Abstract
The endophytic fungi isolated from leaves of Ocimum sanctum Linn. of different ages were examined for antimicrobial activity. The agar plug diffusion assay was used for primary screening. A total of 148 fungal endophytes were successfully isolated and cultured but only 134 of them (90.5%) exhibited inhibitory activity towards at least one test microorganisms. Moreover, the colonization rate indicated that the old leaves were frequently and densely colonized by endophytes. The results suggested that healthy leaves at older stages of growth can be a potential source for the isolation of endophytic fungi with antimicrobial properties. The ethyl acetate extract prepared from the fermentative broth exhibited better antimicrobial activity and it suggested the antimicrobial activity of the isolates was affected by the culture medium. A better antimicrobial activity was observed in the yeast extract sucrose broth as compared to malt extract broth. Significant improvements in the antimicrobial activity of the crude extract were observed after addition of water extract of the host plant in the culture medium. Key words: Ocimum sanctum Linn., endophytic fungi, antimicrobial activity, host plant extract.
Highlights
Endophyte is a group of endosymbiont, mostly filamentous fungi (Tiwari et al, 2010) which inhabits a unique biological niche and is categorized as highly diverse, polyphyletic group of microorganisms that are capable of colonizing plants tissues asymptomatically without initiating any disease or overt negative symptoms
The endophytic fungi isolated from leaves of Ocimum sanctum Linn. of different ages were examined for antimicrobial activity
Six different isolation media: plain potato dextrose agar (PDA), plain malt extract agar (MEA), PDA supplemented with host plant powder (PHP), PDA supplemented with host plant water extract (PPE), MEA supplemented with host plant powder (MHP) and MEA supplemented with host plant water extract (MPE) were studied and the results showed that the isolated endophytic fungi preferred to grow on PDA and MEA supplemented with host plant powder with 47 and 31 isolates, respectively
Summary
Endophyte is a group of endosymbiont, mostly filamentous fungi (Tiwari et al, 2010) which inhabits a unique biological niche and is categorized as highly diverse, polyphyletic group of microorganisms that are capable of colonizing plants tissues asymptomatically without initiating any disease or overt negative symptoms. Endophytes are believed to benefit host plants by preventing them from colonization of pathogenic microorganisms. The endophytic fungi are reported to produce antimicrobial compounds, having unique genetic and biological systems that may be involved in hostendophyte relationship (Strobel, 2003). Many endophytic fungi have been proven to have the ability to produce novel secondary metabolites to overcome pathogenic invasion. The host-endophytic relationship is found to be complex and varies in different hosts or microorganisms (Tan and Zou, 2001; Pullen et al, 2002).
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