RESUMO
BacA is an inner membrane protein associated with maintenance of chronic infections in several diverse host-pathogen interactions. To understand the function of the bacA gene in Mycobacterium tuberculosis (Rv1819c), we insertionally inactivated this gene and analyzed the resulting mutant for a variety of phenotypes. BacA deficiency in M. tuberculosis did not affect sensitivity to detergents, acidic pH, and zinc, indicating that there was no global compromise in membrane integrity, and a comprehensive evaluation of the major lipid constituents of the cell envelope failed to reveal any significant differences. Infection of mice with this mutant revealed no impact on establishment of infection but a profound effect on maintenance of extended chronic infection and ultimate outcome. As in alphaproteobacteria, deletion of BacA in M. tuberculosis led to increased bleomycin resistance, and heterologous expression of the M. tuberculosis BacA homolog in Escherichia coli conferred sensitivity to antimicrobial peptides. These results suggest a striking conservation of function for BacA-related proteins in transport of a critical molecule that determines the outcome of the host-pathogen interaction.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Proteínas de Bactérias/metabolismo , Mycobacterium tuberculosis/metabolismo , Mycobacterium tuberculosis/patogenicidade , Tuberculose/microbiologia , Transportadores de Cassetes de Ligação de ATP/genética , Animais , Bactérias/classificação , Bactérias/genética , Proteínas de Bactérias/genética , Bleomicina/farmacologia , Membrana Celular/genética , Membrana Celular/metabolismo , Farmacorresistência Bacteriana , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Mutagênese Insercional , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/genética , Filogenia , VirulênciaRESUMO
The subunits of DNA gyrase and topoisomerase IV from Staphylococcus haemolyticus were expressed in Escherichia coli, purified to homogeneity, and used to reconstitute active enzymes that were sensitive to known topoisomerase inhibitors. This represents the first description of a method for isolating type II topoisomerases of a coagulase-negative staphylococcal species.
Assuntos
DNA Girase/química , DNA Topoisomerase IV/química , Escherichia coli/metabolismo , Staphylococcus haemolyticus/enzimologia , Antibacterianos/farmacologia , DNA Girase/biossíntese , DNA Girase/isolamento & purificação , DNA Topoisomerase IV/antagonistas & inibidores , DNA Topoisomerase IV/isolamento & purificação , Eletroforese em Gel de Ágar , Eletroforese em Gel de Poliacrilamida , Inibidores Enzimáticos/farmacologia , Escherichia coli/enzimologia , Dados de Sequência Molecular , Proteínas Recombinantes/biossíntese , Staphylococcus haemolyticus/efeitos dos fármacosRESUMO
In many bacteria, the ferric uptake regulator (Fur) protein plays a central role in the regulation of iron uptake genes. Because iron figures prominently in the agriculturally important symbiosis between soybean and its nitrogen-fixing endosymbiont Bradyrhizobium japonicum, we wanted to assess the role of Fur in the interaction. We identified a fur mutant by selecting for manganese resistance. Manganese interacts with the Fur protein and represses iron uptake genes. In the presence of high levels of manganese, bacteria with a wild-type copy of the fur gene repress iron uptake systems and starve for iron, whereas fur mutants fail to repress iron uptake systems and survive. The B. japonicum fur mutant, as expected, fails to repress iron-regulated outer membrane proteins in the presence of iron. Unexpectedly, a wild-type copy of the fur gene cannot complement the fur mutant. Expression of the fur mutant allele in wild-type cells leads to a fur phenotype. Unlike a B. japonicum fur-null mutant, the strain carrying the dominant-negative fur mutation is unable to form functional, nitrogen-fixing nodules on soybean, mung bean, or cowpea, suggesting a role for a Fur-regulated protein or proteins in the symbiosis.
