Download Bacteria and Antibiotics

Mrs. Stewart
Medical Interventions
Central Magnet School

2.
Essential Questions:
How do bacterial cells gain resistance?
GRAM (-)
GRAM (+)

Thin layer of peptidoglycan

Thick layer of
peptidoglycan

Lipopolysaccharides
(endotoxins)

Stain blueish - purple

Stain red
Bacteria are stained with two stains:
1. Crystal Violet stain (blue/purple)
2. Fuchsin counterstain (red)
Gram –
Gram +

Blueish-purple

Red

Peptidoglycan layer
absorbs the crystal violet
stain

LPS cell wall prohibits
peptidoglycan layer from
absorbing crystal violet
stain (absorbs counter
stain)

What cellular components do some bacterial
cells have that make them powerful
pathogens? Explain.
GRAM -

2.
Essential Question:
How do bacterial cells gain resistance?

Antibiotics are drugs used to treat infections
caused by bacteria.

Antibiotic - A substance produced by or
derived from a microorganism and able in
dilute solution to inhibit or kill another
microorganism
History of Antibiotics
•1928- Alexander Fleming
•Accidentally discovered penicillin
•Left lab untidy for a month and went
on vacation
•Came back and found a fungus growing
in one of his bacterial cultures. Fungus
was inhibiting the bacteria.
•Fungus = penicillium notatum
•Later named: penicillin

Gangrene – wound
infections that lead
to many amputations
or sepsis

Sepsis – bacterial
infection in blood
stream – leads to
organ system failures

The early antibiotics = natural products of
other microorganisms (fungi or other
bacteria)

Now = created synthetically (chemically
altering existing natural products)

Depends on
the bacteria
Gram +
OR
 Gram 

Bactericidal – Kills the
bacteria

Bacteriostatic – inhibits
growth & reproduction
* The body’s natural defenses
can usually take it from there




Beta – Lactam
Fluoroquinolones
Tetracyclines
Sulfanomides

Disrupt the synthesis of peptidoglycan
thereby inhibiting cell wall synthesis &
damaging cell wall integrity

Broad spectrum (can work against + or -)

Bactericidal

Example: Penicillins

Why are penicillins often more effective
against gram positive than gram negative
bacteria?

Inhibit topoisomerase enzymes which
prohibit DNA replication and protein
synthesis

Broad spectrum – effective against + and -

Bind the 30s ribosomal subunit,
blocking the attachment of
tRNA, thereby inhibiting protein
synthesis

Broad spectrum – effective
against + and -

1st class of antibiotics ever used

Structurally similar to PABA – a substance that
the bacteria use to synthesize folate (folic acid)

Inhibits the synthesis of folic acid (Folate)

folate is necessary for DNA synthesis

No DNA synthesis (replication) = No cell division

Answer the following question in your journal.
What class of antibiotics would you prescribe
for Sue? Explain.

What class of antibiotics would you
prescribe for Sue? Explain.

With your lab groups, design an experiment
to test your hypothesis.

15 minutes

Bacterial
infections only

Antibiotics
target bacteria
and a few
parasites.

Most colds,
and sore
throats are
viral

They do not share the same structures

Viruses consist of a hereditary material (DNA
or RNA) surrounded by a protein coat or fatty
envelope.

They do not have any organelles – they hijack
host cells to produce more DNA/RNA or
proteins

2.
Essential Question:
How do bacterial cells gain resistance?
1.
How do antibiotics function without harming the
surrounding human cells?
2.
What cellular components do some bacterial cells
have that make them powerful pathogens?
3.
Why are penicillins more effective against Gram +
bacteria?
4.
Why is it important to understand the structure of
a bacterial cell when developing an antibiotic?
5.
Why are antibiotics NOT effective against viruses?

Streptococcus pneumoniae, commonly referred to as
pneumococcus, is a bacterium commonly found in the
back of the nose in healthy people. Occasionally,
pneumococcal bacteria spread to other parts of the body
and cause diseases such as ear infections, sinus infections,
pneumonia, and meningitis. Before the introduction of
penicillin in the early 1940s, a person might die from a
pneumococcal infection. After the introduction of
penicillin, pneumococcal infections were effectively
treated. However, strains of pneumococcal bacteria
resistant to penicillin were discovered in the 1960s. Since
then, new strains of pneumococcal bacteria resistant to
multiple antibiotics have been emerging.

Ear Infections

MRSA

TB – Tuberculosis

Strep throat

Antibiotic resistance has been called one of
the world’s most pressing public health
problems and is one of the Centers for
Disease Control’s top concerns.
Both the GOOD
AND BAD
bacteria in the
body are
attacked.

How does the Theory of Natural Selection
apply to the problem of antibiotic resistance
in bacterium?

Survival of the Fittest
 Those that survive the treatment (change in the
environment) must carry beneficial DNA that
provides resistance
 Eventually, entire population is resistant

How would a genetic mutation (variation) in
the bacteria’s DNA cause the cell to gain
resistance to an antibiotic?



DNA code is where biodiversity occurs
Changes in DNA code gives variety
That variance could be harmful or
beneficial in different environments
 Natural Selection = Survival of the Fittest
What makes bacteria unique?

Bacteria can share their DNA with other
bacteria

NO

That leads to
antibiotic resistance
due to overuse

There are more bacterial cells in/on your body
than there are human cells

Antibiotics will target all susceptible bacteria
– not just the spot of infection

All bacteria living within your body will either
die (susceptible) or will live (resistant)
 Survival of the fittest

Antibiotic resistance does not stop with one
colony of bacteria

Bacterial cells can share the DNA that gives
them resistance.

Animation of bacterial resistance
 Take notes on the sheet provided

You and your lab group will create a 3D model
of one of the mechanisms bacterial cells use
to either gain antibiotic resistance OR to
share antibiotic resistance.

You will present these to the class next block
day

How does a bacterium’s ability to share genes
intensify the problem of antibiotic resistance?

TED talk

Hunting the Nightmare Bacteria