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Tce SR two‐component regulatory system of B rucella melitensis 16M is involved in invasion, intracellular survival and regulated cytotoxicity for macrophages
Author(s) -
Li Z.,
Fu Q.,
Wang Z.,
Li T.,
Zhang H.,
Guo F.,
Wang Y.,
Zhang J.,
Chen C.
Publication year - 2015
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/lam.12408
Subject(s) - brucella melitensis , cytotoxicity , virulence , microbiology and biotechnology , biology , mutant , intracellular , brucella , brucellaceae , wild type , in vitro , immunology , biochemistry , gene , brucellosis
The mechanisms of invasion and intracellular survival of Brucella are still poorly understood. Previous studies showed that the two‐component regulatory systems ( TCS s) play an important role in the intracellular survival of Brucella . To investigate if TCS s involve in the virulence and cytotoxicity of Brucella melitensis , we introduced a mutation into one of the TCS s in chromosome II in Br. melitensis 16M strain, and generated 16MΔTce SR , a mutant of Br. melitensis 16M strain. In vitro infection experiments using murine macrophage cell line ( RAW 264.7) showed that the survival of 16MΔTce SR mutant in macrophages decreased 0·91‐log compared with that of wild type Br. melitensis 16M strain at 2 h postinfection, replication of 16MΔTce SR mutant in macrophages was 5·65‐log, which was much lower than that wild type strain. Results of lactate dehydrogenase cytotoxicity assays in macrophages demonstrated high dose infection with wide type strain produced high level cytotoxicity to macrophages, but 16MΔTce SR mutant had very low level cytotoxicity, indicating mutation of TCS s impaired the cytotoxicity of Br. melitensis to macrophages. Animal experiments showed that the spleen colonization of 16MΔTce SR was significantly reduced compared with its wild type strains. The lower levels of survival of 16MΔTce SR in various stress conditions suggested that the mutation of the TCS s of Br. melitensis was the causative factor of its reduced resistance to stress conditions. Taken together, our results demonstrated TCS Tce SR involves in the intracellular survival, virulence and cytotoxicity of Br. melitensis during its infection. Significance and Impact of the Study Two‐component systems ( TCS s) are predominant bacterial signal transduction mechanisms. The pathogenicity of Brucella is due to its ability to adapt to the intracellular environment including low levels of acidic pH , high‐salt and heat shock. TCS s are designed to sense diverse stimuli, transfer signals and enact an appropriate adaptive physiological response. Here, we show that Br. meilitensis TCS Tce SR is not only involved in regulation of Br. meilitensis virulence and adaptation of environmental stresses, but also can regulate cytotoxicity in macrophages.