Triphenyltin Degradation By Bacillus Thuringiensis And The Changes Of Cell Properties

Due to the widely application, triphenyltin(TPh T) has contaminated the global environment,and it has a variety of biological toxicity. To clarify the mechanism of TPh T degradation and guide the application of microbial degradation, the biosorption and biodegradation of TPh T by Bacillus thuringiensis, cell activity, ion release, change of cellular morphology, molecular properties of phenyltin(Ph Ts) and genome of B. thuringiensis were investigated.TPh T was degraded to diphenyltin(DPh T), monophenyltin(MPh T) and tin by B. thuringiensis. The degradation ratio of 1 mg·L-1 TPh T was 64.4% after biodegradation for 2 d in MSM. When degraded for 7 d, the efficiency was 82.3%. Some coexisted metal ions could be removed during TPT biodegradation by B. thuringiensis. When the concentrations of Mg2+ was 10 mg·L-1 in MSM, TPh T degradation ratio was up to 80.6% after 2 d.Cell membrane permeability, survival rate and protein content of B. thuringiensis were significantly associated with TPh T biodegradation. The change of Cl- concentration could be regarded as an index of cell membrane permeability change. Some intracellular materials, such as endospores, crystalline proteins and part of ions, were released because of the increased membrane permeability and apoptosis of some cells when exposure to TPh T. Existence of TPh T also could reduce the protein content of cells. But most cells were active, and these maintained the normal metabolism and TPh T degradation capability of B. thuringiensis. Na+/K+- and Ca2+/Mg2+-ATPase participated in TPh T degradation and promoted the assimilation of K+ and PO43- by cells.According to the result of whole-genome sequecing and gene annotation, B. thuringiensis contains genes which can encode oxygenases and dehydrogenases, and these two types of enzymes were found to participate in cleavage reactions of aromatic rings on aromatic compounds. According to the molecular properties and the concentrations after degradation of three Ph Ts, the cleavage reactions of benzene rings on TPh T may cause by oxygenase and dehydrogenase individually and synchronously, and oxygenase plays a role at first. Cytochrome P450(CYP450), which can synthesize by B. thuringiensis, is an oxygenase, and it has a broad spectrum of detoxification to contaminations. CYP450 may play an important role in TPh T biodegradation.