Abstract:
Sponges (phylum Porifera) are sessile marine filter feeders that have developed efficient
defense mechanisms against their enemies which include viruses, bacteria, or eukaryotic
organisms. Sponges are a good source of nucleosides, terpenes, sterols, cyclic peptides,
alkaloids, fatty acids, peroxides and amino acid derivatives. These types of extracted bioactive
substances have shown excellent anticancer, antibacterial, antifungal, antiviral, antiprotozoal,
anthelmintic, anti-inflammatory, immunosuppressive, neuro suppressive and antifouling
activities. However, very few studies have been conducted on Sri Lankan sponge fauna to
investigate such properties. Hence, the main objective of this study was to investigate the
antimicrobial activity of selected sponge samples from Pigeon Island, Trincomalee, Sri Lanka.
Methanol (MeOH) and 1:1 dichloromethane:methanol (DCM:MeOH) extracts of Axinella
donnani and Xestospongia sp. were tested for antimicrobial activity via disk diffusion assay
against Gram positive bacteria: Bacillus subtilis, Staphylococcus aureus; Gram negative
bacteria: Pseudomonas aeruginosa, Escherichia coli and two fungi, Penicillium notatum,
Curvularia lunata. Antibacterial assay of the present research revealed that only methanol
extracts of Axinella donnani sponge has antibacterial activity against Gram negative bacteria;
P. aeruginosa showing 10.3 ± 0.1 mm inhibition zone. However, other three extracts did not
show any antibacterial activity against the tested Gram positive and Gram negative
bacteria. The methanol extract of A. donnani was subjected to Minimum Inhibitory
Concentration (MIC) assay and the results showed the MIC value of 300 µg per disk for P.
aeruginosa. Also, antifungal assay with MeOH and DCM:MeOH extracts did not show any
activity against the both fungal species tested in the study. Further studies are ongoing to isolate
antimicrobial compounds from A. donnani sponge.
