Azotobacter vinelandii Aldehyde Dehydrogenase Regulated by ς 54 : Role in Alcohol Catabolism and Encystment

Abstract

ABSTRACT Encystment in Azotobacter vinelandii is induced by n -butanol or β-hydroxybutyrate (BHB). We identified a gene, encoding an aldehyde dehydrogenase, that was named aldA . An aldA mutation impaired bacterial growth on n -butanol, ethanol, or hexanol as the sole carbon source. Expression of aldA increased in cells shifted from sucrose to n -butanol and was shown to be dependent on the alternative ς 54 factor. A mutation in rpoN encoding the ς 54 factor also impaired growth on alcohols. Encystment on n -butanol, but not on BHB, was impaired in aldA or rpoN mutants, indicating that n -butanol is not an inducer of encystment by itself but must be catabolized in order to induce encystment.