Energy sources – chemotrophs vs others: In microbial nutrition, organisms that obtain their energy from chemical compounds (as opposed to light) are specifically called what?

Introduction / Context:
Microbial nutritional classifications distinguish energy source (light vs chemicals), electron source (organic vs inorganic), and carbon source (CO2 vs organic carbon). Using the correct terms is essential for describing metabolic strategies in ecology and biotechnology.

Given Data / Assumptions:

• We are asked specifically about the energy source category.
• Light-driven organisms are phototrophs; chemical-energy organisms are chemotrophs.
• Other terms in the options refer to different aspects (electron or carbon source, or auxotrophy).

Concept / Approach:
Chemotrophs derive energy by oxidizing chemical compounds. Depending on the electron source, chemotrophs are further divided into organotrophs (electrons from organic molecules) and lithotrophs (electrons from inorganic molecules). Carbon source is denoted independently: autotrophs fix CO2, heterotrophs use organic carbon. Prototrophs are organisms that can synthesize all required metabolites from minimal media, unrelated to energy sourcing.

Step-by-Step Solution:
Identify the requested attribute: energy source. Match “energy from chemicals” to “chemotrophs.” Differentiate organotroph/lithotroph (electron source) and autotroph (carbon source). Select “Chemotrophs.”

Verification / Alternative check:
Standard metabolic nomenclature constructs combinations like chemoorganoheterotroph or chemolithoautotroph by stacking energy/electron/carbon terms; the first term is energy, hence “chemo–”.

Why Other Options Are Wrong:
Prototroph concerns biosynthetic capability; organotrophs/lithotrophs denote electron donors; autotrophs denote carbon source, not energy.

Common Pitfalls:
Mixing electron source with energy source; while coupled, they label different dimensions of metabolism.

Final Answer:
Chemotrophs.