Contribution of Mn-cofactored superoxide dismutase (SodA) to the virulence of Streptococcus agalactiae
Contribution of Mn-cofactored superoxide dismutase (SodA) to the virulence of Streptococcus agalactiae
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DOI：
10.1128/iai.69.8.5098-5106.2001
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发表时间：
2001-08-01
影响因子：
3.1
通讯作者：
Trieu-Cuot, P
中科院分区：
文献类型：
--
作者：
Poyart, C;Pellegrini, E;Trieu-Cuot, P
超氧化物歧化酶将超氧化物阴离子转化为分子氧和过氧化氢，过氧化氢又被过氧化氢酶和/或过氧化物酶代谢。这些酶是细胞抗氧化应激的主要防御机制之一，因此在某些细菌的发病机制中起作用。我们之前证明了B群链球菌（GBS）具有单个mn辅助超氧化物歧化酶（SodA）。为了分析该酶在GBS致病性中的作用，我们通过等位基因交换构建了无乳链球菌（Streptococcus无乳链球菌）的钠破坏突变体NEM316。该突变体随后被整合到含有野生型sodA基因的pAT113/Sp染色体上。凝胶分析细胞提取物中SOD的特异性活性证实亲本和互补菌株中存在活性SOD，而sodA突变株中不存在活性SOD。这些菌株在静培养中的生长速度相当，但sodA突变体对培养基中添加百草枯或过氧化氢产生的氧化应激极为敏感，并且在利福平存在时表现出更高的突变频率。在小鼠骨髓源性巨噬细胞中，sodA突变体对巨噬细胞杀死细菌的易感性增加。在小鼠感染模型中，经静脉注射后，sodA突变体在血液和大脑中的存活率明显低于亲本和补充菌株，而在肝脏和脾脏中的存活率仅受到轻微影响。这些结果提示SodA在GBS发病机制中起一定作用。
Superoxide dismutases convert superoxide anions to molecular oxygen and hydrogen peroxide, which, in turn, is metabolized by catalases and/or peroxidases. These enzymes constitute one of the major defense mechanisms of cells against oxidative stress and hence play a role in the pathogenesis of certain bacteria. We previously demonstrated that group B streptococci (GBS) possess a single Mn-cofactored superoxide dismutase (SodA). To analyze the role of this enzyme in the pathogenicity of GBS, we constructed a sodA-disrupted mutant of Streptococcus agalactiae NEM316 by allelic exchange. This mutant was subsequently cis complemented by integration into the chromosome of pAT113/Sp harboring the wild-type sodA gene. The SOD specific activity detected by gel analysis in cell extracts confirmed that active SODS were present in the parental and complemented strains but absent in the sodA mutant. The growth rates of these strains in standing cultures were comparable, but the sodA mutant was extremely susceptible to the oxidative stress generated by addition of paraquat or hydrogen peroxide to the culture medium and exhibited a higher mutation frequency in the presence of rifampin. In mouse bone marrow-derived macrophages, the sodA mutant showed an increased susceptibility to bacterial killing by macrophages. In a mouse infection model, after intravenous injection the survival of the sodA mutant in the blood and the brain was markedly reduced in comparison to that of the parental and complemented strains whereas only minor effects on survival in the liver and the spleen were observed. These results suggest that SodA plays a role in GBS pathogenesis.