Biology 11 - Part C Forero
Name: ______________________________ Date: ___________ Blk: _____
NOTES: BACTERIA
I. Prokaryotic Cells
Eukaryote vs. Prokaryote (review!):
II. The Three Domains
Biology 11 - Part C Forero
III. Archaea Classification
- All members of the domain Archaea are anaerobic
PHYLUM
1. Euryarchaeota
Characteristics
- methanogens (produce methane)
- thermophiles (high temperatures)
- halophiles (high salt)
2. Crenarchaeota
- thermophilic
- sulfur dependent
3. Korarchaeota
- high temperature hydrothermal environments
4. Nanoarchaeota
- one of the smallest organisms in the world
(contains one species)
- thermophilic
- parasitic
IV. Bacterial Classification
PHYLUM
1. Proteobacteria
Characteristics
- pathogenic parasites
(gram-negative)
- free-living nitrogen fixation
2. Chlamydiae
(gram-negative)
3. Spirochetes
- obligate intracellular pathogens
(gram-negative)
- long, corkscrew-shaped cells
4. Cyanobacteria
- photosynthetic
(gram-negative)
- blue-green bacteria
5. Gram-Positive Bacteria
- positive result in gram stain test (purple)
Example
Escherichia coli
Chlamydia trachomatis
- double membrane
Treponema pallidum
Tolypothrix sp.
- absence of outer membrane
- more susceptible to antibiotics
Bacillus anthracis
Biology 11 - Part C Forero
V. Gram Staining
- Gram-positive bacteria take up the crystal violet stain used in the test, and then appear
to be purple-coloured when seen through a microscope.
- This is because the thick peptidoglycan layer in the bacterial cell wall retains the stain
after it is washed away from the rest of the sample, in the decolorization stage of the test.
- Gram-negative bacteria cannot retain the violet stain after the decolorization step;
alcohol used in this stage degrades the outer membrane of gram-negative cells making
the cell wall more porous and incapable of retaining the crystal violet stain.
- Their peptidoglycan layer is much thinner and sandwiched between an inner cell
membrane and a bacterial outer membrane, causing them to take up the counterstain
(safranin or fuchsine) and appear red or pink.
VI. Cell Shape and Grouping
Biology 11 - Part C Forero
VII. Motility
- Flagella: Most motile bacteria move by the use of flagella (singular, flagellum), rigid
structures 20 nm in diameter and 15-20 µm long, which protrude from the cell surface
- E.g. Salmonella
- Spiraling: Spirochetes have a specialized internal structure known as the axial filament,
which is responsible for rotation of the cell in a spiral fashion and consequent locomotion
- E.g. Lyme disease
- Gliding: Gliding bacteria all secrete copious slime, but the mechanism that propels the
cells is not known
- E.g. Disease that affects poultry
VIII. Bacterial Reproduction
ASEXUAL REPRODUCTION
A. Binary Fission
1. Bacterial DNA replicates and cell increases in size.
2. A double wall develops across the midline of the
enlarged cell.
3. The cell separates into two cells at the midline wall.
4. Each cell is then able to function as a separate entity.
B. Budding
1. Bud forms at one end of the mother cell
2. As bud growth proceeds, the size of the mother cell
remains about constant
3. When the bud is about the same size as the mother cell,
it separates.
- Difference between fission and budding:
- daughter buds can have a flagellum for motility
- bud is separated from mother cell by a stalk
Biology 11 - Part C Forero
C. Sporulation: binary fission that is adapted for dispersal and for survival, often for
extended periods of time, in unfavorable conditions
1. Invagination of the cytoplasmic membrane
around a copy of the bacterial chromosome,
thus separating the contents of the smaller cell
from the mother cell.
2. Membrane of the mother cell engulfs the
smaller cell within its cytoplasm, effectively
providing two concentric unit membranes to
protect the spore.
3. Calcium is absorbed by the spore to get ride of water by diffusion.
4. A thin spore membrane and a thick cortex of a peptidoglycan are laid down
between the two unit membranes. A rigid spore coat forms outside the cortex,
enclosing the entire spore structure.
5. Mother cell dies and the mature spore is released into hostile environment. It is
inactive until nutrients become available.
SEXUAL REPRODUCTION
D. Gene transfer through conjugation
1. The plasmid in Species A integrates itself into the chromosome
2. Genes from the chromosome become part of the plasmid
3. The plasmid reverses out of the chromosome and replicates
4. Species A makes contact with Species B by creating a protein bridge (pilus)
5. The plasmid copy is transferred to Species B via the pilus.
6. Incoming plasmid integrates into chromosome of Species B
E. Plasmid transfer through conjugation
1. Plasmid in Species A replicates
2. Pilus is formed by Species A to connect to Species B
3. The copy of the plasmid is transferred through to
Species B via the pilus
4. Once inside the cell, it establishes itself in the new host
Benefits of Conjugation: increased genetic diversity, helps to ensure some bacteria
survive if environment changes
Biology 11 - Part C Forero
IX. Antimicrobial resistance
VIDEO: Antimicrobial Resistance (FDA)
http://www.youtube.com/watch?v=oll8PGmunR0
WHAT IS ANTIMICROBIAL RESISTANCE:
HOW DOES NATURAL SELECTION LEAD TO RESISTANT STRAINS?
MECHANISMS OF ANTIMICROBIAL RESISTANCE
1. MUTATION
2. DESTRUCTION OR INACTIVATION
3. EFFLUX
GENETIC TRASFER OF ANTIMOCROBIAL RESISTANCE
1. CONJUGATION
2. TRANSFORMATION
3. TRANSDUCTION
Biology 11 - Part C Forero
What are Antibiotics?
Antibiotics are drugs used to treat bacterial infections. They act specifically on bacteria, although
some are also able to kill parasites. Antibiotics are not effective against viruses or viral infections.
Bacteria are prokaryotic cells. They are regarded as much more basic and more primitive than
eukaryotic cells, which make up all higher plants and animals, including humans. Antibiotics act on
the cell machinery of bacterial cells, but have little effect on the internal workings of the human body
cells because antibiotics are specific for the systems that are exclusive to bacteria.
Unfortunately, this does not mean that antibiotics are without side effects – they can cause various
adverse reactions, usually in the way that they act on the commensal bacterial populations on the
skin, the body openings and in the digestive system. Antibiotics can disrupt the delicate balance of
friendly bacteria that normally keep us healthy.
Where Do Antibiotics Come From?
The early antibiotics were the natural products of other microorganisms – fungi or other bacteria.
Many of the antibiotics still in use today were originally natural products but all are manufactured
today either by chemical synthesis or bioengineering. Newer antibiotics have also been created
completely synthetically, usually by altering the chemical structure of an existing, naturally produced
antibiotic.
VIDEO DISCUSSION: The End of Antibiotics
http://www.youtube.com/watch?v=M6YqystsKb4
0:00 - 3:25
1. Why is antibiotic resistance a concern that is so much more pressing
today? (4 points of view)
a. Bacteria continue to develop resistance; we’ve stopped developing new
generations of drugs to keep up with them.
b. Big pharmaceutical companies have abandoned the field because they
don’t see enough economic return on their investments.
c. Doctors have patients for whom they only have one or two drugs that still
work. They have to calculate whether these drugs are toxic to their patients
or interact negatively with other drugs to an extent they never did before
because there isn’t a great variety of drugs.
Biology 11 - Part C Forero
d. Canada is in the same circumstance as the US because the world is very
small today. Antibiotic resistant organisms move with people and people
move all over the world, so illnesses like SARS can spread across the globe
within 24 hours.
3:25 - 7:00
2. Why are gram-negative bacteria like NDM1 more concerning than grampositive bacteria?
a. Greater number of gram-negative bacteria exist that we have no drugs for
b. Gram negative bacteria have an extra barrier outside their cell wall that
can make it difficult for the antibiotics to get inside the cell. More
importantly, they have larger genome that enables larger numbers of
resistance mechanisms. Thus, gram-negatives are becoming resistant to
everything. Unlike gram-positive, some species can’t be treated with any
available antibiotics.
c. Severe gram-negative and gram-positive infections (heart, lungs, etc.) are
treated with surgery. It is getting harder to develop chemicals deal with
gram-negatives because of that extra layer around their cell wall.
7:00 – 9:10
3. How do bacteria learn (adapt/evolve) their resistance to antibiotics?
a. Changing their genome quickly through mutations and fast generation
times.
b. Swapping DNA (What is this called?) through plasmids
c. Generation times are too fast to keep up with (10 years to get FDA
approval and costs a billion dollars US)
9:10 – 11:06
Biology 11 - Part C Forero
4. How does an infection with resistant bacteria (e.g. Cipro-resistant
Salmonella) manifest?
11:06 – 13:33
5. Where can you pick up these superbugs? How do they spread?
13:33 – 14:27
6. How different are the superbugs overseas than in our local hospitals?
14:27 – 15: 05
7. What is the trend seen in total numbers of approved antibacterials in the
US in the past few decades? Why is this significant?
15:05 – 19:25
Biology 11 - Part C Forero
8. Why are the pharmaceutical companies not keeping up with the everthreatening resistant strains? (4 issues)
19:25 – 21:35
9. What are the incentives for pharmaceutical companies to invest in
antibiotic development? (3 incentives)
…. Develop your own questions and answers for the rest of the sections in
the video on your own. Especially for that LAST question:
“WHAT HAPPENS WHEN WE’RE LEFT WITH NOTHING THAT
WORKS?”