Practice question

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 continue slight rise due to cell size and storage inclusions but CFU flat. Death phase follows when death exceeds birth yielding negative net. Recognizing stationary zero net growth not absence activity crucial for understanding antibiotic tolerance persister cells that survive bactericidal drugs without resistance by dormancy, for interpreting growth curves where plate counts misleading if aggregated, and for designing fed batch strategies where preventing zero net extends productive exponential phase improving biomass yield and recombinant protein expression.