Beschreibung:
<jats:title>ABSTRACT</jats:title>
<jats:p>
Three genes,
<jats:italic>coxB, coxA</jats:italic>
, and
<jats:italic>coxC</jats:italic>
, found in a clone from a gene library of the cyanobacterium
<jats:italic>Anabaena variabilis</jats:italic>
strain ATCC 29413, were identified by hybridization with an oligonucleotide specific for
<jats:italic>aa</jats:italic>
<jats:sub>3</jats:sub>
-type cytochrome
<jats:italic>c</jats:italic>
oxidases. Deletion of these genes from the genome of
<jats:italic>A. variabilis</jats:italic>
strain ATCC 29413 FD yielded strain CSW1, which displayed no chemoheterotrophic growth and an impaired cytochrome
<jats:italic>c</jats:italic>
oxidase activity. Photoautotrophic growth of CSW1, however, was unchanged, even with dinitrogen as the nitrogen source. A higher cytochrome
<jats:italic>c</jats:italic>
oxidase activity was detected in membrane preparations from dinitrogen-grown CSW1 than from nitrate-grown CSW1, but comparable activities of respiratory oxygen uptake were found in the wild type and in CSW1. Our data indicate that the identified
<jats:italic>cox</jats:italic>
gene cluster is essential for fructose-dependent growth in the dark, but not for growth on dinitrogen, and that other terminal respiratory oxidases are expressed in this cyanobacterium. Transcription analysis showed that
<jats:italic>coxBAC</jats:italic>
constitutes an operon which is expressed from two transcriptional start points. The use of one of them was stimulated by fructose.
</jats:p>