| Abstract |
We compared the TBT-resistant ability of resting cells prepared from isolates that formed colonies on nutrient agar plates containing 100 µM tributyltin (TBT) chloride, such as Photobacterium sp. TKY1, Halomonas sp. TKY2, and Photobacterium sp. NGY1, with those from taxonomically similar type strains. Photobacterium sp. TKY1 showed the highest ability among those three isolates. The number of surviving Photobacterium sp. TKY1 cells was hardly decreased after 1 h of exposure to 100 µM TBTCl, regardless of the number of resting cells in the range from 109.4 to 104.2 CFU mL-1. In such an experimental condition, the maximum number of TBT molecules available to associate with a single cell was estimated to be approximately 6.0 x 1011.8. Resting cells prepared from type strains Photobacterium ganghwense JCM 12487T and P. halotolerans LMG 22194T, which have 16S rDNA sequences highly homologous with those of Photobacterium sp. TKY1, showed sensitivity to TBT, indicating that TBT-resistant marine bacterial species are not closely related in spite of their taxonomic similarity. We also estimated the impact of TBT-resistant bacterial species to indigenous microbial populations of TBT-polluted surface sediments. The number of surviving TBT-sensitive Vibrio natriegens ATCC 14048T cells, 106.2±0.3 CFU mL-1, was reduced to 104.4±0.4 CFU mL-1 when TBT-resistant Photobacterium sp. TKY1 cells, 109.1±0.2 CFU mL-1, coexisted with 109.4±0.2 CFU mL-1 of V. natriegens ATCC 14048T cells in the presence of 100 µM TBTCl. These results indicate that the toxicity of TBT to TBT-sensitive marine bacterial populations might be enhanced when a TBT-resistant marine bacterial species inhabits TBT-polluted surface sediments.
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