The slide that this phot was taken from was split into 3 sort of sections: heterotrophs on the right side, photosynthesizers in the middle (and right), and these purple bacteria on the left. Actually, I had spent so much time with the heterotrophs on the right that I never saw the massive colony of purple bacteria growing on the left. I assume that they are photosynthetic; maybe purple sulfurs, but I doubt it, because I don’t see where they would be getting their sulfur from.
