Abstract
Endophytic fungi associated with medicinal plants are reported as potent producers of diverse classes of secondary metabolites. In the present study, an endophytic fungi, Aspergillus clavatonanicus strain MJ31, exhibiting significant antimicrobial activity was isolated from roots of Mirabilis jalapa L., was identified by sequencing three nuclear genes i.e. internal transcribed spacers ribosomal RNA (ITS rRNA), 28S ribosomal RNA (28S rRNA) and translation elongation factor 1- alpha (EF 1α). Ethyl acetate extract of strain MJ31displayed significant antimicrobial potential against Bacillus subtilis, followed by Micrococccus luteus and Staphylococcus aureus with minimum inhibitory concentrations (MIC) of 0.078, 0.156 and 0.312 mg/ml respectively. In addition, the strain was evaluated for its ability to synthesize bioactive compounds by the amplification of polyketide synthase (PKS) and non ribosomal peptide synthetase (NRPS) genes. Further, seven antibiotics (miconazole, ketoconazole, fluconazole, ampicillin, streptomycin, chloramphenicol, and rifampicin) were detected and quantified using UPLC-ESI-MS/MS. Additionally, thermal desorption-gas chromatography mass spectrometry (TD-GC-MS) analysis of strain MJ31 showed the presence of 28 volatile compounds. This is the first report on A. clavatonanicus as an endophyte obtained from M. jalapa. We conclude that A. clavatonanicus strain MJ31 has prolific antimicrobial potential against both plant and human pathogens and can be exploited for the discovery of new antimicrobial compounds and could be an alternate source for the production of secondary metabolites.
Highlights
Escalating risk of drug resistance by pathogenic microorganisms to available commercial drugs has become a global concern around the world [1, 2]
The present study demonstrates broad spectrum antimicrobial activity of Aspergillus clavatonanicus strain MJ31, against both plant and human pathogens
The antimicrobial activity of strain MJ31 was established by detection and production of known antibiotics and antimicrobial volatile compounds
Summary
Escalating risk of drug resistance by pathogenic microorganisms to available commercial drugs has become a global concern around the world [1, 2]. Methicillin resistant Staphylococcus aureus, penicillin resistant Streptococcus pneumonie and vancomycin resistant Enterococcus faecium are few such examples [3]. This has led to the investigation, to look for an alternative source of new and efficient antimicrobial agent having broad range of antimicrobial activity. Investigating new and specialized ecological niches and habitats may enhance the chances of finding novel bioactive compounds [4]. One such habitat is plant endosphere that harbors microorganisms which reside in inter or intracellular spaces without causing apparent symptoms [5,6,7]. These organisms with endophytic lifestyle appeared to be associated with plants in all ecosystems and believed to play diverse indispensable functions in their natural habitat [8, 9]
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