Research: EFFECTS OF METHANOLIC EXTRACT OF A SOFT SPONGE, Haliclona sp. ON BACTERIAL CELLS: STRUCTURAL DEGENERATION STUDY

In-vitro antimicrobial screening of Haliclona sp. isolated from Malaysian coastal waters was conducted against a selected of pathogenic bacteria, yeast and fungi. It was found that the methanolic extract of this soft sponge only showed antibacterial activity but not antifungal or antiyeast activities. The MIC and MBC values obtained were 0.5 mg ml-1 and 1.0 mg ml-1 for MRSA and Bacillus spizizenii, respectively, whereas 1.0 mg ml-1 and 2.0 mg ml-1 for B. subtilis, B. cereus, Acinetobacter anitratus and Erwinia sp., respectively. The effects of the extract on MRSA and B. subtilis cells were also studied by means of scanning electron microcopy (SEM) and the results revealed that the extract caused internal shrinkage of the cells and finally completely collapsed the cells after prolonged exposure to it. The time-killed study suggested that the extract significantly inhibited the cell growth and possessed bacteriostatic activity at lower concentration and bactericidal activity at higher concentration.