Genus Chryseobacterium Research Articles

Chryseobacterium tagetis sp. nov., a plant growth promoting bacterium with an antimicrobial activity isolated from the roots of medicinal plant (Tagetes patula).

A novel plant growth-promoting and indole acetic acid (IAA) producing strain designated RG1T was isolated from the roots of Tagetes patula (marigold) collected from Goyang, South Korea. The cells of strain RG1T is aerobic, yellow, Gram-stain-negative, pleomorphic and non-motile. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain RG1T belongs to the genus Chryseobacterium and is closely related to Chryseobacterium gwangjuense THG-A18T (98.6%). The strain produced IAA (70.5 µg ml-1) in the presence of L-tryptophan and showed antimicrobial activity against Gram-negative bacterium Xanthomonas campestris pv. campestris KACC 10377T. The isolate had a significant positive effect on rice plant shoot and root growth. The novel strain RG1T had a draft genome size of 4,430,189 bp, with ten scaffolds and 3969 protein-coding genes. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain RG1T and other closely related members ranged from 21.5 to 36.6% and from 79.2 to 86.6%, respectively. The genomic DNA G + C content was 34.8 mol%. Furthermore, anti-SMASH analysis of the whole genome revealed six putative biosynthetic gene clusters responsible for various secondary metabolites. The major respiratory quinone was MK-6 and the major fatty acids were iso-C15:0, summed feature 3 (comprising C16: 1ω7c and/or C16: 1ω6c) and summed feature 9 (comprising iso-C17: 1 ω9c and/or 10-methyl C16:0). The major polar lipid is phosphatidylethanolamine. Based on the genotypic, chemotaxonomic and physiological data, strain RG1T represents a novel species, for which the name Chryseobacterium tagetis sp. nov. is proposed. The type strain is designated as RG1T ( = KCTC 82696T = NBRC 115057T).

Determination of Phylloplane Associated Bacteria of Lettuce from a Small-Scale Aquaponic System via 16S rRNA Gene Amplicon Sequence Analysis

Fresh vegetables harbour diverse bacterial populations on their surfaces which are important for plant health and growth. Information on epiphytic bacteria is limited to only a few types of vegetables and it is unknown how the lettuce epiphytic bacterial community structure may respond when a probiotic product is added to an aquaponic system. In this study, we evaluated lettuce growth and analysed epiphytic bacterial communities of lettuce based on metabarcoding analysis of the V3-V4 region of the 16S rRNA gene obtained from paired-end Illumina MiSeq reads. The addition of Bacillus probiotics resulted in a significant increase of nitrate and phosphate in the deep-water culture solution, as well as increased vegetative growth of lettuce. Metabarcoding analysis revealed that the most abundant phyla on lettuce leaf surfaces were Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. The in-depth bacterial composition analysis indicated that genera Chryseobacterium, Bacillus, Pantoea, Pseudoduganella, Flavobacterium, Paludibacter, and Cloacibacterium were dominant in leaf samples obtained from Bacillus-treated systems. Analysis of lettuce epiphytic bacterial communities of the fresh lettuce leaf surfaces also indicated the presence of food-borne pathogens belonging to the Shigella and Aeromonas genera, which were less abundant in the probiotic treated systems. This study provides the first characterization of the epiphytic bacterial community structure and how it can be modulated by the addition of a probiotic mixture to the nutrient solution of aquaponic systems.

Chryseobacterium lecithinasegens sp. nov., a siderophore-producing bacterium isolated from soil at the bottom of a pond.

Bacterial strain PAGU 2197T, which was isolated from soil collected from the bottom of a pond in Japan, is characterized in this study. Cells of strain PAGU 2197T were aerobic, Gram-negative, short rod-shaped, non-motile, flexirubin-producing, oxidase-positive, catalase-positive and lecithinase-negative. A phylogenetic study based on 16S rRNA gene sequences and multilocus sequence analysis (gyrB, rpoB and rpoD) indicated that strain PAGU 2197T belongs to the genus Chryseobacterium and is a member of an independent lineage including Chryseobacterium tructae CCUG 60111T (sequence similarity, 95.9 %), Chryseobacterium lactis CCUG 60566T (93.4 %) and Chryseobacterium viscerum CCUG 60103T (91.6 %). The average nucleotide identity values were 80.83-85.04 %. Because average nucleotide identity values of 95-96 % exceed the 70 % DNA-DNA hybridization cutoff value for species discrimination, strain PAGU 2197T represents a novel species in the genus Chryseobacterium. The genome of strain PAGU 2197T was 4 967 738 bp with a G+C content of 35.5 mol%. The sole respiratory quinone of strain PAGU 2197T was MK-6; the major cellular fatty acids were iso-C15 : 0, iso-C17 : 0 3OH, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and summed feature 9 (iso-C17 : 1 ω9c and/or C16 : 0 10-methyl); and the major polar lipids were phosphoglycolipids and phosphatidylethanolamine. These results indicate that strain PAGU 2197T should be classified as representing a novel species in the genus Chryseobacterium, for which the name Chryseobacterium lecithinasegens sp. nov. is proposed, with strain PAGU 2197T (=NBRC 114264T=CCUG 75150T) as the type strain.

Chryseobacterium potabilaquae sp. nov., Chryseobacterium aquaeductus sp. nov. and Chryseobacterium fistulae sp. nov., from drinking water systems.

A polyphasic taxonomic study was conducted on three strains isolated from drinking water systems that had previously been deposited as Chryseobacterium species at the Spanish Type Culture Collection in order to complete their classification. Strains CECT 9293T, CECT 9390T and CECT 9393T were isolated from sites in Barcelona, Spain, in the framework of a project aimed at generating the first MALDI-TOF database specific for bacteria present in water for human consumption. Their partial 16S rRNA sequences showed that their closest relatives among the type strains of Chryseobacterium exhibited 98 % similarity or less, supporting their taxonomic novelty. At the same time, comparison between them revealed that strains CECT 9293T and CECT 9393T could perhaps be related at the species level as they shared 99.5 % similarity. However, whole genome sequencing was performed and the subsequent calculation of relatedness indices, average nucleotide identity and estimated DNA–DNA hybridization, ruled out that possibility and confirmed instead that each of the strains should be considered a separate species in the genus Chryseobacterium . Having clarified their status, we also performed phylogenomic analyses and searched for possible environmental or non-type material sequences that could be related to any of them at the species level. In parallel, the strains were characterized phenotypically and compared to their closest relatives to determine diagnostic traits to support their formal proposal. The proposed species are Chryseobacterium potabilaquae sp. nov. with the type strain CECT 9293T (=LMG 32084T), Chryseobacterium aquaeductus sp. nov. with the type strain CECT 9390T (=LMG 32085T) and Chryseobacterium fistulae sp. nov. with the type strain CECT 9393T (=LMG 32086T).

Diversity and Co-Occurrence Patterns of Fungal and Bacterial Communities from Alkaline Sediments and Water of Julong High-Altitude Hot Springs at Tianchi Volcano, Northeast China.

Simple SummaryVolcanic hot springs are considered of particular interest in biology as precious sources of peculiar microorganisms adapted to extreme environmental conditions. The Julong high-altitude volcanic hot springs in northeast China are characterized by alkali, sulfur and metal enrichment. The microbial communities colonizing these intriguing habitats still remain completely unknown. We carried out the present study in order to shed light on the Julong hot springs fungal and bacterial community diversity, structure and interactions, and to understand the impact of pH on the microorganisms colonizing the investigated environment. We detected a large variety of typical photosynthetic, thermophilic, alkalophilic, antimicrobial-active, and sulfide- and metal-oxidizing microbial taxa representing clear links to the extreme properties of the studied environment. Results showed a striking microorganism community variation strongly influenced by pH under clearly alkaline conditions. Our analyses suggests that mutualistic relationships might be common among microorganisms coexisting in the Julong hot springs, especially for the bacterial community. This study provides new insights in the diversity and ecological interactions of microorganisms living in high-altitude volcanic hot springs and contributes to our knowledge of abiotic factors influencing the microbial community in the analyzed extreme environment. The Julong high-altitude volcanic hot springs in northeast China are of undeniable interest for microbiological studies due to their unique, extreme environmental conditions. The objective of this study was to provide a comprehensive analysis of the unexplored fungal and bacterial community composition, structure and networks in sediments and water from the Julong hot springs using a combination of culture-based methods and metabarcoding. A total of 65 fungal and 21 bacterial strains were isolated. Fungal genera Trichoderma and Cladosporium were dominant in sediments, while the most abundant fungi in hot spring water were Aspergillus and Alternaria. Bacterial communities in sediments and water were dominated by the genera Chryseobacterium and Pseudomonas, respectively. Metabarcoding analysis revealed significant differences in the microorganism communities from the two hot springs. Results suggested a strong influence of pH on the analyzed microbial diversity, at least when the environmental conditions became clearly alkaline. Our analyses indicated that mutualistic interactions may play an essential role in shaping stable microbial networks in the studied hot springs. The much more complicated bacterial than fungal networks described in our study may suggest that the more flexible trophic strategies of bacteria are beneficial for their survival and fitness under extreme conditions.

Genetic Characterization of the Tetracycline-Resistance Gene tet(X) Carried by Two Epilithonimonas Strains Isolated from Farmed Diseased Rainbow Trout, Oncorhynchus mykiss in Chile.

The main objective of this study was to characterize the tet(X) genes, which encode a monooxygenase that catalyzes the degradation of tetracycline antibiotics, carried by the resistant strains FP105 and FP233-J200, using whole-genome sequencing analysis. The isolates were recovered from fin lesion and kidney samples of diseased rainbow trout Oncorhynchus mykiss, during two Flavobacteriosis outbreaks occurring in freshwater farms located in Southern Chile. The strains were identified as Epilithonimonas spp. by using biochemical tests and by genome comparison analysis using the PATRIC bioinformatics platform and exhibited a minimum inhibitory concentration (MIC) of oxytetracycline of 128 µg/mL. The tet(X) genes were located on small contigs of the FP105 and FP233-J200 genomes. The sequences obtained for the tet(X) genes and their genetic environment were compared with the genomes available in the GenBank database of strains of the Chryseobacterium clade belonging to the Flavobacterium family, isolated from fish and carrying the tet(X) gene. The Tet(X) proteins synthesized by the Chilean Epilithonimonas strains showed a high amino acid similarity (range from 84% to 100%), with the available sequences found in strains belonging to the genus Chryseobacterium and Flavobacterium isolated from fish. An identical neighborhood of tet(X) genes from both Chilean strains was observed. The genetic environment of tet(X) observed in the two strains of Epilithonimonas studied was characterized by the upstream location of a sequence encoding a hypothetical protein and a downstream located alpha/beta hydrolase-encoding gene, similar to the observed in some of the tet(X) genes carried by Chryseobacterium and Flavobacterium strains isolated from fish, but the produced proteins exhibited a low amino acid identity (25–27%) when compared to these synthesized by the Chilean strains. This study reports for the first time the carriage of the tet(X) gene by the Epilithonimonas genus and their detection in fish pathogenic bacteria isolated from farmed salmonids in Chile, thus limiting the use of therapies based on oxytetracycline, the antimicrobial most widely used in Chilean freshwater salmonid farming. This results suggest that pathogenic strains of the Chryseobacterium clade occurring in Chilean salmonid farms may serve as important reservoirs of tet(X) genes.

Chryseobacterium paridis sp. nov., an endophytic bacterial species isolated from the root of Paris polyphylla Smith var. yunnanensis.

A Gram-negative, yellow-pigmented, rod-shaped bacterial strain YIM B02567T was isolated from the root of Paris polyphylla Smith var. yunnanensis in China. Strain YIM B02567T grew optimally at 25-30°C and at pH 7.0 in the absence of NaCl on nutrient agar. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain YIM B02567T belong to the genus Chryseobacterium, and was closely related to Chryseobacterium piperi CTMT and Chryseobacterium soli DSM 19298T. Whole genome sequencing indicated that the genome size was 4,774,612bp and with a G + C content of 34.5mol%. Values of the ANI and the dDDH between strain YIM B02567T and its closely related Chryseobacterium species were below 81.72% and 24.7%. Strain YIM B02567T contained menaquinone-6 as the sole isoprenoid quinone, anteiso-C15:0, iso-C17:1 ω9c and iso-C17:0 3-OH as major fatty acids and phosphatidylethanolamine as major polar lipid. Based on the polyphasic analyses, strain YIM B02567T could be differentiated genotypically and phenotypically from recognized species of the genus Chryseobacterium. The isolate, therefore, represents a novel species, for which the name Chryseobacterium paridis sp. nov. is proposed. The type strain is YIM B02567T (= CGMCC 1.18657T).

Comparative Genomics Analysis of Keratin-Degrading Chryseobacterium Species Reveals Their Keratinolytic Potential for Secondary Metabolite Production.

A promising keratin-degrading strain from the genus Chryseobacterium (Chryseobacterium sp. KMC2) was investigated using comparative genomic tools against three publicly available reference genomes to reveal the keratinolytic potential for biosynthesis of valuable secondary metabolites. Genomic features and metabolic potential of four species were compared, showing genomic differences but similar functional categories. Eleven different secondary metabolite gene clusters of interest were mined from the four genomes successfully, including five common ones shared across all genomes. Among the common metabolites, we identified gene clusters involved in biosynthesis of flexirubin-type pigment, microviridin, and siderophore, showing remarkable conservation across the four genomes. Unique secondary metabolite gene clusters were also discovered, for example, ladderane from Chryseobacterium sp. KMC2. Additionally, this study provides a more comprehensive understanding of the potential metabolic pathways of keratin utilization in Chryseobacterium sp. KMC2, with the involvement of amino acid metabolism, TCA cycle, glycolysis/gluconeogenesis, propanoate metabolism, and sulfate reduction. This work uncovers the biosynthesis of secondary metabolite gene clusters from four keratinolytic Chryseobacterium species and shades lights on the keratinolytic potential of Chryseobacterium sp. KMC2 from a genome-mining perspective, can provide alternatives to valorize keratinous materials into high-value bioactive natural products.

Temporal Variability in the Rhizosphere Bacterial and Fungal Community Structure in the Melon Crop Grown in a Closed Hydroponic System

Microbes can establish a pathogenetic or symbiotic relationship with plants in soil and aquatic ecosystems. Although change in bacterial and fungal community in soil and their interaction with plants have been widely studied, little is known about their community structure in hydroponic systems across plant growth stages under different nutrient treatments. This study used next-generation sequencing analysis to assess the temporal changes in melon rhizosphere bacterial and fungal community structure across six different nutrient treatments. We found significant changes in the microbial community composition (especially for bacteria) between growth stages (R = 0.25–0.63, p < 0.01) than nutrient treatments. Proteobacteria dominated the bacterial community at the phylum level across melon growth stages (59.8% ± 16.1%). The genera Chryseobacterium, Pseudomonas, and Massilia dominated the rhizosphere in the flowering and pollination stage, while Brevibacillius showed the highest relative abundance in the harvesting stage. However, the rhizosphere was dominated by uncultured fungal taxa, likely due to the application of fungicides (Ridomil MZ). Further, linear regression analysis revealed a weak influence of bacterial community structure on melon yield and quality, while fruit weight and quality moderately responded to Mg and K deficiency. Nevertheless, the relative abundance of bacterial genus Chryseobacterium in the vegetative stage showed a strong correlation with fruit weight (R2 = 0.75, p < 0.05), while genera Brevibacillus, Lysobacter, and Bosea in late growth stages strongly correlated with fruit sweetness. Overall, temporal variability in the microbial (especially bacterial) community structure exceeds the variability between nutrient treatments for the given range of nutrient gradient while having little influence on melon yield.

Bacterial communities associated with sugarcane under different agricultural management exhibit a diversity of plant growth-promoting traits and evidence of synergistic effect

Plant-associated microbiomes have been a target of interest for the prospection of microorganisms, which may be acting as effectors to increase agricultural productivity. For years, the search for beneficial microorganisms has been carried out from the characterization of functional traits of growth-promotion using tests with a few isolates. However, eventually, the expectations with positive results may not be realized when the evaluation is performed in association with plants. In our study, we accessed the cultivable sugarcane microbiome under two conditions of agronomic management: organic and conventional. From the use of a new customized culture medium, we recovered 944 endophytic and epiphytic bacterial communities derived from plant roots, stalks, leaves, and rhizospheric soil. This could be accomplished by using a large-scale approach, initially performing an in planta (Cynodon dactylon) screening process of inoculation to avoid early incompatibility. The inoculation was performed using the bacterial communities, considering that in this way, they could act synergistically. This process resulted in 38 candidate communities, 17 of which had higher Indole-3-acetic acid (IAA) production and phosphate solubilization activity and, were submitted to a new in planta test using Brachiaria ruziziensis and quantification of functional traits for growth-promotion and physiological tests. Enrichment analysis of selected communities has shown that they derived mainly from epiphytic populations of sugarcane stalks under conventional management. The sequencing of the V3-V4 region of the 16S rRNA gene revealed 34 genera and 24 species distributed among the phylum Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. We also observed a network of genera in these communities where the genus Chryseobacterium stands out with a greater degree of interaction, indicating a possible direct or indirect role as a keystone taxon in communities with plant-growth promotion capacities. From the results achieved, we can conclude that the approach is useful in the recovery of a set of sugarcane bacterial communities and that there is, evidence of synergistic action providing benefits to plants, and that they are compatible with plants of the same family (Poaceae). Thus, we are reporting the beneficial bacterial communities identified as suitable candidates with rated potential to be exploited as bioinoculants for crops.

Genome analysis and antimicrobial resistance characteristics of Chryseobacterium aquaticum isolated from farmed salmonids

Fish diseases caused by bacterial genera belonging to the family Flavobacteriaceae, especially Tenacibaculum, Flavobacterium, and Chryseobacterium, are responsible for losses in wild and farmed fish around the world. In the last decade, the genus Chryseobacterium has rapidly grown in parallel with numerous novel Chryseobacterium species described from systemic infections of fish. Members of the family Flavobacteriaceae, isolated from fish, the environment, and clinical samples, have been reported to show low susceptibility to a broad range of antimicrobials. In this study, seventy C. aquaticum strains were isolated from diseased salmonids in Turkey. The phylogenetic analysis of all C. aquaticum strains, together with the reference strains in GenBank, which were obtained from different sources, including fish, plants, soil, water, and other animals, was performed by 16S rRNA gene sequence analysis. The antimicrobial susceptibility of each C. aquaticum strain was determined by a minimum inhibitory concentration (MIC) test. The isolate with the highest level of antimicrobial resistance, strain C-174, underwent a more detailed whole-genome sequence analysis for virulence and antimicrobial resistance genes (AMR) genes, genome size, and guanine-cytosine (GC) content.Phylogenetically, the 70 strains isolated from Turkey were assigned to three genogroups. Strains previously recovered from the rainbow trout, brown trout, and Siberian sturgeon were genetically very close to our strains. Most of the strains isolated in this study grew even in the presence of high concentrations of the tested antimicrobials, excluding enrofloxacin. Strain C-174 carried 74 putative functional genes encoding AMR and virulence. The number of putative AMR genes detected in the genome of strain C-174 was 46. The regulatory mechanisms of these genes involve antibiotic efflux (13), antibiotic target alteration (17), antibiotic inactivation (7), antibiotic target replacement (3), and antibiotic target protection (6). AMR genes confer resistance to multiple antibiotic groups, including among others, macrolides, fluoroquinolones, beta-lactams, tetracyclines, phenicols, sulphonamides, and diaminopyrimidines. We concluded that antimicrobial resistance could be of intrinsic nature. Furthermore, we detected three putative virulence genes in the genome of strain C-174 that have not been reported for C. aquaticum before. The results of this study demonstrated a strong correlation between these genes in the genome of C-174 and mortality in the rainbow trout.

Chryseobacterium cheonjiense sp. nov., isolated from forest soil.

A yellow-pigmented, non-motile and rod-shaped bacterium, designated RJ-7-14T was obtained from forest soil sampled at Cheonji-dong, Seogwipo-si, Jeju-do, South Korea. Cells were Gram-stain-negative and produced flexirubin type pigments. A phylogenetic analysis based on its 16S rRNA gene sequence revealed that strain RJ-7-14T formed a lineage within the family Weeksellaceae and clustered as members of the genus Chryseobacterium. The closest members were Chryseobacterium geocarposphaerae DSM 27617T (98.2% sequence similarity), Chryseobacterium hispalense DSM 25574T (98.0%) and Chryseobacterium nepalense KACC 18907T (98.0%). The sequence similarity for other members was < 98.0%. The genome was 4,276,416bp long with 9 scaffolds and 3779 protein-coding genes. The sole respiratory quinone was MK-6. The major cellular fatty acids were iso-C15:0, summed feature 9 (iso-C17:1 ω9c and/or C16:0 10-methyl), summed feature 3 (iso-C15:0 2-OH and/or C16: 1ω7c) and iso-C17:0 3-OH. The major polar lipid was phosphatidylethanolamine (PE). The DNA G + C content of the type strain was 37.2mol%. In addition, the average nucleotide identity (ANIu) and in silico DNA-DNA hybridization (dDDH) relatedness values between strain RJ-7-14T and phylogenetically closest members were ≤ 88.2% and ≤ 35.0%, respectively, which were below the threshold values of 95-96% (for ANI) and 70% (for dDDH), suggesting the allocation of novel strain to a new species. Based on genomic, chemotaxonomic, phenotypic and phylogenetic analyses, strain RJ-7-14T represents novel species in the genus Chryseobacterium, for which the name Chryseobacterium cheonjiense sp. nov. is proposed. The type strain is RJ-7-14T (= KACC 21625T = NBRC 114362T).

Effect on intestinal microbiota, bioaccumulation, and oxidative stress of Carassius auratus gibelio under waterborne cadmium exposure.

Cadmium (Cd) is a hazardous pollutant known to exert various toxic effects and other sublethal effects on aquatic organisms, and induce a variety of adverse effects on human health, and can be commonly found in environment. The aim of this study was to explore the effects of waterborne Cd exposure on the intestinal microbiota, and Cd accumulation and oxidative response in Carassius auratus gibelio (C. gibelio). The fish were exposed to waterborne Cd at 0, 1, 2, and 4mg/L for 30days. Waterborne Cd exposure resulted marked alterations in the composition of microbiota. At the genus level, Bacteroides, Aeromonas, Akkermansia, Acinetobacter, Chryseobacterium, Shinella, Cetobacterium and Bacillus were significantly changed in Cd groups. The results obtained indicate that Cd exposure significantly increased the bioaccumulation level of Cd and profoundly affected antioxidant enzyme including superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), total antioxidant (T-AOC), malonaldehyde (MDA), and glutathione-S-transferase (GST). The present findings may provide a new framework for the role of gut microbiota in the response to environmental chemical contamination and in the pathogenesis of body disorders.

Chryseobacterium antibioticum sp. nov. with antimicrobial activity against Gram-negative bacteria, isolated from Arctic soil.

A yellow-pigmented, non-motile, Gram-stain-negative, pleomorphic bacterium, designated RP-3-3T was obtained from soil sampled at the Arctic region in Cambridge Bay, NU, Canada. The strain is strictly aerobic, psychrotolerant, grow optimally at 15-20 °C and produces flexirubin type pigments. The strain is able to hydrolyse CM-cellulose, casein, starch and DNA. Strain RP-3-3T showed antimicrobial activity against Gram-negative pathogens. A phylogenetic analysis based on its 16S rRNA gene sequence revealed that strain RP-3-3T formed a lineage within the family Weeksellaceae and clustered as members of the genus Chryseobacterium. The closest members were Chryseobacterium shigense DSM 17126T (98.7% sequence similarity), Chryseobacterium carnipullorum DSM 25581T (98.7%) and Chryseobacterium oncorhychi 701B-08T (98%). The genome is 4,910,468 bp long with 73 scaffolds and 4300 protein-coding genes. The anti-SMASH analysis of whole genome showed ten putative biosynthetic gene clusters responsible for various secondary metabolites. The sole respiratory quinone is MK-6. The major cellular fatty acids are iso-C15:0, iso-C17:1 ω9c, iso-C17:0 3-OH, summed feature 3 (iso-C15 :0 2-OH/C16 :1ω7c) and anteiso-C15:0. The major polar lipid is phosphatidylethanolamine. The DNA G + C content of the type strain is 36.9 mol%. In addition, the average nucleotide identity and in silico DNA-DNA hybridization relatedness values between strain RP-3-3T and phylogenetically closest members are below the threshold value for species delineation. Based on genomic, chemotaxonomic, phenotypic and phylogenetic analyses, strain RP-3-3T represents novel species in the genus Chryseobacterium, for which the name Chryseobacterium antibioticum sp. nov. is proposed. The type strain is RP-3-3T (=KACC 21620T = NBRC 114360T).

Chryseobacterium vaccae sp. nov., isolated from raw cow's milk.

Strain CA7T, a Gram-stain-negative, non-motile, non-spore-forming, aerobic and rod-shaped bacterial strain, was isolated from raw cow's milk collected from a farm affiliated with Chung-Ang University, Anseong, Korea, and characterized by a polyphasic approach. Optimal growth of strain CA7T was observed on tryptic soy agar at 30 °C and pH 7.0 with 0 % NaCl. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain CA7T belonged to the genus Chryseobacterium. The most closely related strains (16S rRNA gene sequence similarity indicated in parentheses), based on the phylogenetic analysis, were Chryseobacterium rhizosphaerae KCTC 22548T (98.08 %), Chryseobacterium nakagawai CCUG 60563T (98.61 %), Chryseobacterium jejuense KACC 12501T (97.85 %) and Chryseobacterium aurantiacum KCTC 62135T (97.78 %). Whole genome sequencing indicated that the genome size was 5 125 723 bp and had a DNA G+C content of 37.4 mol%. Average nucleotide identity values for strain CA7T with C. rhizosphaerae, C. nakagawai, C. jejuense, C. aurantiacum, and the type species of the genus Chryseobacterium, C. gleum, were 80.2, 79.8, 79.8, 79.6 and 80.4 %, respectively. The digital DNA-DNA hybridization values of CA7T compared to C. rhizosphaerae, C. nakagawai, C. jejuense, C. aurantiacum and C. gleum were 24.1, 23.9, 23.9, 23.7 and 24.3 %, respectively. The major fatty acids were iso-C15 : 0, summed feature 9 (iso-C17 : 1 ω9c and/or C16 : 0 10-methyl), iso-C17 : 0 3-OH and summed feature 3 (iso-C15 : 0 2-OH and/or C16 : 1 ω7c). Menaquinone-6 was the only respiratory quinone. The major polar lipid was phosphatidylethanolamine. Based on this polyphasic taxonomic study, strain CA7T represents a novel species of the genus Chryseobacterium for which the name Chryseobacterium vaccae sp. nov. is proposed. The type strain is CA7T (=KACC 21402T=JCM 33749T).

River bacterial community structure and co-occurrence patterns under the influence of different domestic sewage types

Bacterial communities play a critical role in food webs and the biogeochemical cycles of fundamental elements. However, there remains a substantial gap in our knowledge of the anthropogenic impacts on bacterial co-occurrence patterns and ecosystem functions. In this study, we used Illumina high-throughput sequencing to characterize and compare the diversity, composition, co-occurrence patterns, and functional changes in bacterial communities in the Qingliu River under the influence of different types of domestic sewage. Twelve samples had similar dominant phyla, mainly Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes, differing only in the proportions of the microorganisms. However, there was a large difference at the genus level, for example, the relative abundance of the genus Dechloromonas in the school sewage water samples (XXW) was much higher than that in the other samples, the genus Chryseobacterium was the dominant bacteria in the residential sewage water samples (JMW), and there were significant differences between the different samples (P < 0.01). This may indicate that external pollution and environmental induction deeply affect the bacterial community assembly in rivers. Network analysis showed that the river bacterial co-occurrence network has a modular structure (divided into 6 modules), and that the microbial taxonomic units from the same module were involved in the carbon and nitrogen cycle (e.g., the CL500-29 marine group and the genus Pseudomonas) and degradation of organic pollutants and toxic compounds (e.g., the genera Massilia and Exiguobacterium). Functional predictions indicate that the function of ABC transporter was highest in the hospital sewage water samples (YYW), while two-component system was more abundant in the XXW samples. In summary, our research provides a new perspective of community assembly in rivers under the influence of human activity.

Chryseobacterium salivictor sp. nov., a plant-growth-promoting bacterium isolated from freshwater.

A Gram-stain-negative, non-motile, rod-shaped bacterial strain, designated NBC 122T, was isolated from freshwater of the Nakdong River Republic of Korea. Growth occurred at pH 5.0-8.0 (optimum, pH 7.0), at 4-37°C (optimum, 25°C), and with 0-3.5% (w/v) NaCl (optimum, 1%). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain NBC 122T belongs to the genus Chryseobacterium and is most closely related to Chryseobacterium antarcticum AT1013T (97.85%). The average nucleotide identity and in silico DNA-DNA hybridization (DDH) values between strain NBC 122T and related Chryseobacterium species were 77.77-80.28 and 20.9-23.2%, respectively. The strain NBC 122T contained MK-6 as the major respiratory quinone. The major fatty acids included anteiso C15:0, iso C15:0, summed feature 9 (C17:1 iso ω9c, C16:0 10-methyl) and iso C17:0 3-OH, and the polar lipids were phosphatidylethanolamine, five unidentified aminolipids and six unidentified lipids. The DNA G + C content was 37.5mol%. On the basis of a 16S rRNA gene phylogeny and comparative phenotypic analyses, strain NBC 122T represents a novel species in the genus Chryseobacterium, for which the name Chryseobacterium salivictor sp. nov. is proposed. The type strain is NBC122T (= KCTC 72248T = JCM 33980T).

Taxonomic and functional diversity of cultivable endophytes with respect to the fitness of cultivars against Ralstonia solanacearum

The study was conducted to comprehend the facets of culturable endophytic diversity correlating with the fitness of cultivar. Tomato bacterial endophytes from cultivars Arka Rakshak (AR; multi-disease tolerant hybrid) and Pusa Ruby (PR; susceptible check) were isolated. Molecular identification quantified that only two genera Rhizobium and Bacillus were common in both cultivars out of fifteen genera isolated. Genera Microbacterium, Enterobacter, Falsibacillus, Cohnella, Youhaiella, and Fluviicola were found only in AR, whereas genera Chryseobacterium, Pseudomonas, Dyadobacter, Staphylococcus, Micrococcus, Microvirga, and Shinella were found only in PR. Although the genera level diversity indicated cultivar specificity, except for firmicutes (7 in AR and 4 in PR), the distribution of taxonomic class alphaproteobacteria, gammaproteobacteria, bacteroidetes, and actinobacteria was almost similar. Gram-positive class was dominated by firmicutes and Gram-negative by alphaproteobacteria in both cultivars. On contrary, the collective functional profile for the production of hydrogen cyanide, ammonia, and siderophore, apart from phosphate solubilization and indole acetic acid production, indicated the dominance of endophytes from AR (multi-disease tolerant hybrid). The pattern of antagonistic ability against 15 different strains of R. solanacearum indicated that endophytes from tolerant cultivar exhibit higher in vitro suppression. The number of antagonists and the extent of inhibition both were higher in AR endophytes. However, the genetic capability for harboring eight antimicrobial compounds producing genes was found to be well distributed in both cultivars. Results showed that the functional aspects of these bacterial endophytes correlate with cultivar fitness more than that of taxonomic and genetic diversity.

Chryseobacterium lacus sp. nov. Isolated From the Surface Water of Two Lakes With Light-Induced Carotenoid Production.

Two Gram-stain-negative, rod-shaped, gliding, catalase-positive, and facultative anaerobic strains, YLOS41T and XH07, were isolated from surface water of Yilong Lake and West Lake of Dali in Yunnan Province, respectively. Both strains were yellow-colored under light conditions and white-colored under dark conditions. The results of physiological and chemotaxonomic characterization, sequencing and phylogenetic analysis, and draft genome sequence comparison demonstrated that the two strains represented a single novel species within the genus Chryseobacterium, for which the name Chryseobacterium lacus sp. nov. is proposed. The type strain is YLOS41T (= KCTC 62352T = MCCC 1H00300T), and the second strain is XH07 (= KCTC 62993). During the cultivation process, we found that the colony color of the two strains changed from white to yellow with illumination. The study investigated the effects of light irradiation on the strain YLOS41T. Results showed that light irradiation did not affect the growth of cells but significantly increased carotenoid synthesis, which caused the change of colony color. In-depth metabolic analysis was conducted by transcriptome. The predominant changes were found for genes involved in carotenoid synthesis as protection from light damage. Based on the genome and transcriptome, we proved that strain YLOS41T possessed a complete synthetic pathway of carotenoid and speculated that the production was zeaxanthin. This was the first report of Chryseobacterium species with light-induced carotenoid synthesis. This study enhances our present knowledge on how Chryseobacterium species isolated from surface water responds to light damage.

Isolation of Chryseobacterium siluri sp. nov., from liver of diseased catfish (Silurus asotus)

Yellow-pigmented, circular bacteria (strain SNU WT7) were isolated from the liver of moribund eastern catfish (Silurus asotus). Our study focused on the taxonomic description of SNU WT7 using phylogenetic, phenotypic, and chemotaxonomic analyses. The 16S rRNA gene sequence of the SNU WT7 strain was highly similar to that of Chryseobacterium haifense H38T (97.29% similarity), followed by Chryseobacterium hominis P2K6T (97.22% similarity), while other species exhibited similarity values of less than 97.0%. The genome of strain SNU WT7 displayed average nucleotide identity and genome-to-genome distance values of 72.35% and 22.0%, respectively, which clearly indicated that the novel species was distant from the other Chryseobacterium species, with its closest relative being C. haifense H38T. Furthermore, the phenotypic characteristics, including acid production from glucose, D-fructose, lactose, and maltose, of strain SNU WT 7 differed from those of C. haifense H38T. The major polar lipid of the strain was phosphatidylethanolamine, and several unidentified aminolipids and lipids were also present. Similar to other Chryseobacterium species, the quinone system was composed mainly of MK-6. The genome of SNU WT7 is 2,690,367 bp with a G + C content of 43.6%. Taken together, our data indicate that the isolate SNU WT7 represents a novel species of the genus Chryseobacterium. Thus, we present the name Chryseobacterium siluri sp. nov. for the novel type strain SNU WT7T (KCTC 72626, JCM 33707).