Bacteria Lesson

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In the three-domain system, two domains are prokaryotes
(Bacteria and Archaea).
Prokaryotes have no nucleus or membrane – bound organelles
Bacteria - what your used to found everywhere
Organisms in Archaea often live in extreme environments (thought to be the earliest
forms of life)
The third domain is Eukarya
Bacteria exist in very large numbers almost everywhere on Earth
- Your body has 10 times more bacteria cells than human cells!
Some bacteria are harmful, and some are helpful
your colon, but also are toxic when ingested
- cycle nutrients like carbon and nitrogen
- cyanobacteria are very important producers in many
water ecosystems
- E.Coli live in
Bacteria are classified by their Shape, Cell walls and Motility.
Spherical: a.k.a. coccus
- eg.
Pneumonia-causing bacteria
- Cocci appear in
clusters (Staphlococcus) or chains
Rod-Shaped: a.k.a. bacillus
- eg. E. Coli
Spiral: curved or spiral-shaped
- eg. Lyme disease
Microviewer - harmful/helpful
Cell Wall Structure
Nearly all bacteria have cell walls outside their plasma membrane, but they are very
different than plant cell walls.
- Type 1: Composed of peptidoglycan (thick coat of sugars)
- Type 2: Thin coat of peptidoglycan, plus extra membrane
About half of all bacteria cannot move on their own
Methods of bacterial movement include:
tail (most common)
- Flagellum- whip like
- Spiral bacteria
twist like a corkscrew
- Some bacteria glide
on a film of slime
Bacteria obtain their nutrition in a variety of ways
Heterotrophs eat and autotrophs get energy from the Sun
Bacteria essentially live everywhere, in any type of environment
cold, hot
dry, wet
acidic, neutral, basic
w/out light
w/out O2
Bacteria's main form of reproduction is binary fission
One original cell splits into two
This can occur in as little as 20 minutes
Limiting factors like overcrowding, waste and food
- food availability do not allow population to grow this
Produces colonies of bacteria that are genetically identical
Binary Fission Microviewer activity.
Binary Fission
Is cell division the same as reproduction?
Slide 4
Has the nucleus become larger or smaller since division began?
Slide 5
Do you see any evidence that the cytoplasm is getting ready to divide?
Slide 6
Can you describe what is happening to this part of the cell?
Slide 7
Can you explain why in this case cell division accomplished reproduction?
Slide 8
Draw the correct sequence of binary fission using the culture of dividing paramecia.
Assume you started with one paramecium which divided three times daily. If you gave it the best conditions, and
none of the offspring died, how many paramecia would there be in the culture at the end of a week?
To increase genetic diversity, bacteria undergo transformation, conjugation, or transduction
Transformation: bacteria pick up stray DNA from their surroundings
Conjugation: two bacterial cells join to exchange genetic material (plasmids, separate
from main DNA)
Transduction: viruses that infect bacteria transmit genetic material from another source
Conjugation Microviewer Activity!
Slide 2
How did the peculiar looking structure in the middle of the slide develop?
Why is sexual reproduction in the mold called conjugation rather than fertilization?
Slide 5
Can conjugation help explain the frequent appearance of new strains of disease germs which never existed before?
What additional form of reproduction is indicated by the furrow at F?
Slide 7
What difference in activity distinguishes the male and female gametes?
Slide 8
Which filament of cells was male? Which was female? What evidence can you present?
Can you find evidence that all cells of one filament are of the same sex? How do you explain this fact?
Endospores form when environmental conditions make normal functions too difficult
A small amount of cytoplasm and DNA form a tough capsule
Very difficult to get rid of or control bacteria growth
eg. Antiseptics – used on living tissue
Disinfectants – used on surfaces
Antibiotics – taken internally
To Prepare Agar for Bacteria Lab
1) Weigh 2.3 g of nutrient agar
2) Measure 100 mL of water in a clean beaker.
3) Add agar and heat solution.
4) Stir continuously.
Groups of 3
bacteria - YouTube.flv
Bacterial Conjugation - YouTube.flv