Construction of arsB and tetH mutants of the sulfur-oxidizing bacterium Acidithiobacillus caldus by marker exchange

The inactivation of the chromosomally located arsenic resistance gene arsB in Acidithiobacillus caldus [KU.sup.T] is described by using marker exchange mutagenesis to serve as a model system for the knockout of other genes from the microorganism. The functionality of the gene inactivation system is shown by constructing A. caldus arsB and tetH mutants and the effects of these mutations on cell growth are shown in the presence of arsenic and tetrathionate oxidation.