Genetic Features of Resident Biofilms Determine Attachment ofListeria monocytogenes

Abstract

ABSTRACTPlanktonicListeria monocytogenescells in food-processing environments tend most frequently to adhere to solid surfaces. Under these conditions, they are likely to encounter resident biofilms rather than a raw solid surface. Although metabolic interactions betweenL. monocytogenesand resident microflora have been widely studied, little is known about the biofilm properties that influence the initial fixation ofL. monocytogenesto the biofilm interface. To study these properties, we created a set of model residentLactococcus lactisbiofilms with various architectures, types of matrices, and individual cell surface properties. This was achieved using cell wall mutants that affect bacterial chain formation, exopolysaccharide (EPS) synthesis and surface hydrophobicity. The dynamics of the formation of these biofilm structures were analyzed in flow cell chambers using in situ time course confocal laser scanning microscopy imaging. All theL. lactisbiofilms tested reduced the initial immobilization ofL. monocytogenescompared to the glass substratum of the flow cell. Significant differences were seen inL. monocytogenessettlement as a function of the genetic background of resident lactococcal biofilm cells. In particular, biofilms of theL. lactischain-forming mutant resulted in a marked increase inL. monocytogenessettlement, while biofilms of the EPS-secreting mutant efficiently prevented pathogen fixation. These results offer new insights into the role of resident biofilms in governing the settlement of pathogens on food chain surfaces and could be of relevance in the field of food safety controls.