Rice is a symbol of life and a representation of prosperity in South Korea. However, studies on the diversity of the bacterial communities in the rhizosphere of rice plants are limited. In this study, four bundles of root samples were collected from the same rice field located in Goyang, South Korea. These were systematically analyzed to discover the diversity of culturable bacterial communities through culture-dependent methods. A total of 504 culturable bacteria were isolated and evaluated for their plant growth-promoting abilities in vitro. Among them, Arthrobacter sp. GN70 was selected for inoculation into the rice plants under laboratory and greenhouse conditions. The results showed a significantly positive effect on shoot length, root length, fresh plant weight, and dry plant weight. Moreover, scanning electron microscopic (SEM) images demonstrated the accumulation of bacterial biofilm networks at the junction of the primary roots, confirming the root-colonizing ability of the bacterium. The strain also exhibited a broad spectrum of in vitro antimicrobial activities against bacteria and fungi. Here, we first report the rice plant growth-promoting ability of the Arthrobacter species with the biofilm-producing and antimicrobial activities against plant and human pathogens. Genome analyses revealed features attributable to enhance rice plant growth, including the genes involved in the synthesis of plant hormones, biofilm production, and secondary metabolites. This study revealed that the rhizobacteria isolated from the roots of rice plants have dual potential to be utilized as a plant growth promoter and antimicrobial agent.

Two bacterial strains, designated MJB4^T and SJ7^T, were isolated from water samples collected from Jeongbang Falls on Jeju Island, Republic of Korea. Phylogenetic analysis of 16S rRNA gene sequences indicated that the two strains belonged to the genera Nocardioides and Hyunsoonleella , owing to their high similarities to Nocardioides jensenii DSM 29641^T (97.5 %) and Hyunsoonleella rubra FA042 ^T (96.3 %), respectively. These values are much lower than the gold standard for bacterial species (98.7 %). The average nucleotide identity values between strains MJB4^T, SJ7^T and the reference strains, Nocardioides jensenii DSM 29641^T, Nocardioides daejeonensis MJ31^T and Hyunsoonleella flava T58^T were 77.2, 75.9 and 75.4 %, respectively. Strains MJB4^T and SJ7^T and the type strains of the species involved in system incidence have average nucleotide identity and average amino acid threshold values of 60.1–82.6 % for the species boundary (95–96 %), which confirms that strains MJB4^T and SJ7^T represent two new species of genus Nocardioides and Hyunsoonleella , respectively. Based on phylogenetic and phenotypic data, strains MJB4^T and SJ7^T are considered to represent novel species of the genus Nocardioides and Hyunsoonleella , respectively, for which the names Nocardioides donggukensis sp. nov. (type strain MJB4^T=KACC 21724^T=NBRC 114402^T) and Hyunsoonleella aquatilis sp. nov., (type strain SJ7^T=KACC 21715^T=NBRC 114486^T) have been proposed.

In this study, four novel bacterial strains, USB13^T, AW1^T, GTP1^T, and HM2^T, were isolated from various environments in Busan and Jeju Island, Republic of Korea. The 16S rRNA sequencing results indicated that the four novel strains belong to the genusRamlibacter.All four strains were tested for their potential cellulolytic properties, where strain USB13^Twas identified as the only novel bacterium and the first within its genus to show cellulolytic activity. When tested, the highest activities of endoglucanase, exoglucanase,β-glucosidase, and filter paper cellulase (FPCase) were 1.91 IU/mL, 1.77 IU/mL, 0.76 IU/mL, and 1.12 IU/mL, respectively at pH 6.0. Comparisons of draft whole genome sequences (WGS) were also made using average nucleotide identity, digital DNA-DNA hybridization values, and average amino acid identity values, while whole genome comparison was visualized using the BLAST Ring Image Generator. The G + C contents of the strains ranged from 67.9 to 69.9%, while genome sizes ranged from 4.31 to 6.15 Mbp. Based on polyphasic evidence, the novel strains represent four new species within the genusRamlibacter, for which the namesRamlibacter cellulosilyticussp. nov. (type strain, USB13^T = KACC 21656^T = NBRC 114839^T)Ramlibacter aurantiacussp. nov. (type strain, AW1^T = KACC 21544^T = NBRC 114862^T),Ramlibacter albussp. nov. (type strain, GTP1^T = KACC 21702^T = NBRC 114488^T), andRamlibacter pallidussp. nov. (type strain, HM2^T = KCTC 82557^T = NBRC 114489^T) are proposed.

A Gram-negative, moderately halophilic bacterium, designated as strain Y3S6^T, was isolated from a surface seawater sample collected from Dongangyoeng cave, Udo-myeon, Jeju-si, Jeju-do, Repulic of Korea. Cells of strain Y3S6^T were aerobic, rod-shaped, non-sporulated, yellow, catalase- negative, oxidase-negative and motile with one polar flagellum. Growth of strain Y3S6^T occurred at 15–40 °C (optimum: 25–30 °C), at pH 6.0–9.0 (optimum: pH 7.0) and in the presence of 0–13% NaCl (optimum: 1–6 %, w/v). The novel strain was able to produce carotenoids. Its chemotaxonomic and morphological characteristics were consistent with those of members of the genus Halomonas . Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain Y3S6^T formed a clade with Halomonas pellis L5^T (98.97 %) and Halomonas saliphila LCB169^T(98.90%). The average nucleotide identity and digital DNA–DNA hybridization values of strain Y3S6^T with the most closely related strains for which whole genomes are publicly available were 82.3–85.2% and 62.8–66.1 %, respectively. The major fatty acids in strain Y3S6^T were C_16 : 0, C_19 : 0 cyclo ω8c and summed feature 8 (composed of C_18 : 1 ω7c and/or C_18 : 1 ω6c), and the predominant quinone was Q-9. Its polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two unidentified phosphoglycolipid, one unidentified phosphoaminoglycolipid and one unidentified phospholipid. The genomic DNA G+C content based on the draft genome sequence was 64.2 mol%. The results of physiological and biochemical tests and 16S rRNA sequence analysis clearly revealed that strain Y3S6^T represents a novel species in the genus Halomonas , for which the name Halomonas antri sp. nov. has been proposed. The type strain is Y3S6^T (=KACC 21536^T=NBRC 114315=TBRC 15164^T).

A starch-degrading novel strain, designated as strain ITR2^T, was isolated from a soil sample collected from a garden near Dongguk University located in Goyang, Republic of Korea. The strain was identified as Gram-stain-positive, rod-shaped, and motile by means of peritrichous flagella. Moreover, 16S rRNA gene analysis revealed the novel strain to form a separate clade with Tumebacillus permanentifrigoris Eur1 9.5^T (98.3 %) while also clustering with Tumebacillus flagellatus GST4^T (97.9 %). Strain ITR2^T grew optimally at temperatures of 20–30 °C, at pH 6.0–7.0 and at NaCl concentrations of 0–1 %. The sole quinone was menaquinone-7 and the cell-wall peptidoglycan comprised alanine, aspartic acid, glutamic acid, lysine and meso-diaminopimelic acid (type-A1γ peptidoglycan). The major fatty acids (>10%) of the novel strain were C_16 : 0, iso-C_14 : 0, iso-C_15 : 0 and anteiso-C_15 : 0, while the major polar lipids were phosphatidylmonomethylethanolamine, phosphatidylethanolamine, phosphatidylglycerol and one unidentified phospholipid. Other polar lipids of the novel strain included, two unidentified glycolipids, three unidentified phospholipids and one unidentified lipid. The in silico DNA–DNA hybridization values between strain ITR2^T and its reference strains ( T. permanentifrigoris DSM 18773^T and T. flagellatus GST4^T) were 21.3 and 23.9 %, respectively, while the average nucleotide identity values were 78.5 and 81.2 %, respectively. The genomic DNA G+C content was 54.9 mol%. Based on the phylogenetic, chemotaxonomic and genomic data obtained in the present study, we propose Tumebacillus amylolyticus sp. nov. to be a novel species within the genus Tumebacillus . The type strain is ITR2^T (=KCTC 43280^T=NBRC 114753^T).

Microbial exopolysaccharides (EPSs) have attracted attention from several fields due to their high industrial applicability. In the present study, rhizosphere strain CJ11^T was isolated from the root of Glycine max L. in Goyang-si, Republic of Korea, and a novel exopolysaccharide was purified from the Lysobacter sp. CJ11^T fermentation broth. The exopolysaccharide’s average molecular weight was 0.93 × 10⁵ Da. Its monosaccharide composition included 72.2% mannose, 17.2% glucose, 7.8% galactose, and 2.8% arabinose. Fourier-transform infrared spectroscopy identified the exopolysaccharide carbohydrate polymer functional groups, and the structural properties were investigated using nuclear magnetic resonance. In addition, a microstructure of lyophilized EPS was determined by scanning electron microscopy. Using thermogravimetric analysis, the degradation of the exopolysaccharide produced by strain CJ11^T was determined to be 210 °C. The exopolysaccharide at a concentration of 4 mg/mL exhibited 2,2-diphenyl-1-picrylhydrazyl free-radical-scavenging activity of 73.47%. Phylogenetic analysis based on the 16S rRNA gene sequencing results revealed that strain CJ11^T was a novel isolate for which the name Lysobacter soyae sp. nov is proposed.