ABSTRACT
Phototrophic bacteria comprise a large and heterogenous group of organisms, all of which contain chlorophyll. They are distinguished from other bacteria by their ability to carry out photosynthesis; thus, the properties of this process are emphasized in this chapter. Other special features which are found within the phototrophic bacteria and which are discussed in this chapter are nitrogen fixation and their autotrophic way of life. The position of the green nonsulfur bacterium Chloroflexus shows that photosynthesis has deep evolutionary roots, and it has been suggested that photosynthesis was an early trait that spread among several groups of bacteria before the major lines of descent were defined. Based on the fact that Chloroflexus is a thermophile, Brock and Madigan have suggested that the thermophilic property might be of more significance in defining the phylogeny of green bacteria than the phototrophic character. This argument might be complicated by the recent isolation of a thermophilic Chlorobium species from hot springs in New Zealand.
