Summary
A graph of bacterial number over time with lag, log, stationary and death phases.
In depth
Lag: cells adapt and synthesise enzymes. Log: exponential growth. Stationary: growth equals death as nutrients become scarce or waste builds up. Death: decline. Count methods include viable plate counts, turbidity and direct microscopy.
Antibiotics that stop wall synthesis kill best in the log phase.
Doubling time is from the exponential phase. Viable counts and turbidity may differ. Antibiotics act best on growing cells.
Key idea: batch culture eventually runs out of nutrients.
Doubling time (generation time) is read from the log phase: it varies from 20 minutes for E. coli to hours or days for slow growers like Mycobacterium tuberculosis (about 20 hours). Lag phase length depends on the previous conditions and nutrient shift. In the stationary phase, cells may make secondary metabolites such as antibiotics or form spores.
Growth is measured by turbidity (optical density at 600 nm), colony counts, dry weight or direct counts. In a chemostat, continuous culture keeps cells in exponential growth by supplying fresh medium at a constant rate. Diauxic growth occurs when two sugars are used in sequence, with a second lag.
Key idea: bacteria are on a log scale when plotted, so a straight line indicates exponential growth.
Frequently asked questions
What is Growth Curve?
A graph of bacterial number over time with lag, log, stationary and death phases.
Which area of biology covers Growth Curve, and how advanced is it?
Growth Curve is one of the 54 topics in Microbiology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Binary Fission, Bacteria, Antibiotics.
Can you give an example of Growth Curve?
Bacterial secondary metabolites like penicillin are often made in stationary phase.
What should I learn before Growth Curve?
Work through the Beginner topics in Microbiology first, such as Microorganisms, Bacteria, Archaea, then return to Growth Curve. Intermediate topics assume the Beginner vocabulary.
What topics are related to Growth Curve?
The closest topics to Growth Curve are Binary Fission, Bacteria, Antibiotics, Bacterial Cell Wall. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Growth Curve?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Growth Curve. To practise the whole of Microbiology, use the Microbiology quiz.
How is Growth Curve different from Binary Fission?
Growth Curve: A graph of bacterial number over time with lag, log, stationary and death phases. Binary Fission: Asexual reproduction in which a bacterial cell copies its DNA and splits into two identical cells. Read both side by side and note what each one explains.
How should I study Growth Curve step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Binary Fission and explain the difference aloud. Finally, take the Microbiology quiz and come back to this page for any question you miss.