Relationship between the Brucella abortus two component systems PrrB/A and NtrY/X

IGNACIO FERNANDEZ; MARIELA CARRICA; GASTON PARIS; FERNANDO GOLDBAUM

Buenos Aires

Congreso; Brucellosis 2011, International Research Conference Including the 64th Brucellosis Research Conference; 2011

PrrB/PrrA is a highly conserved redox - responding global two-component regulatory system. This system was characterised in many microorganisms and it was shown to control a variety of energy generation and energy utilization biological processes. Brucella abortus genome encodes homologous for the histidine kinase PrrB and the response regulator PrrA with 37% and 67% of identity with the previously characterized Rhodobacter capsulatus PrrB/A component system respectively. We have constructed a Brucella abortus mutant strain in prrB that grows slightly slower than the wild type parental stain. The absence of prrB does not affect Brucella intracellular replication and mice colonisation. We performed qPCR assays to compare the expression of different cytochromes and oxygen/redox sensors of Brucella abortus in the wild type and prrB defective strain. Our results show that PrrB controls the expression of the cytochrome c reductase and the cbb3-type cytochrome c oxidase, previously described as high oxygen affinity cytochromes. Moreover, we found that the presence of PrrB is necessary for the expression of the FNR transcription factor and the NtrY histidine kinase. The FNR (fumarate and nitrate reduction) transcription factor was reported in E. coli as a regulator of anaerobic metabolism; NtrY is involved in nitrogen fixation and metabolism in photosynthetic bacteria, and we have recently demonstrated that Brucella abortus NtrY is a heme-protein that responds to oxygen/redox state. To evaluate whether PrrB and NtrY histidine kinases can act in concert in redox/oxygen sensing and metabolism adaptation, we constructed a double mutant strain in prrB and ntrY. In agreement with our speculations, the in vitro growth of the double mutant was severally affected. These results suggest that Brucella abortus PrrB/PrrA and NtrY/NtrX two-component systems could act coordinately during Brucella abortus adaptation to different environmental conditions.