Impairment of a cyanobacterial glycosyltransferase that modifies a pilin results in biofilm development.

Abstract

SummaryA biofilm inhibiting mechanism operates in the cyanobacterium Synechococcus elongatus. Here, we demonstrate that the glycosyltransferase homologue, Ogt, participates in the inhibitory process – inactivation of ogt results in robust biofilm formation. Furthermore, a mutational approach shows requirement of the glycosyltransferase activity for biofilm inhibition. This enzyme is necessary for glycosylation of the pilus subunit and for adequate pilus formation. In contrast to wild‐type culture in which most cells exhibit several pili, only 25% of the mutant cells are piliated, half of which possess a single pilus. In spite of this poor piliation, natural DNA competence was similar to that of wild‐type; therefore, we propose that the unglycosylated pili facilitate DNA transformation. Additionally, conditioned medium from wild‐type culture, which contains a biofilm inhibiting substance(s), only partially blocks biofilm development by the ogt‐mutant. Thus, we suggest that inactivation of ogt affects multiple processes including production or secretion of the inhibitor as well as the ability to sense or respond to it.