A bacterium requires only a particular amino acid as an...

A bacterium requires only a particular amino acid as an organic nutrient and lives in a completely lightless environment. What mode of nutrition (free energy and carbon) does it use? Justify your response. a. Chemoheterotroph, as it must rely on chemical sources of energy living in a lightless environment and a heterotroph if it uses organic compounds for its carbon source. b. Chemoorganotroph, as it must rely on chemical sources of energy living in a lightless environment and an organotroph if it uses organic compounds other than carbon dioxide for its carbon source. c. Chemolitoautotroph, as it must rely on chemical sources of energy living in a lightless environment and an autotroph if it uses organic compounds other than carbon dioxide for its carbon source. d. Chemoheterotroph, as it must rely on chemical sources of energy living in a lightless environment and a heterotroph if it uses organic compounds other than carbon dioxide for its carbon source.

A bacterium requires only a particular amino acid as an organic nutrient and lives in a completely lightless environment. What mode of nutrition (free energy and carbon) does it use? Justify your response.
a. Chemoheterotroph, as it must rely on chemical sources of energy living in a lightless
environment and a heterotroph if it uses organic compounds for its carbon source.
b. Chemoorganotroph, as it must rely on chemical sources of energy living in a lightless environment and an organotroph if it uses organic compounds other than carbon dioxide for its carbon source.
c. Chemolitoautotroph, as it must rely on chemical sources of energy living in a lightless
environment and an autotroph if it uses organic compounds other than carbon dioxide for its
carbon source.
d. Chemoheterotroph, as it must rely on chemical sources of energy living in a lightless environment and a heterotroph if it uses organic compounds other than carbon dioxide for its carbon source.

Key Concepts

Metabolic Classification by Carbon Source

Metabolic classification by carbon source distinguishes organisms as autotrophs, which fix carbon dioxide to produce organic compounds, or heterotrophs, which obtain carbon from preformed organic compounds. Since the bacterium in question requires an amino acid as an organic nutrient, it is classified as a heterotroph.

Chemoheterotrophy

Chemoheterotrophy is a mode of metabolism in which an organism obtains its free energy by oxidizing chemical compounds and derives its carbon from organic molecules. This combination of energy and carbon acquisition is typical for organisms that do not use light (or other inorganic electron donors) or fix carbon dioxide to build their biomass.

Organic Nutrient Requirement

An organic nutrient requirement means the organism must acquire specific organic compounds (such as amino acids) from its environment, rather than synthesizing them from inorganic precursors. This necessity indicates that the bacterium relies on preformed organic molecules for its carbon needs, a hallmark of heterotrophic nutrition.

Metabolic Classification by Energy Source

Organisms can be classified by the source of their energy into phototrophs and chemotrophs. In a completely lightless environment, organisms must use chemical compounds to harvest free energy, making them chemotrophs. This classification helps explain how bacteria thrive in environments devoid of sunlight.

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