title: A small heat-shock protein (Hsp20) regulated by RpoS is essential for cyst desiccation resistance in Azotobacter vinelandii.
abstract: In Azotobacter vinelandii, a cyst-forming bacterium, the alternative sigma factor RpoS is essential to the formation of cysts resistant to desiccation and to synthesis of the cyst-specific lipids, alkylresorcinols. In this study, we carried out a proteome analysis of vegetative cells and cysts of A. vinelandii strain AEIV and its rpoS mutant derivative AErpoS. This analysis allowed us to identify a small heat-shock protein, Hsp20, as one of the most abundant proteins of cysts regulated by RpoS. Inactivation of hsp20 did not affect the synthesis of alkylresorcinols or the formation of cysts with WT morphology; however, the cysts formed by the hsp20 mutant strain were unable to resist desiccation. We also demonstrated that expression of hsp20 from an RpoS-independent promoter in the AErpoS mutant strain is not enough to restore the phenotype of resistance to desiccation. These results indicate that Hsp20 is essential for the resistance to desiccation of A. vinelandii cysts, probably by preventing the aggregation of proteins caused by the lack of water. To our knowledge, this is the first report of a small heat-shock protein that is essential for desiccation resistance in bacteria.
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
authors.forename: Miguel
authors.initials: M
authors.lastname: Cocotl-Yañez
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
authors.forename: Soledad
authors.initials: S
authors.lastname: Moreno
authors.affiliation: Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos 62210, Mexico.
authors.forename: Sergio
authors.initials: S
authors.lastname: Encarnación
authors.affiliation: Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico.
authors.forename: Liliana
authors.initials: L
authors.lastname: López-Pliego
authors.affiliation: Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico.
authors.forename: Miguel
authors.initials: M
authors.lastname: Castañeda
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Espín
mesh_terms: D016948:Azotobacter vinelandii / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D003890:Desiccation; D020868:Gene Silencing; D050886:HSP20 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D050356:Lipid Metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D020543:Proteome; D040901:Proteomics; D012323:RNA Processing, Post-Transcriptional; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D050886:HSP20 Heat-Shock Proteins; D020543:Proteome; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria