Soon Wo Kwon

Pandoraea thiooxydans sp. nov., a facultatively chemolithotrophic, thiosulfate-oxidizing bacterium isolated from rhizosphere soils of sesame (Sesamum indicum L.)

A facultatively chemolithoautotrophic, thiosulfate-oxidizing, Gram-negative, aerobic, motile, rod-shaped bacterial strain, designated ATSB16(T), was isolated from rhizosphere soils of sesame (Sesamum indicum L.). 16S rRNA gene sequence analysis demonstrated that this strain was closely related to Pandoraea pnomenusa LMG 18087(T) (96.7 % similarity), P. pulmonicola LMG 18016(T) (96.5 %), P. apista LMG 16407(T) (96.2 %), P. norimbergensis LMG 18379(T) (96.1 %) and P. sputorum LMG 18819(T) (96.0 %). Strain ATSB16(T) shared 96.0-96.4 % sequence similarity with four unnamed genomospecies of Pandoraea. The major cellular fatty acids of the strain ATSB16(T) were C(17 : 0) cyclo (33.0 %) and C(16 : 0) (30.6 %). Q-8 was the predominant respiratory quinone. The major polar lipids were phosphatidylmethylethanolamine, diphosphatidylglycerol, phosphatidylethanolamine and two unidentified aminophospholipids. Hydroxyputrescine and putrescine were the predominant polyamines. The genomic DNA G+C content of the strain was 64.0 mol%. On the basis of the results obtained from this study, strain ATSB16(T) represents a novel species of the genus Pandoraea, for which the name Pandoraea thiooxydans sp. nov. is proposed. The type strain is ATSB16(T) (=KACC 12757(T) =LMG 24779(T)).

Mycoflora of Soybeans Used for Meju Fermentation

Abstract Diverse fungi are present in Korean traditional meju and they are known to play an important role in fermented soybean products. To determine the origin of the fungi in meju, we examined the mycoflora of soybeans from 10 traditional meju factories. The samples were untreated or treated with sodium hypochlorite, and placed on malt extract agar (MEA), dichloran 18% glycerol agar (DG18), and dichloran rose bengal chloramphenicol agar (DRBC) medium. A total of 794 fungal strains were isolated and they were identified as 41 genera and 86 species. From sodium hypochlorite untreated soybeans, the genera, Cladosporium (55%), Eurotium (51%), Fusarium (33%), Penicillium (22%), and Aspergillus (exclusion of Eurotium) (20%), were mainly isolated, and Eurotium herbariorum (22%), Eurotium repens (18%), Cladosporium tenuissimum (18%), F. fujikuroi (18%), Aspergillus oryzae/flavus (7%), and Penicillium steckii (6%) were the predominant species. In case of sodium hypochloritetreated soybeans, Eurotium (31%) and Cladosporium (5%) were frequently isolated, but Aspergillus (excluding Eurotium), Penicillium and Fusarium which were frequently isolated from untreated soybeans, were rarely isolated. Eurotium herbariorum (21%), Eurotium repens (8%), and Cladosporium tenuissimum (3%) were the predominant species. Of the 41 genera and 86 species isolated from soybeans, 13 genera and 33 species were also found in meju. These results suggest that the fungi on soybeans may influence the mycoflora of meju.

An Integrated Database and Web Service for Microbial Resources at KACC

The Korean Agricultural Culture Collection (KACC) has developed a web-based system to provide an integrated database with information updates about microbial resources. This integrated database consists of 5 major functions and contains general information, which includes identification numbers, culture media composition, image information, DNA sequences, patent information, and general forms for ordering and depositing microorganisms. In 2008, KACC started providing characterization information. KACC maintains 9,801 cultures of microorganisms, including 3,296 strains of bacteria, 4,734 fungi, 784 actinomycetes, 64 yeasts, and 923 others.

Control of Wilt and Rot Pathogens of Tomato by Antagonistic Pink Pigmented Facultative Methylotrophic Delftia lacustris and Bacillus spp.

The studies on the biocontrol potential of pink pigmented facultative methylotrophic (PPFM) bacteria other than the genus Methylobacterium are scarce. In the present study, we report three facultative methylotrophic isolates; PPO-1, PPT-1, and PPB-1, respectively, identified as Delftia lacustris, Bacillus subtilis, and Bacillus cereus by 16S rRNA gene sequence analysis. Hemolytic activity was tested to investigate the potential pathogenicity of isolates to plants and humans, the results indicates that the isolates PPO-1, PPT-1, and PPB-1 are not pathogenic strains. Under in vitro conditions, D. lacustris PPO-1, B. subtilis PPT-1, and B. cereus PPB-1 showed direct antagonistic effect by inhibiting the mycelial growth of fungal pathogens; Fusarium oxysporum f. sp. lycopersici (2.15, 2.05, and 1.95 cm), Sclerotium rolfsii (2.14, 2.04, and 1.94 cm), Pythium ultimum (2.12, 2.02, and 1.92 cm), and Rhizoctonia solani (2.18, 2.08, and 1.98 cm) and also produced volatile inhibitory compounds. Under plant growth chamber condition methylotrophic bacterial isolates; D. lacustris PPO-1, B. subtilis PPT-1, and B. cereus PPB-1 significantly reduced the disease incidence of tomato. Under greenhouse condition, D. lacustris PPO-1, B. subtilis PPT-1, and B. cereus PPB-1 inoculated tomato plants, when challenged with F. oxysporum f. sp. lycopersici, S. rolfsii, P. ultimum, and R. solani, increased the pathogenesis related proteins (β-1,3-glucanase and chitinase) and defense enzymes (phenylalanine ammonia lyase, peroxidase, polyphenol oxidase, and catalase) on day 5 after inoculation. In the current study, we first report the facultative methylotrophy in pink pigmented D. lacustris, B. subtilis, and B. cereus and their antagonistic potential against fungal pathogens. Direct antagonistic and ISR effects of these isolates against fungal pathogens of tomato evidenced their possible use as a biocontrol agent.