Chemoheterotrophic growth of the Cyanobacterium Anabaena sp. strain PCC 7120 dependent on a functional cytochrome c oxidase.
Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium commonly used as a model organism for studying cyanobacterial cell differentiation and nitrogen fixation. For many decades, this cyanobacterium was considered an obligate photo-lithoautotroph. We now discovered that this strain is also capable of mixotrophic, photo-organoheterotrophic, and chemo-organoheterotrophic growth if high concentrations of fructose (at least 50 mM and up to 200 mM) are supplied. Glucose, a substrate used by some facultatively organoheterotrophic cyanobacteria, is not effective in Anabaena sp. PCC 7120. The gtr gene from Synechocystis sp. PCC 6803 encoding a glucose carrier was introduced into Anabaena sp. PCC 7120. Surprisingly, the new strain containing the gtr gene did not grow on glucose but was very sensitive to glucose, with a 5 mM concentration being lethal, whereas the wild-type strain tolerated 200 mM glucose. The Anabaena sp. PCC 7120 strain containing gtr can grow mixotrophically and photo-organoheterotrophically, but not chemo-organoheterotrophically with fructose. Anabaena sp. PCC 7120 contains five respiratory chains ending in five different respiratory terminal oxidases. One of these enzymes is a mitochondrial-type cytochrome c oxidase. As in almost all cyanobacteria, this enzyme is encoded by three adjacent genes called coxBAC1. When this locus was disrupted, the cells lost the capability for chemo-organoheterotrophic growth.
Institute of Physical Chemistry, University of Vienna, Vienna, Austria.
Ronald
R
Stebegg
Bernhard
B
Wurzinger
Markus
M
Mikulic
Georg
G
Schmetterer
D017033:Anabaena / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism*; D005632:Fructose / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D052836:Heterotrophic Processes; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D052817:Phototrophic Processes; D017384:Sequence Deletion; D046939:Synechocystis / Q000235:genetics
D001426:Bacterial Proteins; D009004:Monosaccharide Transport Proteins; D005632:Fructose; D003576:Electron Transport Complex IV; D005947:Glucose