1. Bacteria

2. What Are Bacteria? Simple unicellular organisms Microscopic
PROKARYOTIC -no nucleus around DNA
Divide by FISSION (asexual) but some are able to exchange DNA (conjugation)‏
Specialize by MUTATIONS
Move using FLAGELLA
Mostly harmless, act as decomposers

3. CLASSIFICATION Bacteria are classified by:
Environment in which they live
Aerobic = need oxygen
Anaerobic = cannot survive with oxygen!
Food sources which are necessary for them
Some need specific sugars to live
Type of Membrane
Some bacteria do not absorb certain stains
Shape:
Spheres, Rods, Spirals, Helixes

4. BACTERIA SHAPES

5. How do Bacteria GROW?
Different bacteria require optimal temperatures to multiply
Some are called thermophile because they need high temperatures to divide
Colder temperatures will slow growth
DNA is copied and the bacteria will elongate and pinch in half forming TWO
Growth is measured in terms of “DOUBLING TIME”
In a few hours, 2 bacteria can become millions!

6. Bacterial Colonies Bacteria grow in clumps called COLONIES
These colonies can be grown on plates (see page 163)‏
Population numbers can be counted by estimation! (see page 165)
Using a SPECTROPHOTOMETER
How cloudy is the test tube?
Using a GRID GROWTH PLATE
How many are in one grid?

7. Growth in a CULTURE Bacteria grown in a lab is called a CULTURE
Bacterial cultures are grown in order to:
Diagnose a bacterial infection
Determine if food or water is contaminated
Grow useful bacteria (making yogurt, cheese etc.)‏
Study and create NEW antibiotics

8. What does it look like?
Bacterial growth follows a predictable pattern:
Lag phase:
Growth is slow because there are only a few bacteria
Exponential phase:
If sufficient food and temperatures are present bacteria population will begin to expand rapidly
Stationary phase:
Bacteria will reach the limit of food etc.
Death: population will begin to decline

9. Graph of Bacterial Growh
A = lag
B = exponential
C = static
D = death
L stands for log scale
T stands for time

10. Photo Gallery Image of E. coli bacteria attacking human cells
This is a rod shaped bacteria

11. Photo Gallery
Image of Streptococcal bacteria infecting human intestines
This is a cocci shaped bacteria

12. Homework: Review pages 159-168 from the textbook hand-out
Answer questions # 1-4 pg 168