Abstract
The invA gene of Brucella melitensis codes for a NUDIX (nucleoside diphosphate linked to moiety X) hydrolase related to invasiveness. The objective of this work was to evaluate invA transcription under acidic conditions. The invA gene transcription was up regulated at pH 3 and pH 5 observed with semiquantitative real-time PCR in B. melitensis 133 strain. Results indicated that invA gene transcription at pH 3 showed a basal and decreased transcription compared to that of pH 5 incubation. Transcription levels of the dnaK gene were similar to those obtained with invA gene. The survival rates of wild type and invA mutant strains at pH 5 were above 90% in all post-incubation times. In contrast, at pH 3 there was a time-dependent reduction on both strains at 15min (P < 0.05). These results suggest that invA gene transcription is promoted under acidic conditions in Brucella melitensis.
Highlights
Members of the genus Brucella are intracellular pathogens that infect animals and humans, producing reproductive disorders in domestic animals and flu-like symptoms with possible human complications (Olsen et al 2010)
Brucella melitensis survival to acid stress is crucial for a successful intracellular infection (Roop et al 2009)
Brucella transition to low-pH environment could be fast. Considering these two pH scenarios, we hypothesized that invA gene transcription could be necessary for the Brucella melitensis acid resistance mechanism
Summary
Members of the genus Brucella are intracellular pathogens that infect animals and humans, producing reproductive disorders in domestic animals and flu-like symptoms with possible human complications (Olsen et al 2010). Brucella bacteria are enclosed in a phagosome (called Brucella containing vacuole, BCV) that matures to phagolysosome, with a pH conditions in the range of 4.5 to 5.0 (Porte et al 1999). Decreased pH is encountered inside of BCV, and nutrient deprivation, oxidative environment and lytic enzymes. This harsh environment worsens until bacteria reach the endoplasmic reticulum (ER), where they became replicative. Of particular interest is the activation of the Type IV Secretion System (TIVSS), a principal virulence mechanism that is promoted under intracellular acidic conditions (Boschiroli et al 2002; Celli et al 2003; Sieira et al 2010)
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