Starvation and stress responses: During which segment of the standard batch-culture growth curve are “starvation proteins” predominantly produced by many bacteria?

Introduction / Context:
When nutrients become limiting and waste accumulates, bacteria enter stationary phase and activate global stress responses. Starvation proteins help cells survive nutrient deprivation, oxidative stress, and other challenges, shaping persistence and culturability.

Given Data / Assumptions:

• Batch culture progresses through lag, exponential, stationary, and death phases.
• Starvation proteins are part of regulated stress responses (e.g., RpoS in Gram-negatives).
• Question asks where production is predominant.

Concept / Approach:
Stationary phase is characterized by slowed net growth as cell division balances cell death. Regulatory networks induce genes for nutrient scavenging, DNA repair, chaperones, antioxidant defenses, and cell envelope modification. These proteins enhance survival until conditions improve, and some persist into the death phase.

Step-by-Step Solution:
Map physiological events to growth phases. Identify that starvation cues (e.g., low carbon, nitrogen) trigger stationary-phase responses. Select “Stationary phase.”

Verification / Alternative check:
Transcriptomics show upregulation of stress regulons (e.g., rpoS-dependent genes) in stationary phase versus log phase, consistent with starvation protein accumulation.

Why Other Options Are Wrong:
Lag/log phases focus on growth preparation and rapid division; death phase features net decline with damage overwhelming defenses, though some stress proteins persist.

Common Pitfalls:
Assuming all stress proteins appear only upon starvation; some are constitutive or induced by other stresses, but the hallmark induction is in stationary phase.

Final Answer:
Stationary phase.