Loss of Flagellum-Based Motility by Listeria monocytogenes Results in Formation of Hyperbiofilms

Abstract

Biofilm formation by the gram-positive, motile, food-borne pathogen Listeria monocytogenes was demonstrated to occur by an ordered series of stages. Biofilm development involves flagellum-based motility, which when blocked decreases initial bacterial surface attachment but subsequently leads to the formation of hyperbiofilms, surface-attached communities reaching high density.Listeria monocytogenes has emerged as a major foodborne pathogen posing a major public health concern because listeriosis has a fatality rate of 25% (13). Therefore, efforts to limit human exposure to L. monocytogenes that focus on defining mechanisms affecting its entry into the food supply have substantial public health value. The survival of L. monocytogenes in the food processing environment is prolonged because of its ability to establish biofilms on the surfaces of equipment. This is postulated to be a major reservoir contributing to food contamination and disease transmission (6,19

Listeria monocytogenes Attachment to and Detachment from Stainless Steel Surfaces in a Simulated Dairy Processing Environment

“…In contrast, Lemon et al (28) showed that flagellum-mediated motility, and not flagella, is critical for both adhesion and biofilm formation of L. monocytogenes on abiotic surfaces. It has been speculated that the differences between studies are mainly due to different experimental approaches which in turn result in bacterial changes, including changes in pH, oxygen tension, and nutrient availability (47). In contrast to temperature, low pH has been shown to stimulate initial adhesion of L. monocytogenes to SS, as negative groups on the cell surface become protonated at low pH (6).…”

“…Initially, the adhesion of L. monocytogenes on SS coupons immersed in milk, custard, and yogurt for 7 days at 5 and 20°C was evaluated. The selection of 7 days of habituation was made in order to allow sufficient time for several cycles of dissociation events and subsequent regrowth of the biofilm to occur (47). This experiment aimed to determine the effect of the environment (i.e., growth medium and temperature) on the ability of L. monocytogenes to attach and to form biofilm on food-soiled SS coupons.…”

The Virulence Regulator PrfA Promotes Biofilm Formation byListeria monocytogenes

“…Similar to most bacteria, L. monocytogenes biofilm formation on surfaces proceeds incrementally, starting with initial surface attachment and proceeding to microcolony formation, biofilm maturation, and, finally, dispersion (41). Flagellum-minus mutants are deficient in biofilm formation (22,41). We have previously shown that flagellum-mediated motility in L. monocytogenes, and not the flagella themselves, is critical for initial surface attachment and subsequent biofilm development (22).…”

“…Similar to most bacteria, L. monocytogenes biofilm formation on surfaces proceeds incrementally, starting with initial surface attachment and proceeding to microcolony formation, biofilm maturation, and, finally, dispersion (41). Flagellum-minus mutants are deficient in biofilm formation (22,41).…”

“…Flagellum-mediated motility appears to be important for initial epithelial cell attachment, and flagellum-minus mutants show an early host invasion defect in a competitive oral infection model (32). Similarly, flagellum-mediated motility is critical for initial abiotic surface attachment, and flagellum-minus mutants are defective in biofilm formation (22,41). This common need for flagellum-mediated motility to transition from an existence as a single, extracellular cell to either environmental biofilm formation or intracellular invasion led us to hypothesize that there might be regulatory cross talk between PrfA and biofilm formation.…”