How are microbes classified according to energy source?

Prepare for the Microbial Metabolism Test. Utilize flashcards and multiple choice questions with helpful hints and detailed explanations. Ace your test with ease!

The main idea here is that microbes are grouped by where they get their energy. Phototrophs use light as their energy source, harnessing it through photosynthesis or other light-driven processes. Chemotrophs obtain energy from chemical compounds, by oxidizing either inorganic or organic molecules.

That’s why the statement Phototrophs → Light and Chemotrophs → Chemicals is the best fit. It cleanly separates energy sources without mixing in carbon sources. Keep in mind that phototrophs and chemotrophs can have different carbon sources as well: some use CO2 (photoautotrophs or chemoautotrophs), while others use organic carbon (photoheterotrophs or chemoheterotrophs). The other options blur energy source with carbon source or misstate what chemotrophs or photo- categories use for energy. For example, chemoautotrophs derive energy from chemicals, not light, and photoheterotrophs use light for energy but rely on organic carbon, not CO2.