The aquaporin gene aqpX of Brucella abortus is induced in hyperosmotic conditions

Abstract

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. b-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.

Disruption of the BMEI0066 gene attenuates the virulence of Brucella melitensis and decreases its stress tolerance

“…To compared the growth of the wild-type strain, the mutants, and the complemented strain in hyperosmotic conditions and at high temperature (42°C), the TSB medium was made hypertonic by adding NaCl up to 250 mM, as described previously 17. Cells were grown in TSB medium at 37°C (control), TSB medium supplemented with 250 mM NaCl at 37°C (hyper-osmotic), and TSB medium at 42°C (high temperature) with the same initial density of 1 × 10 6 CFU/ml.…”

Maltodextrin enhances biofilm elimination by electrochemical scaffold

“…Hence, changes in the biofilm surface coverage (as measured here) are unlikely to be the mechanism enhancing the efficacy of the e-scaffold. The most likely mechanism may be increased permeation of e-scaffold-generated H 2 O 2 into the bacterial membrane due to changes induced by the addition of a low-osmolarity hyperosmotic agent3743. For example, the overexpression of aquaporin proteins in Gram-negative bacteria has been reported in a low-osmolarity medium containing a hyperosmotic agent33353637 that facilitates H 2 O 2 entry through membranes3850.…”

“…For example, bacteria can respond to conditions of low osmolarity by increasing the density of membrane porins, especially aquaporin41424344, which in turn can enhance H 2 O 2 entry into cells2437. A hyperosmotic agent at low osmolarity induces oxidative damage by altering gene expression, including increasing catalase expression may form non-membrane channels permitting water and H 2 O 2 3745464748.…”

Evaluation of the Effects of Erythritol on Gene Expression in Brucella abortus

“…RNA was purified by using the Qiagen RNeasy Protect bacteria mini kit (Quiagen, USA) with on-column RNase free DNase I digestion for removal of genomic DNA according to the manufacturer's instructions. RNA samples were tested for the lack of Brucella genomic DNA contamination by PCR with primers specific for the constitutive IF-1 Brucella gene (BAB1_0282 - BMEI1671) [18],[19] after 30 cycles of amplification and checked for the presence of a 220 bp band. DNAse I treatment was repeated until no band was visible by gel electrophoresis, although usually one treatment was sufficient.…”