Biological and Chemical Approaches for Controlling Harmful Microcystis Blooms.

The proliferation of harmful cyanobacterial blooms dominated by Microcystis aeruginosa has become an increasingly serious problem in freshwater ecosystems due to climate change and eutrophication. Microcystis-blooms in freshwater generate compounds with unpleasant odors, reduce the levels of dissolved O2, and excrete microcystins into aquatic ecosystems, potentially harming various organisms, including humans. Various chemical and biological approaches have thus been developed to mitigate the impact of the blooms, though issues such as secondary pollution and high economic costs have not been adequately addressed. Red clays and H2O2 are conventional treatment methods that have been employed worldwide for the mitigation of the blooms, while novel approaches, such as the use of plant or microbial metabolites and antagonistic bacteria, have also recently been proposed. Many of these methods rely on the generation of reactive oxygen species, the inhibition of photosynthesis, and/or the disruption of cellular membranes as their mechanisms of action, which may also negatively impact other freshwater microbiota. Nevertheless, the underlying molecular mechanisms of anticyanobacterial chemicals and antagonistic bacteria remain unclear. This review thus discusses both conventional and innovative approaches for the management of M. aeruginosa in freshwater bodies.

Peptostreptococcus equinus sp. nov., isolated from horse faeces.

A Gram-stain-positive, non-spore-forming, and obligate anaerobic bacteria designated strain CBA3647T was isolated from a horse faecal sample in Jeju, Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain CBA3647T formed a distinct phyletic lineage from closely related species within the genus Peptostreptococcus. Based on comparative analysis of 16S rRNA gene sequences, Peptostreptococcus anaerobius ATCC 27337T is most closely related to strain CBA3647T with a 16S rRNA gene similarity of 98.31 %, while similarity to other type strains is below 98.0 %. The genomic DNA G+C content of strain CBA3647T was 30.0 mol%. The digital DNA-DNA hybridization values between strain CBA3647T and the six Peptostreptococcus species were equal to or less than 24 %. Cells were non-motile and oval-shaped cocci with catalase-positive and oxidase-negative activities. Growth occurred at 20-40 °C (optimum, 35 °C), pH 6-8 (optimum, pH 7), and in the presence of 0-2 % (w/v) NaCl (optimum, 1 %). Strain CBA3647T contained C14 : 0 iso and C16 : 0 as major fatty acids. Phenotypic, chemotaxonomic, and molecular properties of strain CBA3647T suggest that it represents a novel species in the genus Peptostreptococcus, which has been named Peptostreptococcus equinus sp. nov. The type strain is CBA3647T (=KACC 22891T= JCM 35846T).

Roseibium algicola sp. nov. and Roseibium porphyridii sp. nov., isolated from marine red algae.

Two Gram-stain-negative, strictly aerobic rods, designated as RMAR6-6T and KMA01T, exhibiting catalase- and oxidase-positive activities, were isolated from marine red algae in the Republic of Korea. Cells of strain RMAR6-6T exhibited flagellar motility, while those of strain KMA01T were non-motile. Strain RMAR6-6T exhibited optimal growth at 30-35°C and pH 7.0-8.0 with 4.0-6.0 % (w/v) NaCl, while strain KMA01T grew optimally at 30-35 °C, pH 7.0-8.0 and 2.0-5.0% NaCl. Both strains shared common major respiratory isoprenoid quinone (ubiquinone-10), cellular fatty acids (C18 : 0, C18: 1 ω7c 11-methyl, C20 : 1 ω7c and summed feature 8) and polar lipids (phosphatidylglycerol, phosphatidylmonomethylethanolamine, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and sulphoquinovosyldiacylglycerol). The genomic DNA G+C contents were 59.0 and 55.0 mol% for strains RMAR6-6T and KMA01T, respectively. With 98.5 % 16S rRNA gene similarity, 75.2 % average nucleotide identity (ANI) and 19.8 % digital DNA-DNA hybridization (dDDH) values, strains RMAR6-6T and KMA01T were identified as representing distinct species. Phylogenetic analyses based on both 16S rRNA gene and genome sequences revealed that strains RMAR6-6T and KMA01T formed distinct phylogenic lineages within the genus Roseibium, most closely related to Roseibium aggregatum IAM 12614T and Roseibium album CECT 5094T, respectively. The ANI and dDDH values between strain RMAR6-6T and R. aggregatum IAM 12614T were 87.5 and 33.3 %, respectively. Similarly, the values between KMA01T and R. album CECT 5094T were 74.2 % (ANI) and 19.3 % (dDDH). Based on phenotypic, chemotaxonomic and molecular characteristics, strains RMAR6-6T and KMA01T represent two novel species of the genus Roseibium, for which the names R. algicola sp. nov. (RMAR6-6T=KACC 22482T=JCM 34977T) and R. porphyridii sp. nov. (KMA01T=KACC 22479T=JCM 34597T) are proposed, respectively.

Enzymatic Activity and Amino Acids Production of Predominant Fungi from Traditional Meju during Soybean Fermentation.

To investigate the effect of the predominant fungal species from Korean traditional meju and doenjang on soybean fermentation, the enzymatic activity and amino acid production of twenty-two fungal strains were assessed through solid- and liquid-state soybean fermentation. Enzymatic activity analyses of solid-state fermented soybeans revealed different enzyme activities involving protease, leucine aminopeptidase (LAP), carboxypeptidase (CaP), glutaminase, γ-glutamyl transferase (GGT), and amylase, depending on the fungal species. These enzymatic activities significantly affected the amino acid profile throughout liquid-state fermentation. Strains belonging to Mucoromycota, including Lichtheimia, Mucor, Rhizomucor, and Rhizopus, produced smaller amounts of total amino acids and umami-producing amino acids, such as glutamic acid and aspartic acid, than strains belonging to Aspergillus subgenus circumdati. The genera Penicillium and Scopulariopsis produced large amounts of total amino acids and glutamic acid, suggesting that these genera play an essential role in producing umami and kokumi tastes in fermented soybean products. Strains belonging to Aspergillus subgenus circumdati, including A. oryzae, showed the highest amino acid content, including glutamic acid, suggesting the potential benefits of A. oryzae as a starter for soybean fermentation. This study showed the potential of traditional meju strains as starters for soybean fermentation. However, further analysis of processes such as the production of G-peptide for kokumi taste and volatile compounds for flavor and safety is needed.

Comparative pangenome analysis of Aspergillus flavus and Aspergillus oryzae reveals their phylogenetic, genomic, and metabolic homogeneity.

Aspergillus flavus and Aspergillus oryzae are closely related fungal species with contrasting roles in food safety and fermentation. To comprehensively investigate their phylogenetic, genomic, and metabolic characteristics, we conducted an extensive comparative pangenome analysis using complete, dereplicated genome sets for both species. Phylogenetic analyses, employing both the entirety of the identified single-copy orthologous genes and six housekeeping genes commonly used for fungal classification, did not reveal clear differentiation between A. flavus and A. oryzae genomes. Upon analyzing the aflatoxin biosynthesis gene clusters within the genomes, we observed that non-aflatoxin-producing strains were dispersed throughout the phylogenetic tree, encompassing both A. flavus and A. oryzae strains. This suggests that aflatoxin production is not a distinguishing trait between the two species. Furthermore, A. oryzae and A. flavus strains displayed remarkably similar genomic attributes, including genome sizes, gene contents, and G + C contents, as well as metabolic features and pathways. The profiles of CAZyme genes and secondary metabolite biosynthesis gene clusters within the genomes of both species further highlight their similarity. Collectively, these findings challenge the conventional differentiation of A. flavus and A. oryzae as distinct species and highlight their phylogenetic, genomic, and metabolic homogeneity, potentially indicating that they may indeed belong to the same species.

Comparative pangenome analysis of Enterococcus faecium and Enterococcus lactis provides new insights into the adaptive evolution by horizontal gene acquisitions.

BACKGROUND: Enterococcus faecium and E. lactis are phylogenetically closely related lactic acid bacteria that are ubiquitous in nature and are known to be beneficial or pathogenic. Despite their considerable industrial and clinical importance, comprehensive studies on their evolutionary relationships and genomic, metabolic, and pathogenic traits are still lacking. Therefore, we conducted comparative pangenome analyses using all available dereplicated genomes of these species. RESULTS: E. faecium was divided into two subclades: subclade I, comprising strains derived from humans, animals, and food, and the more recent phylogenetic subclade II, consisting exclusively of human-derived strains. In contrast, E. lactis strains, isolated from diverse sources including foods, humans, animals, and the environment, did not display distinct clustering based on their isolation sources. Despite having similar metabolic features, noticeable genomic differences were observed between E. faecium subclades I and II, as well as E. lactis. Notably, E. faecium subclade II strains exhibited significantly larger genome sizes and higher gene counts compared to both E. faecium subclade I and E. lactis strains. Furthermore, they carried a higher abundance of antibiotic resistance, virulence, bacteriocin, and mobile element genes. Phylogenetic analysis of antibiotic resistance and virulence genes suggests that E. faecium subclade II strains likely acquired these genes through horizontal gene transfer, facilitating their effective adaptation in response to antibiotic use in humans. CONCLUSIONS: Our study offers valuable insights into the adaptive evolution of E. faecium strains, enabling their survival as pathogens in the human environment through horizontal gene acquisitions.

Devosia rhodophyticola sp. nov. and Devosia algicola sp. nov., isolated from a marine red alga.

Two Gram-stain-negative, obligately aerobic, motile rod bacteria, designated as G2-5T and G20-9T, exhibiting catalase- and oxidase-positive activities, were isolated from the phycosphere of a Chondrus species, a marine red alga. Strain G2-5T exhibited optimal growth at 30 °C and pH 5.0-6.0 and in the presence of 0.5-1.0% NaCl. In contrast, strain G20-9T demonstrated optimal growth at 25 °C and pH 6.0 and in the presence of 0.5-1.5% NaCl. Both strains contained ubiquinone-10, summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C18 : 0 and 11-methyl-C18 : 1 ω7c, and diphosphatidylglycerol and phosphatidylglycerol as the major respiratory isoprenoid quinone, cellular fatty acids and polar lipids, respectively. The genomic DNA G+C contents were 57.2 mol% for strain G2-5T and 57.5 mol% for strain G20-9T. Strains G2-5T and G20-9T exhibited 98.2 % 16S rRNA gene sequence similarity, along with 82.3 % average nucleotide identity (ANI) and 25.0 % digital DNA-DNA hybridization (dDDH) values, indicating that they represent different species. Phylogenetic analyses based on both 16S rRNA gene and genome sequences revealed that strains G2-5T and G20-9T formed distinct phylogenic lineages within the genus Devosia. Strains G2-5T and G20-9T were most closely related to Devosia limi DSM 17137T and Devosia beringensis S02T with 97.7 and 96.9 % 16S rRNA gene sequence similarities, respectively. The ANI and dDDH values between strains G2-5T and G20-9T and other Devosia species were lower than 73.9 and 19.2 %, respectively, suggesting that they constitute novel species within the genus Devosia. Based on their distinct phenotypic, chemotaxonomic, and molecular characteristics, strains G2-5T and G20-9T represent two novel species of the genus Devosia, for which the names Devosia rhodophyticola sp. nov. (G2-5T=KACC 22601T=JCM 35404T) and Devosia algicola sp. nov. (G20-9T=KACC 22650T=JCM 35405T) are proposed, respectively.

Drosophila Gut Immune Pathway Suppresses Host Development-Promoting Effects of Acetic Acid Bacteria.

The physiology of most organisms, including Drosophila, is heavily influenced by their interactions with certain types of commensal bacteria. Acetobacter and Lactobacillus, two of the most representative Drosophila commensal bacteria, have stimulatory effects on host larval development and growth. However, how these effects are related to host immune activity remains largely unknown. Here, we show that the Drosophila development-promoting effects of commensal bacteria are suppressed by host immune activity. Mono-association of germ-free Drosophila larvae with Acetobacter pomorum stimulated larval development, which was accelerated when host immune deficiency (IMD) pathway genes were mutated. This phenomenon was not observed in the case of mono-association with Lactobacillus plantarum. Moreover, the mutation of Toll pathway, which constitutes the other branch of the Drosophila immune pathway, did not accelerate A. pomorum-stimulated larval development. The mechanism of action of the IMD pathway-dependent effects of A. pomorum did not appear to involve previously known host mechanisms and bacterial metabolites such as gut peptidase expression, acetic acid, and thiamine, but appeared to involve larval serum proteins. These findings may shed light on the interaction between the beneficial effects of commensal bacteria and host immune activity.

Alishewanella maricola sp. nov., isolated from seawater of the Yellow Sea.

A Gram-stain-negative and facultative aerobic bacterium, strain 16-MAT, was isolated from seawater of Yellow Sea in South Korea. Cells were catalase- and oxidase-positive and non-motile rods. Growth occurred at 4-37 °C (optimum, 30 °C) and pH 6.0-11.0 (optimum, 8.0), and in the presence of 0-7.0% NaCl (optimum, 3 %). Strain 16-MAT contained ubiquinone-8 as the sole isoprenoid quinone, C16 : 0 and summed feature three as the major fatty acids (>10 %), and phosphatidylglycerol, phosphatidylethanolamine, an unidentified phospholipid, an unidentified aminophospholipid, and an unidentified polar lipid as the major polar lipids. The genome size and DNA G+C content of strain 16-MAT were 3.69 Mb and 46.0 mol%, respectively. Strain 16-MAT was most closely related to Alishewanella alkalitolerans LNK-7.1T with a 97.9 % 16S rRNA gene sequence similarity. A phylogenomic tree based on whole genome sequences showed that strain 16-MAT formed a phylogenetic lineage within the genus Alishewanella. Based on the phenotypic, chemotaxonomic, and molecular analyses, strain 16-MAT represents a novel species of the genus Alishewanella, for which the name Alishewanella maricola is proposed. The type strain is 16-MAT (=KACC 22238T =JCM 34596T).

Psychroserpens ponticola sp. nov. and Marinomonas maritima sp. nov., isolated from seawater.

Two Gram-stain-negative, catalase- and oxidase-positive, aerobic non-motile and motile rod bacteria, strains MSW6T and RSW2T, were isolated from surface seawater. Strain MSW6T optimally grew at 20 °C, pH 7.0 and 3 % NaCl, while strain RSW2T optimally grew at 25 °C, pH 7.0-8.0 and 2 % NaCl. Strain MSW6T possessed menaquinone-6 as the major respiratory quinone, and its major fatty acids were iso-C15 : 1 G, iso-C15 : 0 and iso-C15 : 0 3-OH. The major polar lipid identified in strain MSW6T was phosphatidylethanolamine (PE). On the other hand, strain RSW2T had ubiquinone-8 as the predominant respiratory quinone, and its major fatty acids consisted of summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and C16 : 0. The major polar lipids identified in strain RSW2T were PE and phosphatidylglycerol. As the sole respiratory quinone, strain MSW6T possessed menaquinone-6, while strain RSW2T had ubiquinone-8. The DNA G+C contents of strains MSW6T and RSW2T were 31.9 and 43.4 mol%, respectively. Phylogenetic analyses based on 16S rRNA and core gene sequences showed that strain MSW6T formed a phylogenic lineage with Psychroserpens mesophilus KOPRI 13649T, while strain RSW2T formed a phylogenic lineage with Marinomonas primoryensis KMM 3633T. Strain MSW6T shared 97.9 % 16S rRNA gene sequence similarity and 80.7 % average nucleotide identity (ANI) ith P. mesophilus KOPRI 13649T, and strain RSW2T shared 99.1 % 16S rRNA gene sequence similarity and 93.1 % ANI with M. primoryensis KMM 3633T. Based on the results of phenotypic, chemotaxonomic and phylogenetic analyses, strains MSW6T and RSW2T represent novel species of the genera Psychroserpens and Marinomonas, respectively, for which the names Psychroserpens ponticola sp. nov. and Marinomonas maritima sp. nov. are proposed, respectively. The type strain of P. ponticola is MSW6T (=KACC 22338T=JCM 35022T) and the type strain of M. maritima is RSW2T (=KACC 22716T=JCM 35550T).

Hoeflea algicola sp. nov. and Hoeflea ulvae sp. nov., isolated from phycosphere of marine algae.

Two Gram-negative, moderately halophilic, and motile rod bacteria, strains G2-23T and J2-29T, showing catalase- and oxidase-positive activities were isolated from species of the marine algae Chondrus and Ulva, respectively. Both strains optimally grew at 30 °C, pH 7.0 and 2% (w/v) NaCl. Both strains contained ubiquinone-10 as the sole isoprenoid quinone. Strain G2-23T contained summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C16 : 0 and summed feature 3 (iso-C15 : 0 2-OH and/or C16 : 1 ω7c/ω6c) as major cellular fatty acids, and phosphatidylethanolamine (PE), phosphatidyl-N-monomethylethanolamine (PME), phosphatidylglycerol (PG), diphosphatidylglycerol and an unidentified phospholipid (PL) as major polar lipids. Strain J2-29T contained summed feature 8, C18 : 1 ω7c 11-methyl and C16 : 0 as major cellular fatty acids and PE, PME, PG and PL as major polar lipids. The genomic DNA G+C contents of strains G2-23T and J2-29T were 59.5 and 62.2 mol%, respectively. Both strains shared 97.9 % 16S rRNA gene sequence similarity, 79.8 % average nucleotide identity (ANI) and 22.8 % digital DNA-DNA hybridization (dDDH) values, indicating that they represent different species. Phylogenetic and phylogenomic analyses by 16S rRNA gene and genome sequences, respectively, revealed that strains G2-23T and J2-29T formed different phylogenic lineages within the genus Hoeflea. ANI and dDDH values between strains G2-23T and J2-29T and other Hoeflea type strains were less than 79.0 and 22.1% and 80.5 and 23.3 %, respectively, suggesting that they represent novel species of the genus Hoeflea. In summary, based on their phenotypic, chemotaxonomic and molecular properties, strains G2-23T and J2-29T represent two different novel species of the genus Hoeflea, for which the names Hoeflea algicola sp. nov. (G2-23T=KACC 22714T=JCM 35548T) and Hoeflea ulvae sp. nov. (J2-29T=KACC 22715T=JCM 35549T), respectively, are proposed.

Peptoniphilus equinus sp. nov., a novel Gram-stain-positive anaerobic coccus isolated from the faeces of a thoroughbred racehorse.

A novel, anaerobic, Gram-stain-positive coccoid strain, CBA3646T, was isolated from the faeces of a thoroughbred racehorse. Phylogenetic analysis based on 16S rRNA gene sequencing yielded results indicative of CBA3646T representing a member of the genus Peptoniphilus, with the species most closely related to it being Peptoniphilus asaccharolyticus DSM 20463T, with a similarity of 94.79 %. DNA-DNA relatedness and average nucleotide identity values between CBA3646T and P. asaccharolyticus DSM 20463T were 21.4 and 67.6 %, respectively. CBA3646T has a circular chromosomal genome of 1 709 189 bp (45.5 mol% DNA G+C content), containing 1652 genes in total, 1584 predicted protein-coding genes, 3 complete rRNA loci and 47 tRNA genes. The cells were non-motile diplococci, catalase-positive and oxidase-negative. Growth of CBA3646T was observed at 20-40 °C (optimal temperature, 35 °C) and in the presence of 0-4 % (w/v) NaCl (optimum concentration, 1 %). The major fatty acids (>10 %) of CBA3646T were C16 : 0, C18 : 1ω9c and C18 : 1ω9c dimethyl acetal, with its major polar lipids being diphosphatidylglycerol and phosphatidylglycerol. The elucidated phylogenetic, physiological, chemotaxonomic and molecular properties are indicative of strain CBA3646T representing a novel species of the genus Peptoniphilus, or which the name Peptoniphilus equinus sp. nov. is proposed. The type strain is CBA3646T (= KACC 22890T = JCM 35845T).

Alkalicoccobacillus porphyridii sp. nov., isolated from a marine red alga, reclassification of Shouchella plakortidis and Shouchella gibsonii as Alkalicoccobacillus plakortidis comb. nov. and Alkalicoccobacillus gibsonii comb. nov., and emended description of the genus Alkalicoccobacillus Joshi et al. 2022.

A Gram-stain-positive alkali-tolerant and strictly aerobic bacterium, designated strain P16T, was isolated from a marine red alga, Porphyridium cruentum, in the Yellow Sea, Republic of Korea. Cells were motile rods with peritrichous flagella and exhibited catalase and oxidase activities. The optimal growth of strain P16T was observed to occur at 30 °C and pH 8.0 and in the presence of 2.0 % (w/v) NaCl. Menaquinone-7 was identified as the sole respiratory quinone. Strain P16T contained anteiso-C15 : 0, iso-C15 : 0, iso-C14 : 0 and iso-C16 : 0, and diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine as major cellular fatty acids and polar lipids, respectively. The G+C content of strain P16T was 40.8 mol%. Strain P16T was most closely related to Shouchella plakortidis P203T, Shouchella gibsonii DSM 8722T and Alkalicoccobacillus murimartini LMG 21005T with 98.1, 98.1 and 98.0 % 16S rRNA gene sequence similarities, respectively. Phylogenetic analyses based on 16S rRNA gene and genome sequences revealed that strain P16T, S, plakortidis, S. gibsonii and A. murimartini formed a single phylogenetic lineage cluster, and genomic relatedness analyses showed that they are different species. Based on phylogenetic, phenotypic, chemotaxonomic and molecular features, strain P16T represents a novel species of the genus Alkalicoccobacillus, for which the name Alkalicoccobacillus porphyridii sp. nov. is proposed. The type strain is P16T (=KACC 19520T=JCM 32931T). In addition, S. plakortidis and S. gibsonii are reclassified as Alkalicoccobacillus plakortidis comb. nov. (type strain P203T=DSM 19153T=NCIMB 14288T) and Alkalicoccobacillus gibsonii comb. nov. (type strain PN-109T=ATCC 700164T=DSM 8722T=KCCM 41407T), respectively.

Description and Genomic Characteristics of Weissella fermenti sp. nov., Isolated from Kimchi.

A Gram-positive, non-motile, and non-spore-forming lactic acid bacterium, designated as BK2T, was isolated from kimchi, a Korean traditional fermented vegetable food, and the taxonomic characteristics of strain BK2T, along with strain LMG 11983, were analyzed. Both strains optimally grew at 30°C, pH 7.0, and 1.0% NaCl. Cells of both strains were heterofermentative and facultatively anaerobic rods, demonstrating negative reactions for catalase and oxidase. Major fatty acids (>10%) identified in both strains were C18:1 ω9c, C16:0, and summed feature 7 (comprising C19:1 ω6c and/or C19:1 ω7c). The genomic DNA G+C contents of both strains were 44.7 mol%. The 16S rRNA gene sequence similarity (99.9%), average nucleotide identity (ANI; 99.9%), and digital DNA-DNA hybridization (dDDH; 99.7%) value between strains BK2T and LMG 11983 indicated that they are different strains of the same species. Strain BK2T was most closely related to Weissella confusa JCM 1093T and Weissella cibaria LMG 17699T, with 100% and 99.4% 16S rRNA gene sequence similarities, respectively. However, based on the ANI and dDDH values (92.3% and 48.1% with W. confusa, and 78.4% and 23.5% with W. cibaria), it was evident that strain BK2T represents a distinct species separate from W. confusa and W. cibaria. Based on phylogenetic, phenotypic, and chemotaxonomic features, strains BK2T and LMG 11983 represent a novel species of the genus Weissella, for which the name Weissella fermenti sp. nov. is proposed. The type of strain is BK2T (=KACC 22833T=JCM 35750T).

Staphylococcus equorum plasmid pKS1030-3 encodes auxiliary biofilm formation and trans-acting gene mobilization systems.

The foodborne bacterium Staphylococcus equorum strain KS1030 harbours plasmid pSELNU1, which encodes a lincomycin resistance gene. pSELNU1 undergoes horizontal transfer between bacterial strains, thus spreading antibiotic resistance. However, the genes required for horizontal plasmid transfer are not encoded in pSELNU1. Interestingly, a relaxase gene, a type of gene related to horizontal plasmid transfer, is encoded in another plasmid of S. equorum KS1030, pKS1030-3. The complete genome of pKS1030-3 is 13,583 bp long and encodes genes for plasmid replication, biofilm formation (the ica operon), and horizontal gene transfer. The replication system of pKS1030-3 possesses the replication protein-encoding gene repB, a double-stranded origin of replication, and two single-stranded origins of replication. The ica operon, relaxase gene, and a mobilization protein-encoding gene were detected in pKS1030-3 strain-specifically. When expressed in S. aureus RN4220, the ica operon and relaxase operon of pKS1030-3 conferred biofilm formation ability and horizontal gene transfer ability, respectively. The results of our analyses show that the horizontal transfer of pSELNU1 of S. equorum strain KS1030 depends on the relaxase encoded by pKS1030-3, which is therefore trans-acting. Genes encoded in pKS1030-3 contribute to important strain-specific properties of S. equorum KS1030. These results could contribute to preventing the horizontal transfer of antibiotic resistance genes in food.

Comparative Genomic Analysis and BTEX Degradation Pathways of a Thermotolerant Cupriavidus cauae PHS1.

Volatile organic compounds such as benzene, toluene, ethylbenzene, and isomers of xylenes (BTEX) constitute a group of monoaromatic compounds that are found in petroleum and have been classified as priority pollutants. In this study, based on its newly sequenced genome, we reclassified the previously identified BTEX-degrading thermotolerant strain Ralstonia sp. PHS1 as Cupriavidus cauae PHS1. Also presented are the complete genome sequence of C. cauae PHS1, its annotation, species delineation, and a comparative analysis of the BTEX-degrading gene cluster. Moreover, we cloned and characterized the BTEX-degrading pathway genes in C. cauae PHS1, the BTEX-degrading gene cluster of which consists of two monooxygenases and meta-cleavage genes. A genome-wide investigation of the PHS1 coding sequence and the experimentally confirmed regioselectivity of the toluene monooxygenases and catechol 2,3-dioxygenase allowed us to reconstruct the BTEX degradation pathway. The degradation of BTEX begins with aromatic ring hydroxylation, followed by ring cleavage, and eventually enters the core carbon metabolism. The information provided here on the genome and BTEX-degrading pathway of the thermotolerant strain C. cauae PHS1 could be useful in constructing an efficient production host.

Dyadobacter pollutisoli sp. nov., isolated from plastic waste landfill soil.

A Gram-stain-negative, yellow-pigmented and facultatively aerobic bacterium, designated strain U1T, was isolated from plastic dumped soil sampled in the Republic of Korea. Cell of strain U1T were non-motile rods showing catalase-negative and oxidase-positive activities. Strain U1T was shown to grow at 10-37 °C (optimum, 25-30 °C) and pH 6.0-9.0 (optimum, pH 8.0), and in the presence of 0-0.5 % (w/v) NaCl (optimum, 0 %). Strain U1T contained iso-C15 : 0, C16 : 0, C16 : 1 ω5c and summed feature 3 (comprising C16 : 1 ω6c and/or C16 : 1 ω7c) as the major cellular fatty acids (>5 %) and menaquinone-7 as the sole respiratory quinone. Phosphatidylethanolamine, two unidentified aminolipids and three unidentified lipids were identified as the major polar lipids. The DNA G+C content of strain U1T calculated from the whole-genome sequence was 45.5 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain U1T formed a distinct phylogenetic lineage within the genus Dyadobacter. Strain U1T has the highest 16S rRNA sequence similarity to Dyadobacter bucti QTA69T (97.9 %). Average nucleotide identity and digital DNA-DNA hybridization values between strain U1T and D. bucti QTA69T were 74.6 % and 18.9 %, respectively. Based on phenotypic, chemotaxonomic and molecular features, strain U1T represents a novel species of the genus Dyadobacter, for which the name Dyadobacter pollutisoli sp. nov. is proposed. The type strain is U1T (= KACC 22210T=JCM 34491T).

Tahibacter soli sp. nov., isolated from soil and Tahibacter amnicola sp. nov., isolated from freshwater.

Two Gram-stain-negative, facultative aerobic, catalase- and oxidase-positive, and non-motile rod bacteria, strains BLT and W38T, that were isolated from soil and freshwater, respectively, were taxonomically characterized. Both strains optimally grew at 30 °C and pH 7.0 in Reasoner's 2A medium and contained ubiquinone-8 as the sole respiratory quinone. As major fatty acids (>10 %), strain BLT contained iso-C15 : 0 and summed features 3 and 9 (comprising iso-C15 : 0 2-OH and/or C16 : 1 ω7c/ω6c and iso-C17 : 1 ω9c and/or C16 : 0 10-methyl, respectively), whereas strain W38T contained iso-C15 : 0, iso-C16 : 0 and summed feature 9. Diphosphatidylglycerol and phosphatidylmonomethylethanolamine as major polar lipids and phosphatidylethanolamine and phosphatidylglycerol as minor polar lipids were detected in both strains. The DNA G+C contents of strains BLT and W38T were 68.3 and 65.3 %, respectively. Phylogenetic analyses based on 16S rRNA gene and genome sequences revealed that strains BLT and W38T formed a tight phylogenetic lineage with Tahibacter species, and they shared 98.8 % 16S rRNA gene sequence similarity and 75.5 % average nucleotide identity (ANI) and 16.6 % digital DNA-DNA hybridization (dDDH) values, indicating that they are different species. Strains BLT and W38T were most closely related to Tahibacter caeni BUT-6T and Tahibacter aquaticus PYM5-11T with 97.7 and 98.0 % 16S rRNA gene sequence similarities, respectively. ANI and dDDH values between strain BLT and T. caeni BUT-6T and between strain W38T and T. aquaticus DSM 21667T were 78.5 and 21.6% and 75.3 and 21.0 %, respectively. Based on their phenotypic, chemotaxonomic and genomic properties, strains BLT and W38T represent two different novel species of the genus Tahibacter, for which the names Tahibacter soli sp. nov. and Tahibacter amnicola sp. nov. are proposed. The type strains of T. soli and T. amnicola are BLT (=KACC 22831T=JCM 35402T) and W38T (=KACC 22832T=JCM 35749T), respectively.

Neobacillus terrae sp. nov., isolated from mountain soil.

A Gram-stain-positive, spore-forming and facultative aerobic bacterium, designated C11T, was isolated from mountain soil collected in the Republic of Korea. The cells were motile rods with peritrichous flagella, and positive for catalase and oxidase activities. Strain C11T grew at 15-45 °C (optimum, 30-37 °C) and pH 6.0-8.0 (optimum, pH 6.0) and in the presence of 0-1 % (w/v) NaCl (optimum, 0.5 %). Strain C11T contained menaquinone-7 as the sole isoprenoid quinone and iso-C15 : 0, iso-C16 : 0 and anteiso-C15 : 0 as the major fatty acids. Diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine were the major polar lipids. The G+C content of the genomic DNA was 38.8 mol%. Strain C11T was most closely related to Neobacillus drentensis IDA1967T and Mesobacillus foraminis CV53T, with 98.0 and 97.7 %, 71.7 and 69.9 %, and 20.1 and 20.3 % 16S rRNA gene sequence similarity, average nucleotide identity, and digital DNA-DNA hybridization values, respectively. Phylogenetic analyses based on 16S rRNA gene and genome sequences showed that strain C11T was included in a phyletic lineage with members of the genus Neobacillus but was distinct from members of the genus Mesobacillus. Phenotypic, chemotaxonomic and molecular properties suggested that strain C11T represents a novel species of the genus Neobacillus, for which the name Neobacillus terrae sp. nov. is proposed. The type strain is C11T (=KACC 21661T=JCM 33943T).

Exopolysaccharide-producing bacteria enhanced Pb immobilization and influenced the microbiome composition in rhizosphere soil of pakchoi (Brassica chinensis L.).

Lead (Pb) contamination of planting soils is increasingly serious, leading to harmful effects on soil microflora and food safety. Exopolysaccharides (EPSs) are carbohydrate polymers produced and secreted by microorganisms, which are efficient biosorbent materials and has been widely used in wastewater treatment to remove heavy metals. However, the effects and underlying mechanism of EPS-producing marine bacteria on soil metal immobilization, plant growth and health remain unclear. The potential of Pseudoalteromonas agarivorans Hao 2018, a high EPS-producing marine bacterium, to produce EPS in soil filtrate, immobilize Pb, and inhibit its uptake by pakchoi (Brassica chinensis L.) was studied in this work. The effects of strain Hao 2018 on the biomass, quality, and rhizospheric soil bacterial community of pakchoi in Pb-contaminated soil were further investigated. The results showed that Hao 2018 reduced the Pb concentration in soil filtrate (16%-75%), and its EPS production increased in the presence of Pb2+. When compared to the control, Hao 2018 remarkably enhanced pakchoi biomass (10.3%-14.3%), decreased Pb content in edible tissues (14.5%-39.2%) and roots (41.3%-41.9%), and reduced the available Pb content (34.8%-38.1%) in the Pb-contaminated soil. Inoculation with Hao 2018 raised the pH of the soil, the activity of several enzymes (alkaline phosphatase, urease, and dehydrogenase), the nitrogen content (NH4 +-N and NO3 --N), and the pakchoi quality (Vc and soluble protein content), while also raising the relative abundance of bacteria that promote plant growth and immobilize metals, such as Streptomyces and Sphingomonas. In conclusion, Hao 2018 reduced the available Pb in soil and pakchoi Pb absorption by increasing the pH and activity of multiple enzymes and regulating microbiome composition in rhizospheric soil.