Practice question

Generation time also called doubling time is fundamental growth parameter defined as time interval required for microbial population to double during exponential phase under defined optimal conditions. It is calculated as g equals t divided by n where t is time of exponential growth observed and n is number of generations occurring during that interval measured by viable counts. Dividing total duration by generations yields average time per division cycle encompassing chromosome replication, segregation and septum formation via FtsZ ring. Typical fast-growing Escherichia coli in rich LB medium at 37 degrees Celsius doubles approximately every 20 minutes giving three generations per hour, while obligate slow grower Mycobacterium tuberculosis doubles every 18 to 24 hours reflecting complex lipid-rich wall synthesis and lengthy DNA replication. Knowledge of g permits quantitative prediction of cell density after given time via Nt equals N0 times two to power n, essential for timing subculture to avoid overgrowth, calculating specific growth rate mu equals 0.693 over g, and optimizing inoculum ratios to achieve target biomass for fermentation processes and probiotic production.