Virulence Regulator PrfA is Essential for Biofilm Formation in Listeria monocytogenes but not in Listeria innocua

Abstract

The ability of the foodborne pathogen Listeria monocytogenes to develop biofilm in food-processing environment is a major concern for the food safety, because biofilms allow bacteria to better resist environmental stresses. PrfA is a key transcriptional activator that positively regulates most of the known listerial virulence gene expression. In order to explore the role of PrfA on Listeria biofilm development, we compared the abilities of biofilm formation by L. monocytogenes wild type strains (EGD and EGDe) and their prfA deletion mutants (EGD∆prfA and EGDe∆prfA), nonpathogenic Listeria innocua, as well as the recombinant strains that express constitutively active mutant PrfA (PrfA*) in L. innocua (LI-pERL3-prfA*) and in EGDe∆prfA (EGDe∆prfA-pERL3-prfA*) at 37°C in brain heart infusion (BHI) medium using the polyvinyl chloride (PVC) microtiter plate assay and microscopic examination. Our results showed that the wild types of L. monocytogenes had strong abilities to develop biofilm with meshwork of bacterial aggregates, while biofilm with sparse small clumps were observed in L. innocua. The biofilm production of strains EGD∆prfA and EGDe∆prfA that lack funtional PrfA was reduced and could be recovered by the introduction of the PrfA*, however, the PrfA* had no impact on the biofilm forming ability of L. innocua. Our results suggest that PrfA plays a significant role in biofilm formation in L. monocytogenes but not in L. innocua, thus may reflect differences in the molecular mechanisms of biofilm formation by these two closely related species.

Roles of a Novel Crp/Fnr Family Transcription Factor Lmo0753 in Soil Survival, Biofilm Production and Surface Attachment to Fresh Produce of Listeria monocytogenes

“…[15] and Zhou et al . [16]. We also discovered decreased biofilm formation by both Δlmo0753 mutants on polystyrene surface in PW medium, collectively suggesting that lmo0753 may play a major role in biofilm formation in L. monocytogenes .…”

“…Biofilm assays were assessed using the crystal violet assay method as previously described [15], [16], [46], [47] with modifications. Assays were performed using BHI nutrient-rich medium and PW minimum growth medium to compare biofilm production when subjected to varying nutrient availabilities.…”

“…Crp/Fnr family transcription factors can respond to various environmental stimuli, such as changes in temperature, pH, and nutrient availability, and subsequently trigger the expression of many stress response and virulence-related genes [5]. It has been reported that PrfA is necessary for biofilm formation in L. monocytogenes [15], [16] and aids in environmental survival and abiotic surface attachment [17]. Because of the amino acid sequence similarity between Lmo0753 and PrfA, we hypothesize that Lmo0753 may also play a role in environmental persistence-related mechanisms in L. monocytogenes such as biofilm formation and surface attachment.…”

Carbon Catabolite Control is Important for Listeria monocytogenes Biofilm Formation in Response to Nutrient Availability

“…The microtiter plate assay described previously by Zhou et al [23] was used to quantify biofilm production of L. monocytogenes EGDe cultured in BHI or MEM at 37°C after 24, 48, and 72 h.…”

Resilience in the Face of Uncertainty: Sigma Factor B Fine-Tunes Gene Expression To Support Homeostasis in Gram-Positive Bacteria

“…A number of studies show that L. monocytogenes has the ability to rapidly and strongly adhere to inanimate surfaces (103,104). However, attempts to unambiguously show that L. monocytogenes forms true biofilms with the typical accumulation of extracellular matrix find either a lack thereof (105, 106), a very sparse extracellular matrix (107,108) with strain-dependent formation of extracellular fibrils of unclear function (109), or ball-shaped structures held together by chains of interconnected cells (110).…”