Bacteria
and
Humans
Bacteria and Disease
Pathology
= study
of disease
Pathogens
= bacteria
that cause
disease
Bacteria grow best with
warmth,
darkness, and moisture.
Toxins
are
poisons
produced by bacteria
Exotoxins
= toxins that are made of protein
-
excreted by bacteria
Produced by G+ bacteria
*
Steadily secreted into the environment
Example
-
tetanus
can
cause tissue death
-
gas
gangrene
Endotoxins
Made of lipids and carbohydrates found on
the
outer membrane of G
-
bacteria
Example
-
E. coli
*
Only released when bacteria is dead
Cause fever, body aches and weakness
-
damage vessels of circulatory system
Body tissue destruction
Adhere to cells, secrete digestive enzymes
and allow tissue invasion and destruction
Example
-
Streptococci
produce blood
-
clot
dissolving enzymes that spread to other
tissues
Impetigo
infection
Bacterial
Diseases
Which of the above are transmitted by
vectors
?
Antibiotics
**Combat
bacteria by
interfering with
various cellular
functions
Many are derived
from chemicals
that bacteria and
fungi produce
(
penicillin
)
Types of Antibiotics
Penicillin, Ampicillin
= interferes with cell
-
wall
synthesis
Tetracycline
= interferes with bacterial protein
synthesis
Sulfa
drugs
= inhibit cell metabolism
Broad
-
spectrum
antibiotics
= affect many
types of bacteria
Testing Bacteria for Antibiotic Sensitivity
Bacteria are grown in an
agar nutrient gel
covering the bottom of Petri dishes.
A paper disc with an antibiotic is placed on the agar gel.
The
clear area
around the disc shows the area that bacteria have been killed.
The larger the clear area, the more effective the antibiotic
.
Zone of dead
Bacterial
inhibition
Antibiotic Resistance
“
Natural Selection
in Action”
1. Population of bacteria is exposed to
antibiotic.
2. Most susceptible bacteria die.
3. A few mutant (naturally immune) bacteria
survive.
4. Mutant bacteria reproduce and recombine.
5. New population is resistant
Mechanisms of antibiotic resistance
Some bacteria block passage of antibiotic
into cell
Some secrete enzymes that destroy or alter
antibiotic (penicillin resistant bacteria)
Major Reason for Resistance
Overuse of antibiotics
result in many
diseases being more difficult to treat
.
Because there are slight variations in
each species of bacteria, some are
effectively killed while others remain to
reproduce.
Look up “
Flesh eating bacteria
” to see effects
of bacterial resistance to antibiotics.
Useful bacteria
Break down sewage
Recycle dead organisms (composting)
Carbon
fixation
Nitrogen fixation
Oxygen release (photosynthesis}
Food processing
-
milk products
-
buttermilk, sour cream, yogurt
Cheeses
-
ricotta, cottage cheese
Sauerkraut,
pickles,
kimchi
Fiber retting (separating plant fibers for rope)
Produce chemicals and fuels
Insecticides, clean up oil spills
Genetic research
Genetic Engineering
Assignments
Study Guide 18
-
6
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