Two novel Gram-negative, aerobic, asporogenous, motile, rod-shaped, orange and white pigmented, designated as LEGU1^T and G19^T, were isolated from the roots of rice plants, collected from Goyang, South Korea. Phylogenetic analysis based on their 16S rRNA gene sequences revealed that they belonged to the genus Devosia and formed a different lineage and clusters with different members of the genus Devosia. These strains shared common chemotaxonomic features. In particular, they had Q-10 as the sole quinone, phosphatidylglycerol, diphosphatidylglycerol as the principal polar lipids and C_16:0, C_18:1ω7c 11-methyl and summed feature 8 (comprising C_18:1ω7c/C_18:1ω6c) as the main fatty acids. The draft genome sequences of strains LEGU1^T and G19^T were 3,524,978 and 3,495,520 bp in size, respectively. Their average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values were 72.8–81.9% and 18.7–25.1%, respectively, with each other and type strains of related species belonging to the genus Devosia, suggesting that these two strains represent novel species. The G + C content of strains LEGU1^T and G19^T were 62.1 and 63.8%, respectively. Of the two strains, only LEGU1^T produced carotenoid and flexirubin-type pigment. Both strains produced siderophore and indole acetic acid (IAA) in the presence of l-tryptophan. Siderophore biosynthesis genes, auxin responsive genes and tryptophan biosynthesis genes were present in their genomes. The present study aimed to determine the detailed taxonomic positions of the strains using the modern polyphasic approach. Based on the results of polyphasic analysis, these strains are suggested to be two novel bacterial species within the genus Devosia. The proposed names are D. rhizoryzae sp. nov., and Devosia oryziradicis sp. nov., respectively. The plant growth promoting effects of these strains suggest that they can be exploited to improve rice crop productivity. The type strain of} D. rhizoryzae is LEGU1^T (KCTC 82712^T = NBRC 114485^T) and D. oryziradicis is G19^T (KCTC 82688^T = NBRC 114842^T).

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.

A yellow pigmented, Gram-stain-negative, strictly aerobic, rod-shaped, motile by means of gliding, catalase and oxidase positive bacterium, designated strain DS2-A^T, was isolated from soil. Growth was observed at 4–32°C (optimum, 28°C), pH 6–9 (optimum, 7.0), and with 0–0.25% (w/v) NaCl (optimum, 0%). Phylogenetic analysis of 16S rRNA gene sequence revealed that strain DS2-A^T belonged to the genus Flavobacterium and was most closely related to Flavobacterium aquatile LMG 4008^T (96.4%), Flavobacterium terrae DSM 18829^T (95.6%), Flavobacterium vireti THG-SM1^T (95.5%), Flavobacterium inkyongense IMCC27201^T (95.4%), Flavobacterium brevivitae TTM-43^T (95.2%), and Flavobacterium cucumis DSM 18830^T (95.2%). Strain DS2-A^T produces flexirubin-type pigments. The major fatty acids were iso-C_15:0, iso-C_17:0 3-OH, and iso-C_15:0 3-OH. The major respiratory quinone was identified as menaquinone-6. The major polar lipid was found to be phosphatidylethanolamine. The average nucleotide identity values between strain DS2-A^T and selected taxa, F. aquatile LMG 4008^T, F. terrae DSM 18829^T, and F. cucumis DSM 18830^T, were 72, 72.7, and 71.6%, respectively. The draft genome of strain DS2-A^T has a number of 14 contigs, scaffold N50 of 476,310 bp and a total size of 3,563,867 bp. Additionally, strain DS2-A^T contains 3,127 of gene, 41 of tRNA, 6 of rRNA, and 3 of ncRNA. The DNA G + C content of stain DS2-A^T was 40.7 mol%. Based on phylogenetic and phenotypic analyses, strain DS2-A^T is considered as a novel species of the genus Flavobacterium, for which the name Flavobacterium humi sp. nov., (type strain DS2-A^T = KACC 19715^T = JCM 32786^T) has been proposed.

Asian dust or yellow sand events in East Asia are a major issue of environmental contamination and human health, causing increasing concern. A high amount of dust particles, especially called as particulate matter 10 (PM10), is transported by the wind from the arid and semi-arid tracks to the Korean peninsula, bringing a bacterial population that alters the terrestrial and atmospheric microbial communities. In this study, we aimed to explore the bacterial populations of Asian dust samples collected during November–December 2014. The dust samples were collected using the impinger method, and the hypervariable regions of the 16S rRNA gene were amplified using PCR followed by pyrosequencing. Analysis of the sequencing data were performed using Mothur software. The data showed that the number of operational taxonomic units and diversity index during Asian dust events were higher than those during non-Asian dust events. At the phylum level, the proportions of Proteobacteria, Actinobacteria, and Firmicutes were different between Asian dust and non-Asian dust samples. At the genus level, the proportions of the genus Bacillus (6.9%), Arthrobacter (3.6%), Blastocatella (2%), Planomicrobium (1.4%) were increased during Asian dust compared to those in non-Asian dust samples. This study showed that the significant relationship between bacterial populations of Asian dust samples and non-Asian dust samples in Korea, which could significantly affect the microbial population in the environment.