Skip to content
Login Register

#nutrient depletion

3 public questions tagged with this topic.

Microbial Physiology

Which phase of bacterial growth follows nutrient depletion and accumulation of toxic waste?

Batch culture progression from exponential to stationary triggered primarily by depletion of limiting substrates and buildup of inhibitory waste. During log phase glucose, ammonium, phosphate abundant, oxygen well dissolved, growth maximal. Cells actively metabolize producing organic acids acetate via overflow metabolism, carbon dioxide, secondary metabolites that acidify medium, increase osmolarity, reduce water activity. Oxygen consumption outpaces transfer creating microaerophilic conditions, electron transport slows, proton motive force drops. Sensors RelA synthesizes ppGpp upon uncharged

Ref: Madigan et al., Brock Biology of Microorganisms, Chapter 6: Stationary phase triggers - Nutrient depletion.

View Details
Microbial Physiology

What is the primary reason for bacterial death in the death phase?

Transition to death phase reflects inability to maintain energy homeostasis and repair. Prolonged incubation exhausts fermentable carbon, electron acceptors, phosphate, amino acids, halting ATP generation via respiration and substrate level phosphorylation. Concomitantly toxic end products accumulate: organic acids acetate and lactate lower pH below 5, alcohols ethanol, ammonia, hydrogen sulfide inhibit cytochrome oxidases, and reactive oxygen species superoxide and H2O2 from autooxidation damage iron sulfur clusters. Oxidative lesions cause DNA strand breaks, protein carbonylation, membrane l

Ref: Brock Biology of Microorganisms, 16th ed., Chapter 6: Death phase - Toxic metabolites accumulation.

View Details
Microbial Physiology

In which phase do bacteria begin dying exponentially due to nutrient depletion?

Death or post-stationary decline phase follows stationary when lethal stresses exceed repair capacity. Utilizable substrates fully depleted, waste products such as fermentation acids, alcohols, reactive oxygen species and toxic secondary metabolites accumulate to inhibitory levels, extracellular pH shifts outside optimum disrupting proton motive force and increasing competition for maintenance energy. Proteases Lon and Clp degrade non-essential proteins recycling amino acids, nucleases degrade rRNA, membrane depolarization causes ion leakage. Viability loss typically follows exponential first-

Ref: Madigan et al., Brock Biology of Microorganisms, 16th ed., Chapter 4: Death Phase and Nutrient Depletion.

View Details