Listeria monocytogenes Biofilm-Associated Protein (BapL) May Contribute to Surface Attachment of L. monocytogenes but Is Absent from Many Field Isolates

Abstract

Listeria monocytogenes is a food-borne pathogen capable of adhering to a range of surfaces utilized within the food industry, including stainless steel. The factors required for the attachment of this ubiquitous organism to abiotic surfaces are still relatively unknown. In silico analysis of the L. monocytogenes EGD genome identified a putative cell wall-anchored protein (Lmo0435 [BapL]), which had similarity to proteins involved in biofilm formation by staphylococci. An insertion mutation was constructed in L. monocytogenes to determine the influence of this protein on attachment to abiotic surfaces. The results show that the protein may contribute to the surface adherence of strains that possess BapL, but it is not an essential requirement for all L. monocytogenes strains. Several BapL-negative field isolates demonstrated an ability to adhere to abiotic surfaces equivalent to that of BapL-positive strains. BapL is not required for the virulence of L. monocytogenes in mice.Listeria monocytogenes is a food-borne pathogen that causes serious illness, including meningitis, septicemia, and stillbirth, with a mortality rate of up to 30% (37). More recently, there have been reports of listerial gastroenteritis following the consumption of several different food types (16,34). A number of studies have demonstrated that this organism is able to persist in the food-processing environment for several months and even up to 10 years (23, 29). One of the major causes for concern about L. monocytogenes in these environments is its ability to attach to many different surfaces (2). Indeed, there is recent evidence to show that listerial biofilms formed inside the lumens of stainless steel tubes are able to withstand the shears generated by high-Reynolds-number flows (31). Biofilms, including those produced by L. monocytogenes, are more resistant to detergents and disinfectants (33) and also are a potential source of contamination within food-processing plants; hence, they pose a risk to the maintenance of product safety (27). Consequently, there is considerable interest in determining the mechanisms of attachment and biofilm formation.Our in silico analysis of the genome sequence of L. monocytogenes identified an open reading frame (lmo0435) for a protein with similarity to biofilm-associated proteins (Bap) believed to be important for the binding of staphylococci to abiotic surfaces (10). This Bap protein also has been implicated in the virulence of Staphylococcus aureus (10, 11). Thus, the aim of the current study was to establish if this protein (Lmo0435 [BapL]) of L. monocytogenes influenced biofilm formation and virulence and to determine the prevalence of the lmo0435 (bapL) gene within a selection of field isolates. MATERIALS AND METHODS Bacterial strains and plasmids.A list of the L. monocytogenes isolates and plasmids used in this study is given in Table 1. The strains were cultured in tryptone soya broth (TSB; Oxoid) or brain heart infusion agar (Oxoid) with shaking at 37°C unless otherwise stated. Escherichia coli JM...

Attachment of Listeria innocua to Polystyrene: Effects of Ionic Strength and Conditioning Films from Culture Media and Milk Proteins

“…In another study, Zhou et al (48) successfully identified 47 proteins that were either up-or down-regulated in bacteria in the biofdm state. This coordinated gene expression includes the production of regulators associated with the response to stress, the expression of motility genes, the production of biofilm-associated proteins and proteins related to cell-cell communication pathways, and polysac charide biosynthesis (15,16,19,21,37,39). In contrast, a rich culture medium such as TSB supports bacterial growth and biofilm formation but contains biological macromol ecules likely to produce conditioning films, as the present study clearly shows with TSB-coated PS.…”

comK Prophage Junction Fragments as Markers for Listeria monocytogenes Genotypes Unique to Individual Meat and Poultry Processing Plants and a Model for Rapid Niche-Specific Adaptation, Biofilm Formation, and Persistence

“…Putative adaptons in the comK prophage may encode similar adhesins that mediate specific attachment to different foodconditioning films. While such adaptons would probably not fully explain attachment and biofilm formation by L. monocytogenes, as many adhesins are chromosomally encoded (7,51), they may help to explain the persistence of specific L. monocytogenes prophage types in individual food processing plants that manufacture the same food product over an extended period of time (5,70,86) (Fig. 2B).…”

Surface adhesins and exopolymers of selected foodborne pathogens

“…Furthermore, several BapL-negative strains showed higher adherence levels than BapL-positive strains. Collectively, these data suggest that in L. monocytogenes, BapL is neither an essential factor influencing adhesion to surfaces nor is it required for virulence in vivo (Jordan et al, 2008). In marked contrast to all other bacteria possessing a Bap homologue (Lasa & Penadés, 2006), the role of BapL in the course of sessile development could not be established as a reduced level of adhesion did not prevent the formation of a biofilm by the bapL mutant.…”

“…A homologue of the biofilm-associated protein (Bap) was recently identified in L. monocytogenes and was named BapL (Lmo0435) (Jordan et al, 2008). Among the 43 LPXTG proteins identified to date in L. monocytogenes, BapL is the only one characterized as playing a role in adhesion to abiotic surfaces.…”