Flavobacterium chungangensis sp. nov., a Bacterium Isolated from Soil of Chinese Cabbage Garden

Bacterial mediated green synthesis of silver nanoparticles and their antibacterial and antifungal activities against drug-resistant pathogens

In the healthcare sector, the production of bioactive silver nanoparticles (AgNPs) with antimicrobial properties is of great importance. In this study, a novel bacterial strain, Paenibacillus sp. MAHUQ-63, was identified as a potential candidate for facile and rapid biosynthesis of AgNPs. The synthesized AgNPs were used to control the growth of human pathogens, Salmonella Enteritidis and Candida albicans. The bacterial culture supernatant was used to synthesize the nanoparticles (NPs). Field emission transmission electron microscope examination showed spherical-shaped NPs with 15-55 nm in size. Fourier transform-infrared analysis identified various functional groups. The synthesized AgNPs demonstrated remarkable activity against S. Enteritidis and C. albicans. The zones of inhibition for 100 µl (0.5 mg ml-1) of AgNPs against S. Enteritidis and C. albicans were 18.0 ± 1.0 and 19.5 ± 1.3 mm, respectively. The minimum inhibitory concentrations were 25.0 and 12.5 µg ml-1 against S. Enteritidis and C. albicans, respectively. Additionally, the minimum bactericidal concentrations were 25.0 µg ml-1 against both pathogenic microbes. The field emission scanning electron microscopy analysis showed that the treatment of AgNPs caused morphological and structural damage to both S. Enteritidis and C. albicans. Therefore, these AgNPs can be used as a new and effective antimicrobial agent.

Flavobacterium agri sp. nov., a novel bacterial species isolated from rhizospheric soil of Coriandrum sativum

A Gram-stain-negative, strictly aerobic, cream yellow colored, non-motile, rod-shaped bacterial strain, designated MAH-1^T was isolated from rhizospheric soil of Coriandrum sativum. A polyphasic taxonomic study was performed on the isolated strain. Optimal growth occurred at 28-30 °C, pH 6.5 and 0% NaCl. The strain showed activity for both catalase and oxidase tests. Cell growth occurs on R2A agar, nutrient agar and Luria-Bertani agar. Cells were able to hydrolyze starch, aesculin, gelatin, and Tween 20. Alignment of 16S rRNA gene sequences indicated that strain MAH-1^T was associated with the genus Flavobacterium and was most closely related to Flavobacterium longum YIT 12745^T (94.5% sequence similarity) and Flavobacterium caeni LM5^T (93.0%). Strain MAH-1^T had a genome size of 3,975,600 bp. Genome contained 67 contigs encoded by 3,522 protein-coding genes with 38 tRNA and 6 rRNA genes. The genomic DNA G + C contents of strain MAH-1^T was 47.1 mol %. The genomic ANI and dDDH values between strain MAH-1^T and one of the close relatives F. caeni LM5^T were 72.2 and 18.8%, respectively. The major fatty acids were C_{15:0 iso}, C_{16:0 iso} and C_{15:0 anteiso}. The predominant respiratory quinone was menaquinone 6 (MK-6). Based on physiological, biochemical and phylogenetic data for this isolate, it was confirmed that strain MAH-1^T was affiliated to the genus Flavobacterium and represented a novel species, for which the name Flavobacterium agri sp. nov. is proposed. The type strain is MAH-1^T (= KACC 19300^T = CGMCC 1.16617^T).

Flavobacterium sharifuzzamanii sp. nov., Isolated from the Sediments of the East China Sea

A novel bacterial strain A7.6^T was isolated from the sediments collected near the Zhairuo Island located in the East China Sea and characterized using a polyphasic approach. Cells were Gram-stain-negative, rod-shaped, non-spore forming, non-flagellated but motile by gliding. The strain was aerobic, positive for oxidase and catalase activities. The strain can grow at 4-35 °C, pH 5.5-9.0, and 0-3% (w/v) NaCl concentration. The major polar lipid was phosphatidylethanolamine, the predominant fatty acids (> 10%) were iso-C_15:0 and summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c). The genomic G+C content was 33.6 mol% and the major respiratory quinone was menaquinone 6. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain A7.6^T belonged to the genus Flavobacterium and was closely related to Flavobacterium tistrianum GB 56.1^T (98.4% similarity), F. nitrogenifigens NXU-44^T (98.4%), F. ginsenosidimutans THG 01^T (98.0%) and F. anhuiense D3^T (97.7%). Average nucleotide identities and digital DNA-DNA hybridizations values for genomes ranged from 75.9 to 91.4% and 21.4 to 43.9% between strain A7.6^T and its closest phylogenetic neighbors. The polyphasic characterization indicated that strain A7.6^T represented a novel species of the genus Flavobacterium, for which the name Flavobacterium sharifuzzamanii is proposed. The type strain is A7.6^T (= KCTC 62405^T = MCCC 1K03485^T). The NCBI GenBank accession number for the 16S rRNA gene of A7.6^T is MH396692, and for the genome sequence is QJGZ00000000. The digital protologue database (DPD) Taxon Number is TA00643.

Flavobacterium hydrophilum sp. nov. and Flavobacterium cheongpyeongense sp. nov., isolated from freshwater

Two Gram-stain-negative, non-motile, yellow-pigmented bacterial strains, designated IMCC34758^T and IMCC34759^T, were isolated from freshwater. Phylogenetic analysis based on 16S rRNA gene sequences showed that the two strains formed a distinct clade within the genus Flavobacterium and they shared 97.9 % sequence similarity. The average nucleotide identity (ANI) and digital DNA-DNA hybridization values (dDDH) between the two strains were 85.5 and 30.2 %, respectively, indicating that they are separate species. The two strains showed ≤98.5 % 16S rRNA gene sequence similarities, 80.6-81.3 % of ANI and 24.7-25.1 % of dDDH values to closely related species of the genus Flavobacterium, indicating that the two strains each represent novel Flavobacteriumspecies. The respiratory quinone detected in both strains was menaquinone-6 (MK-6). The major polar lipids of the two strains were phosphatidylethanolamine, an unidentified aminolipid, an unidentified aminophospholipid and an unidentified polar lipid. The DNA G+C contents of strains IMCC34758^T and IMCC34759^T were 34.0 and 34.1 mol%, respectively. The major fatty acids of the two strains were very similar to each other, comprising iso-C15 : 0, iso-C15 : 1 G, anteiso-C15 : 0 and summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c). Phenotypic characteristics including enzyme activities and carbon source utilization differentiated the two strains from other Flavobacteriumspecies. Based on these results, strains IMCC34758^T and IMCC34759^T were considered to represent novel species in the genus Flavobacterium, for which the names Flavobacterium hydrophilum (IMCC34758^T=KACC 19591^T=NBRC 113423^T) and Flavobacterium cheongpyeongense (IMCC34759^T=KACC 19592^T=NBRC 113424^T) are proposed, respectively.