Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2008
Publication Date: 6/10/2008
Citation: Chung, S., Kong, H., Buyer, J.S., Lakshman, D.K., Lydon, J., Kim, S., Roberts, D.P. 2008. Isolation and partial characterization of bacillus subtilis me488 for suppression of soilborne pathogens of cucumber and pepper. Applied Microbiology and Biotechnology. 80(1):115-23. Interpretive Summary: New methods to control Fusarium wilt of cucumber and Phytophthora blight of pepper are needed as alternatives to chemical pesticides. Bacillus subtilis isolate ME488 was isolated from greenhouse soil and found to suppress Fusarium wilt of cucumber and Phytophthora blight of red pepper in pot assays. Polymerase chain reaction (PCR) assays were used to screen isolate ME488 for genes involved in biosynthesis of eleven antibiotics. Genes involved in the production of the antibiotics bacilysin, iturin, and mersacidin were detected by PCR and their identity confirmed by DNA sequencing. Bacilysin and iturin production by isolate ME488 was confirmed by gas chromatography coupled with electron-impact mass spectroscopy and thin layer chromatography, respectively. Detection of mersacidin production by isolate ME488 was not attempted. This Bacillus subtilis isolate may be useful in disease management strategies targeting these and other diseases of cucumber and red pepper. This information will be useful to scientists developing integrated pest management strategies for suppression of soilborne diseases of vegetables where methyl bromide was the major disease management tactic.
Technical Abstract: Environmentally friendly control measures are needed for suppression of soilborne pathogens of vegetable crops in the Republic of Korea. In vitro challenge assays were used to screen approximately 500 bacterial isolates from 20 Korean greenhouse soils for inhibition of diverse plant pathogens. Bacillus subtilis ME488 suppressed growth of 39 of 42 plant pathogens tested. Isolate ME488 also suppressed disease caused by Fusarium oxysporum f. sp. cucumerinum on cucumber and Phytophthora capsici on pepper in pot assays. PCR was used to screen isolate ME488 for biosynthetic genes involved in the synthesis of eleven antibiotics known to be produced by various isolates of B. subtilis. Amplicons of the expected sizes were detected for bacD and bacAB, ituC and ituD, and mrsA and mrsM involved in the biosynthesis of bacilysin, iturin, and mersacidin, respectively. The identity of these genes was confirmed by analysis of DNA sequences of the amplicons. Bacilysin and iturin were detected in culture filtrates from isolate ME488 by gas chromatography coupled with mass spectroscopy and by thin layer chromatography, respectively. Detection of mersacidin in ME488 culture filtrates was not attempted. Experiments reported here indicate that B. subtilis ME488 has potential for biological control of pathogens of cucumber and pepper possibly due to the production of antibiotics.