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A yellow-colored bacterium with gliding motility, strain KIS68-18T, was isolated from a soil sample at Bijin Island in Tongyeong city, Republic of Korea. The cells were strictly aerobic, Gram-staining-negative, non-spore-forming, and rod-shaped. The strain grew at the range of 10-35°C (optimum, 25-30°C), pH 5.5-8.0 (optimum, 6.0-7.5), and 0-0.5% (w/v) NaCl. A phylogenetic analysis based on 16S rRNA gene sequences revealed that strain KIS68-18T was closely related to Chryseolinea serpens DSM 24574T (98.9%) and had low sequence similarities (below 92.6%) with other members of the family 'Cytophagaceae' in the phylum Bacteroidetes. The major respiratory quinone system was MK-7 and the predominant cellular fatty acids were C16:1ω5c (38.8%), iso-C15:0 (18.5%), and summed feature 3 (C16:1ω7c and/or C16:1ω6c, 10.6%). The polar lipids consisted of phosphatidylethanolamine, one unidentified phospholipid, three unidentified aminophospholipids, two unidentified aminolipids, and five unidentified lipids. The DNA G + C content was 50.9%. Based on the phylogenetic, physiological, and chemotaxonomic data, stain KIS68-18T represents a novel species of the genus Chryseolinea, for which the name Chryseolinea soli sp. nov. is proposed. The type strain of Chryseolinea soli is KIS68-18T (= KACC 17327T = NBRC 113100T).

Strain 63MJ-2T was isolated from the feces of broad-winged katydid (Pseudorhynchus japonicus) collected in Korea. The 16S rRNA gene sequence of this strain showed the highest sequence similarity with that of Siphonobacter aquaeclarae P2T (96.1%) and had low similarities (below 86.3%) with those of other members of family ‘Flexibacteraceae’. The strain 63MJ-2T is a strictly aerobic, Gram-stain-negative, non-motile, rod-shaped bacterium. The strain grew at 4–35°C (optimum, 25–30°C), pH of 5.0–9.0 (optimum, 6.0–7.0), and 0–2.0% (optimum, 1.0–2.0) (w/v) NaCl. The DNA G+C content of strain 63MJ-2T was 43.5 mol%. The major fatty acids were C16:1ω5c (42.5%), iso-C17:0 3-OH (18.7%), and summed feature 3 (iso-C15:0 2-OH and/or C16:1ω7c, 18.0%). The major menaquinone was MK-7 and polar lipids were phosphatidylethanolamine, six unknown aminolipids, and five unknown lipids. Based on the evidence from our polyphasic taxonomic study, we conclude that strain 63MJ-2T should be classified as a novel species of the genus Siphonobacter, and propose the name Siphonobacter intestinalis sp. nov. The type strain is 63MJ-2T (=KACC 18663T =NBRC 111883T).

The microbiome in the rhizosphere–the region surrounding plant roots–plays a key role in plant growth and health, enhancing nutrient availability and protecting plants from biotic and abiotic stresses. To assess bacterial diversity in the tomato rhizosphere, we performed two contrasting approaches: culture-dependent and -independent. In the culture-dependent approach, two culture media (Reasoner’s 2A agar and soil extract agar) were supplemented with 12 antibiotics for isolating diverse bacteria from the tomato rhizosphere by inhibiting predominant bacteria. A total of 689 bacterial isolates were clustered into 164 operational taxonomic units (OTUs) at 97% sequence similarity, and these were found to belong to five bacterial phyla (Proteobacteria, Actinobacteria, Bacteroidetes, Acidobacteria, and Firmicutes). Of these, 122 OTUs were retrieved from the antibiotic-containing media, and 80 OTUs were recovered by one specific antibiotic-containing medium. In the culture-independent approach, we conducted Illumina MiSeq amplicon sequencing of the 16S rRNA gene and obtained 19,215 high-quality sequences, which clustered into 478 OTUs belonging to 16 phyla. Among the total OTUs from the MiSeq dataset, 22% were recovered in the culture collection, whereas 41% of OTUs in the culture collection were not captured by MiSeq sequencing. These results showed that antibiotics were effective in isolating various taxa that were not readily isolated on antibiotic-free media, and that both contrasting approaches provided complementary information to characterize bacterial diversity in the tomato rhizosphere.