Antioxidants in mangrove plants and endophytic fungal associations

Abstract The manner in which fungal endophytes activate host stress response systems is unknown; the occurrence of additional mechanisms involved in symbiotically-conferred stress tolerance in mangrove plants (the primary producers of estuarine food chain) is also an unresolved issue. Here, we report antioxidant potentials of four different mangroves and their endophytic fungi. We elucidated the possible roles of antioxidants in symbiotic association between mangroves and their endophytic fungi. Four different mangrove species and the predominant endophytic fungus Aspergillus flavus were analyzed using various in vitro assay systems (such as iron chelating capacity, reducing power, and hydroxyl radicals/hydrogen peroxide/l-diphenyl-2-picrylhydrazyl radical scavenging and inhibition of lipid peroxidation using the β-carotene–linoleate model system). In vitro models clearly established the antioxidant potency of extracts of mangrove plants and their respective endophytic fungi, which aids in understanding the mutualistic associations of plant and endophyte against various biotic and abiotic stresses. Re-infection analysis of endophytic A. flavus in tobacco plants confirmed the endophytic status of the fungus and its enhancement effect on plant growth.</jats:p

Antimicrobial activity of Serratia sp isolated from the coralline red algae Amphiroa anceps

1857-1866Bacterial isolates (6 nos) were obtained from the coralline red algae Amphiroa anceps. Crude extract of these isolated were tested for antimicrobial activity against 20 different human pathogenic bacterial and fungal strains. Among this crude extract of a single red pigmented strain AA1 was found to show activity against (12) bacterial pathogens and (1) fungi. Higher range of antibacterial activity was observed against Staphylococcus aureus and antifungal activity against Rhizopus sp, while moderate antibacterial activity was observed with Salmonella typhi, Enteropathogenic E.coli and Klebsiella pneumonia. Identification based on morphological, biochemical and 16S rDNA sequencing showed that the strain AA1 was identified as Serratia sp (KC149511). Fractioned extract of the bacterial isolate was analyzed in a Gas Chromatography Mass Spectrometry (GC-MS). Results showed the presence of certain metabolites such as octadecanoic acid, phenol, 2, 4-bis (1, 1- dimethyl ethyl), nonanoic acid- 9 oxo methyl ester which could be responsible for the antifungal and antibacterial activities. Results showed that the pigmented Serratia sp is a potential source for bioactive substances and could contribute to the discovery of several novel compounds of pharmaceutical importance