Activity and characterization of secondary metabolites produced by a new microorganism for control of plant diseases.

Microorganisms capable of utilizing vegetable tissues for growth in soils were isolated and their vegetable broth cultures were individually sprayed directly on leaves to test their ability to control Phytophthora blight of bell pepper caused by Phytophthora capsici. Liquid culture of Streptomyces strain TKA-5, a previously undescribed species obtained in this study, displayed several desirable disease control characteristics in nature, including high potency, long lasting and ability to control also black leaf spot of spoon cabbage caused by Alternaria brassicicolca. The extract was fungicidal to P. capsici but fungistatic to A. brassicicola. It was stable at high temperature and high pH. However, after exposure to pH 2 for 24h, the extract was no longer inhibitory to P. capsici although it was still strongly inhibitory to A. brassicicola. After treatment with cation or anion exchange resins, the extract lost its inhibitory effect against P. capsici but not A. brassicicola. The results suggest that the extract contained two different kinds of inhibitory metabolites, one against P. capsici with both positive and negative charges on its molecule and another against A. brassicicola with no charges on its molecule. The inhibitory metabolites were soluble in ethanol or methanol but not in water, ether or chloroform. They were dialyzable in the membrane tubing with molecular weight cut-off of 10,000, 1000 or 500 but not 100, indicating that the inhibitors have a molecular weight between 500 and 100. Results also showed that both inhibitors are not proteins.

Paenibacillus taichungensis sp. nov., from soil in Taiwan.

Among a large collection of Taiwanese soil isolates, a novel Gram-variable, rod-shaped, motile, endospore-forming bacterial strain, strain V10537(T), was subjected to a polyphasic study including 16S rRNA and gyrB gene sequence analysis, DNA-DNA hybridization experiments, cell wall peptidoglycan type, cellular fatty acid composition analysis and comparative phenotypic characterization. 16S rRNA gene sequence analysis indicated that the organism belonged to the genus Paenibacillus. Strain V10537(T) possessed meso-diaminopimelic acid as the diagnostic diamino acid of the peptidoglycan. It contained menaquinone MK-7 as the predominant isoprenoid quinone and anteiso-C(15 : 0) (53.6 %) and C(16 : 0) (19.0 %) as the major fatty acids. Phylogenetically, the most closely related species to strain V10537(T) were Paenibacillus pabuli, Paenibacillus xylanilyticus, Paenibacillus amylolyticus, Paenibacillus barcinonensis and Paenibacillus illinoisensis, with 16S rRNA gene sequence similarities of 99.5, 98.8, 98.3, 98.2 and 98.1 % to the respective type strains. The gyrB gene sequence similarities between strain V10537(T) and these strains were 76.9-85.0 %. DNA-DNA hybridization experiments showed levels of relatedness of 8.5-45.6 % between strain V10537(T) and these strains. The DNA G+C content of strain V10537(T) was 46.7 mol%. Strain V10537(T) was clearly distinguishable from other Paenibacillus species and thus represents a novel species of the genus Paenibacillus, for which the name Paenibacillus taichungensis sp. nov. is proposed. The type strain is V10537(T) (=BCRC 17757(T) =DSM 19942(T)).

Evaluation of restriction enzymes for standardizing pulsed-field gel electrophoresis protocol for rapid subtyping of Vibrio parahaemolyticus.

We evaluated the cost-effectiveness of the restriction enzymes with rare-cutting sites in the genome of Vibrio parahaemolyticus RIMD 2210633 for pulsed-field gel electrophoresis (PFGE) analysis. The evaluation indicated that PFGE with both NotI and SfiI was discriminatory, but NotI was more cost-effective. Based on the results of this study, we suggest using NotI and SfiI as the 1st and the 2nd restriction enzyme for standardizing the PulseNet PFGE protocol for molecular subtyping and global surveillance of V. parahaemolyticus.

Foodborne disease outbreaks caused by sucrose-nonfermenting and beta-galactosidase-deficient variants of Vibrio cholerae.

We reported four foodborne disease outbreaks in Taiwan caused by sucrose-nonfermenting and by beta-galactosidase-deficient variants of non-O1, non-O139 Vibrio cholerae. The sucrose-nonfermenting vibrios collected from three outbreaks were biochemically identified to be V. mimicus and the beta-galactosidase-deficient vibrios from an outbreak to be V. alginolyticus. However, molecular methods including DNA-DNA hybridization, fatty acid profile analysis, and sequence analysis of 16S rRNA, oriC, pyrH, recA, and rpoA indicated that these vibrios should be V. cholerae. These V. cholerae variants carried two hemolysin genes, hlyA and hlx, but contained neither cholera toxin gene, ctx, V. mimicus hemolysin gene, vmh, nor thermo-directed hemolysin, tdh. The sucrose-nonfermenting variants of V. cholerae shared a high level of genetic relatedness; they could derive from a common clone. In our record from 1995 to date, this was the first time that V. cholerae variants were discovered as etiologic agents for foodborne disease outbreaks in Taiwan.

Chitinibacter tainanensis gen. nov., sp. nov., a chitin-degrading aerobe from soil in Taiwan.

Five strains with strong chitinolytic activity were isolated from a soil sample collected from southern Taiwan. The strains shared more than 92% DNA-DNA similarity, indicating membership of the same genospecies. This close relationship was supported by high similarities in fatty acid composition and biochemical characteristics. A 16S rRNA gene sequence analysis indicated that the isolates were members of the class 'Betaproteobacteria', in which they formed an individual subline of descent that was distantly related (<94% similarity) to lineages defined by Formivibrio citricus DSM 6150T and Iodobacter fluviatilis DSM 3764T. On the basis of the phylogenetic and phenotypic distinctness of these novel chitin-degrading organisms, a new genus, Chitinibacter, is proposed, with Chitinibacter tainanensis (type strain, S1T=BCRC 17254T=DSM 15459T) as the type species.