Green sulfur bacteria Chlorobiaceae

Interestingly, reaction centers of apparently all photosynthetic organisms may be assigned to one or the other of these two types. For instance, the reaction center of both purple bacteria and the green filamentous bacteria, Chloroflexaceae, and green-plant PS II are of the OQ-type. On the other hand, the green sulfur bacteria, Chlorobiaceae, the Heliobacteria, and photosystem I all have the FeS-type reaction centers. 

In green bacteria, there is no intracytoplasmic membrane rather the cell membrane carries on its inner surface special light-harvesting pigment assemblies known as chlorosomes which project into the cytoplasm. Chlorosomes are an important feature common to both green sulfur bacteria (Chlorobiaceae) and fdamentous green bacteria (Chloroflexaceae), as illustrated schematically in Fig. 1 ... 

According to modern taxonomy, four divisions of photosynthetic bacteria are discerned (1) the purple bacteria, the green sulfur bacteria (Chlorobiaceae), the green filamentous (or gliding) bacteria (Chloroflexaceae) and the heliobacteria. This contribution concerns the antenna properties of the last three groups groups which have been studied less extensively than the purple bacteria, but which are not less interesting from the scientific point of view. 

Ribulosa b/ phosphate carboxylase, ribulose bisphosphate carboxylase/oxygeiuise, Rubisco, car-boxydismutase, Fraetion-l protein (EC 4.1.1.39) the enzyme responsible for catalysing photosynthetic CO2 fixation in all photosynthetic organisms except green sulfur bacteria (Chlorobiaceae). In plants it occurs in the chloroplast stroma where it constitutes about 50% of the total protein it should be noted. 

The Chlorobiaceae are green sulfur bacteria. They forms a tight phylogenetic group, and grow only under strictly anaerobic conditions (Imhoff, 1995). Their RC resembles that of PS I of green plants. Their major BChl is Bchl c, d or e. 

Like the purple bacterial species mentioned above, Prostheocochloris aestuarii and other members of the Chlorobiaceae subgroup of the green photosynthetic bacteria appear to use a BChl dimer as an initial electron donor, but they evidently use BChl c istead of BPh as an initial electron acceptor [82-85]. The Chlorobiaceae also differ in using iron-sulfur proteins as the next electron carriers, instead of quinones. Their electron acceptor system appears to resemble that found in PS 1 of plants and cyanobacteria more than it does that of other groups of photosynthetic bacteria. 

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