Question

5. (2pts)One of the following organisms is a photoheterotroph. Which one is it?

• Enterobacter aerogenes, a lactose fermenter in the same family as E. coli

• Rhodospirillum rubrum, which can be cultured anaerobically in media containing

  succinate, macrominerals, and yeast extract, under a tungsten lamp

• Sulfolobus acidocaldarius, an archaeon that grows in hot, acidic soils and utilizes

  the energy from the oxidation of sulfide to fix carbon dioxide

• Nostoc punctiforme, a cyanobacterium that utilizes visible light to fix CO2 and N2

  What is the Genus of the photoheterotroph? _______________________________ Explain how you identified this organism as a photoheterotroph.

Answer 1

Rhodospirillum rubrum is a photoheterotrophic bacteria, the organism that can use light as a source for energy but cannot use carbon dioxide as carbon source. Photoheterotrophs use organic compounds from environment to satisfy their carbon requirements.

​​​R. rubrum is an purple non sulfur bacteria. R.rubrum is a facultative anaerobe thus capable of using oxygen for aerobic respiration under aerobic condition or an alternative terminal electron acceptor for anaerobic respiration under anaerobic conditions.

Rhodospirillum rubrum can use succinate as carbon source for growth under microaerophilic conditions. The photosynthetic internal membranes are produced sourcing succinate as a carbon source.  

R .rubrum use light tungsten lamp as energy, succinate as carbon source and other minerals for growth under anaerobic conditions.