Environmental Impact of Tributyltin-Resistant Marine Bacteria in the Indigenous Microbial Population of Tributyltin-Polluted Surface Sediments.

摘要

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 10(9.4) to 10(4.2) 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 10(11.8). Resting cells prepared from type strains Photobacterium ganghwense JCM 12487(T) and P. halotolerans LMG 22194(T), 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 14048(T) cells, 10(6.2±0.3) CFU mL(-1), was reduced to 10(4.4±0.4) CFU mL(-1) when TBT-resistant Photobacterium sp. TKY1 cells, 10(9.1±0.2) CFU mL(-1), coexisted with 10(9.4±0.2) CFU mL(-1) of V. natriegens ATCC 14048(T) 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.