Shahbudin Saad

Antimicrobial activity of mangrove plant (Lumnitzera littorea).

OBJECTIVE To investigate the antimicrobial activities of n-hexane, ethyl acetate and methanol extracts of the leaves of Lumnitzera littorea (L. littorea) against six human pathogenic microbes. METHODS The antimicrobial activity was evaluated using disc diffusion and microdilution methods. RESULTS The antimicrobial activities of the crude extracts were increased with increasing the concentration. It is clear that n-hexane extract was the most effective extract. Additionally, Gram positive Bacillus cereus (B. cereus) appear to be the most sensitive strain while Pseudomonas aeruginosa (P. aeruginosa) and the yeast strains (Candida albicans (C. albicans) and Cryptococcus neoformans (C. neoformans)) appear to be resistance to the tested concentrations since no inhibition zone was observed. The inhibition of microbial growth at concentration as low as 0.04 mg/mL indicated the potent antimicrobial activity of L. littorea extracts. CONCLUSIONS The obtained results are considered sufficient for further study to isolate the compounds responsible for the activity and suggesting the possibility of finding potent antibacterial agents from L. littorea extracts.

In vitro antimicrobial activity of mangrove plant Sonneratia alba

OBJECTIVE To investigate the antimicrobial property of mangrove plant Sonneratia alba (S. alba). METHODS The antimicrobial activity was evaluated using disc diffusion and microdilution methods against six microorganisms. Soxhlet apparatus was used for extraction with a series of solvents, n-hexane, ethyl acetate and methanol in sequence of increasing polarity. RESULTS Methanol extract appeared to be the most effective extract while n-hexane extract showed no activity. The antimicrobial activities were observed against the gram positive bacteria Staphylococcus aureus (S. aureus) and Bacillus cereus (B. cereus), the gram negative Escherichia coli (E. coli) and the yeast Cryptococcus neoformans. Pseudomonas aeruginosa and Candida albicans appeared to be not sensitive to the concentrations tested since no inhibition zone was observed. E. coli (17.5 mm) appeared to be the most sensitive strain followed by S. aureus (12.5 mm) and B. cereus (12.5 mm). CONCLUSIONS From this study, it can be concluded that S. alba exhibits antimicrobial activities against certain microorganisms.

Reduced Cannibalistic Behavior of African Catfish, Clarias gariepinus, Larvae Under Dark and Dim Conditions

In general, African catfish shows higher survival rates in the dark conditions than in the light conditions. In this study, larval behavior of African catfish was observed under 0, 0.01, 0.1, 1, 10, and 100 lx using a CCD camera to investigate the reason why African catfish larvae show higher survival rates in dark conditions. The larvae showed significantly higher swimming activity under 0, 0.01, and 0.1 lx than that under 10 and 100 lx. The larvae also showed significantly increased aggressive behavior under 10 and 100 lx; the swimming larvae attacked resting individuals more frequently under 10 and 100 lx than under 0, 0.01, and 0.1 lx. The aggressive behavior and sharp teeth of the attacking larvae appeared to induce skin surface lesions on injured larvae. Chemical substances were then generated from the injured skin surface, and these chemical stimuli triggered cannibalistic behavior in other fish near the injured fish. The results of this study demonstrate that the higher survival rates of African catfish larvae under dark conditions are a result of inactivity and subsequent increase in chemical releasing stimuli concentrations around inactive individuals that triggers feeding behavior in nearby active catfish. Therefore, we recommend larval rearing of African catfish in dark or dim conditions, as it improves catfish survival rates.

Coastal water quality of Tioman Island: effects of human activity and the distance from shoreline

A study was conducted to know the (i) effect of anthropogenic activity and (ii) effects of distance from shoreline on the coastal water quality of Tioman Island, Malaysia. This study was a part of marine expedition conducted on 4 July 2012 to understand coral diversity and distribution around coastal water of Tioman Island. A series of physicochemical parameters namely temperature, dissolved oxygen (DO), pH, salinity, transparency, total suspended solids, nitrate, ammonia, phosphate phosphorus, and silicate were determined in this study. A total of 16 different study sites (stations 1‐16) were selected in the coastal water around the Tioman Island. Half of the study sites was located within 1 km from the shoreline and other half was located approximately 6 km away from the shoreline. Some study sites are characterized by no human activity, while some sites are characterized by diving activities. A few study sites are characterized with both diving activity and near residential area. The overall mean values of different water quality parameters recorded in the all sampling stations were temperature 27.98 ± 0.40˚C, pH 8.34 ± 0.02, DO 6.92 ± 0.43 (mg l �1 ), salinity 33.54 ± 0.11 pss, TSS 0.39 ± 0.03 g l �1 , nitrate 0.85 ± 0.55 μM, ammonia 1.89 ± 0.56 μM, phosphate 0.16 ± 0.09 μM, and silicate 2.62 ± 0.76 μM. Temperature, DO, transparency, salinity, and ammonia were significantly affected by anthropogenic activity, while anthropogenic activity had no significant effect on pH, total suspended solids, nitrate, and phosphate. No significant difference was observed between the water quality of 1 km from shoreline and 6 km away from shoreline. Good and careful management by the authorities of this island may save the biodiversity and beauty of the coastal water of Tioman Island. Therefore, a balance between human activity and conservation of biodiversity on the coastal water of Tioman Island is needed.

Relationship between adult abundance and successive coral recruitment density in the Tioman Island Marine Park, Malaysia

AbstractIt is important to understand coral recruitment as coral reefs are regionally in decline. The pattern and magnitude of coral recruitment strongly influence conservation options and manageme...