International Journal of ELSEVIER Food Microbiology 26 (1995) 147-164 Intemational Journal of Food Microbiology Influence of culture conditions on biofilm formation by Escherichia coli 0157:H7 Ratih Dewanti, Amy c.L. Wong • Food Research Institute, Department of Food Microbiology and Toxicology, 1925 Willow Drive, University of WISconsin-Madison, Madison, WI 53705, USA Received 22 February 1994; revision received 27 June 1994; accepted 14 July 1994 Abstract Biofilms of Escherichia coli 0157:H7 were developed on stainless steel chips in trypti- case soy broth (TSB), 1/5 dilution of TSB, 0.1 % Bacto peptone (BP) and a minimal salts medium (MSM) supplemented with 0.04% of one of the following carbon sources: glucose, glycerol, lactose, mannose, succinic acid, sodium pyruvate or lactic acid. It was found that biofilms developed faster and a higher number of adherent cells (ca. 10 6 CFU /cm 2 ) were recovered when the organisms were grown in the low nutrient media. Regardless of the carbon source, biofilms developed in MSM consisted of shorter bacterial cells and thicker extracellular matrix (ECM), with glucose as the best substrate for stable biofilm formation. Fewer bacteria in initial attachment, non-hydrophobicity of bacterial cells, lack of ECM formation and easy detachment of the biofilm bacteria may contribute to poor biofilm formation in TSB. ECM is probably important for the stability of biofilms; however, at 10°C and under anaerobic conditions, ECM seems to be unnecessary. Keywords: Biofilm; Escherichia coli 0157:H7; Culture conditions; Extracellular matrix 1. Introduction Microbial attachment to surfaces and the development of biofilms are known to occur in many environments. Biofilms have been studied most extensively in marine and aquatic environments and medical areas (Characklis and Marshall, 1990). Often biofilms in these situations create economic and health problems. For example, they cause fouling of industrial equipment such as heat exchangers (Bott, • Corresponding author. Tel. (608)-263-1168. Fax: (608)-263-1114. 0168-1605/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0168-1605(94)00103-0