19. Anoxigenic photosynthesis: processes and organisms 19.1 Light-driven redox processes. Electron sources for photosynthesis: oxidation of reduced sulfur, ferro-iron, hydrogen and carbon compounds. Missing processes: photosynthesis with methane (?), ammonia (?) are they feasible ? Variations of van Niel's unifying concept of photosynthesis. 19.2 Morphological and physiological diversity Enrichment and isolation of anoxigenic phototrophic bacteria. Phylogeny of anaerobic phototrophs, a clue to the evolution of photosynthesis. Phenotypic traits of anoxic phototrophs: pigments, metabolism, membrane structures. Distinguishing features of Chromatiaceae, Ectothiorhodospiraceae, Chlorobiaceae, Heliobacteriaceae, "Chloroflexaceae" and Rhodospirillaceae. Pigment diversity: bacteriochlorophylls, carotenoids, phycobilins. Diversity of metabolisms: C-fixation, carboxylases and electron transfer in phototrophs. Phototrophs living chemotrophically: How phototrophs survive in the dark.
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