Bacteriochlorophyll a-containing non-phototrophic bacteria

The rRNA catalogs for the various eubacterial phyla do not permit us to infer a branching order, because the 5 8 (association coefficient) values between the major branches are too low to be significant. For example, between members of the green sulfur bacteria and members of the filamentous photosynthetic bacteria 5 8 values range from 0.12 to 0.20 [111]. These values are too low to establish branching orders with respect to other phyla , for example Escherichia coli (purple bacteria and relatives, 5 8 = 0.17-0.28) and Bacillus pumilus (gram-positive bacteria, 5 8 = 0.18-0.24). As shown in Fig. 1, the various phyla disappear into 

All known photosynthetic eubacteria (including cyanobacteria) contain Chi a, BChl g, BChl a or BChl b in their RCs. Chi a is restricted to the cyanobacteria and BChl g to the gram-positive line (as far as we know). As shown in Fig. 5 chlo-rophyllide a and BChl-ide g are isomers of one another [65]. BChl a is found in the RCs of green bacteria, purple bacteria and filamentous bacteria. So far BChl b has been found only in purple bacteria. We have suggested that all photosynthetic eubacteria are descendents of a common ancestor containing Chi a in an RC-1 type RC [112], and we suppose that the gram-positive line of bacteria (BChl g) 

Reaction center and light-harvesting pigments of photosynthetic bacteria. 

0 = quinone UO = ubiquinone MQ = menaquinone. Question marks ( ) denote uncertainty or lack 

More detailed speculations about the origin and evolution of photosynthesis may be found in Chapter 15. 

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