Which factor is most critical for bacterial doubling time?
Bacterial doubling time influenced multifactorially because growth rate emerges from integrated functioning of transport, catabolism, respiration, biosynthesis. Type of medium richness determines carbon supply glucose versus acetate, amino acids availability bypassing biosynthesis costs, trace elements iron cofactor for cytochromes. Oxygen levels dictate energetics aerobic respiration using NADH dehydrogenase, succinate dehydrogenase, cytochrome bo3 generating proton motive force giving up to 38 ATP per glucose versus anaerobic fermentation 2 ATP dramatically altering mu. Temperature near optimum increases enzyme kcat following Arrhenius, influences membrane fluidity controlling nutrient uptake diffusion, deviating causes heat shock cold shock stress. pH, osmolarity also matter but question highlights three major listed; all contribute synergistically. Regulatory networks integrate signals CRP for carbon, Fnr Arc for oxygen, RpoH for heat to modulate gene expression adjusting metabolism. Therefore accurate prediction generation time requires considering all above factors together rather than single parameter isolation explaining variability observed between laboratory flasks and natural habitats like gut where nutrients oxygen gradients produce differing growth rates.
Ref: Prescott's Microbiology, 11th ed., Chapter 7: Factors controlling doubling time - Medium oxygen temperature.