Study of the antifungal activity of <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis> LCH001 in vitro and identification of its antifungal components |
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Authors: | C H Liu X Chen T T Liu B Lian Yucheng Gu V Caer Y R Xue B T Wang |
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Institution: | (1) State Key Laboratory of Pharmaceutical Biotechnology, School of Life Science, Nanjing University, 22# Hankou Road, Nanjing, 210093, People’s Republic of China;(2) Institute of Geochemistry, CAS, 73 Guanshui Road, Guiyang, 550002, People’s Republic of China;(3) Syngenta, Jealott’s Hill International Research Centre, Bracknell, Berkshire, RG42 6EY, UK;(4) Plant Protection College, Northwestern Sci-tech University of Agricultural and Forestry, Yangling, 712100, People’s Republic of China |
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Abstract: | An Acinetobacter strain, given the code name LCH001 and having the potential to be an endophytic antagonist, has been isolated from healthy
stems of the plant Cinnamomum camphora (L.) Presl, guided by an in vitro screening technique. The bacterium inhibited the growth of several phytopathogenic fungi
such as Cryphonectria parasitica, Glomerella glycines, Phytophthora capsici, Fusarium graminearum, Botrytis cinerea, and Rhizoctonia solani. Biochemical, physiological, and 16S rDNA sequence analysis proved that it is Acinetobacter baumannii. When the filtrate from the fermentation broth of strain LCH001 was tested in vitro and in vivo, it showed strong growth
inhibition against several phytopathogens including P. capsici, F. graminearum, and R. solani, indicating that suppression of the growth of the fungi was due to the presence of antifungal compounds in the culture broth.
Moreover, the antifungal activity of the culture filtrate was significantly correlated with the cell growth of strain LCH001.
The active metabolites in the filtrate were relatively thermally stable, but were sensitive to acidic conditions. Three antifungal
compounds were isolated from the culture broth by absorption onto macropore resin, ethanol extraction, chromatography on silica
gel or LH-20 columns, and crystallization. The structures of the bioactive compounds were identified by spectroscopic methods
as isomers of iturin A, namely, iturin A2, iturin A3, and iturin A6. The characterization of an unusual endophytic bacterial
strain LCH001 and its bioactive components may provide an alternative resource for the biocontrol of plant diseases. |
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Keywords: | Acinetobacter baumannii LCH001 Antifungal activity Iturin A |
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