In the natural environment, bacteria grow predominantly within sessile, matrix-enclosed communities known as biofilms, rather than as unattached planktonic cells. Biofilms protect resident bacteria from attack by the immune system, compromise antimicrobial therapy, and disperse planktonic cells, which promote the spread of infection to distant body sites. Biofilms complicate about 65 percent of recalcitrant bacterial infections. Nevertheless, the regulatory mechanisms of biofilm development, especially biofilm dispersal, remain poorly defined in any species. Our studies revealed that the RNA-binding global regulatory protein CsrA is a potent repressor of biofilm formation in Escherichia coli K-12 and pathogenic relatives. This effect is mediated primarily through its regulation of intracelluar glycogen synthesis and turnover. Further evidence supports a role for glycogen in the synthesis of a polysaccharide adhesin. Mutations that inhibit biofilm formation were isolated in a 4-gene operon, which was cloned and found to needed for the production of a GIcN-rich polysaccharide. Remarkably, csrA-induction within cells of a preformed biofilm caused extensive dispersal, releasing viable planktonic cells. This finding offers a key to unlock the biochemical and genetic bases of biofilm dispersal.
The Aims of this proposal are to: 1) Characterize a novel polysaccharide adhesin needed for E. coli biofilm formation. The molecular genetics of its synthesis, its chemistry, and its function in biofilm formation will be assessed. 2) Investigate the genetic and metabolic determinants of polysaccharide production. The precursor-product relationship of glycogen to the polysaccharide adhesin will be examined by ELISA analysis of existing mutants and by 13C NMR labeling studies in conjunction with appropriate structural and regulatory mutations. The genetic regulation of its biosynthesis will be examined with reporter fusions and other approaches. 3) Biofilm dispersal will be assessed systematically by examining the effects of csrA induction on the polysaccharide adhesin, membrane and periplasmic proteins, LPS and the transcriptome. Results will pave the way for studies defining the mechanisms of the dispersal process.The long-range goal of these studies is to develop a full understanding of the regulatory factors, metabolic pathways and structural elements that interact in biofilm formation, and thereby obtain useful information for combating biofilm infections.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM066794-04
Application #
7122028
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Program Officer
Anderson, James J
Project Start
2003-09-19
Project End
2008-03-31
Budget Start
2006-09-01
Budget End
2008-03-31
Support Year
4
Fiscal Year
2006
Total Cost
$283,800
Indirect Cost
Name
Emory University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Wang, Yan; Andole Pannuri, Archana; Ni, Dongchun et al. (2016) Structural Basis for Translocation of a Biofilm-supporting Exopolysaccharide across the Bacterial Outer Membrane. J Biol Chem 291:10046-57
Vakulskas, Christopher A; Potts, Anastasia H; Babitzke, Paul et al. (2015) Regulation of bacterial virulence by Csr (Rsm) systems. Microbiol Mol Biol Rev 79:193-224
Romeo, Tony; Vakulskas, Christopher A; Babitzke, Paul (2013) Post-transcriptional regulation on a global scale: form and function of Csr/Rsm systems. Environ Microbiol 15:313-24
Pannuri, Archana; Yakhnin, Helen; Vakulskas, Christopher A et al. (2012) Translational repression of NhaR, a novel pathway for multi-tier regulation of biofilm circuitry by CsrA. J Bacteriol 194:79-89
Boto, Agedi N; Xu, Wenlian; Jakoncic, Jean et al. (2011) Structural studies of the Nudix GDP-mannose hydrolase from E. coli reveals a new motif for mannose recognition. Proteins 79:2455-66
Edwards, Adrianne N; Patterson-Fortin, Laura M; Vakulskas, Christopher A et al. (2011) Circuitry linking the Csr and stringent response global regulatory systems. Mol Microbiol 80:1561-80
Irie, Yasuhiko; Starkey, Melissa; Edwards, Adrianne N et al. (2010) Pseudomonas aeruginosa biofilm matrix polysaccharide Psl is regulated transcriptionally by RpoS and post-transcriptionally by RsmA. Mol Microbiol 78:158-72
Jonas, Kristina; Edwards, Adrianne N; Ahmad, Irfan et al. (2010) Complex regulatory network encompassing the Csr, c-di-GMP and motility systems of Salmonella Typhimurium. Environ Microbiol 12:524-40
Babitzke, Paul; Baker, Carol S; Romeo, Tony (2009) Regulation of translation initiation by RNA binding proteins. Annu Rev Microbiol 63:27-44
Ryan, Robert P; Romeo, Tony; De Keersmaecker, Sigrid C J et al. (2009) Nurturing scientific mutualism: a report from the 'Young Microbiologists Mini-Symposium on microbe signalling, organisation and pathogenesis'. Mol Microbiol 73:760-74

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