Azotobacter chroococcum does not contain sodA or its gene product Mn-superoxide dismutase

Azotobacter chroococcum and Azotobacter vinelandii grown in Burk medium with 1% mannitol (BM) or in BM supplemented with 2.2 mg/mL ammonium acetate (BM+N) were found to have only iron-containing and CuZn-containing superoxide dismutase. Furthermore, genomic DNA from A. chroococcum and A. vinelandii were subjected to polymerase chain reaction analysis using sodA- and sodB-specific primers and yielded only a sodB product. These results dispute the assertion by Buchanan and Lees (Can. J. Microbiol. 26: 441-447, 1980) that A. chroococcum contains Mn-superoxide dismutase.