Abstract
An endophytic fungus displaying considerable antimicrobial activity was isolated from stem tissue of an invasive plant species, Ipomoea carnea. The fungus was identified as Quambalaria sp. and confirmed by ITS rDNA sequence analysis. A BLAST search result of the sequence indicated 97 % homology with Quambalaria cyanescens. Crude metabolites of the fungus showed considerable antimicrobial activity against a panel of clinically significant microorganisms. The metabolites showed highest in vitro activity against Shigella dysenteriae followed by Escherichia coli and Candida albicans. Optimum metabolites production required neutral pH and a 15-day incubation period. Bark extracts amended with fungal media demonstrated higher antimicrobial activity. Optimum metabolites activity was recorded in Czapek Dox broth amended with leaf extracts (CDB + LE) of the host plant. The metabolites showed UV λ-max in ethyl acetate at 284.6 nm with an absorbance value of 1.093. Phylogenetic tree generated by the Maximum Parsimony method showed clustering of our isolate with Q. cyanescens with supported bootstrap of 65 %. Species of Quambalaria are pathogens to Eucalyptus and occurrence of this fungus as endophytes support it to be a latent pathogen. Sequence base analysis and RNA secondary structure study also confirmed such a relationship. Secondary structural features like two hinges and a 5’ dangling end were found to be unique to our isolate. These structural features can also be used as potential barcodes for this fungus. The findings indicate that invasive plant species can be a reliable source of novel endophytes with rich antimicrobial metabolites. The study also validates the assumption that endophytes can become parasites and share a close affinity.
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Acknowledgements
The authors are grateful to the coordinator, Bioinformatics Infrastructure facility (BIF), and the Head, Department of Botany, North Orissa University, India, for providing necessary facilities to carry out the work. Financial support in the form of studentship by DBT-BIF, Govt. of India, to the first author is greatly acknowledged.
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ESM Fig. 1
Colonial morphology (a) and spores (b) of Quambalaria sp. (DOC 87 kb)
ESM Fig. 2
Antagonistic activity of the metabolites of Quambalaria sp. under different cultural conditions against some bacteria and fungi. (DOC 1112 kb)
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Padhi, S., Tayung, K. Antimicrobial activity and molecular characterization of an endophytic fungus, Quambalaria sp. isolated from Ipomoea carnea . Ann Microbiol 63, 793–800 (2013). https://doi.org/10.1007/s13213-012-0534-4
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DOI: https://doi.org/10.1007/s13213-012-0534-4