Construction and characterization of a proU-gfp transcriptional fusion that measures water availability in a microbial habitat.
We constructed and characterized a transcriptional fusion that measures the availability of water to a bacterial cell. This fusion between the proU promoter from Escherichia coli and the reporter gene gfp was introduced into strains of E. coli, Pantoea agglomerans, and Pseudomonas syringae. The proU-gfp fusion in these bacterial biosensor strains responded in a quantitative manner to water deprivation caused by the presence of NaCl, Na(2)SO(4), KCl, or polyethylene glycol (molecular weight, 8000). The fusion was induced to a detectable level by NaCl concentrations of as low as 10 mM in all three bacterial species. Water deprivation induced proU-gfp expression in both planktonic and surface-associated cells; however, it induced a higher level of expression in the surface-associated cells. Following the introduction of P. agglomerans biosensor cells onto bean leaves, the cells detected a significant decrease in water availability within only 5 min. After 30 min, the populations were exposed, on average, to a water potential equivalent to that imposed by approximately 55 mM NaCl. These results demonstrate the effectiveness of a proU-gfp-based biosensor for evaluating water availability on leaves. Furthermore, the inducibility of proU-gfp in multiple bacterial species illustrates the potential for tailoring proU-gfp-based biosensors to specific habitats.
Department of Microbiology, Iowa State University, Ames, Iowa 50011, USA.
Catherine A
CA
Axtell
Gwyn A
GA
Beattie
D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins / Q000235:genetics*; D015374:Biosensing Techniques; D002352:Carrier Proteins / Q000235:genetics*; D004926:Escherichia coli / Q000502:physiology; D007887:Fabaceae / Q000382:microbiology; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics*; D020636:Pantoea / Q000502:physiology; D018515:Plant Leaves / Q000382:microbiology*; D010957:Plasmids / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics; D014158:Transcription, Genetic; D014867:Water / Q000502:physiology*; D014881:Water Supply
D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins; D002352:Carrier Proteins; D008164:Luminescent Proteins; C060774:ProU protein, Bacteria; D011993:Recombinant Fusion Proteins; D014867:Water; D049452:Green Fluorescent Proteins