title: A phosphate-starvation-inducible outer-membrane protein of Pseudomonas fluorescens Ag1 as an immunological phosphate-starvation marker.
abstract: A phosphate-starvation-inducible outer-membrane protein of Pseudomonas fluorescens Ag1, expressed at phosphate concentrations below 0.08-0.13 mM, was purified and characterized. The purification method involved separation of outer-membrane proteins by SDS-PAGE and extraction of the protein from nitrocellulose or PVDF membranes after electrotransfer of proteins to the membranes. The N-terminal amino acid sequence of the purified protein, called Psi1, did not show homology to any known proteins, and in contrast to the phosphate-specific porin OprP of P. aeruginosa its mobility in SDS-PAGE was not affected by solubilization temperature. An antiserum against Psi1 recognized a protein of M, 55,000 in four other P. fluorescens strains among 24 tested strains representing Pseudomonas rRNA homology group I, showing antigenic heterogeneity within this group. A method for immunofluorescence microscopy involving cell permeabilization was adapted to visualize cell-specific expression of Psi1 in P. fluorescens exposed to limiting amounts of phosphate. This approach should be useful for further exploration of Psi1 as a marker to study the availability of phosphate to P. fluorescens in natural environments.
authors.affiliation: Section of Genetics and Microbiology, Department of Ecology and Molecular Biology, The Royal Veterinary and Agricultural University,Thorvaldsensvej 40, DK-1871 Frederiksberg C,Denmark.
authors.forename: Kristine
authors.initials: K
authors.lastname: Leopold
authors.affiliation: Department of Biochemistry and Nutrition, Building 224, The Technical University of Denmark,DK-2800 Lyngby,Denmark.
authors.forename: Susanne
authors.initials: S
authors.lastname: Jacobsen
authors.affiliation: Section of Genetics and Microbiology, Department of Ecology and Molecular Biology, The Royal Veterinary and Agricultural University,Thorvaldsensvej 40, DK-1871 Frederiksberg C,Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Nybroe
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology / Q000378:metabolism*; D015415:Biomarkers; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D010710:Phosphates / Q000172:deficiency*; D011551:Pseudomonas fluorescens / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D015415:Biomarkers; D010710:Phosphates