General Introduction to Bacteria With Special Thanks to Megan
Rokop and Ms. Boehm
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Fun Facts about Bacteria Necessary to make many everyday foods
including yogurt, cheese, sauerkraut, soy sauce, vinegar Used to
clean up various forms of pollution including oil spills,
pesticides, sewage Produce antibiotics that we can use to the fight
bacteria that make us sick Produce Botox so we can all have
wrinkle-free foreheads Fun Fact: Bacteria comprise about 1/20 th of
your total body weight!
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Bacteria are the most abundant organisms on earth.
Classification of Bacteria
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The domain Bacteria is often referred to as eubacteria The most
common type of bacteria found on earth Examples: Streptococcus,
Escherichia coli, Clostridium botulinum, Salmonella The domain
Archaea are prokaryotic like bacteria but are not bacteria Archaea
are thought to resemble the very first cells on earth Some live in
extreme conditions such as the halophiles (salt lovers) in Utahs
Great Salt Lake May be at least as closely related to eukaryotes as
they are to bacteria
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Identification of Bacteria
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Bacteria have three basic shapes. These images are magnified by
more than 10,000 times! They are all surrounded by some type of
cell wall Sphere shaped: coccus Rod shaped: bacillus Spiral shaped:
spirochete Bacterial Shapes
Peptidoglycan Plasma Membrane Gram-Negative Gram-Positive
Plasma Membrane Peptidoglycan Outer Membrane Holds Purple Dye Will
Not Hold Purple Dye DNA Cell Wall Structure
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The Genetics of Bacteria
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The main DNA is a long circular loop, one single chromosome,
not contained within a nucleus Many bacteria also contain plasmids,
a smaller loop of DNA It is the plasmid that allows these asexual
organisms to have variation, and can also make the bacteria
pathogenic! Bacteria Are Prokaryotic
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Bacterial Conjugation Often it is the plasmid that contains
genes that are pathogenic to humans!
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Bacterial Growth and Division
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Most bacteria divide every 20 minutes They will form bacterial
colonies Bacteria divide by a process called prokaryotic fission
The product from one bacterium dividing would be two genetically
identical daughter cells
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Good vs. Bad Bacteria There are many different kinds of
bacteria, most of which will not make you sick and may actually
help you: Staphylococcus epidermidis lives harmlessly on your skin
Escherichia play a nutritional role in the intestinal tract by
synthesizing vitamins, especially vitamin K. Neisseria subflava
lives harmlessly in most peoples mouths Fun Fact: The human body
contains 20 times more microbes than it does cells! But, there are
also some that can make you sick
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Strep Throat - Streptococcus pyogenes Ear Infections -
Streptococcus pneumonia, Haemophilus influenzae, Moraxella
catarrhalis Meningitis Neisseria meningitidis, Haemophilus
influenzae Tuberculosis Mycobacterium avium, M. tuberculosis
Gonorrhea Neisseria gonorrhoeae Syphilis Treponema pallidum
Bacteria Can Cause Many Different Illnesses
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Food Microbiology Delicious or Dangerous?
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Food Microbiology Microorganisms are a part of the food we eat
every day, specifically bacteria Most of these bacteria are
harmless, non-pathogenic BUT some of these bacteria are harmful to
us, pathogenic Is the food delicious or dangerous????
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Delicious Food Microbiology Yogurt has bacteria added to it
that give it a slightly sour taste active yogurt cultures
Lactobacillus bulgaricus and Bifidobacteria Cheeses can be
fermented with various bacteria Swiss cheese -Propionibacterium
Blue cheese -Penicillium roqueforti and Lactobacillus Finally, many
pickled vegetables get their flavor from bacteria Sauerkraut
Leuconostoc and Lactobacillus Pickles Lactic acid bacteria
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Dangerous Food Microbiology Contaminated Food Can Make You Sick
Escherichia coli O157:H7 *Source: spinach, ground beef, frozen
pizza * *Symptoms: vomiting, diarrhea (often bloody) Clostridium
botulinum -botulism *Source: soil, water, non-acid canned foods
*Symptoms: flaccid paralysis and possible death (or a smooth face )
Salmonella typhimurium salmonella *Source: eggs, chicken meat,
dairy products *Symptoms: headache, chills, vomiting, diarrhea
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Facts about Foodborne Illness The CDC estimates that 76 million
people get sick, more than 300,000 are hospitalized, and 5,000
Americans die each year from foodborne illness. Uncooked foods are
the largest source of foodborne illness in the US (raw meat,
uncooked eggs, raw vegetables, etc.)
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Case Study Outbreak of E. coli in Spinach, 2006
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What happened? There are rare cases of E. coli 0157:H7
contamination each year In late August of 2006, the CDC noticed a
dramatic spike in cases The hypothesis was that this was a
foodborne illness, but the source was unknown
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Who was affected? E. coli O157:H7 outbreak resulted in 205
confirmed illnesses and three deaths The contaminated spinach was
found in 26 states.
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Source traced to spinach The CDC narrowed the source down to
fresh spinach coming from an isolated farm in southern California
Normally fresh vegetables do not harbor pathogenic bacteria The
CDC, in September 2006, reported an apparent outbreak of E. coli
O157:H7 linked to the consumption of bagged spinach
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How did the spinach get contaminated? Environmental risk
factors for E. coli O157:H7 contamination at or near the spinach
field: the presence of wild pigs in the proximity of irrigation
wells used to grow produce for ready-to- eat packaging surface
waterways exposed to feces from cattle and wildlife The strain of
E. coli is normally found in the intestinal tract of cows, pigs and
deer.
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How did the CDC identify E. coli 0157:H7? The CDC cultured the
bacteria from the spinach and placed it on a food source E. coli
likes to eat, such as EMB (eosin methylene blue) agar E. coli grows
pink colonies on EMB agar No other bacteria will grow pink on this
media. The CDC was able to distinguish the E. coli 0157:H7 strain
from other E. coli strains by doing gel electrophoresis of the DNA.
The genetic fingerprint will be different- do you know why?
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How could our class identify E. coli? 3 methods of potential
identification methods: 1.Look at shape under the microscope 2.Gram
staining 3.EMB agar 1.2. 3.
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Symptoms of E. coli 0157:H7 infection Type of enterohemorrhagic
Escherichia coli (EHEC) Hemorrhagic (bloody) diarrhea Abdominal
pain Kidney failure
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How does E. coli 0157:H7 make you sick? E. coli 0157:H7
produces a toxin, verotoxin, similar to a shiga toxin Verotoxin
invades the cells of the intestine and inhibits protein synthesis
Inhibition of protein synthesis = cell death
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How can we avoid getting sick? Cook the food E. coli 0157:H7
(on spinach) can be killed by cooking at 160 F for 15 seconds Cook
meat until grey/brown in color and juices run clear to kill
bacteria
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How can food contamination be prevented pre-consumer?
Irradiation is one possible solution Process of irradiating foods
with ionizing radiation (gamma rays or high energy electrons) to
destroy microorganisms contaminating the food According to CDC,
irradiation does NOT change nutritional value, composition of the
food, or make the food dangerous Cool fact: astronauts eat
irradiated food in space!
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Summary Bacteria are the most abundant organisms on earth Some
bacteria never cause us harm and can be helpful to us
(non-pathogenic) Some bacteria are harmful to us (pathogenic)
Toxins produced by bacteria can damage our cells Outbreak of E.
coli 0157:H7 in spinach Contamination and infection can be
prevented by a variety of methods Cooking you can do at home
Irradiation can be done by producers