Cyanobacteria are the major group of photosynthetic bacteria. Some early cyanobacteria may have formed the oxygen released into the early atmosphere. In addition to chlorophyll a , cyanobacteria also have the blue pigment phycocyanin and the red pigment phycoerythrin . Filamentous Cyanobacterium, Anabaena sp. Heterotrophic Bacteria Members of this large and diverse group must derive their energy from another organism by feeding.
Saprophytes feed on dead or decaying material and are important nutrient recyclers.
Symbiotic bacteria live within a host multicellular organism and contribute to the health of the host. Normally cellulose is nondigestible. Possible symbiosis of bacteria within early eukaryotic cells was a major step in the evolution of eukaryotic cells. In 1980, Lynn Margulis proposed the theory of endosymbiosis to explain the origin of mitochondria and chloroplasts from permanent resident prokaryotes. Steps in endosymbiosis.