Genome-wide screening of genes required for Listeria monocytogenes biofilm formation

Listeria monocytogenes is a ubiquitous Gram-positive food-borne pathogen, which can cause serious infections in immunocompromised individuals due to the intake of L. monocytogenes contaminated food. In addition to planktonic growth, this pathogen can also grow as biofilms. Biofilm bacteria are highly resistant to sanitizers and are thus difficult to eradicate, posing a big challenge to food processing industries and food service departments. Here, we report the results from a systematic genome-wide study of genes involved in biofilm formation. Using transposon mutagenesis in combination with microtiter plate assays, we surveyed 10,000 transposon mutants. 17 mutants were isolated that showed more than 50% decrease in biofilm formation. The insertions were localized within 13 genes (11 operons) and two intergenic regions, which affect various cellular pathways such as wall and lipoteichoic acid biosynthesis and modification, cell wall turnover, flagella synthesis, ATP synthesis, and transcription regulation. Of these genes or regions, only the two flagella-related genes were previously known to be crucial for L. monocytogenes biofilm formation. All other genes are newly identified from our library screen. Further investigations on these genes will provide a better understanding of the molecular basis of L. monocytogenes biofilm formation, which will undoubtedly reveal important insights on effective measures to prevent and control contaminations in the food industry.