Flavobacterium dauae sp. nov., isolated from rhizosphere soil of a tomato plant.

A bacterial strain, designated TCH3-2T, was isolated from the rhizosphere of tomato plant grown at Dong-A University Agricultural Experiment Station, Republic of Korea. The strain was Gram-stain-negative, obligate aerobic, orange yellow-coloured, motile by gliding and short rod-shaped. Strain TCH3-2 T only grew on 1/2 tryptic soy agar and Luria-Bertani agar among the media tested, with optimum growth at 28 °C and pH 7. Salt of 1 % NaCl was necessary to support the growth of TCH3-2T. Strain TCH3-2T produced flexirubin-type pigments. The predominant cellular fatty acids were iso-C15 : 0 (55.6 %), iso-C17 : 0 3-OH (17.9 %), summed feature 9 (comprising C16 : 0 10-methyl and/or iso-C17 : 1 ω9c; 10.5 %), iso-C15 : 0 3-OH (4.8 %) and anteiso-C15 : 0 (2.3 %). The major menaquinone was menaquinone-6 and the major polar lipids were phosphatidylethanolamine, five unknown aminolipids and three unknown lipids. Phylogenetic analysis based on 16S rRNA sequences indicated that TCH3-2T was closely related to Flavobacterium ummariense DS-12T (95.16 %), Flavobacterium marinum SW105T (95.14 %) and Flavobacterium viscosus YIM 102796T (94.54 %). The draft genome of TCH3-2T comprised ca. 2.8 Mb with a G+C content of 34.61 mol%. The average nucleotide identity and digital DNA-DNA hybridization values between TCH3-2T and closely related Flavobacterium species showed that it belongs to a distinct species. Furthermore, the results of morphological, physiological and biochemical tests allowed further phenotypic differentiation of TCH3-2T from its closest relatives. Thus, chemotaxonomic characteristics together with phylogenetic affiliation illustrate that TCH3-2T represents a novel species of the genus Flavobacterium, for which the name Flavobacterium dauae sp. nov. (type strain TCH3-2T=KACC 19054T=JCM 34025T) is proposed.

Genome Analysis of Erwinia amylovora Strains Responsible for a Fire Blight Outbreak in Korea.

Erwinia amylovora is a plant-pathogenic bacterium that causes fire blight disease in Rosaceae plants. Since fire blight is highly contagious and results in serious losses once introduced, it is regulated as a quarantine disease. Recently, for the first time in East Asia, fire blight emerged in Korea with strains of E. amylovora being isolated from lesions of infected trees. Five of those strains were selected and subjected to whole-genome shotgun sequencing. Each strain had two circular replicons, a 3.8-Mb chromosome and a 28-kb plasmid. The genome sequences were compared with those of other E. amylovora strains isolated from different hosts or geographical regions. Genome synteny was analyzed and sequence variations including nucleotide substitutions, inversions, insertions, and deletions were detected. Analysis of the population genomic structure revealed that the five strains form a distinct structural group. Phylogenomic analysis was performed to infer the evolutionary relationships among E. amylovora strains, which indicated that the Korean isolates, all descended from a common ancestor, are closely related to a lineage of North American strains. These results provide useful information for understanding the genomic dynamics of E. amylovora strains including those in Korea, developing genetic markers for surveillance of the pathogen or diagnosis of the disease, and eventually developing measures to eradicate it.

Rhizobacterial syntrophy between a helper and a beneficiary promotes tomato plant health.

Microbial interactions impact the functioning of microbial communities. However, microbial interactions within host-associated communities remain poorly understood. Here, we report that the beneficiary rhizobacterium Niallia sp. RD1 requires the helper Pseudomonas putida H3 for bacterial growth and beneficial interactions with the plant host. In the absence of the helper H3 strain, the Niallia sp. RD1 strain exhibited weak respiration and elongated cell morphology without forming bacterial colonies. A transposon mutant of H3 in a gene encoding succinate-semialdehyde dehydrogenase displayed much attenuated support of RD1 colony formation. Through the subsequent addition of succinate to the media, we found that succinate serves as a public good that supports RD1 growth. Comparative genome analysis highlighted that RD1 lacked the gene for sufficient succinate, suggesting its evolution as a beneficiary of succinate biosynthesis. The syntrophic interaction between RD1 and H3 efficiently protected tomato plants from bacterial wilt and promoted tomato growth. The addition of succinate to the medium restored complex II-dependent respiration in RD1 and facilitated the cultivation of various bacterial isolates from the rhizosphere. Taken together, we delineate energy auxotrophic beneficiaries ubiquitous in the microbial community, and these beneficiaries could benefit host plants with the aid of helpers in the rhizosphere.

Rhizobacterial syntrophy between a helper and a beneficiary promotes tomato plant health.

None declared.Conflicts of interestMicrobial interactions impact the functioning of microbial communities. However, microbial interactions within host-associated communities remains poorly understood. Here, we report that the beneficiary rhizobacterium Niallia sp. RD1 requires the helper Pseudomonas putida H3 for bacterial growth and beneficial interactions with the plant host. In the absence of the helper H3 strain, the Niallia sp. RD1 strain exhibited weak respiration and elongated cell morphology without forming bacterial colonies. A transposon mutant of H3 in a gene encoding succinate-semialdehyde dehydrogenase displayed much attenuated support of RD1 colony formation. Through subsequent addition of succinate to the media, we found that succinate serves as a public good that supports RD1 growth. Comparative genome analysis highlighted that RD1 lacked the gene for sufficient succinate, suggesting its evolution as a beneficiary of succinate biosynthesis. The syntrophic interaction between RD1 and H3 efficiently protected tomato plants from bacterial wilt and promoted the tomato growth. The addition of succinate to the medium restored complex II-dependent respiration in RD1 and facilitated the cultivation of various bacterial isolates from the rhizosphere. Taken together, we delineate energy auxotrophic beneficiaries ubiquitous in the microbial community, and these beneficiaries could benefit host plants with the aid of helpers in the rhizosphere.

Genome sequence of the thermotolerant yeast Kluyveromyces marxianus var. marxianus KCTC 17555.

Kluyveromyces marxianus is a thermotolerant yeast that has been explored for potential use in biotechnological applications, such as production of biofuels, single-cell proteins, enzymes, and other heterologous proteins. Here, we present the high-quality draft of the 10.9-Mb genome of K. marxianus var. marxianus KCTC 17555 (= CBS 6556 = ATCC 26548).

Draft genome sequence of the antifungal-producing plant-benefiting bacterium Burkholderia pyrrocinia CH-67.

Burkholderia pyrrocinia CH-67 was isolated from forest soil as a biocontrol agent to be utilized in agriculture. Here, we report the 8.05-Mb draft genome sequence of this bacterium. Its genome contains genes involved in biosynthesis of secondary metabolites and plant growth promotion, which may contribute to probiotic effects on plants.

Genome sequence of the agar-degrading marine bacterium Alteromonadaceae sp. strain G7.

Here, we present the high-quality draft genome sequence of the agar-degrading marine gammaproteobacterium Alteromonadaceae sp. strain G7, which was isolated from coastal seawater to be utilized as a bioresource for production of agar-derived biofuels. The 3.91-Mb genome contains a number of genes encoding algal polysaccharide-degrading enzymes such as agarases and sulfatases.

Genome sequence of the leaf-colonizing Bacterium Bacillus sp. strain 5B6, isolated from a cherry tree.

Plant growth-promoting bacteria colonize various habitats, including the phyllosphere. Here, we present the high-quality draft genome sequence of Bacillus sp. strain 5B6, which was isolated from the leaf of a cherry tree. The 3.9-Mb genome uncovers its potential for understanding the nature of leaf colonization as well as antibiosis against plant pathogens.

Genome sequence of an oligohaline hyperthermophilic archaeon, Thermococcus zilligii AN1, isolated from a terrestrial geothermal freshwater spring.

Thermococcus zilligii, a thermophilic anaerobe in freshwater, is useful for physiological research and biotechnological applications. Here we report the high-quality draft genome sequence of T. zilligii AN1(T). The genome contains a number of genes for an immune system and adaptation to a microbial biomass-rich environment as well as hydrogenase genes.

Complete genome sequence of the endophytic bacterium Burkholderia sp. strain KJ006.

Endophytes live inside plant tissues without causing any harm and may even benefit plants. Here, we provide the high-quality genome sequence of Burkholderia sp. strain KJ006, an endophytic bacterium of rice with antifungal activity. The 6.6-Mb genome, consisting of three chromosomes and a single plasmid, contains genes related to plant growth promotion or degradation of aromatic compounds.

Complete genome sequence of the probiotic bacterium Bifidobacterium bifidum strain BGN4.

Bifidobacterium bifidum, a common endosymbiotic inhabitant of the human gut, is considered a prominent probiotic microorganism that may promote health. We completely decrypted the 2.2-Mb genome sequence of B. bifidum BGN4, a strain that had been isolated from the fecal sample of a healthy breast-fed infant, and annotated 1,835 coding sequences.

Genome sequence of the hemolytic-uremic syndrome-causing strain Escherichia coli NCCP15647.

Enterohemorrhagic Escherichia coli (EHEC) causes a disease involving diarrhea, hemorrhagic colitis, and hemolytic-uremic syndrome (HUS). Here we present the draft genome sequence of NCCP15647, an EHEC isolate from an HUS patient. Its genome exhibits features of EHEC, such as genes for verotoxins, a type III secretion system, and prophages.

Genome sequence of enterohemorrhagic Escherichia coli NCCP15658.

Enterohemorrhagic Escherichia coli causes severe food-borne disease in the guts of humans and animals. Here, we report the high-quality draft genome sequence of E. coli NCCP15658 isolated from a patient in the Republic of Korea. Its genome size was determined to be 5.46 Mb, and its genomic features, including genes encoding virulence factors, were analyzed.

Genome sequence of the Shiga toxin-producing Escherichia coli strain NCCP15657.

Shiga toxin-producing Escherichia coli causes bloody diarrhea and hemolytic-uremic syndrome and serious outbreaks worldwide. Here, we report the draft genome sequence of E. coli NCCP15657 isolated from a patient. The genome has virulence genes, many in the locus of enterocyte effacement (LEE) island, encoding a metalloprotease, the Shiga toxin, and constituents of type III secretion.

Genome sequence of the plant growth-promoting rhizobacterium Bacillus sp. strain JS.

Volatile and nonvolatile compounds emitted from the plant growth-promoting rhizobacterium Bacillus sp. strain JS enhance the growth of tobacco and lettuce. Here, we report the high-quality genome sequence of this bacterium. Its 4.1-Mb genome reveals a number of genes whose products are possibly involved in promotion of plant growth or antibiosis.

Draft genome sequence of Streptomyces clavuligerus NRRL 3585, a producer of diverse secondary metabolites.

Streptomyces clavuligerus is an important industrial strain that produces a number of antibiotics, including clavulanic acid and cephamycin C. A high-quality draft genome sequence of the S. clavuligerus NRRL 3585 strain was produced by employing a hybrid approach that involved Sanger sequencing, Roche/454 pyrosequencing, optical mapping, and partial finishing. Its genome, comprising four linear replicons, one chromosome, and four plasmids, carries numerous sets of genes involved in the biosynthesis of secondary metabolites, including a variety of antibiotics.

Clavulanic acid biosynthesis and genetic manipulation for its overproduction.

Clavulanic acid, a ß-lactamase inhibitor, is used together with ß-lactam antibiotics to create drug mixtures possessing potent antimicrobial activity. In view of the clinical and industrial importance of clavulanic acid, identification of the clavulanic acid biosynthetic pathway and the associated gene cluster(s) in the main producer species, Streptomyces clavuligerus, has been an intriguing research question. Clavulanic acid biosynthesis was revealed to involve an interesting mechanism common to all of the clavam metabolites produced by the organism, but different from that of other ß-lactam compounds. Gene clusters involved in clavulanic acid biosynthesis in S. clavuligerus occupy large regions of nucleotide sequence in three loci of its genome. In this review, clavulanic acid biosynthesis and the associated gene clusters are discussed, and clavulanic acid improvement through genetic manipulation is explained.

Complex extracellular interactions of proteases and a protease inhibitor influence multicellular development of Streptomyces coelicolor.

Streptomyces coelicolor produces an extracellular protease inhibitor protein, STI (Streptomyces trypsin inhibitor). We show that post-growth elimination of STI is needed for colonies to develop aerial mycelium efficiently. Inactivation of STI, and thus the normal progression of colony development, at least partly involves an extracellular protease specified by gene SCO5913. Two-hybrid analysis identified two possible targets of STI inhibition (the products of SCO1355 and SCO5447), both extracellular proteases containing a domain homologous with the P-domain of eukaryotic convertases, proteases that mediate the processing of many precursors with important cellular or developmental roles. At least the SCO1355 protease is needed for the normal progression of development. Two components of the proposed cascade are dependent on the tRNA for the rare UUA (leucine) codon, which is specified by the developmental gene bldA. A model is presented that links intracellular regulatory events with an extracellular protease cascade to facilitate normal development.

Crystallization and X-ray diffraction data collection of topoisomerase IV ParE subunit from Xanthomonas oryzae pv. oryzae.

Topoisomerase IV is involved in topological changes in the bacterial genome using the free energy from ATP hydrolysis. Its functions are the decatenation of daughter chromosomes following replication by DNA relaxation and double-strand DNA breakage. In this study, the N-terminal fragment of the topoisomerase IV ParE subunit from Xanthomonas oryzae pv. oryzae was overexpressed in Escherichia coli, purified and crystallized. Diffraction data were collected to 2.15 A resolution using a synchrotron-radiation source. The crystal belonged to space group P4(2)2(1)2, with unit-cell parameters a = b = 105.30, c = 133.76 A. The asymmetric unit contains one molecule, with a corresponding V(M) of 4.21 A(3) Da(-1) and a solvent content of 69.6%.

A gene located downstream of the clavulanic acid gene cluster in Streptomyces clavuligerus ATCC 27064 encodes a putative response regulator that affects clavulanic acid production.

Three open reading frames denoted as orf21, orf22, and orf23 were identified from downstream of the currently recognized gene cluster for clavulanic acid biosynthesis in Streptomyces clavuligerus ATCC 27064. The new orfs were annotated after in silico analysis as genes encoding a putative sigma factor, a sensor kinase, and a response regulator. The roles of the individual genes were explored by disruption of the corresponding orfs, and the morphological and antibiotic production phenotypes of the resulting mutants were compared. In orf21 and orf22 mutants, no growth or morphological differences were noted, but modest reduction of cephamycin C (orf21), or both cephamycin C and clavulanic acid production (orf22) compared with wild-type, were observed. In orf23 mutant, cell growth and sporulation was retarded, and clavulanic acid and cephamycin C production were reduced to 40 and 47% of wild-type levels, respectively. Conversely, overexpression of orf23 caused precocious hyperproduction of spores on solid medium, and antibiotic production was increased above the levels seen in plasmid control cultures. Transcriptional analyses were also carried out on orf23 and showed that mutation had little effect on transcription of genes associated with the early stages of cephamycin C or clavulanic acid production but transcription of claR, which regulates the late stages of clavulanic acid production, was reduced in orf23 mutants. These observations suggest that the orf23 product may enable S. clavuligerus to respond to environmental changes by altering cell growth and differentiation. In addition, the effects of ORF23 on growth might indirectly regulate the biosynthesis of secondary metabolites such as clavulanic acid and cephamycin C.