Isolation of proline-based cyclic dipeptides from Bacillus sp. N strain associated with rhabitid entomopathogenic nematode and its antimicrobial properties

• Published in: World journal of microbiology & biotechnology 2013-02, Vol.29 (2), p.355-364
• Main Authors: Kumar, Nishanth, Mohandas, C., Nambisan, Bala, Kumar, D. R. Soban, Lankalapalli, Ravi S.
• Format: Article
• Language: English
• Subjects: Analysis; Antibiotics; Antimicrobial agents; Applied Microbiology; Bacillus; Bacteria; Biochemistry; Biological control; Biomedical and Life Sciences; Biotechnology; Chemicals; Chromatography; Crops; Environmental Engineering/Biotechnology; Farming; Farms; Filtrate; Fungi; Fungicides; Fusarium oxysporum; Gram-negative bacteria; Life Sciences; Metabolites; Microbiology; Microorganisms; Nematoda; Nematodes; NMR; Nuclear magnetic resonance; Original Paper; Pencillium expansum; Peptides; Research centers; Rhabditis; Rhizoctonia solani; Secondary metabolites; Solanum tuberosum; Spectrum analysis; Strain; Studies
• ISSN: 0959-3993; 1573-0972
• DOI: 10.1007/s11274-012-1189-9

Entomopathogenic nematodes (EPN) are well-known as biological control agents and are found to have associated bacteria which can produce a wide range of bioactive secondary metabolites. We report herewith isolation of six proline containing cyclic dipeptides cyclo( d -Pro- l -Leu), cyclo( l -Pro- l -Met), cyclo( d -Pro- l -Phe), cyclo( l -Pro- l -Phe), cyclo( l -Pro- l -Tyr) and cyclo( l -Pro- d -Tyr) from ethyl acetate extract of the Luria Broth (LB) cell free culture filtrate of Bacillus sp. strain N associated with a new EPN Rhabditis sp. from sweet potato weevil grubs collected from Central Tuber Crops Research Institute farm. Antimicrobial studies of these 2,5-diketopiperazines (DKPs) against both medicinally and agriculturally important bacterium and fungi showed potent inhibitory values in the range of μg/mL. Cyclic dipeptides showed significantly higher activity than the commercial fungicide bavistin against agriculturally important fungi, viz., Fusarium oxysporum , Rhizoctonia solani , and Pencillium expansum . The highest activity of 2 μg/mL by cyclo( l -Pro- l -Phe) was recorded against P. expansum , a plant pathogen responsible for causing post harvest decay of stored apples and oranges. To our knowledge, this is the first report on the isolation of these DKPs from Rhabditis EPN bacterial strain Bacillus sp.