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NOTES: 20.2 (& 20.3)
How are Bacteria Different
from Viruses?
 Bacteria are different from viruses in that they:
-are much bigger
-have a different structure (made of cells) 
therefore are considered “LIVING”
-can reproduce (unlike viruses, which require a
host cell)
 Bacteria are PROKARYOTES (no nucleus)
 Bacteria have 2 Kingdoms:
Kingdom Archaebacteria and Eubacteria
Some bacteria you
are probably
familiar with…
Bacteria…
 are unicellular
 are prokaryotes
 have ribosomes
 have genes (typically in a single circular
chromosome)
 often have a cell wall (protection)
**many antibacterial drugs target the
cell wall
The Size of Bacteria
 Prokaryotes typically range in size from
1-5 μm (micrometers)
The Structure of Bacteria
 3 basic shapes: rod-shaped,
spherical, spiral
 they may form long chains, large
clumps / clusters, or colonies
 movement: propelled by flagella
or cilia
“Breathing” (RESPIRATION) in Bacteria
 some are aerobic: respiration requires oxygen
-obligate aerobes - cannot survive without oxygen
EX: Mycobacterium tuberculosis (TB)
 some are anaerobic: respiration without oxygen
-obligate anaerobes - cannot survive with
oxygen
EX: Treponema pallidum (syphilis)
How Do Bacteria Obtain Energy?
 some make their own food (like plants) =
AUTOTROPHS
 some obtain their food (like us) =
HETEROTROPHS
These bacteria eat the
nutrients in the agar.
Reproduction in Bacteria
 most reproduce through
BINARY FISSION (asexual) =
offspring are clones
 other bacteria exchange genetic information
through CONJUGATION (a.k.a. bacteria
“sex”)
-a hollow bridge forms between the 2
bacterial cells and genes move from 1
bacterium to the other
-ADVANTAGE: increases genetic diversity
in the bacterial population
 if food and space are not an issue, bacteria divide at
astonishing rates!
 some can divide every 20 minutes!!
 if this were to continue to happen, the bacteria would
reach a mass of 4000x the mass of the Earth in 48
hours!
EXPONENTIAL GROWTH!!!
How Bacteria Can Be Controlled:
 STERILIZATION:
-heating / boiling OR use a disinfectant
(i.e. alcohol, bleach)
 FOOD PROCESSING:
-boiling, frying, steaming, refrigeration, salt,
vinegar
As labeled by
humans, there are
both “BAD”
bacteria and
“GOOD” bacteria.
 Bacteria that cause illness and
disease (PATHOGENIC)
 Bacterial diseases:
-diptheria, tuberculosis, typhoid fever, tetanus,
syphilis, cholera, bubonic plague
 How are the diseases caused?
-bacteria damage the cells & tissues of an organism
directly by breaking down the tissues for food
-OR…bacteria release toxins (poisons) that travel
through the organism’s body
WARNING:
Disturbing Picture!!
Ocean warning!
Flesh-eating bacteria
Diseases caused by bacteria:
Disease
Transmission
Symptoms
Tuberculosis
Inhale
Fatigue, cough, antibiotics
fever, chest pain
Tetanus
Puncture
wound
Stiff jaw, muscle Clean wound,
spasms,
antibiotics,
paralysis
antitoxin
Strep throat
Inhale or
ingest through
mouth
Fever, sore
throat, swollen
gland
Antibiotic
Lyme disease
Bite of infected Rash at site of
tick
bite, chills,
aches
Antibiotic
Cholera
Contaminated
water
Antibiotics,
replace fluids
Diarrhea,
vomiting,
dehydration
Treatment
 Since 1900, the life expectancy in the U.S.
has increased from 47 years to 75
years…WHY???
 better public health
 improved water / sewage treatment
 nutrition, medical care
 ANTIBIOTICS
• bacteria that humans use and need in
their everyday lives.
Escherichia coli (Esh-er-ish-eah coal-eye): one of many kinds
of microbes that live in your gut.
Wanted for helping you digest
your food every day.
Lactobacillus acidophilus (lacktoe-bah-sill-us acid-off-ill-us): one
of the bacteria gang wanted for
turning milk into yogurt.
Saccharomyces
cerevisiae (sack-arrowmy-seas sair-uh-vis-eeay): a.k.a. baker's yeast.
Wanted for making bread
rise.
Pseudomonas putida
(sue-doe-moan-us pootea-dah): one of many
microbes wanted for
cleaning wastes from
sewage water at water
treatment plants.
Streptomyces
(strep-toe-myseas): soil bacteria
wanted for making
streptomycin, an
antibiotic used to
treat infections.
Arbuscular
mycorrhizas (ar-busque-ler my-kuh-ryezuh): one of a soilliving fungus family.
Wanted for helping
crops take up
nutrients from the soil.
Bacillus thuringiensis (bahsill-us ther-in-gee-in-sis): a.k.a
"Bt", a common soil bacterium.
Wanted as a natural pest-killer
in gardens and on crops.
Good Bacteria in Summary:
1) Nitrogen Fixation
 most organisms need
nitrogen for DNA, RNA,
proteins, and ATP
 few organisms can
convert nitrogen gas into
useable nitrogen so they
need the help of bacteria that
live in the roots of legumes
(beans, peas, etc…)
Good Bacteria in Summary:
2) Recycling of Nutrients
 decomposing bacteria break down dead
organisms and wastes, returning nutrients
to the environment
Good Bacteria in Summary:
3) Foods and Medicines
 EX: Swiss cheese, pickles, yogurt
 EX: antibiotics that destroy other
types of bacteria (streptomycin,
erythromycin, etc.)
Antibiotics
How Do You Treat a
Bacterial Infection?
 if prevention fails, take ANTIBIOTICS
 antibiotics kill bacteria without harming the
cells of humans or animals
-they interfere with the cellular processes of
bacteria (e.g. stop cell wall synthesis)
 many antibiotics are produced naturally by
living organisms
-ex: penicillin
 others are synthetic (man-made)