Marine bacteria as an aid in TBT degradation.

Tributyltin (TBT) is well known biocide used for control of a broad spectrum of organisms. It belongs to the trialkyl organotin family and it’s often used in antifouling paints. As many biocides it is quite toxic to many organism, including non-target ones. It is also considered to be endocrine disruptor and it has been shown to induce imposex in some of the female mollusc. Although is now banned in all of the European countries its high persistence in marine environments still pose high risk of toxicity to marine organisms. The degradation of TBT in marine waters happens mainly due to microbial activity rather than physical or chemical actions, therefore certain types of bacteria have the potential of TBT degradation similar to bacteria that can biodegrade crude oil.

Current study, by Sampath et al. (2012) investigated the potential of TBT degradation by 5 bacterial isolates and their consortium, belonging to the Pseudomonas genus (Pseudomonas pseudoalcaligenes, P. stutzeri, P. mendocina, P. putida, and P. balearica) isolated from Indian coastal waters and grown in MSM broth containing TBT, the control samples contained ethanol instead of TBT. The growth of bacteria (measured as CFU/ml), the ability to produce rhamnolipids biosurfactants and siderphores were measured in order to evaluate the degradation potential of TBT by these strains.

The results revealed that out of 5 bacterium P. putida was found to grow the best in the presense of TBT but the consortium have shown to achieve the highest growth (higher than any individuals) as well as produced high quantities of rhamnolipids and extracellular proteins (ECP). The consortium of bacteria have been recognised as much better candidate for TBT water treatment as they achieved higher cell growth densities in much less incubation time. Also normally sidrophores are produced under ion limiting conditions but this study showed that they have been produced under TBT stress and that indicates their biocatalytic action in TBT breakdown.

In general this study showed some potential of these bacteria in biodegradation of TBT which may have its use in water treatment plants, however this study was carried out in the laboratory at stable temperature therefore the outcome might have been quite different under field conditions , also the authors indicated the ability of bacteria under TBT stress , however they haven’t really explained the biochemistry of this process as the title would suggest therefore it was slightly misleading. In overall it was an interesting study from an ecological point of view especially that TBT is still a persisting problem in marine environments , however more filed studies need to be carried out and take into the account many other environmental factors which can have big impact on these results.

A review of Sampath et al. (2012). Biochemistry of TBT-Degrading Marine Pseudomonads Isolated from Indian Coastal Waters.Water Air Soil Pollut. 223:99-106.