Review: Biodegradation of tributyltins (organotins) by marine bacteria

Abstract

Many marine bacterial strains have an inherent capability to degrade toxic organotin compounds, especially tributyltins (TBTs), that enter into the environment in the form of insecticides, fungicides and antifouling paints as a result of anthropogenic and industrial activities. Significant degradation of these compounds in the ambient environment may take several years, and it is necessary to consider methods or strategies that can accelerate the degradation process. There have been few demonstrations of biological degradation of these organotin biocides exclusively in laboratory-scale experiments. Compared with the few bench-scale degradation processes, there are no reports of field-scale processes for TBT bioremediation, in spite of its serious environmental threat to nontarget organisms in the aquatic environment. Implementation of field-scale biodegradation of TBT requires inputs from biology, hydrology, geology, chemistry and civil engineering. A framework is emerging that can be adapted to develop new processes for bioremediation of toxic environmental wastes. In the case of TBT bioremediation, this framework incorporates screening and identification of natural bacterial strains, determination of optimal conditions for growth of isolates and TBT degradation, establishment of new metabolic pathways involved in TBT degradation, identification, localization and cloning of genes involved in degradation and in TBT resistance, development of suitable microbial strains using genetic manipulation techniques for practical applications and optimization of practical engineering processes for bioremediation of organotin-contaminated sites. The present review mainly addresses the aspect of TBT biodegradation with special reference to environmental sources of TBT, chemical structure and biological activity, resistant and degrading bacterial strains, possible mechanisms of resistance and degradation and the genetic and biochemical basis of TBT degradation and resistance. It also evaluates the feasibility and potential of natural and genetically modified TBT-degrading bacterial strains in field-scale experiments to bioremediate TBT-contaminated marine sites, and makes recommendations for more intensive and focused research in the area of TBT bioremediation mediated by marine bacterial strains.

Synthesis, characterization and in vitro cytotoxicity of homobimetallic complexes of palladium(II) with 2‐thiouracil ligands. Crystal structure of [Pd2(TU)(PPh3)3Cl2]

“…The complexation of two Pd atoms with one ligand through both N atoms is confirmed by the absence Bioorganometallic Chemistry of the (N6-)H6 and (N2-)H2 signals that were present in the spectrum of 2-thiouracil, whereas the (N2-)H2 singlet appears at 12.54 ppm in the one Pd atom complexes 3-5. The (C4-)H4 and (C5-)H5 protons resonances are shifted downfield at 5.97 ppm (unresolved doublet) and 5.86 ppm (well resolved doublet) as compared with the free 2-thiouracil ( δ = 0.026, 3 J H,H = 7.8 Hz), respectively, in the complexes 1-5, 32 implying a lowering of the bond order as a consequence of the thione → thiol tautomerization during complexation. 33 During complexation, 2-thiouracil behaves as bidentate via S/N in one-Pd complexes 3-5 and as a bridging moiety coordinated to palladium via N and S/N atoms in complexes 1 and 2.…”

“…A summary of data collection and structure refinement for [Pd 2 (µ-thiouracyl)(PPh 3 ) 3 Cl 2 ] is reported in Table 1. The crystal was mounted on a glass capillary and the crystal data were collected with a Bruker AXS Smart 1000 area detector diffractometer (Mo Kα; λ = 0.71073Å).…”

“…3 Palladium(II) and platinum(II) compounds are not only cytotoxic but also show radio-sensitizing activity. 4 -8 Cisplatin complexes and a few carboxylato analogs are effective antitumor drugs.…”

Developing Microbial Inocula to Support Biofuel Crop Cultivation on Tributyltin Contaminated Marine Sediments

“…and a methyl ethyl ketone becoming increasingly less toxic in the process. In addition MBT may degrade finally into inorganic tin which is stable and of low toxicological risk to humans and other mammals (Figure 3) [1,2,17]. Nonetheless information on the mechanism of sequential dealkylation of TBT is still limited therefore, for this study gas chromatography (GC) was employed for the analysis of sediment on seedlings roots for the identification of TBT and degrading species to determine the mechanism of interest.…”

“…Restoring TBT contaminated ecosystems using nature-based solutions, such as bioremediation, is both non-invasive and sustainable. Several studies have suggested marine and estuarine bacterial are the primary pathway for TBT removal via biological degradation, in particular the genera, Alcaligenes, Aeromonas, Enterobacter, Bacillus and Pseudomonas [5,8,[16][17][18][19][20][21].…”