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.
|Number of pages||11|
|State||Published - Jul 2017|
Bibliographical noteFunding Information:
Studies in the laboratories of Rakefet Schwarz and Susan Golden were supported by the program of the National Science Foundation and the US-Israel Binational Science Foundation (NSF-BSF 2012823). This study was also supported by a grant from the Israel Science Foundation (ISF 1406/14) to Rakefet Schwarz. We thank Yishai Levin and Alon Savidor at the de Botton Institute for Protein Profiling, The Nancy and Stephen Grand Israel National Center for Personalised Medicine (Weizmann Institute of Science) and Tamar Ziv at The Smoler Protein Research Center (Technion, Israel Institute of Technology) for mass spectrometry analyses.
© 2017 Society for Applied Microbiology and John Wiley & Sons Ltd