Article: Four Superoxide Dismutases Contribute to Bacillus anthracis Virulence and Provide Spores with Redundant Protection from Oxidative Stress
Infection and immunity. 2009 Jan., v. 77, no. 1
2009
Abstract: ... Δsod15 ΔsodA1) mutant of B. anthracis Sterne strain 34F2 and assessed its lethality in an A/J mouse ... generated oxidative stress and to macrophage-mediated killing correlated with virulence in A/J mice. Allelic ...
Abstract | The Bacillus anthracis genome encodes four superoxide dismutases (SODs), enzymes capable of detoxifying oxygen radicals. That two of these SODs, SOD15 and SODA1, are present in the outermost layers of the B. anthracis spore is indicated by previous proteomic analyses of the exosporium. Given the requirement that spores must survive interactions with reactive oxygen species generated by cells such as macrophages during infection, we hypothesized that SOD15 and SODA1 protect the spore from oxidative stress and contribute to the pathogenicity of B. anthracis. To test these theories, we constructed a double-knockout (Δsod15 ΔsodA1) mutant of B. anthracis Sterne strain 34F2 and assessed its lethality in an A/J mouse intranasal infection model. The 50% lethal dose of the Δsod15 ΔsodA1 strain was similar to that of the wild type (34F2), but surprisingly, measurable whole-spore SOD activity was greater than that in 34F2. A quadruple-knockout strain (Δsod15 ΔsodA1 ΔsodC ΔsodA2) was then generated, and as anticipated, spore-associated SOD activity was diminished. Moreover, the quadruple-knockout strain, compared to the wild type, was attenuated more than 40-fold upon intranasal challenge of mice. Spore resistance to exogenously generated oxidative stress and to macrophage-mediated killing correlated with virulence in A/J mice. Allelic exchange that restored sod15 and sodA1 to their wild-type state restored wild-type characteristics. We conclude that SOD molecules within the spore afford B. anthracis protection against oxidative stress and enhance the pathogenicity of B. anthracis in the lung. We also surmise that the presence of four SOD alleles within the genome provides functional redundancy for this key enzyme. |
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Keywords | Bacillus anthracis ; alleles ; exine ; lethal dose ; macrophages ; mice ; models ; mutants ; oxidative stress ; proteomics ; reactive oxygen species ; spores ; superoxide dismutase ; virulence |
Language | English |
Size | p. 274-285. |
Publishing place | American Society for Microbiology |
Document type | Article |
ZDB-ID | 218698-6 |
ISSN | 1098-5522 ; 0019-9567 |
ISSN (online) | 1098-5522 |
ISSN | 0019-9567 |
Database | NAL-Catalogue (AGRICOLA) |
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