1. Binary fission of bacteria

2. E.coli genome size: 4.6 x 10 6 nucleotides Generation time at optimal conditions: 20min DNA replication rate: 1000nt/s ≈ 1.2 x 10 6 nt/20min About 25% of genome can be replicated in one generation time

3. Population growth Growth rate: change of cell number per unit time When growth is unlimited, growth rate is low at first, increases logarithmically Plotted on semi-log paper, growth is a straight line Generation time: time required for one cell to grow into two cells (varies from several minutes to months) Specific growth: instantaneous change in relative cell numbers (µ) µ = ln(2)/generation time

4. Logarithmic growth

5. Batch growth stages

6. Lag and Exponential Lag phase –Longer when inoculum conditions differed –Some inocula may require synthesis –Apparent lag caused by partial death of inoculum Exponential phase –Logarithm of cell numbers increases linearly –Specific growth rate is constant—characteristic of growth conditions –Cell physiology is constant—best source for biochemical studies is late exponential phase

7. Stationary and Death Stationary phase –Culture is eventually limited by substrate or nutrient exhaustion or product accumulation –Metabolism changes to accommodate the limitation –Lysis of some cells may lead to growth in others –Cell increase equals decrease (cryptic growth) Death phase –Death is generally logarithmic, but slower than growth –Sometimes death rate changes after hours or days

8. Calculating specific growth rate

9. Counting Chamber

10. Counting cells in a chamber

11. Quantitative plating

12. Pour plates

13. Pour-plating techniques

14. Optical density