Practice question

Log phase also termed exponential phase represents balanced growth state where every cellular constituent doubles at identical specific rate. Under saturating nutrients and aeration, DNA replication initiates synchronously via DnaA ATP activation at oriC, elongation by PolIII, segregation by MukBEF SMC complex, and cytokinetic ring FtsZ with FtsA ZipA divides cells with constant interdivision time. Specific growth rate mu maximal, defined by mu equals ln2 over generation time g. Equation dN over dt equals mu N integrated yields N equals N0 times e to mu t, producing straight line on semi-log plot. Ribosome fraction highest, RNA to DNA ratio elevated, cell size uniform and most sensitive to inhibitors targeting peptidoglycan synthesis penicillin, protein synthesis tetracycline. Generation time for Escherichia coli in rich medium 20 minutes, Mycoobacterium tuberculosis 18 hours. Studying log phase ideal for physiology because global regulation governed by housekeeping sigma RpoD, stress sigma RpoS inactive, providing steady state transcriptome useful for mutation rate, proteomics, and cell cycle analyses without starvation artifacts.