Wednesday, October 19, 2011

Wednesday, October 19, 2011

Today in class:

- Passed back the Understanding Bacteria worksheet

- Did two labs on pgs. 19-25

- The first one was How Common Are Bacteria and How Quickly Do They Reproduce?

- The second one was Using Antibiotics to Stop Bacterial Growth

- In this experiment we’re using the bacteria Bacillus subtilis.

- Then we took notes on Prokaryotes and bacterial cell and reproduction (pgs. 8-11)


- You can start answering the analysis questions on pg.21 and 25. For some of these questions, you don’t need to know the results of the experiment in order to answer them.

- Read and highlight key points on Unit Packet p.27-29

- Fill in Unit Packet p. 31-32 (use text/internet)- DUE FRIDAY 10/21

-Work on disease project due Monday 10/31

-Work on Spice Lab due by 10/25


- You need a sterile petri dish w/agar, a wax glass marking pencil and tape.

- First divide your petri dish into quarters and mark the outside bottom surface and number the sections 1-4.

- Next, select 3 objects to test for the presence of bacteria. Each object or surface selected is to be touched to its own numbered quarter of agar. Objects can we lightly and directly touched onto the agar and then removed. Surfaces can be tested by rubbing a sterile cotton swab across one of the agar quarters. Use a new swab for each surface tested.

- Cover of the dish should only be partly raised when samples are being applied to the agar.

- Leave one section unexposed, so this will be your control.

- Then record the type of surface or object exposed to each section of the agar.

- Put your name at the bottom and tape the petri dish shut to prevent contamination.

- Place the dish upside down in an incubator at 37 degrees Celsius and wait 24 to 48 hrs until you remove the petri dish.

Side notes

- The agar looks yellowish

- Label sections on agar side

- Number the quadrants in a small font, so you can see the result later on.

2nd LAB

- You need prepared nutrient agar sterile Petri dishes, sterile cotton swabs, tweezers, antibiotic disks- 3 different kinds, wax marking pencil, broth culture of bacteria (Bacillus subtilis), sterile paper disk and an incubator.

- Get a sterile Petri dish w/nutrient agar and label the top w/your intials.

- Use a cotton swab dipped in the bacteria broth to cover the entire surface of agar in the Petri dish. (use a back and forth motion to guarantee the entire surface was covered w/ the broth culture

- Divide the dish into four quarters w/ a wax pencil and label them 1-4.

- Add a sterile plain paper disk in the remaining quarter to serve as a control.

- Incubate the dish for 24-48 hrs. at 37 degrees Celsius. If the antibiotics are affective against the bacteria, there will be a clear zone around the disk.

Class Notes


- Evolved and lived all alone on Earth for 2 billion yrs.

- Found where ever there is life and outnumber all eukaryotes combined

- Inhabit soil, skin, and human mouths or habitats that are too cold, too hot, too salty, to acidic, or too alkaline for any eukaryote.

Ex,) black plague, tuberculosis, food poisoning all caused by bacteria

- MOST bacteria are beneficial or benign

6 Kingdom Classification Scheme:


  1. Archea
  2. Bacteria
  3. Protist
  4. Plantae
  5. Fungi Soil Bacteria
  6. Animalia

Prokaryotes lack membrane-enclosed nucleus and numerous other membrane-enclosed organelles.

Two main Branches of Prokaryotes:

1. Archaea (ancient)

- Originate from Earth’s earliest cells

- Most inhabit extreme enviroments Ex.) Thermophiles- heat lovers, Methanogens- give off methane gas and aid in digestion

2. Bacteria

- Causes human diseases

Typical Bacteria Cell

- Absense of nucleus

- Most have cell walls exterior to plasma membrance

- Absense of membrane-enclosed organelles

- About 50% are motile

Shapes of Bacteria: helps to identify prokaryotes

Cocci – spheres Greek for “berries” (sing. Coccus)

Bacilli- rod-shaped (sing. Bacillus)

Spirochete – spiral-shaped (sometimes called spirillum)

Bacterial Reproduction

- Can reproduce at a phenomenal rate if conditions are favorable

- The cells divide by a process called binary fission (copying DNA and then dividing)

- In 24 hrs on cell could create a colony equivalent in mass to 15000 humans.

Bacterial Nourishment: obtaining energy and carbon

Prokaryotic evolution “invented” every type of nutrition we observe in all living organisms, plus some modes unique to prokaryotes.

See you tomorroww! ~ Nazia

Next Scribe: *****HELEN*****

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