1. Bacterial Growth
and
Reproduction

2. Reproduction Bacteria can reproduce using three methods:
1. Binary Fission
2. Conjugation
3. Spore Formation

3. Binary Fission A form of asexual reproduction
When a cell has almost doubled in size it will replicate its DNA and divide in half
This produces 2 identical daughter cells
Asexual reproduction does not invovle the exchange of genetic material

4. Binary Fission

5. Conjugation Is a form of sexual reproduction
A long bridge of proteins forms between two bacterial cells
DNA is transferred from one cell (donor) to another (recipient)
Genetic Information is exchanged between individuals

6. Conjugation

7. Spore Formation Bacteria form spores during unfavorable conditions
One type is called an endospore
Cell forms a thick internal wall the encloses its DNA
Spores can remain dormant for months or even years until conditions improve
When conditions become favorable, the endospore will open, and the bacterium will grow again

8. Spore formation

9. Generation time Time required for one cell to produce two new cells.
Varies depending on the type of organism and environmental conditions.
Average min. (varies - 10 minutes to 24 hrs.)

10. Bacterial Growth Increase in numbers (size of population)
Constantly doubles - increases exponentially
Expressed as logarithmic function of base 2 x
Population doubles - 2
X - # times population doubles
1 cell reproducing every 20 min.  over 1 million cells in 7 hours  1 billion in 10 hrs.

11. Generation Time

12. Factors Affecting Bacterial Growth
1. Temperature Oxygen
2. Light Ph (acidity)
3. Nutrients Moisture

13. Temperature All bacteria grow within temperature range
(minimum  maximum)
Most rapid reproduction occurs at the optimal temperature
Starting at minimum temp. growth slowly increases
Reaches maximum rate at optimum.
As temp. continues to rise growth rapidly decreases.

14. Bacteria can be divided into 3 groups according to their growth temperature
Mesophiles - 20C - 45C (50C)
Ex. Environmental bacteria, pathogen
Thermophiles - 45C (50) - 80C
Extreme thermophiles - up to 110C
Ex. Hot springs, volcanoes in ocean, decomposers
Psychrophiles - 0C - 20C
Ex. Cold springs, lakes; polar regions; refrigerator.

15. Light (Radiation)
Very small group photosynthetic bacteria (cyanobacteria) - require UV light
Non-photosynthetic bacteria (eubacteria) UV light is lethal (causes mutations)

16. Oxygen
Bacteria can be divided into 3 groups based on requirement of gaseous oxygen:
Aerobes - require the presence of gaseous (molecular) oxygen
Anaerobes - require absence of gaseous oxygen (utilize O in oxygen containing compounds - chemical oxygen).
Facultative - either condition

17. Nutrients Basic requirements for growth :
C - building blocks of cell components
N2 - production of proteins, nucleic acids
H2 - occur in organic compounds
O2 - involved in the production of energy
Minerals, Trace Elements - required in small amounts
Special metabolites ( growth factors )
Substances required for growth that the cell cannot produce using the basic requirements already listed. ( Ex. : vitamins, amino acids, carbohydrates, blood factors )

18. Two types of organisms based on source of nutrients
Autotrophs - utilize inorganic compounds
( C - CO2, carbonates; N - NH4, N2, NO3 )
Heterotrophs - utilize organic compounds
( C - CHO, lipids; N - proteins )

19. Ph Concentration of H+, OH- ions
Acid Neutral Basic
Bacteria grow within a pH range
Optimum pH - pH at which maximum growth occurs

20. Bacteria can be divided into three groups according to PH
Neutrophiles (5 -8) (optimal 7-7.2)
Acidophiles (0-5)
Alkalinophiles (8-12)
(Soil Bacteria)

21. Moisture All metabolically active bacteria require presence of water:
Cells largely water
Most nutrients, wastes soluble in water to cross cell membrane.
Site of metabolic reactions (cytoplasm)