Distribution of extracellular DNA in Listeria monocytogenes biofilm

Extracellular DNA (eDNA) is an abundant matrix component that protects biofilm from environmental stress, facilitate horizontal gene transfer, and serve as a source of nutrients. eDNA is also found in Listeria monocytogenes biofilm, but it is unknown to which extent its importance as a matrix component varies in terms of phylogenetic relatedness. This study aims to determine if these variations exist. Biofilm forming capacity of ten L. monocytogenes strains of different phylogenetic lineages and serotypes was examined using crystal violet assay at 37 degrees C and 22 degrees C. eDNA content was evaluated fluorometrically at 37 degrees C and at 22 degrees C, then the 3D structure of biofilm was studied by confocal laser scanning microscopy (CLSM). Biofilm forming capacity differed significantly between the culturing conditions and was higher at 37 degrees C than at ambient temperature. eDNA signal distribution was found to be influenced by strain and lineage. CLSM images revealed information about spatial distribution in the biofilm. The information about the eDNA spatial organisation in the biofilm contributes to the understanding of the role of eDNA in a biofilm formation.