Antibacterial activity from co-culture of a Papua New Guinea fungal endophyte with bacillus subtilis

Fungal endophytes are fungi that reside in tissues of healthy living plants offering chemical protection and promoting growth of host plants. The chemistry and biological properties of their secondary metabolites from monoaxenic cultures have been extensively studied, but co-culture techniques using endophytes remain largely unexplored. Co-culture of bacteria with endophytic fungi have shown to be effective, leading to the discovery of novel chemistry while simultaneously addressing the problem of rediscovery of known metabolites from the monoaxenic culture techniques. Forty microliters (40μL) of culture broth consisting of monoaxenic and co-cultures were placed in separate agar wells with 5μg ciprofloxacin as positive control. The co-culture broth from one unidentified endophytic fungus with B. subtilis showed a marked zone of inhibition measuring 24.7 ±0.6 mm in comparison to ≥21.0 mm as the sensitivity range for ciprofloxacin against Escherichia coli while its monoaxenic culture exhibited no inhibition, but furthermore showed moderate activity (16.7 ± 1.2 mm) against B. subtilis. The isolation and chemical characterization of the active component and the mechanism of B.subtilis induction is under investigation. It is hoped that this unique Papua New Guinea endophyte will provide broad-spectrum antibiotic to combat the growing global problem of drug resistant infections.

Antimicrobial activity of endophytes in six medicinal plants collected in the Central Province, Papua New Guinea

Endophytic microorganisms are recognized as potential source of novel chemical molecules that might be useful in the treatment of infectious diseases. In this study, six medicinal plants (Morinda citrifolia, Plumeria rubra, Artocarpus altilis, Musa nana, Sansevieria trifasciata and Saccharum officinarum) traditionally. They are used for treatment or management of symptoms such as cough, fever and skin diseases, were investigated for the antimicrobial activity of metabolites produced by endophytic microorganisms. Seven endophytes were isolated using the mycological media, potato dextrose agar (PDA). Three of the endophytes were identified as fungi from the Aspergillus species, three as actinomycetes and one as a gram negative bacterium. All endophytic isolates were subjected to anti-bacterial, anti-tuberculosis (TB), anti-fungal, anti-HIV, and cytotoxicity assays using micro-broth dilution assay technique in sterile 96-well plates. All isolates displayed antimicrobial activity inhibiting at least one of the test pathogens at the concentration of 100μg/ml. Of the 7 endophytic isolates, 6 isolates were active against TB, 7 were active against the bacterial test pathogens, and 2 were active against fungi while none were active against HIV. From the 7 isolates, 3 were non-toxic to mammalian cells at a concentration of 100μg/ml.