Detail of types of Photoautotrophs

1)     Purple sulphur bacteria:-

         These bacteria contain purplish pigment called bacteriochlorophyll. It uses water and hydrogen donor to convert CO₂ as food in presence of sunlight. The function of bacteriochlorophyll is similar to chlorophyll of green plants.

  Reaction

 2CO₂ +35H₂O→2(CH₂O)+2NaHSO₄+Energy

Example: Chromatium okeni

2)     Purple non sulphur bacteria

               In this bacteria food is prepared in presence of light with CO₂ and organic substance.Here CO₂ is reduced to food by the hydrogen donor organic substance.

Reaction

  6CO₂+12CH₃CHOHCH₃→C6H₁₂O₆+12CH₃COCH₃+6H₂O

Example:- Rhodospirillum rubrum

3)     Green sulphur bacteria:-

          These bacteria converts CO₂ into organic compounds by reducing with H2S. Example Chlorobium limicola

Reaction    light

  2H₂S+CO₂→CH₂O+2S+H₂O+Energy