How do heterotrophic microorganisms obtain carbon for growth?

Heterotrophic microorganisms obtain the carbon necessary for growth by utilizing preformed organic compounds rather than carbon dioxide. Unlike autotrophs, which synthesize their own nutrients from inorganic sources, heterotrophs must acquire carbon from external organic matter.123

These microorganisms commonly derive carbon from a variety of sources, including:

• Carbohydrates, lipids, and proteins: These are primary organic substrates used by many microbes.2
• Other organic compounds: Many microbes are capable of metabolizing diverse substances, such as hydrocarbons.2
• Particulate or dissolved matter: Depending on the species, heterotrophs may ingest particulate food through processes like phagotrophy (engulfment) or absorb dissolved nutrients from their environment via osmotrophy.3

In ecological systems, these organisms often act as decomposers, breaking down organic materials to sustain their metabolic needs. By utilizing these preformed organic molecules, heterotrophic microorganisms play a vital role in the cycling of matter within their environments.12