Bacterial Metabolism of Isoproturon

Abstract

With the increase in world’s population the demand for food is increasing rapidly. In order to achieve the goals of food security, many plant protection products are being used that result in high yield and quality product. Among these plant protection products pesticides are of importance. In spite of enhancing crop productivity and quality, pesticides also put living organisms in jeopardy and contaminate environment via food chain. Pesticides are responsible for the contamination of soil, surface and sub-surface water and atmospheric pollution. In addition to this, they also produce health effects in plants, animals and human beings. Among herbicides, Isoproturon plays a vital role in the elimination of broad leaf herbs from wheat, rice and other cereal crops. It belongs to phenyl urea herbicides with chemical formula of [3-(4 isopropylpheny)-1,1-dimethylurea]; consists of a phenyl ring (C6H4) with a methyleurea [(NH2)-CO-NH-CH3] branched on C1 and dimethyl branched on C4. Isoproturon (IPU) contributes in water as well as soil pollution by posing major threats to aquatic life and public health and safety. It can penetrate in food chain and may cause carcinogenic and mutagenic effects. However due to lower vapor pressure, its contribution to air pollution is very less. Due to its persistency in water and soil with combination of hazardous effects, it requires serious attention to eliminate it from environment. Among many remediation techniques, biological remediation is cost effective, reliable and environment friendly. Degradation of isoproturon mostly occur in agriculture soils by microbes. IPU-degrading microorganisms have been isolated from different soils and out of eleven identified bacteria, seven belong to Sphingomonas genus. However, member of genus Arthrobacter, Methylophila and Pseudomonas are also known to metabolize isoproturon. The goal of this study was to assess the IPU degradation potential of Pakistani soils, enrich the bacteria capable of metabolizing isoproturon from soil and sludge samples and attempt to isolate them. Results revealed that Pakistani soils exposed to isoproturon are able to degrade isoproturon. Enrichment cultures were obtained that could be further transferred. However, isoproturon degradation occurred in mixed community only. Pure strains capable of metabolizing IPU could not be obtained. There could be multiple reasons for this. Large number of microbial communities are still unknown and uncultivated and more than 99% of microbes existing in the environment cannot be cultivated easily using traditional microbiological techniques. Nutrient availability was another xiii Abstract reason as our media was devoid of any trace elements or vitamins. Moreover, the toxicity of isoproturon and its intermediate metabolites might also have affected the results. Key words: Isoproturon, Soil, Enrichments, Pesticides, Degradation, Environment, Pakistan.