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Media type:
E-Article
Title:
A Staphylococcal GGDEF Domain Protein Regulates Biofilm Formation Independently of Cyclic Dimeric GMP
Contributor:
Holland, Linda M.;
O'Donnell, Sinéad T.;
Ryjenkov, Dmitri A.;
Gomelsky, Larissa;
Slater, Shawn R.;
Fey, Paul D.;
Gomelsky, Mark;
O'Gara, James P.
imprint:
American Society for Microbiology, 2008
Published in:
Journal of Bacteriology, 190 (2008) 15, Seite 5178-5189
Description:
<jats:title>ABSTRACT</jats:title><jats:p>Cyclic dimeric GMP (c-di-GMP) is an important biofilm regulator that allosterically activates enzymes of exopolysaccharide biosynthesis. Proteobacterial genomes usually encode multiple GGDEF domain-containing diguanylate cyclases responsible for c-di-GMP synthesis. In contrast, only one conserved GGDEF domain protein, GdpS (for<jats:italic>G</jats:italic>GDEF<jats:italic>d</jats:italic>omain<jats:italic>p</jats:italic>rotein from<jats:italic>Staphylococcus</jats:italic>), and a second protein with a highly modified GGDEF domain, GdpP, are present in the sequenced staphylococcal genomes. Here, we investigated the role of GdpS in biofilm formation in<jats:italic>Staphylococcus epidermidis</jats:italic>. Inactivation of<jats:italic>gdpS</jats:italic>impaired biofilm formation in medium supplemented with NaCl under static and flow-cell conditions, whereas<jats:italic>gdpS</jats:italic>overexpression complemented the mutation and enhanced wild-type biofilm development. GdpS increased production of the<jats:italic>icaADBC</jats:italic>-encoded exopolysaccharide, poly-<jats:italic>N</jats:italic>-acetyl-glucosamine, by elevating<jats:italic>icaADBC</jats:italic>mRNA levels. Unexpectedly, c-di-GMP synthesis was found to be irrelevant for the ability of GdpS to elevate<jats:italic>icaADBC</jats:italic>expression. Mutagenesis of the GGEEF motif essential for diguanylate cyclase activity did not impair GdpS, and the N-terminal fragment of GdpS lacking the GGDEF domain partially complemented the<jats:italic>gdpS</jats:italic>mutation. Furthermore, heterologous diguanylate cyclases expressed in<jats:italic>trans</jats:italic>failed to complement the<jats:italic>gdpS</jats:italic>mutation, and the purified GGDEF domain from GdpS possessed no diguanylate cyclase activity in vitro. The<jats:italic>gdpS</jats:italic>gene from<jats:italic>Staphylococcus aureus</jats:italic>exhibited similar characteristics to its<jats:italic>S. epidermidis</jats:italic>ortholog, suggesting that the GdpS-mediated signal transduction is conserved in staphylococci. Therefore, GdpS affects biofilm formation through a novel c-di-GMP-independent mechanism involving increased<jats:italic>icaADBC</jats:italic>mRNA levels and exopolysaccharide biosynthesis. Our data raise the possibility that staphylococci cannot synthesize c-di-GMP and have only remnants of a c-di-GMP signaling pathway.</jats:p>