Abstract
S.typhimurium can form nitrate reductase A, chlorate reductase C, thiosulfate reductase, tetrathionate reductase and formic dehydrogenase. None of these enzymes are formed in chlorate-resistant mutants. Conjugation experiments showed the presence of a strong linkage between thechl andgal markers of the bacterial chromosome. By deletion mapping the gene ordernic A aro G gal bio chl D uvr B chl A was found. Strains with deletions terminating betweenbio anduvr B or betweenuvr B andchl A have a number of aberrant properties. Though resistant against chlorate they reduce nitrate and form gas. After growth with nitrate they form less nitrate reductase than the wild type which may explain the resistance against chlorate. After growth with thiosulfate they form small amounts of thiosulfate reductase and chlorate reductase C. In crosses between anE.coli Hfrchl + strain and aS.typhimurium chl A strain recombinants were obtained, forming nitrate reductase A and chlorate reductase C. These recombinants do not form gas, which indicates that thechl + gene fromE.coli does not function normally inS.typhimurium.
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