title: Regulation of biofilm formation and cellular buoyancy through modulating intracellular cyclic di-GMP levels in engineered cyanobacteria.
abstract: The second messenger cyclic dimeric (3'→5') GMP (cyclic di-GMP or c-di-GMP) has been implicated in the transition between motile and sessile lifestyles in bacteria. In this study, we demonstrate that biofilm formation, cellular aggregation or flocculation, and cellular buoyancy are under the control of c-di-GMP in Synechocystis sp. PCC 6803 (Synechocystis) and Fremyella diplosiphon. Synechocystis is a unicellular cyanobacterium and displays lower levels of c-di-GMP; F. diplosiphon is filamentous and displays higher intracellular c-di-GMP levels. We transformed Synechocystis and F. diplosiphon with a plasmid for constitutive expression of genes encoding diguanylate cylase (DGC) and phosphodiesterase (PDE) proteins from Vibrio cholerae or Escherichia coli, respectively. These engineered strains allowed us to modulate intracellular c-di-GMP levels. Biofilm formation and cellular deposition were induced in the DGC-expressing Synechocystis strain which exhibited high intracellular levels of c-di-GMP; whereas strains expressing PDE in Synechocystis and F. diplosiphon to drive low intracellular levels of c-di-GMP exhibited enhanced cellular buoyancy. In addition, the PDE-expressing F. diplosiphon strain showed elevated chlorophyll levels. These results imply roles for coordinating c-di-GMP homeostasis in regulating native cyanobacterial phenotypes. Engineering exogenous DGC or PDE proteins to regulate intracellular c-di-GMP levels represents an effective tool for uncovering cryptic phenotypes or modulating phenotypes in cyanobacteria for practical applications in biotechnology applicable in photobioreactors and in green biotechnologies, such as energy-efficient harvesting of cellular biomass or the treatment of metal-containing wastewaters.
authors.affiliation: Cell and Molecular Biology Graduate Program, Michigan State University, East Lansing, Michigan.|Department of Energy Plant Research Laboratory, Michigan State University, Plant Biology Laboratories, 612 Wilson Road, East Lansing, Michigan, 48824.
authors.forename: Marco
authors.initials: M
authors.lastname: Agostoni
authors.affiliation: Cell and Molecular Biology Graduate Program, Michigan State University, East Lansing, Michigan.|Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Waters
authors.affiliation: Cell and Molecular Biology Graduate Program, Michigan State University, East Lansing, Michigan. montg133@msu.edu.|Department of Energy Plant Research Laboratory, Michigan State University, Plant Biology Laboratories, 612 Wilson Road, East Lansing, Michigan, 48824. montg133@msu.edu.|Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan. montg133@msu.edu.
authors.forename: Beronda L
authors.initials: BL
authors.lastname: Montgomery
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D000458:Cyanobacteria / Q000235:genetics* / Q000502:physiology*; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D060847:Metabolic Engineering / Q000379:methods*; D010727:Phosphoric Diester Hydrolases / Q000235:genetics / Q000378:metabolism; D019761:Phosphorus-Oxygen Lyases / Q000235:genetics / Q000378:metabolism; D014734:Vibrio cholerae / Q000201:enzymology / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; C062025:bis(3',5')-cyclic diguanylic acid; D010727:Phosphoric Diester Hydrolases; D019761:Phosphorus-Oxygen Lyases; C060720:diguanylate cyclase; D006152:Cyclic GMP
keywords: aggregation; biofilm; buoyancy; c-di-GMP; cyanobacteria