Sequential Substrate Utilization — What is the term for the phenomenon where a microbe consumes available substrates one after another rather than simultaneously?

Introduction:When cultures encounter multiple carbon sources, regulatory mechanisms often prioritize one substrate before another. The resulting growth profile features a characteristic two-step pattern. This question asks for the established term describing sequential use rather than simultaneous co-utilization.

Given Data / Assumptions:

• Two or more utilizable substrates present in the medium.
• Organism possesses regulatory networks such as catabolite repression.
• Batch conditions permit observation of growth phases and lags.

Concept / Approach:

Diauxie refers to two-phase growth. The preferred substrate is consumed first, leading to rapid growth. After depletion, cells undergo a lag to induce catabolic enzymes for the second substrate, resuming growth at a different rate. This sequential pattern reflects hierarchical regulation of metabolic pathways.

Step-by-Step Solution:

Verification / Alternative check:

Experiments with glucose and lactose demonstrate diauxic growth: glucose is consumed first due to catabolite repression, followed by lactose utilization after lac operon induction.

Why Other Options Are Wrong:

A and B are unrelated terms. D denotes multiplicity but not sequential consumption. E concerns enzyme variants, not growth phases.

Common Pitfalls:

Assuming co-utilization in all cases; many organisms enforce substrate hierarchies that cause diauxic patterns.

Final Answer:

Diauxie