auxotroph
Very LowTechnical/Scientific
Definition
Meaning
A microorganism that requires specific organic growth factors (e.g., vitamins, amino acids) to survive, which it cannot synthesize itself.
In genetics and microbiology, an organism (typically a bacterium, yeast, or fungus) with a mutation that disrupts its ability to synthesize a particular essential nutrient, making it dependent on an external supply of that nutrient for growth. The term is also used to describe the mutant strain itself.
Linguistics
Semantic Notes
The term is almost exclusively used in microbiology, genetics, and molecular biology. It describes a nutritional requirement, not a general dependency. The opposite is a 'prototroph'.
Dialectal Variation
British vs American Usage
Differences
No significant differences in meaning or usage. Spelling and pronunciation are consistent.
Connotations
Purely technical with no regional connotations.
Frequency
Equally rare and specialised in both varieties, confined to scientific literature and discourse.
Vocabulary
Collocations
Grammar
Valency Patterns
[auxotroph] for [nutrient][auxotroph] requiring [nutrient][auxotroph] of [organism/strain]Vocabulary
Synonyms
Neutral
Weak
Vocabulary
Antonyms
Usage
Context Usage
Business
Not used.
Academic
Used in microbiology, genetics, and biochemistry research papers and textbooks.
Everyday
Never used.
Technical
Core term in laboratory protocols, strain descriptions, and genetic engineering.
Examples
By Part of Speech
adjective
British English
- The auxotrophic mutant failed to grow on minimal media.
- We identified an auxotrophic phenotype in the screened colonies.
American English
- The auxotrophic mutant failed to grow on minimal medium.
- We identified an auxotrophic phenotype in the screened colonies.
Examples
By CEFR Level
- Scientists often use auxotrophs in genetic experiments because their growth can be controlled.
- If you don't add methionine to the medium, the methionine auxotroph will not grow.
- The researcher employed a leucine auxotroph of Saccharomyces cerevisiae to study amino acid biosynthesis pathways.
- Complementation of the auxotrophic mutation restored the strain's ability to grow on minimal agar.
Learning
Memory Aids
Mnemonic
Think: 'AUXiliary feeding is needed for this microbe to grow' + 'TROPH' (nourishment). An auxotroph needs auxiliary nutrients.
Conceptual Metaphor
A 'defective factory' – the organism's internal production line for a specific part (nutrient) is broken, so it must import the finished part from outside.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Do not confuse with 'автотроф' (autotroph). They are opposites. An auxotroph is 'ауксотроф' or 'гетеротрофный мутант'.
Common Mistakes
- Misspelling as 'auxotrophe' or 'auxotrophic' (the latter is the adjective).
- Using it to refer to any dependent organism, rather than specifically a mutant with a nutritional requirement.
Practice
Quiz
What is the defining characteristic of an auxotroph?
FAQ
Frequently Asked Questions
No. All auxotrophs are heterotrophs (they obtain carbon from organic compounds), but not all heterotrophs are auxotrophs. An auxotroph is specifically a mutant heterotroph that has lost the ability to make a particular essential nutrient.
The term is almost exclusively applied to microorganisms like bacteria, yeast, and fungi. While humans require vitamins we cannot synthesize (making us auxotrophic for them), the term is not standardly used for complex multicellular organisms in biology.
They are crucial tools in genetics. For example, they are used in replica plating to identify mutants, in selection experiments (only cells that gain a functional gene can grow without the nutrient), and in studying metabolic pathways.
'Auxotroph' is a noun referring to the organism or strain (e.g., 'a leucine auxotroph'). 'Auxotrophic' is the corresponding adjective used to describe the mutant or its properties (e.g., 'an auxotrophic strain', 'auxotrophic for histidine').