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Diversity and In Situ Quantification of Tributyltin-Degrading/resistant Bacteria Under Different Cultivating Conditions

Young Haeng Lee1, Soohyun Park1, Yongsu Choi1, and Hee-Deung Park2. (1) Center for Environment Technology Research, Korea Institute of Science and Technology, 39-1 Howelgok-Dong, Sungbuk-Gu, Seoul, 130-650, South Korea, (2) R&D Institute, Kolon Engineering & Construction, 199-5 Chundae-Ri, Pogok-Myun, Yongin-si, 449-815, South Korea

All organotin compounds are toxic, but the effect varies according to the number and the type of organic moiety present, as butyl-group bearing organotin is more toxic to fungi and bacteria. Tributyltin (TBT) is an organometallic compound used as antifouling agent in marine paints.

Based on the literature review, a few researchers have reported evidence for the presence of TBT-resistant bacteria in natural seawater and marine sediment.

The objective of this study was to assess the diversity and community composition of TBT-resistant bacteria under different conditions (TBT, monobutyltin (MBT) known as microbial degradation product of TBT, and dextrin/peptone mixture as an external carbon source).

Resistant to TBT was examined in bacterial populations enriched using TBT-contaminated marine sediment (Ulsan Bay, South Korea) sample as inoculum, at the initial TBT concentration of 10 and 100 ppm which was much higher level than the observed TBT level in the contaminated sediment.

Phylogenetic trees based on the 16S rDNA sequence revealed that Marinobacter sp. and alpha proteobacterium sp. were identified for 100 ppm TBT-amended culture samples regardless of the presence or absence of carbon source and 100 ppm MBT. Those bacteria to date have never been reported from the TBT-contaminated marine sediments. Quantitative fluorescence in situ hybridization (FISH) analysis confirmed that the Alphaproteobacteria were the most dominant group in all 100 ppm TBT-amended cultures. For 10 ppm TBT-amended cultures, along with Marinobacter sp. and alpha proteobacterium sp., Halomonas sp. were identified in the absence of carbon source, and in the presence of carbon source, Marinobacterium sp., Desulfovibrio sp., Thiomicrospira sp., Soehngenia sp., Acholeplasma sp. were additionally identified. However, in the presence of 10 ppm MBT, phylogenetic analysis revealed that only Marinobacter sp. and alpha proteobacterium sp. were identified for all 10 ppm TBT-amended cultures. Similar to the results obtained in 100 ppm TBT-amended cultures, quantitative FISH analysis resulted that the Alphaproteobacteria were the most dominant group in all 10 ppm TBT-amended cultures. Both quantitative FISH and restriction fragment length polymorphism (RFLP) analyses resulted that the community composition of TBT-resistant bacteria changed significantly when the external carbon source and/or MBT were amended.