3. Results and discussion
Anthropogenic activities have led to metal pollution in the water bodies as it threatened some of the aquatic
Fatimah Hashim et al. / Procedia Environmental Sciences 30 ( 2015 ) 15 – 20 17
organism and this includes the free-living amoebae. Decreasing population of amoebae due to the presence of heavy
metal will leads to imbalance of the natural ecosystem as amoebae act as predator for bacteria.
The presence of heavy metal in the aquatic environments makes them a suitable toxicant to be evaluated for their
effects towards amoebae. To date, there are only a few reports on cytotoxic and genotoxic effects of heavy metal on
amoebae like cadmium, mercury, lead and zinc on these free-living amoebae [7]. However, there are no study
focusing the effect of Mn on Acanthamoeba. Therefore, it is important to evaluate the effect of Mn towards
Acanthamoeba as it would indicate the presence of exceed level of Mn in aquatic environment.
3.1 Determination of Mn Fifty percent inhibition concentration (IC50) on Acanthamoeba sp.
In this study, Acanthamoeba sp. were exposed to various concentrations of Mn i.e 0, 30, 60, 90, 120, 150 and
180 ppm for 24 hours at 30qC in a 96-well plate to determine the cytotoxicity of the metal. The MTT assay was
carried out to assess the viability of Acanthamoeba sp. Fig.1 shows the graph of viability of cell against different
concentrations of Mn. Based on the graph, the IC50 value obtained was 24 ppm and Acanthamoeba sp. showed the
reduction in viability upon exposure to increasing in Mn concentration.