Polyphosphate-mediated modulation of Campylobacter jejuni biofilm growth and stability

Biofilms increase C. jejuni's resilience to detergents, antibiotics, and environmental stressors. In these investigations, we studied the modulation of biofilm in response to phosphate related stressors. We found that the deletion of ppk1, phoX, and ppk2 (polyphosphate associated [poly P] genes) in C. jejuni modulated different stages of biofilm formation such as attached microcolonies, air-liquid biofilms, and biofilm shedding. Additionally, inorganic phosphate also modulated attached microcolonies, air-liquid biofilms, and biofilm shedding both independently of and additively in the poly P associated mutants. Furthermore, we observed that these different biofilm stages were affected by biofilm age: for example, the adherent microcolonies were maximum on day 2, while biofilm growth at the air-liquid interface and shedding was highest on day 3. Also, we observed altered calcofluor white reactive polysaccharides in poly P-associated mutants, as well as increased secretion of autoinducer-2 (AI-2) quorum sensing molecules in the ∆ppk2 mutant. Further, the polysaccharide and flagellar biosynthesis genes, that are associated with biofilm formation, were altered in these poly P-associated mutants. We conclude that the phosphate limiting condition modulates C. jejuni biofilm formation.