| Summary: | 碩士 === 國立臺灣海洋大學 === 海洋生物研究所 === 92 === Abstract
In this study, the fate of tributyltin(TBT) in estuarine sediments was investigated by adding TBT to sediments collected from the Tamsui River and incubated under aerobic-light, aerobic-dark, anaerobic-light and anaerobic-dark conditions. The maximum TBT degradation rates under anaerobic conditions about 0.05~0.07 μM/ day, were lower than those under aerobic conditions, about 0.09~0.13 μM/ day. Light had no effect on the rates of TBT degradation under aerobic or anaerobic conditions. The maximum TBT degradation rates under abiotic conditions were about 0.01 μM/ day, which indicated that physical and chemical factors have lower influence on TBT degradation .
Our results indicated that mono- (MBT)and dibutyltin (DBT) were produced simultaneously during biodegradation of TBT under all conditions. Sometimes tetrabutyltin (TeBT) was detected during incubation. It seems that stepwise debutylation was not the only mechanism for TBT degradation. Disproportionation reaction may be an another mechanism of TBT biodegradation. Although during incubation the concentrations of total tin and total organotin fluctuated, but they were equilibrated finally. The missing total organotin may be degradated to inorganic tin or methylated to methyltin compounds. On the other hand, twenty eight TBT-resistant bacteria were isolated from TBT-adapted sediments under aerobic-light conditions. Those bacteria were all gram-negative, rod-shaped, strictly aerobic bacteria and they were different in subtrates utilization, growth rate and degradating rate on TBT. Based on 16S rDNA gene sequence analysis these isolates could be classified into three groups but they represents a distinct phyletic lineage within the γ-Proteobacteria and have about 93~98% sequence similarity to many marine bacteria. One group have low similarity (92~94%) to Marinobacterium sp. DMS S1, Marinobacterium georgiense, Marinobacterium halophilum strain, and Pseudomonas iners. One group have high similarity (97~98%) to Pseudomonas sp., Arctic seawater bacterium R7078, Thalassolituus oleivorans, and Bacterium JB17. Another group haved low similarity (94%) to Pseudomonas fragi, Bacterium Ph20 and Acinetobacter radioresistens.
Further research is needed to find the suitable strains to apply to bioremediation of the TBT contaminated sediments.
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