Arabinose Induces Pellicle Formation by Vibrio fischeri

Abstract

ABSTRACTBiofilms are multicellular communities of bacteria attached to a surface and embedded in a protective matrix. In many cases, the signals that induce biofilm formation are unknown. Here, we report that biofilm formation by the marine bacteriumVibrio fischerican be induced by the addition of arabinose to LBS (Luria-Bertani-salt), a tryptone-based medium. Growth of cells in the presence of 0.2% arabinose, but not other sugars, induced the production of a pellicle at the air/liquid interfaces of static cultures.V. fischerifailed to grow on arabinose as the sole carbon source, suggesting that pellicle production did not occur as a result of increased growth, but experiments using the acid/base indicator phenol red suggested thatV. fischerimay partially metabolize arabinose. Pellicle production was independent of thesyppolysaccharide locus but was altered upon disruption of thebcscellulose locus. Through a screen for mutants defective for pellicle production, we found that loss of motility disrupted the formation of the arabinose-induced pellicle. Among the ∼20 mutants that retained motility were strains with insertions in a putativemshpilus locus and a strain with a defect inyidK, which is involved in galactose catabolism. Mutants with themshgene disrupted grew poorly in the presence of arabinose, while theyidKmutant appeared to be “blind” to the presence of arabinose. Finally, arabinose impaired symbiotic colonization byV. fischeri. This work thus identifies a novel signal and new pathways involved in control of biofilm formation byV. fischeri.