RESUMO
BACKGROUND: Bacteria of the suborder Corynebacterineae include significant human pathogens such as Mycobacterium tuberculosis and M. leprae. Drug resistance in mycobacteria is increasingly common making identification of new antimicrobials a priority. Mycobacteria replicate intracellularly, most commonly within the phagosomes of macrophages, and bacterial proteins essential for intracellular survival and persistence are particularly attractive targets for intervention with new generations of anti-mycobacterial drugs. METHODOLOGY/PRINCIPAL FINDINGS: We have identified a novel gene that, when inactivated, leads to accelerated death of M. smegmatis within a macrophage cell line in the first eight hours following infection. Complementation of the mutant with an intact copy of the gene restored survival to near wild type levels. Gene disruption did not affect growth compared to wild type M. smegmatis in axenic culture or in the presence of low pH or reactive oxygen intermediates, suggesting the growth defect is not related to increased susceptibility to these stresses. The disrupted gene, MSMEG_5817, is conserved in all mycobacteria for which genome sequence information is available, and designated Rv0807 in M. tuberculosis. Although homology searches suggest that MSMEG_5817 is similar to the serine:pyruvate aminotransferase of Brevibacterium linens suggesting a possible role in glyoxylate metabolism, enzymatic assays comparing activity in wild type and mutant strains demonstrated no differences in the capacity to metabolize glyoxylate. CONCLUSIONS/SIGNIFICANCE: MSMEG_5817 is a previously uncharacterized gene that facilitates intracellular survival of mycobacteria. Interference with the function of MSMEG_5817 may provide a novel therapeutic approach for control of mycobacterial pathogens by assisting the host immune system in clearance of persistent intracellular bacteria.
Assuntos
Proteínas de Bactérias/genética , Genes Bacterianos/genética , Macrófagos/microbiologia , Viabilidade Microbiana/genética , Mycobacterium smegmatis/citologia , Mycobacterium smegmatis/genética , Sequência de Aminoácidos , Animais , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Linhagem Celular , Elementos de DNA Transponíveis/genética , DNA Intergênico/genética , Regulação Bacteriana da Expressão Gênica , Rearranjo Gênico/genética , Marcação de Genes , Teste de Complementação Genética , Humanos , Espaço Intracelular/microbiologia , Macrófagos/citologia , Camundongos , Dados de Sequência Molecular , Mutagênese Insercional/genética , Infecções por Mycobacterium não Tuberculosas/microbiologia , Mycobacterium smegmatis/crescimento & desenvolvimento , NF-kappa B/metabolismo , Fagocitose , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Estresse Fisiológico/genéticaRESUMO
Mitochondria have a dual role in cellular life and death as life-promoting energy providers and as contributors to programmed cell death (apoptosis). The precise sequence of events resulting in the permeabilization of the mitochondrial membrane and the release of mitochondrial resident proteins remains an actively explored topic. Hansen and Nagley describe results from mammalian cells and from the nematode C. elegans that lead to a feedforward model for mitochondrial destabilization. Furthermore, they describe the mitochondrial and apoptotic functions of several proteins released from mitochondria during progression toward cell death.