Calculate bacterial or cell doubling time from OD600 or cell count data. Two-point and time-series modes with automatic exponential phase detection.
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Microbial growth in batch culture follows the exponential model during the log phase:
Where: • N(t) = Population at time t (cells, OD600, CFU, etc.) • N₀ = Initial population • µ = Specific growth rate (h⁻¹) • t = Time
The doubling time is derived by setting N(t) = 2N₀:
This relationship holds only during balanced, unrestricted exponential growth. During lag or stationary phases, the model does not apply.
A typical microbial growth curve has four distinct phases:
• Lag phase: Cells adapt to new conditions — metabolic activity without division. Duration depends on inoculum age, media shift, and stress. • Exponential (log) phase: Constant µ, population doubles at regular intervals. This is the ONLY phase where Td is valid. • Stationary phase: Growth rate equals death rate. Nutrient depletion, waste accumulation, or quorum sensing limit growth. • Death (decline) phase: Viability decreases as nutrients are exhausted.
Common pitfall: measuring doubling time across phases (e.g., from lag into log) underestimates the true exponential growth rate. Always restrict your measurement to the log phase.
