Aeromonas molluscorum Av27: A Potential Natural Tool for TBT Decontamination

Tributyltin (TBT) is a toxic compound employed in several industrial processes. Its discharge into the environment has been recognized worldwide as a pollution problem. The importance of bacteria in decontamination processes has been long acknowledged. The aim of this work was to screen TBT resistant/ degrading bacteria in order to investigate the involved mechanisms. Aeromonas molluscorum Av27, isolated from Ria de Aveiro (Portugal), showed high TBT resistance (up to 3 mM). From a genomic library, a TBT resistant clone (5.4 kbp fragment) was selected. In this fragment, ORF P6 was able to confer TBT resistance to E. coli. P6 has homology with a sugE gene, which encodes SugE protein, belonging to small multidrug resistant family, a lipophilic drug transporter. Reverse transcriptase-PCR analysis indicated that increased expression of the sugE gene was found in the original strain (A. molluscorum Av27) when the cells were grown in the presence of high concentrations of TBT. A. molluscorum Av27 degrades TBT in dibutyltin (DBT) and monobutyltin (MBT) and uses it as carbon source. Microcosm experiments with TBT contaminated sediments revealed that the addition of Av27 strain does not affect the natural bacterial community. Given the interesting characteristics exhibited by Av27, it can potentially be used to develop a bioreporter system to monitor on-site TBT contamination and also be employed as a remediator of TBT polluted sites.