Type 4 pili are dispensable for biofilm development in the cyanobacterium Synechococcus elongatus

Elad Nagar, Shaul Zilberman, Eleonora Sendersky, Ryan Simkovsky, Eyal Shimoni, Diana Gershtein, Moshe Herzberg, Susan S. Golden, Rakefet Schwarz

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

The hair-like cell appendages denoted as type IV pili are crucial for biofilm formation in diverse eubacteria. The protein complex responsible for type IV pilus assembly is homologous with the type II protein secretion complex. In the cyanobacterium Synechococcus elongatus PCC 7942, the gene Synpcc7942_2071 encodes an ATPase homologue of type II/type IV systems. Here, we report that inactivation of Synpcc7942_2071 strongly affected the suite of proteins present in the extracellular milieu (exo-proteome) and eliminated pili observable by electron microscopy. These results support a role for this gene product in protein secretion as well as in pili formation. As we previously reported, inactivation of Synpcc7942_2071 enables biofilm formation and suppresses the planktonic growth of S. elongatus. Thus, pili are dispensable for biofilm development in this cyanobacterium, in contrast to their biofilm-promoting function in type IV pili-producing heterotrophic bacteria. Nevertheless, pili removal is not required for biofilm formation as evident by a piliated mutant of S. elongatus that develops biofilms. We show that adhesion and timing of biofilm development differ between the piliated and non-piliated strains. The study demonstrates key differences in the process of biofilm formation between cyanobacteria and well-studied type IV pili-producing heterotrophic bacteria.

Original languageEnglish
Pages (from-to)2862-2872
Number of pages11
JournalEnvironmental Microbiology
Volume19
Issue number7
DOIs
StatePublished - 1 Jul 2017

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