2. Based upon these classes, most microbes can be divided into four different nutritional types: 2.1 Photolithotrophic c 2.2 Photo organotrophic heterotrophy 2.3 Chemolithotrophic autotrophy 2.4 Chemo organotrophic heterotrophy 3. Some microbes (mixotrophs) alter their metabolic patterns in response to particular environment, e.g., purple nonsulfur bacteria ahan 3.1 Absence of oxygen function as phot trophic heterotrophs dum 1 0,lau ids 3.2 Normal oxygen levels function as chemotrophs cu 3.3 Low oxygen levels photosynthesis and oxidative metabolism is present