Azotobacter vinelandii aldehyde dehydrogenase regulated by sigma(54): Rolein alcohol catabolism and encystment

Encystment in Azotobacter vinelandii is induced by n-butanol or beta -hydro xybutyrate (BHB). We identified a gene, encoding an aldehyde dehydrogenase, that was named aldA. An aldA mutation impaired bacterial growth on n-butan ol, ethanol, or hexanol as the sole carbon source. Expression of aldA incre ased in cells shifted from sucrose to n-butanol and was shown to be depende nt on the alternative sigma (54) factor. A mutation in rpoN encoding the si gma (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-but anol is not an inducer of encystment by itself but must be catabolized in o rder to induce encystment.