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sigE facilitates the adaptation of Bordetella bronchiseptica to... » Isaúde
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BMC microbiology [electronic resource]
2012-08-17 03:28:52

sigE facilitates the adaptation of Bordetella bronchiseptica to stress conditions and lethal infection in immunocompromised mice

Descrição: Background:The cell envelope of a bacterial pathogen can be damaged by harsh conditions in theenvironment outside a host and by immune factors during infection. Cell envelope stressresponses preserve the integrity of this essential compartment and are often required forvirulence. Bordetella species are important respiratory pathogens that possess a large number of putative transcription factors. However, no cell envelope stress responses have beendescribed in these species. Among the putative Bordetella transcription factors are a numberof genes belonging to the extracytoplasmic function (ECF) group of alternative sigma factors,some of which are known to mediate cell envelope stress responses in other bacteria. Here weinvestigate the role of one such gene, sigE, in stress survival and pathogenesis of Bordetellabronchiseptica.Results:We demonstrate that sigE encodes a functional sigma factor that mediates a cell envelopestress response. Mutants of B. bronchiseptica strain RB50 lacking sigE are more sensitive tohigh temperature, ethanol, and perturbation of the envelope by SDS-EDTA and certain beta-lactam antibiotics. Using a series of immunocompromised mice deficient in differentcomponents of the innate and adaptive immune responses, we show that SigE plays animportant role in evading the innate immune response during lethal infections of mice lackingB cells and T cells. SigE is not required, however, for colonization of the respiratory tract ofimmunocompetent mice. The sigE mutant is more efficiently phagocytosed and killed byperipheral blood polymorphonuclear leukocytes (PMNs) than RB50, and exhibits decreasedcytotoxicity toward macrophages. These altered interactions with phagocytes couldcontribute to the defects observed during lethal infection.Conclusions:Much of the work on transcriptional regulation during infection in B. bronchiseptica hasfocused on the BvgAS two-component system. This study reveals that the SigE regulon alsomediates a discrete subset of functions associated with virulence. SigE is the first cellenvelope stress-sensing system to be described in the bordetellae. In addition to its roleduring lethal infection of mice deficient in adaptive immunity, our results indicate that SigEis likely to be important for survival in the face of stresses encountered in the environmentbetween hosts.

Identificador: doi:10.1186/1471-2180-12-179
Volume: 0
Página: 1 a

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