Xenobiotic Metabolizing Bacteria of the Indian Ocean - Getting More Common?

A review of: Rodrigues, J., Madhukar, A., Kumar, N., Sangodkar, U.M.X., (2010), Isolation and characterization of a marine bacterium belonging to the genus Alkalignes capable of the complete mineralization of the dibenzothiopene, Indian Journal of Geo Marine Sciences, 40, 3, 391-397

With a rising demand for fossil fuels from the ever expanding human population, there is always a need for the transportation of products between countries, this is most commonly done via tanker on the worlds oceans. But in recent years this method of transport has resulted in the contamination and near destruction of many of the worlds marine ecosystems. In many places around the world this is a huge threat, but considering that there are many areas with a vast concentration of marine life bordered and regulated by developing countries, this threat can be further increased. 

This study directly looks at the western coast of India region of Goa, where, in 1995, the M.V. Sea transporter ran aground during a cyclone, resulting in the spillage of furnace oil. A marine microbe of genus Alkaligenes was found to be live here and was observed to completely mineralize the xenobiotic compound dibenzothiopene (DBT), an aromatic hydrocarbon found in the tar balls of the contaminated site. The purpose of this test is to look directly at the relationship between the Alkaligenes and the DBT.

During the study, sequential enrichment techniques were favoured, whereby cultures of the bacteria were grown in artificial sea water and to this, 1g of DBT was added and mixed thoroughly to simulate conditions found at the site of contamination. Cultures were then acidified at different times and extracted using an ethyl acetate extract and thoroughly dried. Preparative silica gel G was used to apply the extracts to TLC plates and then exposed to UV light. Residual chemicals were then compared using  industry standard chemicals. The different strains were then separated and tested further against the DBT.

Results show that there are 5 strains of the bacteria that utilizes the DBT, and out of these, the JR110 strain. This was then sent to the IMTECH facility in Chandigarh, India for detailed testing with results as follows, the JR110 strain was seen to degrade 8 different aromatic compounds also with degradation of DBT intermediates to form a red pigmented colony. Tests carried out exposing only the JR110 strain to the DBT were largely successful, showing a clean sigmoid curve of reduced contamination as the growth of the bacteria increases.

Conclusions are drawn that due to the highly contaminated nature of the west coast of India, there is likely to be continuous evolution of degradation processes of xenobiotic compounds, which is believed to be due to the intermediates of benzoate utilizing the pathways in marine bacteria, thus exerting a positive pressure on the mineralization of xenobiotic compounds such as DBT.