Helicobacter pylori biofilm cells are metabolically distinct, express flagella, and antibiotic tolerant

Biofilm growth protects bacteria against harsh environments, antimicrobials, and immune responses. Helicobacter pylori is a bacterium that has a robust ability to maintain colonization in a challenging environment. Over the last decade, H. pylori biofilm formation has begun to be characterized, however, there are still gaps in our understanding about how this growth mode is defined and its impact on H. pylori physiology. To provide insights into H. pylori biofilm growth properties, we characterized the antibiotic susceptibility, gene expression, and genes required for biofilm formation of a strong biofilm-producing H. pylori. H. pylori biofilms developed complex 3D structures and were recalcitrant to multiple antibiotics. Disruption of the protein-based matrix decreased this antibiotic tolerance. Using both transcriptomic and genomic approaches, we discovered that biofilm cells demonstrated lower transcripts for TCA cycle enzymes but higher ones for hydrogenase and acetone metabolism. Interestingly, several genes encoding for the natural competence Type IV secretion system 4 (tfs4) were up-regulated during biofilm formation along with several genes encoding for restriction-modification (R-M) systems, suggesting DNA exchange activities in this mode of growth. Flagella genes were also discovered through both approaches, consistent with previous reports about the importance of these filaments in H. pylori biofilm. Together, these data suggest that H. pylori is capable of adjusting its phenotype when grown as biofilm, changing its metabolism and elevating specific surface proteins including those encoding tfs4 and flagella.