ABSTRACT
During infection, Brucella species have to adapt to a range of different environments. Environmental sensing in bacteria often involves the concerted action of two-component regulatory systems consisting of sensor and response regulator components. In this study, we identified, cloned and sequenced four independent response regulator gene fragments from Brucella melitensis. One amplified gene fragment showed nearly 90% identity to the response regulator subfamily of NtrC transcriptional activators, and further analysis revealed the presence of an adjacent gene encoding the sensor protein NtrB. The NtrBC two-component regulatory system has been shown to play varying roles in nitrogen metabolism and potentially in virulence in other bacterial species. A B. suis ntrC isogenic mutant was constructed which showed no significant differences in growth rates compared to the wild-type strain when grown at different temperatures in vitro. However, the mutant exhibited a reduction in metabolic activity in the presence of many amino acids. The mutation did not affect survival or multiplication of B. suis in macrophages, but during the initial stages of infection in the murine brucellosis model, the ntrC mutant showed a reduced ability to multiply rapidly in splenic tissue.
Subject(s)
Bacterial Proteins , Brucella/genetics , Brucellosis/microbiology , DNA-Binding Proteins/physiology , Trans-Activators , Amino Acid Sequence , Amino Acids/metabolism , Animals , Base Sequence , Brucella/metabolism , Brucella/pathogenicity , Brucella melitensis/genetics , Brucella melitensis/metabolism , Brucella melitensis/pathogenicity , Carbohydrates/chemistry , Cloning, Molecular , DNA Primers/chemistry , DNA, Bacterial/chemistry , DNA-Binding Proteins/genetics , Formazans/chemistry , Mice , Mice, Inbred BALB C , Molecular Sequence Data , Mutagenesis , PII Nitrogen Regulatory Proteins , Polymerase Chain Reaction , Sequence Alignment , Sequence Homology, Amino Acid , Tetrazolium Salts/chemistry , Transcription Factors/physiology , VirulenceABSTRACT
To cause disease, Brucella species have to adapt to a range of different environments. Environmental sensing and adaptive responses in bacteria often involve the concerted action of a two-component regulatory system, consisting of sensor and response regulator components. Amplification and sequence analysis of response regulators from Brucella species identified a response regulator sequence with 96% similarity to Rhizobium leguminosarum FeuP. In R. leguminosarum, the FeuPQ two-component system is involved in the regulation of iron uptake. A Brucella suis feuP isogenic mutant was constructed but was not attenuated in the murine brucellosis model. The survival and multiplication of the mutant in macrophages was also unaffected. The FeuPQ regulon represents a newly characterised sub-family of response regulators.
