Biofilm formation and modulation of luxS and rpoD expression by Helicobacter pylori.

Bacteria often choose a sessile biofilm lifestyle as a strategy to overcome environmental stress. In this study, we describe biofilm formation by Helicobacter pylori on a polystyrene surface, evaluating the viability and the morphological dynamics of bacterial cells during multicellular aggregate development. Moreover, we investigate expression of the luxS and rpoD genes, which are involved in biofilm formation. Two clinically susceptible and resistant strains of H. pylori were analyzed, as well as H. pylori ATCC 43629 for reference. The dominant form of expression, clustered bacterial cells arranged in an abundant matrix, was recorded after 2 days of incubation without shaking. Coccoid (spherical) cells with a “wrinkled” aspect presented the prevalent morphology (59.26%) among cells in the biofilm structure as observed by scanning electron microscopy. In aged H. pylori cultures, death occurred in single cells or cells grouped into microcolonies in which degenerated bacteria were localized inside the aggregates. The expression of luxS and rpoD genes among the sessile bacterial population reached a maximum after 2 days, with a significant reduction at subsequent time-points. No differences in gene expression and biofilm formation were recorded in the three evaluated strains. The morphological fickleness expressed in the life cycle by H. pylori strains emphasizes the bacterium’s ability to overcome environmental stress, balancing its spread both outside and inside the host.