Time-Dependent Effect of Surface Material on Lactobacillus rhamnosus GG Biofilm Formation and Gene Expression

Formation of Lactobacillus rhamnosus GG biofilm on three different abiotic supports (glass, stainless steel, and polystyrene) over a five-day incubation period was investigated. The changes in expression of the regulatory genes were assessed at 4, 6, 8, 24, 48, and 72 h. These genes, including MaAb, LuxS, and the extracellular polysaccharides (EPS) gene cluster, are involved in biofilm formation and adhesion. The biofilm quantification tests involved crystal violet staining of biofilms exposed to different combinations of two treatments: biofilm pipetting and heat fixation. The supports were classified based on the strength of adhesion of L. rhamnosus GG biofilm. We found that the strongest adhesion was on stainless steel, then glass, and the weakest was on polystyrene. Days four, two, and three showed the highest biofilm formation on glass, stainless steel, and polystyrene, respectively. Regarding the molecular aspect, we considered only two supports: stainless steel and polystyrene. MaAb, which was identified as a putative modulator, showed a high expression at the first 8 h of biofilm formation on polystyrene and low expression on stainless steel. In vitro expression of the EPS cluster genes showed an upregulation in the expression of most of the genes in the cluster over the first 6 to 8 h on both tested supports. Moreover, the LuxS gene, which is associated with the regulation of biofilm formation, was upregulated at 24 and 48 h on polystyrene and stainless steel supports, respectively. This revealed different expression levels of biofilm-related genes at different times of biofilm formation and on different supports.