title: Small secreted proteins enable biofilm development in the cyanobacterium Synechococcus elongatus.
abstract: Small proteins characterized by a double-glycine (GG) secretion motif, typical of secreted bacterial antibiotics, are encoded by the genomes of diverse cyanobacteria, but their functions have not been investigated to date. Using a biofilm-forming mutant of Synechococcus elongatus PCC 7942 and a mutational approach, we demonstrate the involvement of four small secreted proteins and their GG-secretion motifs in biofilm development. These proteins are denoted EbfG1-4 (enable biofilm formation with a GG-motif). Furthermore, the conserved cysteine of the peptidase domain of the Synpcc7942_1133 gene product (dubbed PteB for peptidase transporter essential for biofilm) is crucial for biofilm development and is required for efficient secretion of the GG-motif containing proteins. Transcriptional profiling of ebfG1-4 indicated elevated transcript levels in the biofilm-forming mutant compared to wild type (WT). However, these transcripts decreased, acutely but transiently, when the mutant was cultured in extracellular fluids from a WT culture, and biofilm formation was inhibited. We propose that WT cells secrete inhibitor(s) that suppress transcription of ebfG1-4, whereas secretion of the inhibitor(s) is impaired in the biofilm-forming mutant, leading to synthesis and secretion of EbfG1-4 and supporting the formation of biofilms.
authors: The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, 5290002, Israel.
authors: Rami
authors: R
authors: Parnasa
authors: The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, 5290002, Israel.
authors: Elad
authors: E
authors: Nagar
authors: The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, 5290002, Israel.
authors: Eleonora
authors: E
authors: Sendersky
authors: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors: Ziv
authors: Z
authors: Reich
authors: Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
authors: Ryan
authors: R
authors: Simkovsky
authors: Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
authors: Susan
authors: S
authors: Golden
authors: The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, 5290002, Israel.
authors: Rakefet
authors: R
authors: Schwarz
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D057056:Cysteine Proteases / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005998:Glycine; D009154:Mutation; D046940:Synechococcus / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D057056:Cysteine Proteases; D005998:Glycine