Terminal Oxidases of Bacillus subtilis Strain 168: One Quinol Oxidase, Cytochrome aa 3 or Cytochrome bd , Is Required for Aerobic Growth

Abstract

ABSTRACT The gram-positive endospore-forming bacterium Bacillus subtilis has, under aerobic conditions, a branched respiratory system comprising one quinol oxidase branch and one cytochrome oxidase branch. The system terminates in one of four alternative terminal oxidases. Cytochrome caa 3 is a cytochrome c oxidase, whereas cytochrome bd and cytochrome aa 3 are quinol oxidases. A fourth terminal oxidase, YthAB, is a putative quinol oxidase predicted from DNA sequence analysis. None of the terminal oxidases are, by themselves, essential for growth. However, one quinol oxidase (cytochrome aa 3 or cytochrome bd ) is required for aerobic growth of B. subtilis strain 168. Data indicating that cytochrome aa 3 is the major oxidase used by exponentially growing cells in minimal and rich medium are presented. We show that one of the two heme-copper oxidases, cytochrome caa 3 or cytochrome aa 3 , is required for efficient sporulation of B. subtilis strain 168 and that deletion of YthAB in a strain lacking cytochrome aa 3 makes the strain sporulation deficient.