Type IV pili are required for biofilm formation by Moraxella bovis

CLAUDIA PRIETO, PABLO MARTINA, DIEGO SERRA, BOSCH ALEJANDRA AND OSVALDO YANTORNO

San Miguel de Tucumán

Congreso; VII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL - SAMIGE DEL BICENTENARIO; 2011

Sociedad Argentina de Microbiología General

Infectious bovine keratoconjunctivitis (IBK) is a highly contagious ocular disease of cattle caused by Moraxella bovis. The economic impact of IBK in the cattle industry and the lack of effective strategies to its control, highlight the need to better understand the infectious process of M. bovis and its pathogenesis. We have recently begun to explore the ability of this pathogen to form biofilm hypothesizing that this surface-attached, community-based mode of growth is adopted by M. bovis as a strategy to colonize bovine ocular surface. Here we demonstrate that M. bovis forms biofilm on multiple abiotic surfaces. In addition we present evidences that the type IV pili (TFP) of M. bovis play an important role for biofilm development. The addition of MgCl2 to culture medium was shown to prevent biofilm formation by a wild type M. bovis strain on polypropylene and glass surfaces. The inhibitory action of MgCl2 in biofilm formation was found to correlate with the disruption and release of TFP from cell surfaces. Examination of biofilm growth on abiotic surfaces of a phenotypically non-piliated M. bovis strain, which does not produce TFP, revealed severe defects in biofilm biomass accumulation. This strain showed at an early time-point to exhibit similar defects to grow on corneal epithelial cells. The absence of TFP was further demonstrated to impair microcolonies formation, as well as the development of structured biofilm. Our studies support the idea that TFP contribute to these events by governing both cell-substrate and cell-cell interactions. We propose that TFP-mediated biofilm formation in corneal epithelia may allow M. bovis to establish persistent ocular infections in cattle.