Mixotrophic: many purple nonsulfur bacteria 1. No oxygen: photoorganotrophic heterotrophs 2. Normal oxygen: oxidize organic molecules and function chemotrophically 3. Low oxygen: photosynthesis and oxidative metabolismMixotrophic: many purple nonsulfur bacteria 1. No oxygen: photoorganotrophic heterotrophs 2. Normal oxygen: oxidize organic molecules and function chemotrophically. 3.Low oxygen: photosynthesis and oxidative metabolism