Abstract
The lethal effect of bis (tri-n-butyltin [IV]) oxide (TBTO) on the halotolerant Brevibacterium sp. was examined as a function of NaCl concentrations added externally. More than 99.9% of the viable cells were killed after 20 min exposure to 20 μM TBTO in the absence of NaCl. In the presence of NaCl, however, the viability was greatly increased, i.e., about 1% of the cells survived in the presence of 0.5 M NaCl even after 8 h exposure to TBTO. Maximal survival (7.6%) was observed in the presence of 1.8 M NaCl. These results suggest that the lethal effect of TBTO on Brevibacterium sp. was efficiently reduced by NaCl. Reductive ability of other salts on TBTO was examined in the same manner, and the lethal effect of TBTO was decreased in the order : NaCl > KCl > NaNO3 > NaSCN. This indicated that Cl- as well as Na+ has the most protective action against TBTO lethality. The addition of TBTO caused the release of Na+ ion from the cells. Increase of the percentage of survival was connected with the decrease of Na+ efflux from the cells, indicating that the efflux of Na+ is an important factor in the viability of Brevibacterium sp.
