title: Characterization of the fungicidal activity of Calothrix elenkinii using chemical methods and microscopy.
abstract: An investigation was directed towards biochemical characterization of cyanobacterium Calothrix elenkinii and analysis of the chemical nature and mode of action of its fungicidal metabolite(s) against oomycete Pythium debaryanum. Biochemical characterization of the culture in terms of carbohydrate utilization revealed the facultative nature of C. elenkinii. Unique antibiotic markers were also found for this strain. 16S rDNA sequencing of the strain revealed 98% similarity with Calothrix sp. PCC7101. The fungicidal activity was tested by disc diffusion assay of different fractions of the culture filtrate. A minimum inhibitory concentration of 10 microl was recorded for ethyl acetate fraction of the 7-weeks old culture filtrates. HPLC, followed by NMR spectral analysis demonstrated the presence of a substituted benzoic acid in the ethyl acetate fraction. Microscopic examination revealed distinct granulation, followed by disintegration of the hyphae of Pythium sp., indicating the presence of an active metabolite in the culture filtrates of Calothrix sp. The fungicidal activity of C. elenkinii can be attributed to the presence of 3-acetyl-2-hydroxy-6-methoxy-4-methyl benzoic acid. This is the first report of a benzoic acid derivative having fungicidal activity in cyanobacteria.
authors.affiliation: Division of Microbiology, Indian Agricultural Research Institute (IARI), New Delhi - 110012, India.
authors.forename: C
authors.initials: C
authors.lastname: Natarajan
authors.forename: R
authors.initials: R
authors.lastname: Prasanna
authors.forename: V
authors.initials: V
authors.lastname: Gupta
authors.forename: P
authors.initials: P
authors.lastname: Dureja
authors.forename: L
authors.initials: L
authors.lastname: Nain
mesh_terms: D000085:Acetates / Q000737:chemistry; D000935:Antifungal Agents / Q000378:metabolism / Q000494:pharmacology; D001565:Benzoates / Q000378:metabolism* / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media; D000458:Cyanobacteria / Q000302:isolation & purification / Q000378:metabolism*; D052978:Disk Diffusion Antimicrobial Tests; D005374:Filtration; D025301:Hyphae / Q000187:drug effects* / Q000254:growth & development; D007194:India; D009682:Magnetic Resonance Spectroscopy; D008826:Microbial Sensitivity Tests; D008853:Microscopy; D010802:Phylogeny; D011775:Pythium / Q000187:drug effects* / Q000254:growth & development; D012336:RNA, Ribosomal, 16S / Q000032:analysis*; D012988:Soil Microbiology; D013379:Substrate Specificity
chemical_list: D000085:Acetates; D000935:Antifungal Agents; D001565:Benzoates; D003470:Culture Media; D012336:RNA, Ribosomal, 16S; C007650:ethyl acetate