Microcystis blooms deteriorate water quality and pose significant threats to aquatic ecosystems. Understanding how micro-organisms contribute to their formation is essential for developing effective control strategies. Although Flavobacterium species frequently coexist with Microcystis in natural environments, their role in Microcystis bloom formation remains largely unexplored. In the present study, a novel Gram-negative, designated strain RS13.1T, was isolated from freshwater during a Microcystis bloom. Phylogenetic analysis based on 16S rRNA gene sequences placed strain RS13.1ᵀ within the genus Flavobacterium, closely related to Flavobacterium limi THG-AG6.4ᵀ (98.89%) and Flavobacterium hibisci THG-HG1.4ᵀ (97.98%). The average nucleotide identity and digital DNA-DNA hybridization between strain RS13.1T and Flavobacterium species were below 89.39% and 37.60%, respectively. The growth of Microcystis increased by 26.6 % after 7 days when cultured with strain RS13.1ᵀ at 10% (v/v), demonstrating its growth-promoting effect. Furthermore, Microcystis exhibited tolerance to 20 mg l-1 H2O2, and its photosynthesis remained unaffected even with exposure to 5 mg l-1 H2O2 in the presence of RS13.1T. Genome annotation of strain RS13.1T revealed the presence of genes associated with carbohydrate-active enzyme, vitamin, heme and catalase biosynthesis, verifying mutualistic interaction between strain RS13.1T and Microcystis. Overall, these findings suggest that strain RS13.1T may contribute to the formation and persistence of Microcystis bloom by alleviating oxidative stress and supplying beneficial nutrients. Based on polyphasic features, strain RS13.1ᵀ was identified as a distinct species within the genus, for which the name Flavobacterium adiutor sp. nov. is proposed. The type strain is Flavobacterium adiutor RS13.1T (=KCTC 102193T=LMG 33484T).

Two aerobic, Gram-stain-negative, gliding motility and rod-shaped bacterial strains, designated as B11T and D4T, were isolated from rhizosphere soil of Litchi (Litchi chinensis Sonn.) in Guangzhou, Guangdong Province, P.R. China. Phylogenetic analysis based on the 16S rRNA gene sequences showed that strains B11T and D4T belonged to the genus Flavobacterium and shared the highest similarity to Flavobacterium ginsenosidimutans THG 01T (98.2%) and Flavobacterium daemonensis JCM 19455T (98.0%), respectively. The DNA G+C contents of strains B11T and D4T were 33.9 and 34.1 mol%, respectively. Both the genome-derived average nucleotide identity and digital DNA-DNA hybridization values between the two strains and their closely related type species Flavobacterium sharifuzzamanii KCTC 62405T and Flavobacterium denitrificans DSM 15936T were below 39.3 and 90.5%, respectively. They all took iso-C15:0 and summed feature 3 (C16:1 ω6c and/or C16:1 ω7c) as the major fatty acids. The polar lipids of strain B11T contained phosphatidylethanolamine (PE), two unidentified aminophospholipids (APL1-2) and four unidentified lipids (L1-4), while strain D4T took phosphatidylethanolamine (PE), three aminophospholipids (APL1-3) and four unidentified lipids (L1-4). Menaquinone-6 was their predominant quinone. Based on the phenotypic, chemotaxonomic, phylogenetic and genomic analyses, strains B11T and D4T should be considered as two novel species of the genus Flavobacterium, for which the names Flavobacterium movens (type strain B11T=GDMCC 1.4103T=JCM 36423T) and Flavobacterium mesophilum (type strain D4T=GDMCC 1.4105T=JCM 36424T) are proposed.

Dynamic changes of resistance genes and carbohydrate enzyme genes in different agricultural waste fermentation beds based on metagenomics analysis.

Strain SYSU M80003T, a Gram-stain-negative and aerobic bacterium, was isolated from water sample of the Pearl River Estuary, Guangzhou, Guangdong, PR China. The strain could grow at 4-37°C (optimal: 28°C), pH 6.0-8.0 (optimal: 7.0), and with 0-1% NaCl (w/v, optimal: 0%). The main fatty acids were anteiso-C14:0, Summed Feature 3 (C16:1 ω7c and/or C16:1 ω6c) and iso-C15:0. The predominant respiratory quinone was MK-6. The polar lipids contained phosphatidylethanolamine, three unidentified aminolipids, two unidentified aminophospholipids, and two unidentified polar lipids. The genomic DNA G + C content was 35.06%. Phylogenetic analysis based on the 16S rRNA gene revealed that strain SYSU M80003T was closely related to Flavobacterium aquicola JCM 30987T with similarity of 97.28%. Furthermore, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain SYSU M80003T and F. aquicola JCM 30987T were 83.8% and 28.1%, respectively. Based upon the consensus of phylogenetic and ANI analyses, we conclude that strain SYSU M80003T represents a novel species within the genus Flavobacterium, for which the name Flavobacterium aestuarii sp. nov. is proposed. The type strain is SYSU M80003T (= GDMCC 1.4521T = KCTC 102267T).

Bacterial communities play an important role in nutrient cycling in riverine wetland ecosystems, and the study of rhizosphere microbial community composition of different plants is of great scientific significance in revealing the relationship between microorganisms and plant interactions in riverine wetlands. In this study, samples were collected from four plant congeries dominated by Artemisia argyi (AH), Acorus calamus (CP), Miscanthus sacchariflorus (DC), and Paspalum distichum (QB), respectively. High-throughput sequencing technology was employed to investigate the rhizosphere microbial community structures associated with these distinct plant species. The results showed that soil water content could effectively regulate the functional diversity of soil microbial communities. Different plant congeries types significantly affected soil bacterial community diversity, and at the phylum level, both Proteobacteria and Acidobacteria were absolutely dominant groups, followed by Bacteroidetes. At the genus level, Flavobacterium, Sphingomonas, Gp6 and Gp4 were the dominant bacteria in the rhizosphere soil of plants along the river. Soil pH, water content, NO3-N, NO2-N and TOC were the main factors affecting the composition of microbial communities. This study broadens our understanding of the composition of rhizosphere microbial communities in the river buffer zone, and provide data support for river ecological environment protection.

Two Gram-stain-negative, aerobic, non-motile, non-gliding, rod-shaped bacterial strains, designated as TBRC 19031T and TBRC 19032, were isolated from water samples collected from the Mekong River, Thailand. Strain TBRC 19031T was obtained from Chiang Saen in the upstream section near the borders with China and Myanmar, while TBRC 19032 originated from Khong Chiam, in the downstream section where the river exits Thailand. Colonies of both strains were circular, smooth and deep yellow on Reasoner's 2A agar and did not produce flexirubin-type pigments. Phylogenetic analysis with 16S rRNA gene sequences placed both strains within the genus Flavobacterium, showing the highest sequence similarity to Flavobacterium cheonhonense ARSA-15T (98.29% for TBRC 19031T and 98.22% for TBRC 19032). However, whole-genome comparisons between the strains and F. cheonhonense ARSA-15T revealed average nt identity (89.39% and 89.29%), average aa identity (92.84% and 92.95%) and digital DNA-DNA hybridization (35.00% and 34.70%). The predominant fatty acids were iso-C15:1, iso-C15:0 and iso-C15:0 3-OH, and menaquinone MK-6 was the major respiratory quinone. The major polar lipids of both strains included phosphatidylethanolamine, steryl ester and diacylglycerol. The genome sizes were 3.02 and 3.04 Mbp, with G+C contents of 38.3% and 38.2% for TBRC 19031T and TBRC 19032, respectively. Comparative genomic analyses revealed the absence of genes involved in sulphate reduction and denitrification pathways and the presence of a gene encoding phosphatidylinositol synthase, distinguishing them from other Flavobacterium within the clade. Ecological profiling using public metagenomic datasets showed that both strains were associated with lotic freshwater environments. This study not only introduces Flavobacterium mekongense sp. nov. as a new species but also provides broader insights into the ecology, metabolism and environmental distribution of freshwater Flavobacterium. The genomic features identified here offer promising leads for future studies in microbial ecology, comparative genomics and functional gene mining in aquatic ecosystems. The type strain is TBRC 19031T (TBRC 19031T=NBRC 117006T).

BackgroundSix novel cold-adapted bacteria, LB3P122T, LT1R49T, ZT3R17T, ZT3R25T, XS2P12T, and GB2R13T, were isolated from glaciers on the Tibetan Plateau. This study aimed to characterize their taxonomic status and elucidate their molecular adaptations to cold environments using a polyphasic approach.ResultsAll strains were Gram-stain-negative, rod-shaped, and psychrophilic, growing at 0 °C with an optimum at 14–20 °C and at pH values of 6.0–8.0 (optimum pH 7.0). Analysis of the 16S rRNA gene sequences placed their taxonomic positions within the genus Flavobacterium, with similarities ranging from 97.2 to 98.4% to species with validly published names. Phylogenetic analysis of the 16S rRNA gene sequences revealed that the six strains formed distinct clades with Flavobacterium gawalongense GSP16T. Phylogenomic analysis showed that these strains clustered with Flavobacterium gawalongense GSP16T and exhibited a close relationship with Flavobacterium urumqiense CGMCC 1.9230T and Flavobacterium xinjiangense CGMCC 1.2749T. Average nucleotide identity (ANI) values ranging from 82.5 to 93.6% and digital DNA-DNA hybridization (dDDH) values ranging from 26.1 to 51.5% between these strains and their closest relatives were well below the bacterial species delineation thresholds (95–96% ANI, 70% dDDH). The predominant fatty acids were iso-C15:0 and summed feature 3 (C16:1ω7c and/or C16:1ω6c). Genomic analysis identified genes associated with cryoprotection, oxidative stress response, cold-shock response, and osmoprotection in these strains, underscoring their adaptations to glacial environments.ConclusionsBased on polyphasic taxonomic evidence, the strains represent six novel species within the genus Flavobacterium, with the proposed names Flavobacterium algoriphilum sp. nov. (LB3P122T = CGMCC 1.11443 T = NBRC 114820T), Flavobacterium arabinosi sp. nov. (LT1R49T = CGMCC 1.11617T = NBRC 114822T), Flavobacterium cryoconiti sp. nov. (ZT3R17T = CGMCC 1.11707T = NBRC 114824T), Flavobacterium galactosi sp. nov. (ZT3R25T = CGMCC 1.11711T = NBRC 114825T), Flavobacterium melibiosi sp. nov. (XS2P12T = CGMCC 1.23198T = NBRC 114826T), and Flavobacterium algoris sp. nov. (GB2R13T = CGMCC 1.24741T = NBRC 114830T). These findings enhance our understanding of Flavobacterium diversity and cold adaptation in cryospheric ecosystems.

Flavobacterium is a gram-negative bacterium that are commonly found in soil and water, and they also form endophytic relationships with host organisms. This study reports the draft genome and taxonomic characterization of Flavobacterium spp. strain CGRL1 and strain CGRL2 isolated from citrus Huanglongbing-infected trees. In the result of sequence and assembly, strain CGRL1 had a total genome length of 5,642,596 bp, 5,191 coding sequences (CDSs), and a genome CG content of 34%. Strain CGRL2 had a total genome length of 5,254,724 bp, 4,778 CDSs, and a genome CG content of 34%. Phylogenetic analysis of the 16S ribosomal RNA (rRNA) gene revealed that both strain CGRL1 and strain CGRL2 were members of the genus Flavobacterium, clustering with Flavobacterium johnsoniae strain UW101 and Flavobacterium resistens strain BD-b365. Multilocus sequence analysis (MLSA) using six housekeeping genes and average nucleotide identity (ANI) analysis were performed. These results, based on both MLSA and ANI analyses, indicate that strain CGRL1 is closely related to F. johnsoniae, with 99.15% MLSA similarity and 96.26% ANI value. In contrast, strain CGRL2 showed only 94.04% MLSA similarity and 82.20% ANI value with F. resistens. In addition, we identified two gene clusters in strain CGRL1 and strain CGRL2 that are responsible for the biosynthesis of pigments and antibiotic compounds. Notably, in strain CGRL2, one specific gene cluster was found to be associated with biofilm formation, and mitigation of host organisms aging. The genome sequences of strain CGRL1 and strain CGRL2 enhance our understanding of bacterial interactions, including interbacterial competition and colonization.

BackgroundDuring the screening of pigment-producing microbes from domestic sources, 102 yellow- or orange-pigmented bacteria were isolated. Among these, two novel Flavobacterium strains, F. sedimentum SUN046T and F. fluvius SUN052T, were identified as zeaxanthin producers. A polyphasic taxonomic characterization, combined with comparative genomic analysis of 45 Flavobacterium species, was conducted to determine their taxonomic positions and explore potential evolutionary relationships in zeaxanthin biosynthesis.ResultsBoth strains utilized the mevalonic acid (MVA) pathway and possessed the crt gene cluster (crtB, crtI, crtY/crtYcd, and crtZ). Strain SUN046T exhibited unique features in the carotenoid biosynthesis pathway, notably the absence of HMG-CoA synthase (HMGCS) in the upper MVA pathway and the presence of the rare lycopene β-cyclase crtYcd, which is uncommon among bacteria. The CrtYcd in SUN046T possessed a single active site and direct lycopene-binding modes. Conversely, CrtY in SUN052T exhibited multiple active sites, which is flavin adenine dinucleotide (FAD) dependent. These structural differences has impacted catalytic efficiencies, as evidenced by zeaxanthin yields of 6.49 µg/mL in SUN046T and 13.23 µg/mL in SUN052T. Variations in carotenoid biosynthetic pathway among other Flavobacterium species were also observed.ConclusionThese findings suggest that both strains represent valuable new resources for zeaxanthin production and provide foundational insights for biotechnological applications involving the genus Flavobacterium, highlighting the genetic and evolutionary complexity of microbial carotenoid biosynthesis.

Two novel, non-motile, Gram-stain-negative, rod-shaped bacterial strains, designated AS60T and WG47T, were isolated from freshwater in South Korea. To clarify their taxonomic positions, both strains were characterized based on genomic information, including 16S rRNA gene and draft genome sequences. Phylogenetic analyses revealed that both isolates belong to the genus Flavobacterium. Based on 16S rRNA gene sequencing, AS60T clustered with Flavobacterium silvisoli KACC 21178T (96.09%), Flavobacterium cheonhonense KACC 14967T (96.07%) and Flavobacterium sangjuense KACC 17473T (95.96%). Strain WG47T showed the highest similarity to Flavobacterium dankookense KACC 23179T (97.14%), F. cheonhonense KACC 14967T (97.07%) and Flavobacterium chungnamense KACC 14971T (96.71%). The draft genomes of AS60T and WG47T were 3.07 and 3.30 Mb, with G+C contents of 35.6 and 38.9 mol%, respectively. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values were calculated. For AS60T, ANI values compared to F. silvisoli KACC 21178T, F. cheonhonense KACC 14967T and WG47T were 76.67, 79.38 and 76.01%, respectively, with dDDH values of 20, 19.6 and 22.1%. For WG47T, ANI values compared to F. dankookense KACC 23179T and F. cheonhonense KACC 14967T were 75.12 and 74.75%, with dDDH values of 19.9 and 19.2%. Both strains exhibited MK-6 as the predominant respiratory quinone, and their fatty acid profiles included iso-C15:1, iso-C15:0 3OH, iso-C15:1 G, iso-C16:0, iso-C16:0 3OH and iso-C17:0 3OH. Phosphatidylethanolamine was the major polar lipid. Strain WG47T was found to produce flexirubin-type pigments, while AS60T did not. These results, combined with phenotypic and biochemical data, suggest that strains AS60T and WG47T represent two novel species of Flavobacterium, for which the names Flavobacterium anseongense sp. nov. (AS60T=KACC 22413T=LMG 32491T) and Flavobacterium wongokense sp. nov. (WG47T=KACC 22407T=LMG 32500T) are proposed.

Numerous studies have demonstrated that micro- and nanoplastics can induce adverse effects in both zebrafish and mice, primarily targeting the intestine in oral exposure scenarios. Organisms under disease conditions are suggested to exhibit increased susceptibility to environmental pollutants, with inflammatory bowel disease (IBD) serving as a relevant model for understanding toxicity initiated in a diseased intestine. Here, we compared the adverse outcomes of polystyrene micro- (PSMPs) and nanoplastics (PSNPs) in both normal and IBD-like zebrafish and mouse models. We found that in zebrafish, no significant difference in mortality was elicited by the two particles, while IBD-like fish exhibited greater susceptibility to exposure. Conversely, transcriptomic analysis of surviving fish revealed that PSNPs disrupted metabolic pathways, particularly galactose metabolism, and induced more pronounced apoptosis in intestinal epithelial cells compared to PSMPs in IBD-like fish. These effects were further associated with an increase in the genus Flavobacterium. Similarly, in IBD-like mice, PSNPs induced a more significant increase in crypt length than control mice and more severe histological injury and greater disruptions in gut microbial diversity compared to PSMPs, mirroring the findings in zebrafish. Notably, two shared pathways, glycosphingolipid synthesis (globo and isoglobo series) and NOD-like receptor signaling, were identified in response to PSNP and PSMP exposure in two models, respectively, along with a consistent decline in Firmicutes abundance. These findings suggest that smaller-sized PSNPs may pose higher environmental and health risks compared to larger-sized PSMPs, providing key insights into the interactions between polystyrene particles and compromised biological systems and their resulting adverse outcomes.

Three novel strains, designated LB3P45T, LS2P90T and ZS1P70T, were isolated from glaciers located on the Tibetan Plateau, PR China. These strains were Gram-stain-negative, aerobic, rod-shaped and yellow or orange coloured. Phylogenetic analysis based on the 16S rRNA gene and genomic sequences indicated that they belong to the genus Flavobacterium. The 16S rRNA gene sequence similarity among the three strains ranged from 97.4 to 98.6%. Strain LB3P45T showed 98.9% and 98.7% similarity to Flavobacterium urumqiense CGMCC 1.9230T and Flavobacterium xinjiangense JCM 11314T, respectively. Strain LS2P90T displayed 99.0% and 98.7% similarity to F. xinjiangense JCM 11314T and F. urumqiense CGMCC 1.9230T. Strain ZS1P70T had the highest sequence similarity with F. xinjiangense JCM 11314T (98.0%) and F. urumqiense CGMCC 1.9230T (97.8%). The average nucleotide identity and digital DNA-DNA hybridization values between these strains and their closest relatives were lower than 93.0% and 47.9%, respectively. All three strains contained summed feature 3 (comprising C16:1 ω7c and/or C16:1 ω6c) as the major fatty acids. Based on phenotypic characteristics, phylogenetic analysis and genotypic data, the three novel species are proposed: Flavobacterium fructosi sp. nov. (LB3P45T=CGMCC 1.11439T=NBRC 114819T), Flavobacterium xylosi sp. nov. (LS2P90T=CGMCC 1.11685T=NBRC 114823T) and Flavobacterium zhouii sp. nov. (ZS1P70T=CGMCC 1.24124T=NBRC 114829T).

Polysaccharides are recognized for their extensive biological functions, holding significant promise for applications in both medicine and food industries. However, their utilization is frequently constrained by challenges such as high molecular weights and indistinct sugar chain structures. Recently, two novel bacterial strains, N6T and J3T, were isolated from the Nakdong River in Korea. These strains, which belong to the phylum Bacteroidota, are Gram-stain-negative, non-motile, aerobic, rod-shaped bacteria and have shown polysaccharide-degrading capabilities. Through comprehensive analyses, including 16S rRNA gene sequencing, whole-genome sequencing, and detailed morphological, physiological, and chemotaxonomic characterizations, these strains have been identified as new species within the genus Flavobacterium. KEGG pathway analysis further confirmed their robust capabilities for carbohydrate utilization. Additional investigations using the dbCAN and dbCAN-PUL databases identified the presence of carbohydrate-hydrolyzing enzymes (CAZymes) and polysaccharide utilization loci (PULs) within these strains, suggesting their potential to degrade various polysaccharides. Subsequent in vitro growth experiments demonstrated that strains N6T and J3T can degrade chitin, β-glucan, κ-carrageenan, and cellulose. Given their diverse polysaccharide degradation abilities, these strains are formally proposed to be named Flavobacterium polysaccharolyticum sp. nov. and Flavobacterium aureirubrum sp. nov. The type strains are designated as N6T (= KCTC 102173T = GDMCC 1.4609T) and J3T (= KCTC 102172T = GDMCC 1.4608T), respectively.

Three bacterial strains, designated FZUC8N2.13T, FBOR7N2.3T and FZUR7N2.5, were isolated from distinct magnesite residues in Spain. Phylogenetic and phylogenomic analysis places them within the genus Flavobacterium. Strains FBOR7N2.3T and FZUR7N2.5 share 100% of similarity in the 16S rRNA gene sequence, and both are most closely related to Flavobacterium cellulosilyticum AR-3-4T with which they share 97.5% of 16S rRNA gene similarity. Strain FZUC8N2.13T forms a distinct lineage most closely related to Flavobacterium lacustre IMCC36792T with 97.7% 16S rRNA gene similarity. The closest phylogenomic neighbours of these three strains are Flavobacterium flevense DSM 1076T, 'Flavobacterium undicola' BBQ-18T and Flavobacterium commune PK15T. The average nucleotide identity and digital DNA-DNA hybridization values between the three strains and closest members of the genus Flavobacterium are below the threshold values of 95% and 70%, respectively. Strains FZUC8N2.13T, FBOR7N2.3T and FZUR7N2.5 stain Gram-negative, are rod-shaped and form yellow colonies. Optimum growth occurs at 25 °C and pH 7. The genomic G+C contents are 33.4 mol% for strain FZUC8N2.13T and 33.2 mol% for strains FBOR7N2.3T and FZUR7N2.5. The major isoprenoid quinone is menaquinone 6. The major fatty acids are summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) (22.6-31.1%), iso-C15 : 0 (13.6-16.2 %) and anteiso-C15 : 0 (8.7-10.5%). The polar lipids consist of two aminolipids, two aminophospholipids and one glycolipid. The phylogenetic, phylogenomic, phenotypic and chemotaxonomic data indicate that FZUC8N2.13T, FBOR7N2.3T and FZUR7N2.5 are distinct from the described species of Flavobacterium and should be classified as novel species, for which we propose the names Flavobacterium zubiriense for strain FZUC8N2.13T (=UCCCB 179T=CECT 30977T) and Flavobacterium magnesitis for strains FBOR7N2.3T (=UCCCB 178T=CECT 30976T) and FZUR7N2.5 (=UCCCB 216=CECT 31036).

A novel bacterium, designated 19SA41, was isolated from the air of the Icelandic volcanic island Surtsey. Cells of strain 19SA41 are Gram-stain-negative, strictly aerobic, non-motile rods and form pale yellow-pigmented colonies. The strain grows at 4-30 °C (optimum, 22 °C), at pH 6-10 (optimum, pH 7.5) and with 0-4% NaCl (optimum, 0.5%). Phylogenetic analyses based on 16S rRNA gene sequences showed that 19SA41 belonged to the genus Flavobacterium and is most similar to Flavobacterium xinjiangense DSM 19743T, with a sequence similarity of 96.52%. The new strain contained iso-C15 : 0 (22%) and summed feature 3 (C16∶1ω6c/C16∶1ω7c) (20%) as the predominant fatty acids. The major respiratory quinone was menaquinone-6 (100%). The polar lipid profile consisted of phosphatidylethanolamine and several uncharacterized amino lipids, glycolipids and lipids. The genome of the new strain was 4.01 Mbp, and its G+C content was 33.2 mol%. Based on characterization and comparative results, using a polyphasic taxonomic approach, we propose that the new isolate represents a novel species of the genus Flavobacterium with the name Flavobacterium aerium sp. nov. The type strain is ISCaR-07695T (=DSM 116640T =UBOOC-M-3567T).

During wastewater reclamation, organic matter is considered the dominant foulant that shortens the lifetime of ultrafiltration (UF) membranes during operation. Additionally, the mineralization efficiency of organic matter in secondary effluent is typically low due to nonbiodegradable carbon sources. Herein, a combination of ozone and a porous biocarrier reactor was applied as a novel pretreatment system to enhance organic matter removal in the effluent in a lab-scale evaluation and pilot test. The results indicated that 70% of the biopolymer was removed, and the chemical oxygen demand (COD) removal efficiency was 1.8 times higher in this combined process than in the process with a porous biocarrier alone. The UF flux increased by 16% after the combined ozonation and porous biocarrier pretreatment process compared with the process with no pretreatment. Interestingly, the genus Flavobacterium (15.59%), containing biopolymer-degrading bacteria, was observed only in the combined ozone plus porous biocarrier process. Moreover, the results show that biopolymers can be removed through the combined ozone and porous biocarrier process due to partial ozone degradation, confirming that this combined process is one of the better pretreatment procedures for organic matter removal and improves the flux of UF during the wastewater reclamation process.

Here we present the complete genome sequence of the Flavobacterium sp. strain PLB03 isolated from the primmorphs cell culture of the Lubomirskia baikalensis sponge and compare it with pathogenic free-living members of the genus Flavobacterium. Strain Flavobacterium sp. PLB03 exhibits pronounced lytic activity towards sponge cells and causes death of symbiotic microalgae (the Trebouxiophyceae). The Flavobacterium sp. PLB03 genome has 5,925,828 bp and a GC content of 34.3%. An average nucleotide identity (ANI) of 98.9% revealed that strain Flavobacterium sp. PLB03 has the highest similarity to Flavobacterium CSZ. Comparative genomic analysis of the strain and phylogenetically related Flavobacterium indicated that Flavobacterium sp. PLB03 has a large genome size characteristic of the environmental genus Flavobacterium, and the peptidase (PEP) to glycoside hydrolase (GH) gene ratio is 1.8, suggesting that strain PLB03 exhibits characteristics similar to nonpathogenic strains.

The photosynthetic activity of plants has a significant effect on the intensity of nitrogen fixation, as a result of which the productivity of crops increases. At the moment, there is a shortage of scientific data on the nitrogen fixation process and the quantitative assessment of its activity in agroecosystems. The true role of nitrogen fixing microorganisms in the nitrogen balance of soils has not been established. There is also insufficient data on nutrition, growth and development of plants against the background of atmospheric nitrogen fixation (due to associative nitrogen fixation). The relevance of the study lies in the biological assessment of the effect of seed inoculation with fungicide-stimulating biologics on the degree of associative nitrogen fixation in the rhizosphere, the survival rate of introduced diazotrophic strains, plant growth and development, and yield formation in the southern forest-steppe zone of Western Siberia. The work was carried out in field experiments on the varieties of spring soft wheat Omsk 42, Omsk 44, Tarskaya 12 and the variety of spring durum wheat Omsk coral. Pre-sowing bacterization of seeds was carried out with an inoculant of diazotrophic bacteria of the genus Arthrobacter mysorens 7 and an inoculant of fungicidal-stimulating bacteria of the genus Flavobacterium sp. L-30. Rhizosphere sampling was carried out in the following phenological phases: tillering (June), earing (July), grain filling (August). The activity of the associative nitrogen fixation process in the rhizosphere of cereals varied significantly depending on the use of biological products and the type of culture. During the growing season, when introducing Flavobacterium sp. bacteria and Arthrobacter mysorens 7, an increase in nitrogen-fixing ability in the rhizosphere and a high survival rate of introduced bacteria were found. The highest level of nitrogen-fixing activity was in the rhizosphere of soft wheat varieties Omsk 42 and durum wheat Omsk coral, amounting to 151–322 and 140–393 nM C2H2/100 g of soil during the introduction of bacteria of the genus Arthrobacter mysorens 7, 149–281 and 86.2–555 nM C2H2/100 g of soil when Flavobacterium sp. was introduced, accordingly. In parallel, an increase in the number of CFU introduced bacteria was observed, as a result of which the nitrogen fixation process was activated. The complex nature of the interaction of the studied indicators is noted – from the average direct to the average inverse conjugacy, depending on the phase of development. The activity of associative nitrogen fixation in the earing phase was characterized by a positive correlation with yield and the formation of the number of grains in the ear (r = 0.55 and 0.35), in the phases of tillering and filling of grain – with the weight of the ear grain (r = 0.36 and 0.75).

The genus Flavobacterium constitutes a vast pool of microorganisms living in multiple environmental niches including fish pathogens and species in the fish microbiome. Veterinary reports have identified flavobacteria in fish from Quebec's fish farms, confirming their association with infections. However, these reports have not conducted in-depth characterization, and the diversity of nonpathogenic flavobacteria in Quebec remains unknown. This study is the first step in assessing the diversity of Flavobacterium in Quebec's fish farms, without focusing solely on pathogenic strains. Seventeen isolates were collected from different fish farms, from either the water or fish. Microbial species identification was performed using PCR genotyping of the gyrB gene, whole-genome sequencing, and phylogenetic analysis. Antimicrobial susceptibility tests for tetracycline and florfenicol, the two most commonly used antibiotics in Quebec aquaculture, along with predictive tools, were employed to assess resistance. This study revealed potential new species among the isolates. No known pathogenic species were detected, and all 17 isolates clustered within CIIIb or CIIIc, recently described phylogenetic clades of Flavobacterium found in various environments, and the majority showed resistance to antibiotics. This study highlights the expanding diversity of Flavobacterium, particularly among species associated with fish, and underscores the need for further research in Quebec.

The general lack of knowledge in the conditions of Western Siberia (Omsk region), the nitrogen fixation process and quantitative data on its activity in agroecosystems do not allow us to establish the true role of nitrogen fixing microorganisms in the nitrogen balance of soils and plant nutrition, to estimate the proportion of biological nitrogen (due to associative nitrogen fixation). The relevance of the research lies in the biological assessment of the reception of inoculation of agricultural seeds with biological preparations of fungicidal-stimulating action of Russian production (ARRIAM, Pushkin). The research were study the infiuence of biological products of associative diazotrophs on the activity of the associative nitrogen fixation process in the rhizosphere of cereals, the survivability of introduced bacteria, and crop productivity in the conditions of the southern forest-steppe abd subtaiga of Western Siberia. The work was carried out in field experiments on varieties of Omsk breeding of spring wheat Omsk 42, Omsk 44, Tarskaya 12, Omsk Coral, barley Omsk 101, oats Siberian Hercules. Pre-sowing bacterization of seeds was carried out with an inoculant of diazotrophic bacteria of the genus Arthrobacter mysorens 7 and an inoculant of fungicidal-stimulating bacteria of the genus Flavobacterium sp. L-30. Rhizosphere sampling was leaded out in tillering (June), earing (July), grain filling (August). The activity of the associative nitrogen fixation process in the rhizosphere of cereals varied significantly depending on the use of biological products, the type of crop and the zone of their cultivation. Under the cultivation of cereals during the growing seasons with the introduction of Flavobacterium sp. bacteria. and Arthrobacter mysorens 7, an increase in nitrogen-fixing activity in the rhizosphere and dinamic survivability of introduced bacteria were found. On gray forest soil, for all crops of the experiment, the absolute sizes of nitrogen fixation were lower than on meadow-chernozem soil. In the conditions of the southern forest-steppe zone, the highest level of nitrogen-fixing activity was in the rhizosphere of soft wheat variety Omsk 42 and durum wheat Omsk Coral variety, amounting to 150.7-322.0 and 140.0-393.0 nM C2H2/100 g of soil with the introduction of bacteria of the genus Arthrobacter mysorens 7, 149.0-281.0 and 86.2-554.5 nM C2H2/100 g of soil with introduction of Flavobacterium sp. accordingly. In parallel, an increase in the number of CFU introduced bacteria was observed, as a result of which the nitrogen fixation process was activated. In the subtaiga zone of the Omsk region, the largest sizes of associative nitrogen fixation were found in the rhizosphere of soft wheat varieties Omsk 44 and Tarskaya 12, amounting to 46.3-230.7 and 24.0-130.0 nM C2H2/100 g of soil with the introduction of bacteria of the genus Arthrobacter mysorens 7, 62.0-208.3 and 52.0-178.7 nM C2H2/100 g of soil with the introduction of Flavobacterium sp. accordingly. Simultaneously with the increase in the size of nitrogen fixation, the number of bacterial cells of diazotrophs of the genus Arthrobacter mysorens 7 in the rhizosphere of these wheat varieties was also significant, during the growing season it varied between 1.28-5.23 × 106 CFU/g and 0.28-7.45 × 106 CFU/g. Barley was isolated from grain crops, the activity of the process in the rhizosphere of this crop was up to 164.3 nM C2H2/100 g of soil when Flavobacterin was used. A statistically significant (p<0.05) positive correlation between the process of associative nitrogen fixation and the yield of agricultural crops was revealed, in the southern forest-steppe zone r=0.927, r=0.986, r=0.897 (Omsk wheat 42, Omsk Coral, Siberian oats Hercules), in the subtaiga zone r=0.998, r=0.991, r=0.916, r=0.990 (Omsk wheat 42, Omsk 44, Omsk barley 101). EDN: NILFDX