Purple sulfur bacteria are phototrophic bacteria that oxidize hydrogen sulfide ($$H_2S$$) into elemental sulfur and sulfuric acid. They obtain their purple color from the pigments bacteriochlorophylls and carotenoids.

Purple Sulfur Bacteria *Chromatium*

Green sulfur bacteria perform anoxygenic photosynthesis, using sulfites as electron donors to release free elemental sulfur, while utilizing sulfide ($$S^{2-}$$) to produce green bacteriochlorophyll.

Green sulfur bacteria

Green nonsulfur bacteria are phototrophic bacteria that are similar to green sulfur bacteria but use substrates other than sulfides, such as organic substrates or molecular hydrogen, as electron donors for oxidation.

Green non-sulfur bacteria

Purple nonsulfur bacteria are phototrophic bacteria that are similar to purple sulfur bacteria but use hydrogen instead of hydrogen sulfide for oxidation, utilizing organic substrates like succinate and malate as electron donors.

Purple non-sulfur bacteria

Phototrophic purple and green bacteria are classified based on their utilization of sulfur compounds for oxidation. Sulfur bacteria perform anoxygenic photosynthesis using sulfur compounds as electron donors, while nonsulfur bacteria use organic compounds, such as succinate and malate, as electron donors.

University of Wisconsin - Madison

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Purple and green bacteria are a group of phototrophic bacteria that carry out photosynthesis using bacteriochlorophylls, which are green, purple, or blue pigments similar to plant chlorophyll. Some of these bacteria also contain carotenoids—red or orange pigments—enabling them to absorb light at different wavelengths and display colors ranging from orange and red to purple and green.

Purple and Green Bacteria 

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

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