© by PSP Volume 18 – No 8. 2009 Fresenius Environmental Bulletin 1390 EFFECT OF PESTICIDES ON SOIL AND AQUATIC ENVIRONMENTAL MICROORGANISMS – A SHORT REVIEW Sylwia Lew 1* , Marcin Lew 2 , Józef Szarek 3 and Tomasz Mieszczyński 3 1 University of Warmia and Mazury, Faculty of Biology, Department of Microbiology, Oczapowskiego St. 1a, 10-719 Olsztyn, Poland 2 University of Warmia and Mazury, Faculty of Veterinary Medicine, Department of Surgery, Oczapowskiego St. 14, 10-719 Olsztyn, Poland 3 University of Warmia and Mazury, Faculty of Veterinary Medicine, Chair of Pathophysiology, Forensic Veterinary Medicine and Administration, Oczapowskiego St. 13, 10-719 Olsztyn, Poland ABSTRACT Extensive applications of pesticides in agriculture and industry result in contamination of the natural environment, thus exerting a negative impact on organisms inhabiting various trophic levels, including humans. The article shows that microorganisms are the first to respond to those syn- thetic compounds deposited in the environment with changes in their both quantitative and qualitative composition. With- drawn from use, yet remaining in the environment, the pesti- cides pose a severe and still unresolved ecotoxicological problem. The publication presents an overview of available knowledge on the effect of various pesticides on bacteria of aquatic and soil ecosystems. KEYWORDS: pesticide, aquatic microorganisms, soil bacteria, microbial ecotoxicology. INTRODUCTION Modern agriculture and industry are dependent on a variety of synthetic chemical compounds, including pesti- cides, e.g. zoocides, fungicides, herbicides and others. Their extensive exploitation has resulted in the contami- nation of natural environment, e.g. natural aquifers which are both major and intermediate receivers of the applied pesticides. While pesticides elicit an acute or chronic toxic effect upon microorganisms, the latter are capable of accu- mulating, detoxifying and metabolizing these compounds and, additionally, use them as a source of carbon [1, 2]. The detrimental effect of pesticides on the species compo- sition of microorganisms triggers changes in higher tro- phic levels. This modification involves both qualitative and quantitative changes [3]. It seems indispensable, therefore, to identify the impact of the mentioned xenobiotics on soil and aquatic microorganisms, and thus on the process of primary production, nutrient circulation and decomposi- tion of matter, in which bacteria serve an important func- tion. In addition, due to the significant role of bacteria in the degradation process of toxic compounds in the natural environment, gaining knowledge on the decomposition of these compounds in pure and mixed cultures is also of key significance, as well as their effects on natural popula- tions of microorganisms. In Stockholm, in 2001, over 100 countries signed a convention on “Persistent Organic Pollutants” – POPs (organic substances that permanently contaminate the natu- ral environment). Its objective is to withdraw from world- wide production or exploitation, or to diminish the impact on the environment, of twelve of the most deleterious toxic substances with high stability in the natural environment, e.g. active substances in plant protection, polychlorinated biphenyls, dioxins and furans. The list of enumerated sub- stances also includes DDT (pp’-dichloro-diphenyltrichloro- ethane). DDT was applied all over the world as a modern chemi- cal weapon in the fight against plant pests and contributed to the eradication of a number of insects transmitting dan- gerous infectious diseases (malaria, typhoid fever, plague and dysentery). However, despite small acute toxicity, it has been demonstrated to exert a detrimental effect on physio- logical and biological functions. DDT is poorly metabo- lizable in nature with a half-life of 60 years. It is estimated that over a million of tons of DDT are still spread world- wide [1]. Unfortunately, in developing countries, it is still being exploited for agricultural control of pests and mos- quitoes [4]. These facts indicate that the problems of envi- ronmental pollution with pesticides are still valid, and that DDT and its metabolites are still being detected in a num- ber of waters, bottom deposits and soils. The major source of these toxic compounds in aquatic ecosystems is the erosion of soils contaminated in the past and atmospheric precipitation [5]. Pesticides are one of the most hazardous groups of organic compounds contaminating the environ- ment. Due to their toxicity, stability, capability for bioac- cumulation and their widespread application, they are the focus of interest of scientists working in this field. The iso- lation of microorganisms capable of pesticide decomposi- tion or biotransformation from various ecosystems has also become an important research problem in recent decades.