title: Porin expression in clinical isolates of Klebsiella pneumoniae.
abstract: Two porins, OmpK36 and OmpK35, have been described previously in Klebsiella pneumoniae, and they are homologous to the Escherichia coli porins OmpC and OmpF, respectively, at both the DNA and amino acid levels. Optimal resolution of the two K. pneumoniae porins by electrophoresis on polyacrylamide gels is not achieved using gel systems already described for E. coli and requires modifications of the bisacrylamide content of the resolving gels. Once resolved, identification of porins OmpK36 and OmpK35 cannot be based solely on their apparent molecular masses since in some strains the OmpK36 porin migrates faster than the OmpK35 porin, whilst in other strains OmpK35 is the faster-migrating porin. Expression of OmpK35 porin is increased in low-osmolarity medium and, combined with Western blot analysis, this allows for the identification of both porins. Application of this identification system showed that most isolates lacking expression of extended-spectrum beta-lactamases express the two porins, whereas most isolates producing these beta-lactamases express only porin OmpK36, and the OmpK35 porin is either very low or not expressed.
authors.affiliation: Área de Microbiología, Departamento de Biología, Universidad de las Islas Baleares, Palma de Mallorca, and Unidad de Recursos Naturales, Instituto Mediterráneo de Estudios Avanzados, IMEDEA (CSIC-UIB), Carretera de Valldemosa Km 7·5, E-07071 Palma de Mallorca, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Hernández-Allés
authors.affiliation: Área de Microbiología, Departamento de Biología, Universidad de las Islas Baleares, Palma de Mallorca, and Unidad de Recursos Naturales, Instituto Mediterráneo de Estudios Avanzados, IMEDEA (CSIC-UIB), Carretera de Valldemosa Km 7·5, E-07071 Palma de Mallorca, Spain.
authors.forename: Sebastián
authors.initials: S
authors.lastname: Albertí
authors.affiliation: Área de Microbiología, Departamento de Biología, Universidad de las Islas Baleares, Palma de Mallorca, and Unidad de Recursos Naturales, Instituto Mediterráneo de Estudios Avanzados, IMEDEA (CSIC-UIB), Carretera de Valldemosa Km 7·5, E-07071 Palma de Mallorca, Spain.
authors.forename: Dolores
authors.initials: D
authors.lastname: Álvarez
authors.affiliation: Área de Microbiología, Departamento de Biología, Universidad de las Islas Baleares, Palma de Mallorca, and Unidad de Recursos Naturales, Instituto Mediterráneo de Estudios Avanzados, IMEDEA (CSIC-UIB), Carretera de Valldemosa Km 7·5, E-07071 Palma de Mallorca, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Doménech-Sánchez
authors.affiliation: Departamento de Microbiología, Universidad de Sevilla, Avenida Sánchez Pizjuan s/n, E-41080 Sevilla, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Martínez-Martínez
authors.affiliation: Servicio de Microbiología, Hospital Son Dureta, Andrea Doria 55, E-07014 Palma de Mallorca, Spain.|Área de Microbiología, Departamento de Biología, Universidad de las Islas Baleares, Palma de Mallorca, and Unidad de Recursos Naturales, Instituto Mediterráneo de Estudios Avanzados, IMEDEA (CSIC-UIB), Carretera de Valldemosa Km 7·5, E-07071 Palma de Mallorca, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Gil
authors.affiliation: Departamento de Microbiología, Universidad de Barcelona, Avenida Diagonal 645, E-08071 Barcelona, Spain.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Tomás
authors.affiliation: Área de Microbiología, Departamento de Biología, Universidad de las Islas Baleares, Palma de Mallorca, and Unidad de Recursos Naturales, Instituto Mediterráneo de Estudios Avanzados, IMEDEA (CSIC-UIB), Carretera de Valldemosa Km 7·5, E-07071 Palma de Mallorca, Spain.
authors.forename: Vicente J
authors.initials: VJ
authors.lastname: Benedí
mesh_terms: D001426:Bacterial Proteins; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007710:Klebsiella Infections / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000378:metabolism*; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D018272:Porins / Q000096:biosynthesis* / Q000302:isolation & purification; D001618:beta-Lactamases / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; C119261:OmpK35 porin, Klebsiella pneumoniae; C092233:OmpK36 protein, Klebsiella pneumoniae; D018272:Porins; D001618:beta-Lactamases