Skip to content
Login Register

#stationary phase

8 public questions tagged with this topic.

Microbial Physiology

The primary role of the stationary phase in bacterial growth is:

Upon entry into stationary phase nutrient exhaustion does not equate to dormancy but triggers extensive differentiation for long term survival. Genome wide expression reprogrammed by ppGpp alarmone binding RNA polymerase, sigma factor switch from RpoD to RpoS general stress sigma encoded by rpoS. RpoS regulon includes oxidative protection catalase HPII, exonuclease, DNA protection Dps compacting chromosome sequestering iron preventing Fenton chemistry, acid resistance Gad system glutamate decarboxylase, trehalose synthesis. Secondary metabolism activated nonribosomal peptide synthetases, polyk

Ref: Prescott's Microbiology, 11th ed., Chapter 7: Stationary phase role - Sporulation and secondary metabolites.

View Details
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

In the stationary phase, the rate of bacterial growth and death is:

In batch culture, cell number increases exponentially until limitations impose plateau termed stationary phase. Analytical expression net growth rate equals birth rate minus death rate. Initially birth vastly exceeds death. As substrates deplete and metabolic acids acetate, reactive oxygen species accumulate, growth slows, death accelerates. At equilibrium point, average number of divisions per hour equals number of cells losing viability per hour, so dN over dt equals zero. Viable count plateaus, optical density may still increase slightly due to cell mass and inclusion bodies but colony form

Ref: Prescott's Microbiology, 11th ed., Chapter 7: Stationary phase - Growth equals death rate.

View Details
Microbial Physiology

In which growth phase do bacteria prepare for sporulation?

Sporulation is energy expensive differentiation reserved for conditions where vegetative growth cannot continue. Throughout exponential phase nutrients abundant, ribosome content high, cells divide via FtsZ divisome and elongasome MreB. As population density rises and carbon nitrogen phosphate become scarce, quorum peptides ComX CSF and nucleotide second messengers ppGpp c-di-GMP accumulate, sensed by KinA KinB KinC histidine kinases. Kinases activate phosphorelay transferring phosphate from Spo0F to Spo0B to Spo0A master regulator. Phosphorylated Spo0A binds 0A boxes activating over 120 genes

Ref: Prescott's Microbiology, 11th ed., Chapter 7: Bacterial sporulation - Stationary phase Spo0A phosphorelay.

View Details
Microbial Physiology

What is the relationship between growth rate (kg) and death rate (kd) in the stationary phase?

Population dynamics of batch cultures are quantitatively described by balance between formation of new cells and loss of viability. Growth rate constant kg represents frequency of new cell formation per existing cell per unit time via binary fission, while death rate constant kd represents probability per cell per time of losing ability to form colony due to irreversible damage or lysis. In lag ks slight excess over kd but numbers appear unchanged; in log kg far exceeds kd generating rapid increase. As nutrients limit and inhibitory metabolites accumulate, replication slows, cell cycle checkpo

Ref: Lodish et al., Molecular Cell Biology, 8th ed., Chapter 4: Stationary Phase Growth Rate and Death Rate Equality.

View Details
Microbial Physiology

Which of the following occurs in the stationary phase of bacterial growth?

When batch cultures exhaust carbon, nitrogen or phosphate and accumulate organic acids like acetate lowering pH, growth rate decelerates and matches death rate producing plateau termed stationary phase. This phase triggers global reprogramming governed by alternative sigma factor sigmaS encoded by rpoS in Escherichia coli and master regulator Spo0A in Bacillus subtilis. Cells activate stringent response via RelA sensing uncharged tRNA and SpoT synthesizing alarmones ppGpp and pppGpp which inhibit stable RNA promoters and redirect transcription to survival genes. Adaptations include highly resi

Ref: Prescott's Microbiology, 11th ed., Chapter 6: Stationary Phase, Sporulation and Secondary Metabolites.

View Details
Chromatography

Stationary phase in ion exchange is selected based on:

Ion exchange selectivity depends on net surface charge of analyte at operating pH relative to matrix charge. For proteins, net charge is determined by relationship between buffer pH and isoelectric point pI. At pH above pI, protein is negatively charged and binds anion exchanger; below pI, it binds cation exchanger. Therefore stationary phase choice and pH optimization require consideration of pI, ensuring target molecule bears appropriate charge for binding while contaminants differ. Molecular mass influences gel filtration but not ion exchange, while solubility governs partition methods. Und

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details
Chromatography

Which stationary phase delays polar compounds?

Chromatographic retention depends on strength of solute-stationary phase interaction. Polar stationary phases such as silica with silanol groups exhibit strong dipole interactions, hydrogen bonding, and electrostatic attraction with polar analytes, causing longer retention and delayed elution. Non-polar matrices like C18 in reversed-phase preferentially retain hydrophobic molecules. Principle of like interacts with like governs normal-phase chromatography where polar compounds are held more strongly. Understanding polarity matching allows prediction of elution order, optimization of solvent sy

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details