1. Bacterial Growth and Reproduction Kelly Spiller East View High School Georgetown TX 78628

2. Definitions  Growth in this case means increase in numbers not size  Binary fission is the process of cell division of prokaryotic bacteria  Daughter cells are the resulting cells of binary fission  Generation time is the time for a complete life cycle of a cell from daughter cell to division  Plasmid is an extra, usually circular piece of DNA in some bacteria; it often carries genes for resistance

3. Four growth phases: # of cells LAG

4. Four phases explained  Lag – adjusting to new conditions or environment  Log – exponential growth; 1,2,4,8,16….  Stationary – depletion of nutrients or accumulation of wastes  Death – continued depletion or accumulation

5. Four factors that affect growth

6. Temperature  Temperature:  Psychrophiles – optimum growth is at 10 Celsius  Mesophiles – optimum is at 25-35 C.  Thermophile – optimum is at 60C.  Extreme Thermophile – optimum is higher

7. pH  Acidophile – optimum is acidic conditions  Neutrophile – optimum is close to neutral  Alkalophile – optimum is basic conditions

8. Water and osmotic pressure  Prefer saturated conditions  Osmotic pressure is based on the concentration gradient.  Too high = rupture  Too low = shrivel  Hypertonic = conc. is higher (must define)  Hypotonic = conc. of lower (must define) http://www.youtube.com/watch?v=Ji1wetFn gLo

9. Oxygen  Obligate aerobes – require O 2  Facultative – can grow with or without but are better with  Aerotolerant – can grow with or without but are better without  Obligate anaerobe – die in the presence of O 2  Microaerophile – require O 2 but 20% too high  Capnophile – require CO 2

10. Mechanisms of variation and reproduction http://www.youtube.com/watch?v=7sZ5Nz8_cfc

11. Binary Fission  Very fast but very low variation in species 1. DNA Replication 2. Cell elongation 3. Cleavage All daughter cells are genetically identical except for mutations which occur at a very low rate.

12. Mutation  Mutation – random accidental changes in DNA of an individual. May be passed on to daughter cells via binary fission  Critical to create diversity to avoid extinction  Can be good, bad or no effect http://www.youtube.com/watch?v=eDbK0 cxKKsk

13. Conjugation  Occurs through the pilus = conjugation tube  Extra DNA found in Plasmids can be transferred to cells which lack them  Occasionally the tube breaks too early and the entire sequence is not transferred = more variation http://www.youtube.com/watch?v=EtxkcS GU698

14. Transformation  DNA can be “picked up” by cells from the environment  Increases variation but not new cells  Griffith’s experiment:  Two type of strep. (1 with capsule “S” and 1 without “R”)  S strain with capsule is deadly because…….?  Heat killed S strain mixed with R strain can transform the R into S because of “transformation” http://www.youtube.com/watch ?v=hSbTWaR6Lzk

15. Transduction  New DNA is acquired via viral vector  Virus injects the cell with its DNA  DNA incorporates into host DNA  When it is “cut out” it sometimes can pick up extra pieces.  When the new virus infects the new DNA containing bacterial genes it creates variation. http://www.youtube.com/wa tch?v=oFMRnEnkr0g