Action of tributyltin on enzymes of four bacteria

Abstract

AbstractThe effect of tributyltin (TBT) was examined on six enzymes in intact cells and in cytosol and wall/membrane fractions of four bacteria. The organisms′ TBT resistance varied over 2,400‐fold: Pseudomonas putida TBT‐6 > Pseudomonas sp. BP‐4 > Bacillus sp. Me‐I > Bacillus sp. MC‐24S. TBT is not a general toxicant for enzymes since β‐galactosidase, glucose dehydrogenase, and alkaline phosphatase were not affected by it. ATPase was detected in cells of all four organisms but not in their cell fractions; it was inhibited by TBT in cells of Bacillus sp. MC‐24S. In intact cells and the membrane fraction, TBT stimulated NADH oxidase at low levels and inhibited it at higher levels, and the more resistant organisms had a higher threshold concentration. In Pseudomonas sp. BP‐4, TBT had no effect on glucose‐6‐phosphate dehydrogenase in cells, but inhibited it in the cytosol fraction. TBT did not affect the periplasmic alkaline phosphatase, which was present in the two Pseudomonas spp. The results support the conclusion that the cell membrane is a site of action of TBT, but that it can also act in the cytoplasm, for the cytosolic enzyme glucose‐6‐phosphate dehydrogenase was stimulated in cells of Bacillus sp. MC‐24S. Enzymes requiring free sulfhydryl groups were inhibited. The patterns of enzyme sensitivity to TBT suggest there may be two resistance mechanisms among these four organisms.