly involved in biofilm formation, unlike PAMC21962, PAMC22086 possessed csrA, glgC, and glgB, which are responsible for attachment and glycogen biosynthesis. Additionally, in PAMC22086, additional functional genes rsmA, which is involved in mobility and polysaccharide production, and dksA, GTPase, and oxyR, which play roles in cell cycle and stress response, were identified. In addition, the biofilm-forming ability of the two isolates was examined in vivo using the standard crystal violet staining technique, and morphological differences in the biofilm were investigated. It is evident from the different distribution of biofilm-associated genes between the two strains that the bacteria can survive in different niches by employing distinct strategies. Both strains exhibit distinct morphologies. PAMC22086 forms a biofilm that attaches to the side, while PAMC21962 indicates growth starting from the center. The biofilm formation-related genes in Microbacterium are not well understood. However, it has been observed that Microbacterium species form biofilm regardless of the number of genes they possess. Through comparison between different Microbacterium species, it was revealed that specific core genes are involved in cell adhesion, which plays a crucial role in biofilm formation. This study provides a comprehensive profile of the Microbacterium genus's genomic features and a preliminary understanding of biofilm in this genus, laying the foundation for further research.

Description of Microbacterium neungamense sp. nov. isolated from a hot spring.

The Gram-positive, nonmotile, rod-shaped bacterium EF45044T was isolated from a hot spring in Chungju, South Korea. The strain was able to grow at concentrations of 0‒5% (w/v) NaCl, at pH 6.0‒10.0 and in the temperature range of 18‒50°C. Strain EF45044T showed the highest 16S rRNA gene sequence similarity (98.2%) with Microbacterium ketosireducens DSM 12510T, and the digital DNA‒DNA hybridization (dDDH), average amino acid identity (AAI), and average nucleotide identity (ANI) values were all lower than the accepted species threshold. Strain EF45044T contained MK‒12 and MK‒13 as the predominant respiratory quinones and anteiso‒C17:0, anteiso‒C15:0, and iso‒C16:0 as the major fatty acids. Diphosphatidylglycerol, phosphatidylglycerol, and glycolipid were detected as the major polar lipids. The cell-wall peptidoglycan contained ornithine. The DNA G + C content was 71.4mol%. Based on the polyphasic data, strain EF45044T (= KCTC 49703T) presents a novel species of the genus Microbacterium, for which the name Microbacterium neungamense sp. nov. is proposed.

Biological characteristics and antibacterial activity against gram-positive bacteria of Microbacterium sp. C21 isolated from soil

Most commercial antibiotics are derived from Streptomyces. The search for new potential microbial sources (non-Streptomyces) for antibacterial activity is proposed to prevent drug resistance by current pathogenic microbes. Strain C21 was isolated from soil, with small colonies (0.8-1.2 mm in size) on an intensive soil extract medium (ISEM). Sequence analysis of the 16S rRNA gene revealed strain C21 belongs to the group of bacteria that are difficult to cultivate, and is considered a candidate for novel species of genus Microbacterium. Except for R2A medium, strain C21 was only able to grow in nutrient-poor media such as NB/3, TSB/10, and R4/10. N-acetylglucosamine, maltose, D-glucose, L-proline, L-rhamnose, inositol, sodium acetate and 3-hydroxybutyric acid were suitable carbon sources for the growth of strain C21. Crude extract from fermentation liquid of strain C21 can inhibit Enterococcus faecalis CCARM 5168 at a concentration of 16 μg/ml, 8 μg/ml for E. faecalis CCARM 5171, 32 μg/ml for E. faecalis CCARM 5024, 64 μg/ml for E. faeciumCCARM 5025, 32 μg/ml for Streptococcus agalactiaeCCARM 4504, and 8 μg/ml for S. pyogenes CCARM 4520. Results of this study established a basis for future studies on finding potential antibacterial compounds from difficult-to-culture bacteria.

Microbacterium kunmingensis sp. nov., an attached bacterium of Microcystis aeruginosa.

A Gram-stain positive, aerobic, rod-shaped actinobacterial strain designated as JXJ CY 27-2T was isolated from the culture of Microcystis aeruginosa FACHB-905 (Maf) collected from Lake Kunming, southwest China. The isolate was catalase positive, oxidase negative, and able to grow at 10.0-44.0 °C, pH 5.0-10.0 and 0-5.0% NaCl. Based on the 16S rRNA gene sequences, JXJ CY 27-2T showed high similarities of 98.54-98.55% with Microbacterium invictum DSM 19600T, Microbacterium saccharophilum DSM 28107T, and Microbacterium aoyamense DSM 19461T, and less than 98.47% similarities with other members of the genus. Its major cellular fatty acids were anteiso-C17:0 and anteiso-C15:0. The predominant menaquinones were MK-11 and MK-12. The diagnostic diamino acid in the cell wall peptidoglycan was lysine. Whole cell sugars contained mannose, ribose, galactose, rhamnose and arabinose. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids, and an unidentified lipid. The DNA G + C content was 69.8%. The digital DNA-DNA hybridization and average nucleotide identity values between strain JXJ CY 27-2T and its three closest similar strains were 18.4-20.3% and 74.9-75.7%, respectively. Based on the above data, strain JXJ CY 27-2T was identified as a new species of the genus Microbacterium, for which the name Microbacterium kunmingensis sp. nov. is proposed. The type strain is JXJ CY 27-2T (=CGMCC 1.17506T = KCTC 49382T). Strain JXJ CY 27-2T could promote the growth of Maf by providing it with available phosphorus, nitrogen and probably other nutrients such as vitamins and indole-3-acetate.