Flavobacterium amniphilum sp. nov., isolated from a stream

Overproduction of Xanthophyll Pigment in Flavobacterium sp. JSWR-1 under Optimized Culture Conditions

Flavobacterium can synthesize xanthophyll, particularly the pigment zeaxanthin, which has significant economic value in nutrition and pharmaceuticals. Recently, the use of carotenoid biosynthesis by bacteria and yeast fermentation technology has shown to be very efficient and offers significant advantages in large-scale production, cost-effectiveness, and safety. In the present study, JSWR-1 strain capable of producing xanthophyll pigment was isolated from a freshwater reservoir in Wanju-gun, Republic of Korea. Based on the morphological, physiological, and molecular characteristics, JSWR-1 classified as belonging to the Flavobacterium species. The bacterium is strictly aerobic, Gram-negative, rod-shaped, and psychrophilic. The completed genome sequence of the strain Flavobacterium sp. JSWR-1 is predicted to be a single circular 3,425,829-bp chromosome with a G+C content of 35.2% and 2,941 protein-coding genes. The optimization of carotenoid production was achieved by small-scale cultivation, resulting in zeaxanthin being identified as the predominant carotenoid pigment. The enhancement of zeaxanthin biosynthesis by applying different light-irradiation, variations in pH and temperature, and adding carbon and nitrogen supplies to the growth medium. A significant increase in intracellular zeaxanthin concentrations was also recorded during fed-batch fermentation achieving a maximum of 16.69 ± 0.71 mg/l, corresponding to a product yield of 4.05 ± 0.15 mg zeaxanthin per gram cell dry weight. Batch and fed-batch culture extracts exhibit significant antioxidant activity. The results demonstrated that the JSWR-1 strain can potentially serve as a source for zeaxanthin biosynthesis.

Arthrobacter hankyongi sp. nov., Isolated From Wet Land

A Gram-staining-positive, catalase positive and oxidase negative, non-motile, non-flagellated, and oval-shaped bacterium, was designated as I2-34 ^T, isolated from wetland in Soul South Korea. Colonies were round, entire, raised, and cream colored after two days of incubation on R2A agar plates at 25 °C. Based on genomes (both 16S rRNA gene and draft genome) sequence analysis, strain I2-34 ^T belongs to the genus Arthrobacter and was most closely related to Arthrobacter deserti YIM CS25^T (98.0%). The strain I2-34 ^T had a circular genome with length of 5,186,447 base pairs (67 contigs) and 4830 total genes. Out of 4696 were protein-coding genes, 54 tRNA and 4 rRNA genes. The chemotaxonomic analysis indicates iso-C_16:0, anteiso-C_15:0, and anteiso_-C_17:0 as major fatty acids, phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), and two unidentified glycolipids (GL1, GL2) as major polar lipids. The predominant quinone was MK-8(H₂). The peptidoglycan type was A3α with an. L-Lys-L-Ala interpeptide bridge. Thus, the experimental data demonstrated here show that the novel isolate shares the similar major fatty acids, major polar lipid PG, DPG, and GLs, major and major quinone MK8-(H₂) with the described members of the genus Arthrobacter. However, the low 16S rRNA gene sequence (98.0%), and some physiological and biochemical characteristics differentiate the I2-34 ^T from its closest phylogenetic neighbors. As a result, the isolate represents a novel species in within the genus Arthrobacter and family Micrococcaceae for which the name Arthrobacter hankyongi sp. nov. is proposed. The type strain is I2-34 ^T (= KACC 22217 ^T, LMG 32197 ^T).

Characterization and Genome Analysis of Arthrobacter bangladeshi sp. nov., Applied for the Green Synthesis of Silver Nanoparticles and Their Antibacterial Efficacy against Drug-Resistant Human Pathogens

The present study describes the isolation and characterization of novel bacterial species Arthrobacter bangladeshi sp. nov., applied for the green synthesis of AgNPs, and investigates its antibacterial efficacy against drug-resistant pathogenic Salmonella Typhimurium and Yersinia enterocolitica. Novel strain MAHUQ-56T is Gram-positive, aerobic, non-motile, and rod-shaped. Colonies were spherical and milky white. The strain showed positive activity for catalase and nitrate reductase, and the hydrolysis of starch, L-tyrosine, casein, and Tween 20. On the basis of the 16S rRNA gene sequence, strain MAHUQ-56T belongs to the Arthrobacter genus and is most closely related to Arthrobacter pokkalii P3B162T (98.6%). Arthrobacter bangladeshi MAHUQ-56T has a genome 4,566,112 bp long (26 contigs) with 4125 protein-coding genes, 51 tRNA and 6 rRNA genes. The culture supernatant of Arthrobacter bangladeshi MAHUQ-56T was used for the easy and green synthesis of AgNPs. Synthesized AgNPs were characterized by UV-vis spectroscopy, FE-TEM, XRD, DLS, and FT-IR. Synthesized AgNPs were spherical and 12-50 nm in size. FT-IR analysis revealed various biomolecules that may be involved in the synthesis process. Synthesized AgNPs showed strong antibacterial activity against multidrug-resistant pathogenic S. typhimurium and Y. enterocolitica. MIC values of the synthesized AgNPs against S. typhimurium and Y. enterocolitica were 6.2 and 3.1 ug/mL, respectively. The MBC of synthesized AgNPs for both pathogens was 12.5 ug/mL. FE-SEM analysis revealed the morphological and structural alterations, and damage of pathogens treated by AgNPs. These changes might disturb normal cellular functions, which ultimately leads to the death of cells.

Ecofriendly Synthesis of Silver Nanoparticles by Terrabacter humi sp. nov. and Their Antibacterial Application against Antibiotic-Resistant Pathogens

It is essential to develop and discover alternative eco-friendly antibacterial agents due to the emergence of multi-drug-resistant microorganisms. In this study, we isolated and characterized a novel bacterium named Terrabacter humi MAHUQ-38^T, utilized for the eco-friendly synthesis of silver nanoparticles (AgNPs) and the synthesized AgNPs were used to control multi-drug-resistant microorganisms. The novel strain was Gram stain positive, strictly aerobic, milky white colored, rod shaped and non-motile. The optimal growth temperature, pH and NaCl concentration were 30 °C, 6.5 and 0%, respectively. Based on 16S rRNA gene sequence, strain MAHUQ-38^T belongs to the genus Terrabacter and is most closely related to several Terrabacter type strains (98.2%-98.8%). Terrabacter humi MAHUQ-38^T had a genome of 5,156,829 bp long (19 contigs) with 4555 protein-coding genes, 48 tRNA and 5 rRNA genes. The culture supernatant of strain MAHUQ-38^T was used for the eco-friendly and facile synthesis of AgNPs. The transmission electron microscopy (TEM) image showed the spherical shape of AgNPs with a size of 6 to 24 nm, and the Fourier transform infrared (FTIR) analysis revealed the functional groups responsible for the synthesis of AgNPs. The synthesized AgNPs exhibited strong anti-bacterial activity against multi-drug-resistant pathogens, Escherichia coli and Pseudomonas aeruginosa. Minimal inhibitory/bactericidal concentrations against E. coli and P. aeruginosa were 6.25/50 and 12.5/50 μg/mL, respectively. The AgNPs altered the cell morphology and damaged the cell membrane of pathogens. This study encourages the use of Terrabacter humi for the ecofriendly synthesis of AgNPs to control multi-drug-resistant microorganisms.

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 amnicola sp. nov., isolated from a sub-tropical stream

Strain LLJ-11^T, isolated from water sampled from a freshwater stream in Taiwan, was characterized using a polyphasic taxonomy approach. Cells of strain LLJ-11^T were Gram-stain-negative, strictly aerobic, motile by gliding, rod-shaped and formed translucent yellow colonies. Optimal growth occurred at 25 °C, pH 7 and 0 % NaCl. Phylogenetic analyses based on 16S rRNA gene sequences and coding sequences of 92 protein clusters indicated that strain LLJ-11^T is affiliated with species in the genus Flavobacterium. Strain LLJ-11^T was most closely related to Flavobacterium amniphilum KYPY10^T with 98.0 % 16S rRNA gene sequence identity. The DNA-DNA relatedness of strain LLJ-11^T with respect to Flavobacterium species was less than 35 %. Average nucleotide identity and digital DNA-DNA hybridization values between strain LLJ-11^T and the type strains of other closely related Flavobacterium species were 70.0-76.3 % and 21.1-23.9 %, respectively. Strain LLJ-11^T contained iso-C15 : 0, iso-C15 : 1 G, iso-C17 : 0 3-OH, iso-C15 : 0 3-OH, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) and summed feature 9 (iso-C17 : 1ω9c and/or 10-methyl C16 : 0) as the predominant fatty acids. The major isoprenoid quinone was MK-6. The polar lipid profile consisted of phosphatidylethanolamine, three uncharacterized aminophospholipids and two uncharacterized phospholipids. The major polyamine was homospermidine. The DNA G+C content was 34.8 mol%. On the basis of the phylogenetic inference and phenotypic data, strain LLJ-11^T is considered a representative of a novel species within the genus Flavobacterium. The name Flavobacterium amnicola sp. nov. is proposed, with strain LLJ-11^T (=BCRC 81124^T=LMG 30599^T=KCTC 62514^T) as the type strain.

Flavobacterium niveum sp. nov., isolated from a freshwater creek

Strain TAPW14^T was isolated from a freshwater creek in Taiwan. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain TAPW14^T belonged to the genus Flavobacterium and was most closely related to Flavobacterium akiainvivens IK-1^T (96.6 % sequence identity) and Flavobacterium hauense BX12^T (96.0 %) and less than 96 % sequence similarity to other members of the genus. Cells of strain TAPW14^T were Gram-negative, strictly aerobic, motile by gliding, rod-shaped and formed white colonies. Optimal growth occurred at 20 °C, pH 7 and in the presence of 0.5 % NaCl. Strain TAPW14^T contained summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c), iso-C15 : 0 and C16 : 0 as the predominant fatty acids. The polar lipid profile consisted of phosphatidylethanolamine, three uncharacterized aminophospholipids, one uncharacterized phospholipid and one uncharacterized lipid. The major polyamine was homospermidine. The major isoprenoid quinone was MK-6. The DNA G+C content of the genomic DNA was 46.0 mol%. On the basis of the phylogenetic inference and phenotypic data, strain TAPW14^T should be classified as a novel species, for which the name Flavobacteriumniveum sp. nov. is proposed. The type strain is TAPW14^T (=BCRC 81055^T=LMG 30057^T=KCTC 52808^T).

Flavobacterium parvum sp. nov., isolated from soil polluted by sewer water

A novel Gram-stain-negative, motile by means of gliding, and short rod-shaped bacterium, designated HS916T, was isolated from soil polluted by sewer water in Cheonan-si, South Korea. Growth occurred at 10-35°C (optimum 30°C), pH 6.0-8.0 (optimum pH 7.0), and 0-1% sodium chloride (NaCl, w/v). Based on similarities of 16S rRNA gene sequences, strain HS916^T was closely related to members of the genus Flavobacterium, exhibiting the highest sequence similarities with Flavobacterium glycines Gm-149^T (96.4%), followed by F. granuli Kw05^T (96.3%), F. fluminis 3R17^T (96.3%), F. aquicola TMd3a3^T (96.2%), and F. nitratireducens N1^T (96.2%). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain HS916T was placed in a monophyletic cluster with F. nitratireducens N1^T and F. fluminis 3R17^T. The predominant fatty acids (> 5% of the total) of strain HS916^T were iso-C_15:0, anteiso-C_15:0, iso-C_15:0 3-OH, C_17:1ω6с, C_16:0 3-OH, iso-C_17:0 3-OH, and summed feature 3 (C_16:1ω7с and/or C_16:1ω6с). The major polar lipids of the strain comprised phosphatidylethanolamine, unidentified aminolipids, and five unidentified lipids. The predominant respiratory quinone and the major polyamine were menaquinone-6 (MK-6) and symhomospermidine, respectively. The DNA G + C content of strain HS916^T was 34.9 mol%. Based on polyphasic analyses, strain HS916^T represents a novel species belonging to the genus Flavobacterium, for which the name Flavobacterium parvum sp. nov. is proposed. The type strain is HS916T (= KACC 19448^T = JCM 32368^T).