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#bacterial growth phases

3 public questions tagged with this topic.

Microbial Physiology

In a batch culture, which phase has zero net growth?

In batch culture population dynamics defined by net rate birth minus death. Lag phase net near zero during adaptation, log phase net strongly positive with mu dominant, stationary net zero because division still occurs using scavenged nutrients from lysed cells cryptic growth at rate equal to death rate from oxidative damage, acid stress, toxin accumulation. Viable counts plateau because new cells forming balance those losing colony forming ability. Microscopically heterogeneity high some cells dividing, some filamentous, some entering persistence via toxin antitoxin HipA. Optical density may

Ref: Brock Biology of Microorganisms, 16th ed., Chapter 6: Batch culture - Zero net growth in stationary.

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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.

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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.

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