The Study On The Degradation Properties Of Three Thiodiglycol-degrading Bacteria

Thiodiglycol (TDG or TG) is a kind of hydrolysate of mustard gas that is the most erosive chemical arm. As a kind of pollutant being difficult to decompose and persisting to exist in soil, it is also easy to mix with water to cause water resource pollution and threat to the ecosystem. It is an effective way to utilize bioremediation to handle residual hydrolyzate of mustard gas, TDG. In this study, three common soil bacteria (S, Y and W) which were separated from the soils uncontaminated by Professor Hong Li in the British Lancaster University in their early stage of research were used as the object to explore the metabolic pathway of the degradation of TDG preliminarily.The main results are as follows:1. The molecular biological identification of the three degrading bacteria strains had been done in the study.Based on the appraisal results of16S rDNA gene sequences, we identified these three bacteria strains as Stenotrophomonas maltophilia (Y), Achromobacter piechaudii (W) and Mesorhizobium camelthorni (S) respectively through BLAST on NCBI and DNAman analysis.2. The investigation of the TDG degrading activity of these three bacteria strains S. maltophilia, A. piechaudii and M. camelthorni had been done in the study. The results showed that all of them can degrade TDG independently. Strains could make most use of TDG when the concentration of TDG was500ppm. When the concentration was1000ppm, growths of the strains are relatively poor. Whille the concentration exceed1200ppm, strains almost didn’t grow. The degrading rate will be higher when any two or three bacteria were co-cultured. In both single and combined cultivation, the growth rate of M. camelthorni are faster than A. piechaudii and S. Maltophilia, especially in combined cultivation in which the number of M. camelthorni is almost tenfold than A. piechaudii and S. maltophilia. The growth of S. maltophilia is poor and A. piechaudii looks like the poorest.3. The preliminary investigation of the TDG degrading pathways by these three bacteria strains had been done in the study. After ruling out the possibility of abiotic loss of TDG by HPLC and LC-MS analysis of mesostate, we proved that all the three bacteria strains can degrade TDG independently, and we found the rough metabolic pathways that had been reported.The innovation of this thesis were listed as follow:1. This is the first report about bacteria of Mesorhizobium and Stenotrophomonas that could degrade TDG.2. The TDG biodegrading properties by S. maltophilia, M. camelthorni and A. piechaudii have been described for the first time.