The aquaporin gene aqpX of Brucella abortus is induced in hyperosmotic conditions.
An aquaporin gene (aqpX) was previously detected in the pathogenic bacterium Brucella abortus. Earlier studies showed that AqpX mediated rapid and large water fluxes in both directions in response to sudden osmotic up- or downshifts. Here, to study the role and the expression of the aqpX gene in B. abortus, an aqpX null mutant was constructed using an aqpX : : lacZ gene fusion. This mutant showed no significant difference in growth rate compared to the wild-type strain when grown in rich and minimal media, demonstrating that disruption of the aqpX gene was not lethal for B. abortus. The role of the B. abortus AqpX water channel was investigated by exposing the cells to hypo- and hyperosmolar conditions. While in hyperosmolar environments the growth rate of the knockout mutant was not affected, in hypo-osmolar conditions this mutant showed reduced viability after 50 h of growth. beta-Galactosidase assays and RT-PCR revealed that aqpX gene expression and the amount of aqpX mRNA were markedly increased in hyperosmolar conditions. Moreover, B. abortus aqpX expression levels were enhanced during the mid-exponential phase of growth. These results indicated that the expression of aqpX was regulated during the growth curve and induced in hyperosmolar conditions. This report is believed to be the first example of the induction of a bacterial aquaporin in hypertonic conditions.
Departamento de Microbiología e Inmunología, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Coyoacan 04510, Mexico DF, Mexico.|Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad Asociada al Centro de Investigaciones Biológicas (CSIC), Cardenal Herrera Oria s/n, 39011 Santander, Spain.
Rigoberto
R
Hernández-Castro
Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad Asociada al Centro de Investigaciones Biológicas (CSIC), Cardenal Herrera Oria s/n, 39011 Santander, Spain.
María Cruz
MC
Rodríguez
Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad Asociada al Centro de Investigaciones Biológicas (CSIC), Cardenal Herrera Oria s/n, 39011 Santander, Spain.
Asunción
A
Seoane
Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad Asociada al Centro de Investigaciones Biológicas (CSIC), Cardenal Herrera Oria s/n, 39011 Santander, Spain.
Juan María
JM
García Lobo
D020346:Aquaporins / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002003:Brucella abortus / Q000235:genetics*; D017931:DNA Primers; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D010957:Plasmids / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001616:beta-Galactosidase / Q000235:genetics
C480943:AqpX protein, Brucella abortus; D020346:Aquaporins; D001426:Bacterial Proteins; D017931:DNA Primers; D011994:Recombinant Proteins; D001616:beta-Galactosidase