The lead (Pb2+) bioaccumulation capacities and mechanisms of three different physiological structures (vegetative cells, decay cells and spores) of B. coagulans R11 isolated from a lead mine were examined in this study. The results showed that the total Pb2+ removal capacity of vegetative cells (17.53 mg/g) was at its optimal and higher than those of the spores and decay cells at the initial lead concentration of 50 mg/L. However, when the initial lead concentration surpassed 50 mg/L, Pb2+ removal capacity of decay cells was more efficient. Zeta potential, Fourier transform infrared (FTIR) and functional group modification analyses demonstrated that the electrostatic attraction and chelating activity of the functional groups were the primary pathways involved in the extracellular accumulation of Pb2+ by the vegetative cells and spores. However, the primary Pb2+ binding pathway in the decay cells was hypothesized to be due to physical adsorption, which easily led to Pb2+ desorption. Based on these results, we conclude that the vegetative cell is the ideal lead sorbent. Therefore, it is important to inhibit the transformation of the vegetative cells into decay cells and spores, which can be achieved by culturing the bacteria under anaerobic conditions to prevent spore formation. Heat stimulation can effectively enhance spore germination to generate vegetative cells.
Bacillus thuringiensis (Bt), an ubiquitous gram-positive spore-forming bacterium forms parasporal proteins during the stationary phase of its growth. Recent findings of selective human cancer cell-killing activity in non-insecticidal Bt isolates resulted in a new category of Bt parasporal protein called parasporin. However, little is known about the receptor molecules that bind parasporins and the mechanism of anti-cancer activity. A Malaysian Bt isolate, designated Bt18 produces parasporal protein that exhibit preferential cytotoxic activity for human leukaemic T cells (CEM-SS) but is non-cytotoxic to normal T cells or other cancer cell lines such as human cervical cancer (HeLa), human breast cancer (MCF-7) and colon cancer (HT-29) suggesting properties similar to parasporin. In this study we aim to identify the binding protein for Bt18 in human leukaemic T cells.