Toxicity of butyltin, phenyltin and inorganic tin compounds to sulfate-reducing bacteria isolated from anoxic marine sediments
Résumé
The toxicity of butyltin, phenyltin and inorganic tin compounds to three pure strains of sulfate-reducing bacteria (SRB), isolated from a tributyltin (TBT)-polluted sediment, was determined. The isolated strains were identified as belonging to the genus Desulfovibrio. A new toxicological index (GR25) was developed to assay the toxicity of organotin compounds. Deleterious effects on suspended anaerobic cell cultures were observed for concentrations ranging between 500 and 600 μM for tin tetrachloride, 55 and 260 μM for triorganotins, 30 and 90 μM for diorganotins, and 1 and 6 μM for mono-organotins. Whereas the number of substituents influenced the toxicity of organotins, the type of substituent (butyl or phenyl) proved to have little or no impact. Trisubstituted compounds (tributyl-and triphenyl-tin) were less toxic to these strains of SRB than the monosubstituted forms (monobutyl- and monophenyl-tin). This is the opposite trend to that currently reported for aerobic organisms. Under the given anoxic conditions, the toxicity of organotin compounds obtained yielded a significant negative correlation with the total surface area (TSA) of the tested molecules. Comparison of the TBT toxicity data observed for different microbial groups suggests that the tolerance of bacteria to organotin compounds might be related to organotin-cell wall interactions as well as to aerobic or anaerobic metabolise pathways.