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Antimicrobial activities of endophytic fungi obtained from the arid zone invasive plant Opuntia dillenii and the isolation of equisetin, from endophytic Fusarium sp.

Ratnaweera PB, de Silva ED, Williams DE, Andersen RJ - BMC Complement Altern Med (2015)

Bottom Line: The most bioactive fungus was identified as Fusarium sp. and the second most active as Aspergillus niger.O. dillenii, harbors several endophytic fungi capable of producing antimicrobial substances with selective antibacterial properties.Further investigations on the secondary metabolites produced by these endophytes may provide additional drug leads.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Colombo, Colombo 03, Sri Lanka. pamoda.b@gmail.com.

ABSTRACT

Background: Opuntia dillenii is an invasive plant well established in the harsh South-Eastern arid zone of Sri Lanka. Evidence suggests it is likely that the endophytic fungal populations of O. dillenii assist the host in overcoming biotic and abiotic stress by producing biologically active metabolites. With this in mind there is potential to discover novel natural products with useful biological activities from this hitherto poorly investigated source. Consequently, an investigation of the antimicrobial activities of the endophytes of O. dillenii, that occupies a unique ecological niche, may well provide useful leads in the discovery of new pharmaceuticals.

Methods: Endophytic fungi were isolated from the surface sterilized cladodes and flowers of O. dillenii using several nutrient media and the antimicrobial activities were evaluated against three Gram-positive and two Gram-negative bacteria and Candida albicans. The two most bioactive fungi were identified by colony morphology and DNA sequencing. The secondary metabolite of the endophyte Fusarium sp. exhibiting the best activity was isolated via bioassay guided chromatography. The chemical structure was elucidated from the ESIMS and NMR spectroscopic data obtained for the active metabolite. The minimum inhibitory concentrations (MICs) of the active compound were determined.

Results: Eight endophytic fungi were isolated from O. dillenii and all except one showed antibacterial activities against at least one of the test bacteria. All extracts were inactive against C. albicans. The most bioactive fungus was identified as Fusarium sp. and the second most active as Aspergillus niger. The structure of the major antibacterial compound of the Fusarium sp. was shown to be the tetramic acid derivative, equisetin. The MIC's for equisetin were 8 μg mL(-1) against Bacillus subtilis, 16 μg mL(-1) against Staphylococcus aureus and Methicillin Resistant Staphylococcus aureus (MRSA).

Conclusions: O. dillenii, harbors several endophytic fungi capable of producing antimicrobial substances with selective antibacterial properties. By producing biologically active secondary metabolites, such as equisetin isolated from the endophytic Fusarium sp., the endophytic fungal population may be assisting the host to successfully withstand stressful environmental conditions. Further investigations on the secondary metabolites produced by these endophytes may provide additional drug leads.

No MeSH data available.


Related in: MedlinePlus

Endophytic aFusarium sp. (dorsal view), bFusarium sp. (ventral view), cAspergillus niger (dorsal view) and dA. niger (ventral view) in culture
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Fig1: Endophytic aFusarium sp. (dorsal view), bFusarium sp. (ventral view), cAspergillus niger (dorsal view) and dA. niger (ventral view) in culture

Mentions: The Fusarium sp. had a white puffy mycelium with a peach colour pigment that secreted into the medium within seven to ten days of culture growth while A. niger produced black spores in a concentric ring pattern on PDA medium (Fig. 1). According to DNA sequence data and blast results obtained, these fungi showed 99 % identity to previously reported Fusarium sp. (GQ505759.1) and A. niger (JN561274.1) [21, 22]. In addition on the basis of 18S ribosomal RNA gene, partial sequence; internal transcribed spacer 1, 5.8S ribosomal RNA gene, and internal transcribed spacer 2, complete sequence and 28S ribosomal RNA gene, partial sequence, the major active fungi isolated in the current study were assigned to Fusarium sp. and A. niger.Fig. 1


Antimicrobial activities of endophytic fungi obtained from the arid zone invasive plant Opuntia dillenii and the isolation of equisetin, from endophytic Fusarium sp.

Ratnaweera PB, de Silva ED, Williams DE, Andersen RJ - BMC Complement Altern Med (2015)

Endophytic aFusarium sp. (dorsal view), bFusarium sp. (ventral view), cAspergillus niger (dorsal view) and dA. niger (ventral view) in culture
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4496918&req=5

Fig1: Endophytic aFusarium sp. (dorsal view), bFusarium sp. (ventral view), cAspergillus niger (dorsal view) and dA. niger (ventral view) in culture
Mentions: The Fusarium sp. had a white puffy mycelium with a peach colour pigment that secreted into the medium within seven to ten days of culture growth while A. niger produced black spores in a concentric ring pattern on PDA medium (Fig. 1). According to DNA sequence data and blast results obtained, these fungi showed 99 % identity to previously reported Fusarium sp. (GQ505759.1) and A. niger (JN561274.1) [21, 22]. In addition on the basis of 18S ribosomal RNA gene, partial sequence; internal transcribed spacer 1, 5.8S ribosomal RNA gene, and internal transcribed spacer 2, complete sequence and 28S ribosomal RNA gene, partial sequence, the major active fungi isolated in the current study were assigned to Fusarium sp. and A. niger.Fig. 1

Bottom Line: The most bioactive fungus was identified as Fusarium sp. and the second most active as Aspergillus niger.O. dillenii, harbors several endophytic fungi capable of producing antimicrobial substances with selective antibacterial properties.Further investigations on the secondary metabolites produced by these endophytes may provide additional drug leads.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Colombo, Colombo 03, Sri Lanka. pamoda.b@gmail.com.

ABSTRACT

Background: Opuntia dillenii is an invasive plant well established in the harsh South-Eastern arid zone of Sri Lanka. Evidence suggests it is likely that the endophytic fungal populations of O. dillenii assist the host in overcoming biotic and abiotic stress by producing biologically active metabolites. With this in mind there is potential to discover novel natural products with useful biological activities from this hitherto poorly investigated source. Consequently, an investigation of the antimicrobial activities of the endophytes of O. dillenii, that occupies a unique ecological niche, may well provide useful leads in the discovery of new pharmaceuticals.

Methods: Endophytic fungi were isolated from the surface sterilized cladodes and flowers of O. dillenii using several nutrient media and the antimicrobial activities were evaluated against three Gram-positive and two Gram-negative bacteria and Candida albicans. The two most bioactive fungi were identified by colony morphology and DNA sequencing. The secondary metabolite of the endophyte Fusarium sp. exhibiting the best activity was isolated via bioassay guided chromatography. The chemical structure was elucidated from the ESIMS and NMR spectroscopic data obtained for the active metabolite. The minimum inhibitory concentrations (MICs) of the active compound were determined.

Results: Eight endophytic fungi were isolated from O. dillenii and all except one showed antibacterial activities against at least one of the test bacteria. All extracts were inactive against C. albicans. The most bioactive fungus was identified as Fusarium sp. and the second most active as Aspergillus niger. The structure of the major antibacterial compound of the Fusarium sp. was shown to be the tetramic acid derivative, equisetin. The MIC's for equisetin were 8 μg mL(-1) against Bacillus subtilis, 16 μg mL(-1) against Staphylococcus aureus and Methicillin Resistant Staphylococcus aureus (MRSA).

Conclusions: O. dillenii, harbors several endophytic fungi capable of producing antimicrobial substances with selective antibacterial properties. By producing biologically active secondary metabolites, such as equisetin isolated from the endophytic Fusarium sp., the endophytic fungal population may be assisting the host to successfully withstand stressful environmental conditions. Further investigations on the secondary metabolites produced by these endophytes may provide additional drug leads.

No MeSH data available.


Related in: MedlinePlus