Characteristics of bacteria Most bacterial species are heterotrophic , that is, they acquire their food from organic matter. The largest number of bacteria are saprobic , meaning that they feed on dead or decaying organic matter. A few bacterial species are parasitic . These bacteria live within host organisms and cause disease. Certain bacteria are autotrophic , that is, they synthesize their own foods. Such bacteria often engage in the process of photosynthesis. They use pigments dissolved in their cytoplasm for the photosynthetic reactions. Two groups of photosynthetic bacteria are the green sulfur bacteria and the purple bacteria. The pigments in these bacteria resemble plant pigments. Some autotrophic bacteria are chemosynthetic . These bacteria use chemical reactions as a source of energy and synthesize their own foods using this energy.
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