Biofilms of Lactobacillus plantarum and Lactobacillus fermentum: Effect on stress responses, antagonistic effects on pathogen growth and immunomodulatory properties
Few studies have extensively investigated probiotic functions associated with biofilms. Here, we show
that strains of Lactobacillus plantarum and Lactobacillus fermentum are able to grow as biofilm on abiotic
surfaces, but the biomass density differs between strains. We performed microtiter plate biofilm assays
under growth conditions mimicking to the gastrointestinal environment. Osmolarity and low concentrations
of bile significantly enhanced Lactobacillus spatial organization. Two L. plantarum strains were
able to form biofilms under high concentrations of bile and mucus. We used the agar well-diffusion
method to show that supernatants from all Lactobacillus except the NA4 isolate produced food pathogen
inhibitory molecules in biofilm. Moreover, TNF-a production by LPS-activated human monocytoid
cells was suppressed by supernatants from Lactobacillus cultivated as biofilms but not by planktonic
culture supernatants. However, only L. fermentum NA4 showed anti-inflammatory effects in zebrafish
embryos fed with probiotic bacteria, as assessed by cytokine transcript level (TNF-a, IL-1b and IL-10). We
conclude that the biofilm mode of life is associated with beneficial probiotic properties of lactobacilli, in a
strain dependent manner. Those results suggest that characterization of isolate phenotype in the biofilm
state could be additional valuable information for the selection of probiotic strains.