Evaluation of tributyltin resistance in marine sediment bacteria

Abstract

Tributyltin (TBT) resistance of aerobic and anaerobic bacteria isolated from TBT-contaminated coastal sediments in Arcachon Bay, France, was determined and compared with taxonomically similar bacteria originating from diverse non-TBT-contaminated environments. The minimum inhibitory concentrations (MICs) showed that TBT was toxic to most of the bacteria studied at concentrations above 2.1 μM (0.7 mg/L) for clostridia, 76 μM (25 mg/L) for pseudomonads, and 3 mM (1000 mg/L) for enterobacteria. The aerobic or facultative anaerobic Gram-negative bacteria (pseudomonads and enterobacteria) presented the highest TBT tolerance. No difference in TBT resistance was observed between strains originating from the polluted site and strains originating from non-TBT-polluted environments (thermal muds, Hospital of Bordeaux, etc.), suggesting that a TBT-polluted environment did not select for more specific resistant bacteria. It should be noted that the bacteria tested were found to be tolerant to TBT concentrations 1000 times higher than those found in the polluted site. Further, all strains presented the same pattern of metal and pharmaceutical antibiotic sensitivity despite the origin of the environment (TBT-polluted or non-TBT-polluted sediments). Six strains of Pseudomonas stutzeri isolated from Arcachon Harbor and one strain of Pseudomonas aeruginosa originating from the bacterial collection of Bordeaux Hospital have been selected for their TBT resistance. As antibiotic resistance, metal or organometal resistance can be plasmid mediated. However, among these TBT-resistant strains no plasmid was detected.Key words: TBT resistance, coastal environment, clostridia, pseudomonads, enterobacteria.