The microbes that use chemical compounds as a source of energy are known as:

RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Applied Microbiology & Infection control

Easy

Appeared in: RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Explanation

Chemotrophs are organisms that derive their energy from chemical reactions.
The term 'chemo' refers to chemical, and 'troph' refers to nourishment or feeding.
This group is broad and includes microbes that can use either organic chemicals (chemoorganotrophs) or inorganic chemicals (chemolithotrophs) for energy.
Many bacteria of medical importance, such as E. coli, are chemotrophs.

Option A: This term refers to the organism's electron source, not its energy source. Lithotrophs use inorganic molecules (like H₂S or ammonia) as a source of electrons.
Option B: This term also refers to the organism's electron source, not its energy source. Organotrophs use organic molecules (like sugars or fats) as a source of electrons.
Option D: Phototrophs use light (photons) as their primary source of energy, not chemical compounds. The prefix 'photo-' indicates light.

Visual 1: Flowchart: A flowchart illustrating the classification of organisms based on energy, electron, and carbon sources. It would start with 'All Organisms' and branch into Phototrophs and Chemotrophs, then further subdivide based on electron and carbon sources.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Microbial classification based on energy source as background academic context rather than a clinical decision trigger.
Understanding a microbe's metabolism is crucial in medicine. For example, knowing that most human pathogens are chemoheterotrophs helps in designing culture media in the lab to grow and identify them.
The metabolic needs of a pathogen determine where it can thrive in the human body (e.g., aerobic vs. anaerobic environments).
This knowledge is fundamental for developing antimicrobial drugs that can target specific metabolic pathways unique to the microbes, minimizing harm to the human host.

How to Approach the Question

First, identify the key terms in the question: 'microbes', 'chemical compounds', and 'source of energy'.
The question is asking for the specific name for organisms classified by their use of chemical energy.
Analyze the prefixes of the options for clues: 'Photo-' means light, 'Chemo-' means chemical, 'Organo-' means organic, and 'Litho-' means rock or inorganic.
Based on the prefixes, 'Chemotrophs' directly relates to using chemical compounds for nourishment.
Evaluate the other options to confirm your choice. 'Phototrophs' use light. 'Organotrophs' and 'Lithotrophs' refer to the electron source, not the primary energy source, making them less precise answers to this specific question.

Concept Tested & Keywords

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