Molecular and physiological bacterial diversity of a semi-arid soil contaminated with different levels of formulated atrazine M. Ros a, * , M. Goberna b , J.L. Moreno a , T. Hernandez a , C. Garcı ´a a , H. Insam c , J.A. Pascual a a Centro de Edafologia y Biologia Aplicada del Segura (CEBAS-CSIC), Department of Soil and Water Conservation and Organic Waste Management, P.O. Box 164, 30100 Espinardo-Murcia, Spain b Centro de Investigaciones sobre Desertificacio ´n (CIDE-GV, CSIC, UV), 4647O Albal (Valencia), Spain c Institut fu ¨r Mikrobiologie, Leopold-Franzens-University, A-6020 Innsbruck, Tecknikerstrasse 25, Austria Received 3 October 2005; received in revised form 30 March 2006; accepted 31 March 2006 Abstract A semi-arid soil treated with different concentrations of formulated atrazine in a laboratory experiment was studied over 45 days, by different biological and molecular parameters (bacterial enumeration (cfu), community level physiological profiles (CLPPs) measured by Biolog 1 and denaturing gradient gel electrophoresis (DGGE)), to study the bacterial community diversity. Formulated atrazine was almost totally degraded at different concentrations after this incubation time. The number of colony forming units (cfu) for soils with 100 and 1000 mg kg 1 atrazine was significantly ( p  0.05) higher than for the control, 1 and 10 mg kg 1 treatments. DGGE banding patterns showed that regardless of time elapsed, concentrations of 10, 100 and 1000 mg kg 1 atrazine in soil, affected the bacterial community compared to control and 1 mg kg 1 . The Shannon diversity index (H 0 ) based on CLPP data showed a significant ( p  0.05) decrease at atrazine concentrations of 100 and 1000 mg kg 1 . The Shannon diversity indices for different guilds of source carbon and the parameters K and r (based on the kinetics of colour formation rather than on the degree of colour development) were related to guilds of carbon substrates and atrazine concentration at a sampling time. The parameter K was very sensitive to atrazine effects on microbial communities. These biological and molecular parameters can be used to monitor changes in soils treated with atrazine at different concentrations, even when the pesticide is degraded. # 2006 Elsevier B.V. All rights reserved. Keywords: Atrazine; CLPPs; PCR–DGGE; Bacterial communities 1. Introduction The ideal pesticide should be toxic only to target organisms, be totally biodegradable to CO 2 and H 2 O, but not leave intermediate compounds in the environ- ment or leached into the groundwater. Unfortunately, this is rarely the case and the widespread use of pesticides in modern agriculture is of increasing concern. The main problems arising from the use of pesticides in agriculture are their toxicity to non-target organisms, the growth of resistant species and their persistence in soil. Formulated atrazine (2-chloro-4-ethylamino-6-iso- propylamino-1,3,5-triazine) is used widely to control www.elsevier.com/locate/apsoil Applied Soil Ecology 34 (2006) 93–102 * Corresponding author. Tel.: +34 968396259; fax: +34 968396213. E-mail address: margaros@cebas.csic.es (M. Ros). 0929-1393/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.apsoil.2006.03.010