Heterotrophs, by consuming reduced carbon compounds, are able to use all the energy that they obtain from food (and often oxygen) for growth and reproduction, unlike autotrophs, which must use some of their energy for carbon fixation. Both heterotrophs and autotrophs alike are usually dependent on the metabolic activities of other organisms for nutrients other than carbon, including nitrogen, phosphorus, and sulfur, and can die from lack of food that supplies these nutrients. This applies not only to animals and fungi but also to bacteria.