2299 Our knowledge of Escherichia coli (E. coli) ecology in the field is very limited in the case of dairy alpine grassland soils. Here, our objective was to monitor field survival of E. coli in cow pats and underlying soils in four different alpine pasture units, and to determine whether the soil could constitute an environmental reservoir. E. coli was enumerated by MPN using a selective medium. E. coli survived well in cow pats (10 7 to 10 8 cells g -1 dry pat), but cow pats disappeared within about 2 mo. In each pasture unit, constant levels of E. coli (10 3 to 10 4 cells g -1 dry soil) were recovered from all topsoil (0–5 cm) samples regardless of the sampling date, that is, under the snow cover, immediately after snow melting, or during the pasture season (during and after the decomposition of pats). In deeper soil layers below the root zone (5–25 cm), E. coli persistence varied according to soil type, with higher numbers recovered in poorly-drained soils (10 3 to 10 4 cells g -1 dry soil) than in well-drained soils (< 10 2 cells g -1 dry soil). A preliminary analysis of 38 partial uidA sequences of E. coli from pat and soils highlighted a cluster containing sequences only found in this work. Overall, this study raises the possibility that fecal E. coli could have formed a naturalized (sub)population, which is now part of the indigenous soil community of alpine pasture grasslands, the soil thus representing an environmental reservoir of E. coli. Persistence of Culturable Escherichia coli Fecal Contaminants in Dairy Alpine Grassland Soils Stéphanie Texier INRA - Université de Savoie and CNRS - Université de Lyon Claire Prigent-Combaret CNRS - Université de Lyon Marie Hélène Gourdon INRA - Université de Savoie Marie Andrée Poirier CNRS - Université de Lyon Pierre Faivre, Jean Marcel Dorioz, and Jérome Poulenard INRA - Université de Savoie Lucile Jocteur-Monrozier and Yvan Moënne-Loccoz CNRS - Université de Lyon Dominique Trevisan* INRA - Université de Savoie F ecal microbial contamination of water is considered a worldwide problem for public and animal health, and the presence of fecal bacteria has been monitored in various water bodies (Fisher et al., 2000; Cassell et al., 2001; Entry and Farmer, 2001; Celico et al., 2004; George et al., 2004; Muirhead et al., 2006a). Often, fecal bacteria involved in water contamination originate from farmlands (Jamieson et al., 2002), where they have been deposited as feces (i.e., in pastures) or spread manure, both of which contain high amounts of fecal bacteria and potential human pathogens (Avery et al., 2004; Ogden et al., 2002; Gagliardi and Karns, 2000; Faust, 1982). Survival of fecal bacteria in soil will be an important factor determining the extent of subsequent stream contamination. Soil survival of fecal contaminants such as Escherichia coli (E. coli) has been mainly assessed in the case of manure or sludge ap- plication, in which fecal matter and associated bacteria are spread onto large field surfaces. Despite the fact that survival of fecal bac- teria is favored in soils with higher organic matter content (Oliver et al., 2005a; Crane et al., 1983), it appears that survival of E. coli added with manure or sludge contaminants is generally limited in planted soil (Williams et al., 2007; Tyrrel and Quinton, 2003; Tre- visan et al., 2002; Chandler et al., 1981). he presence of plants has a major impact on the ecology of bacteria in soil (Troxler et al., 1997). On one hand, the rhizosphere is a microbial habitat receiv- ing significant amounts of organic substrates as root exudates, leading to proliferation of a wide range of root-colonizing bacteria, for example fluorescent pseudomonads (Troxler et al., 1997). On the other hand, many root-colonizing bacteria produce antibiotics, which can affect (via competition and/or antagonism) the survival Abbreviations: ANOVA, analysis of variance; bp, base pair; DNA, deoxyribonucleic acid; K, saturated permeability constant; MANOVA, multiple analysis of variance ; MPN, most probable number; MU/Ec, 4-methylumbelliferyl-β-D-glucuronide/Escherichia coli; PCR, polymerase chain reaction; UV, ultraviolet; 16S rRNA, small subunit ribosomal ribonucleic acid. S. Texier, M.H. Gourdon, P. Faivre, J.M. Dorioz, J. Poulenard, and D. Trevisan, UMR42 CARRTEL, INRA F74203, Thonon-les-Bains, France; Université de Savoie, F73376 Le Bourget du Lac, France. S. Texier, C. Prigent-Combaret, M.A. Poirier, L. Jocteur- Monrozier, and Y. Moënne-Loccoz, Université de Lyon, F69003, Lyon France; CNRS, UMR5557, Ecologie Microbienne, F69622, Villeurbanne, France. Copyright © 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including pho- tocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Published in J. Environ. Qual. 37:2299–2310 (2008). doi:10.2134/jeq2008.0028 Received 17 Jan. 2008. *Corresponding author (trevisan@thonon.inra.fr). © ASA, CSSA, SSSA 677 S. Segoe Rd., Madison, WI 53711 USA TECHNICAL REPORTS: VADOSE ZONE PROCESSES AND CHEMICAL TRANSPORT