Hi, Another question from me If you want to perform an experiment with log phase bugs at a known cfu/ml is there a difference between culturing the bugs until they are 0.1 OD and diluting a culture of bugs to 0.1 OD (from say 0.25) after having subbed them to promote log phase growth?
I know that I could do the experiment to compare but it’s so labourious I thought I would ask on the offchance that anyone knew. Thnks
Laura
Yes, there’s a crucial difference. Culturing bacteria up to OD₆₀₀ = 0.1 ensures they are in true log phase, actively dividing, and physiologically uniform—ideal for consistent CFU/mL and reproducible results. In contrast, diluting down from OD₆₀₀ = 0.25 to 0.1 reduces cell density but doesn’t reset their growth state. These cells may be transitioning out of log phase, leading to mixed metabolic states and inaccurate CFU estimates. For precise experiments—especially involving infection, transformation, or drug testing—always grow fresh cultures to the desired OD instead of diluting older ones. This ensures reliable cell behavior and more accurate results.
Thanks for your help Dr. Gaganjot singh