A heterotroph is an organism that cannot make its own food and must rely on other organic carbon sources, primarily plant or animal materials, for nourishment.
Heterotrophs are primary, secondary, and tertiary consumers in the food chain, but not producers.
Heterotrophs are a type of microbe (yeast, molds, and bacteria) that feed on organic carbon rather than sunlight (as do autotrophs like algae).
All bacteria that depend on organic substances for growth fall under the category of "heterotrophic bacteria."
Agrobacterium, Pseudomonas, Salmonella, Escherichia, Rhizobium, etc. are a few examples of heterotrophic bacteria.