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Microorganisms – Protists,
Bacteria and Viruses
Protists are eukaryotic – Which means they
are cells with a nucleus.
They can be unicellular or multicellular
They can be animal-like, fungus-like or
Some protists:
amoeba ingesting a
information on
Giardiasis (GEE-are-DYE-uhsis) is a diarrheal illness
caused by a one-celled,
microscopic parasite, Giardia
intestinalis (also known as
Giardia lamblia). Once an
animal or person has been
infected with Giardia
intestinalis, the parasite lives
in the intestine and is passed
in the stool. The Giardia
parasite lives in the intestine
of infected humans or animals.
Millions of germs can be
released in a bowel movement
from an infected human or
animal. Giardia is found in
soil, food, water, or surfaces
that have been contaminated
with the feces from infected
humans or animals. You can
become infected after
accidentally swallowing the
Plasmodium develops in the gut of
the mosquito and is passed on in the
saliva of an infected insect each time
it takes a new blood meal. The
parasites are then carried by the
blood in the victim's liver where they
invade the cells and multiply.
Malaria is caused by protozoan
parasites of the genus Plasmodium.
Malaria is currently endemic in 91
countries with small pockets of
transmission occurring in a further
eight countries. Plasmodium
falciparum is the predominant
parasite. More than 120 million
clinical cases and over 1 million
deaths occur in the world each
disappear in phases and may come
and go at various time frames. These
cyclic symptoms of malaria are
caused by the life cycle of the
parasites - as they develop, mature,
reproduce and are once again
released into the blood stream to
infect even more blood and liver
When this happens a high swinging
fever can develop, with marked
shivering and intense perspiration.
involving the kidneys and brain can
then develop leading to delirium
and coma.
Bacteria are prokaryotic cells.
This means, they do NOT contain a
They have a Cell Wall and a Cell
Their genetic material (DNA) simply
floats around in the cytoplasm.
Many have flagella for locomotion.
The structure of a bacterium
e-class on bacteria
Spherical Bacteria - Cocci
Rod-Shaped Bacteria – Bacilli
(eg. E-coli)
Spirial Shaped Bacteria - Spirilla
Helpful Bacteria on/in our bodies
It has been calculated that the normal
human houses about 1012 bacteria on
the skin, 1010 in the mouth, and 1014
in the gastrointestinal tract. This
number is much greater than the
number of our own cells in the human
1014 = 100 000 000 000 000
Some bacteria are necessary for our
survival. For example in the intestine we
have Lactobacillus acidophilus (the most
famous), Lactobacillus bifidus (more
common to the baby colon), and
Streptococcus faecium. Bacteria help
extract water from the feces and
produce Vitamin K in our large intestine
Harmful (Pathogenic) Bacteria
What is E. coli O157:H7?
Escherichia coli (E. coli) is a bacterium that is
commonly present in the intestines of humans and
What makes E. coli O157:H7 so dangerous?
Most strains of E. coli are harmless, the exception
being the strain O157:H7 that causes severe
diarrhea leading to renal (kidney) damage and
other serious complications including death.
E. coli O157: H7 also has the ability to cause
disease at a very low dose, survive at low
temperatures and under acidic conditions.
Who is more susceptible to infection from E. coli
People of all age groups are susceptible to these
bacteria; however immunocompromised, elderly and
young children are at a higher risk.
What diseases are caused by E. O157:H7?
Infection with Escherichia coli O157:H7 can range
from being asymptomatic to having mild to severe
gastrointestinal symptoms. These symptoms
manifest as abdominal cramping, bloody or
nonbloody diarrhea. In an uncomplicated case, the
illness should recover in less than 5-10 days.
Complications: Hemolytic uremic syndrome (HUS) is one of
the complications following E. coli O157:H7 infection
especially in children below the age of 5. HUS is one of
the most common causes of acute renal failure in children.
Hemolytic uremic syndrome is characterized by acute renal
failure, and a type of anemia and fever. One-third of the
children diagnosed with HUS do not recover completely and
will eventually need a dialysis.
The disease causing pathogen can be transmitted
a) Eating uncooked/ undercooked ground beef
b) Consumption of contaminated sprouts, lettuce,
salami, unpasteurized milk
c) Swimming in or drinking sewage contaminated
d) Feco-oral transmission through an infected
person to a healthy individual due to unhygienic
spinach warning Sept 2006
latest tainted spinach linked to pigs
In May 2000, seven residents of Walkerton died
after drinking water contaminated with E.coli,
and in April 2001, nearly 6,000 people in North
Battleford became ill after drinking water
contaminated with the Cryptosporidium parvum
In May 2000, bacteria seeped into Walkerton's town
well. The deadly E. coli then slipped quietly through a
maze of pipes and into the homes of Walkerton, Ont.
Unsuspecting residents thirstily drank the polluted water
and bathed in their bacteria-ridden tubs. But soon after,
they began experiencing common symptoms of infection;
bloody diarrhea and throbbing cramps. Seven people would
eventually die and another 1286 would fall ill. The
investigation which followed exposed an alarmingly
unstable waterworks system made fragile by government
A few diseases in humans caused by bacteria:
cholera, diphtheria, leprosy, plague, pneumonia,
strep throat, tetanus, tuberculosis, and typhoid
Antibiotics are used to kill harmful
bacteria, but have the side-effect of also
killing useful bacteria. Also, the over-use
of antibiotics can lead to resistant strains
of bacteria that are hard to fight.
The CDC estimates that each year, nearly 2 million people
in the United States acquire an infection while in a
hospital, resulting in 90,000 deaths. More than 70
percent of the bacteria that cause these infections are
resistant to at least one of the antibiotics commonly used
to treat them.
Some Other Harmful Bacteria
Salmonella enteritidis bacterium
A person infected with the Salmonella
enteritidis bacterium usually has fever,
abdominal cramps, and diarrhea beginning 12
to 72 hours after consuming a contaminated
food or beverage.
The illness usually lasts 4 to 7 days, and most persons recover
without antibiotic treatment. However, the diarrhea can be
severe, and the person may be ill enough to require
The elderly, infants, and those with impaired immune systems
may have a more severe illness. In these patients, the infection
may spread from the intestines to the blood stream, and then to
other body sites and can cause death unless the person is treated
promptly with antibiotics. It can be found in Raw meats, poultry,
eggs, milk and dairy products, fish, shrimp, frog legs, yeast,
coconut, sauces and salad dressing, cake mixes, cream-filled
desserts and toppings, dried gelatin, peanut butter, cocoa, and
Clostridium botulinum is the name of a group
of bacteria commonly found in soil. These
rod-shaped organisms grow best in low
oxygen conditions. The bacteria form spores
which allow them to survive in a dormant
state until exposed to conditions that can
support their growth.
Botulism is a rare but serious paralytic illness caused by a nerve toxin that is
produced by the bacterium Clostridium botulinum.
three main kinds of botulism:
Foodborne botulism is caused by eating foods that contain the botulism toxin.
Wound botulism is caused by toxin produced from a wound infected with
Clostridium botulinum.
Infant botulism is caused by consuming the spores of the botulinum bacteria,
which then grow in the intestines and release toxin.
All forms of botulism can be fatal and are considered medical emergencies.
Foodborne botulism can be especially dangerous because many people can be
poisoned by eating a contaminated food.
The respiratory failure and paralysis that occur with severe botulism
may require a patient to be on a breathing machine (ventilator) for
weeks, plus intensive medical and nursing care. After several weeks,
the paralysis slowly improves. If diagnosed early, foodborne and wound
botulism can be treated with an antitoxin which blocks the action of
toxin circulating in the blood. This can prevent patients from
worsening, but recovery still takes many weeks. Physicians may try to
remove contaminated food still in the gut by inducing vomiting or by
using enemas. Wounds should be treated, usually surgically, to remove
the source of the toxin-producing bacteria. Good supportive care in a
hospital is the mainstay of therapy for all forms of botulism. Botulism
can result in death due to respiratory failure. However, in the past 50
years the proportion of patients with botulism who die has fallen from
about 50% to 8%. A patient with severe botulism may require a
breathing machine as well as intensive medical and nursing care for
several months. Patients who survive an episode of botulism poisoning
may have fatigue and shortness of breath for years and long-term
therapy may be needed to aid recovery.
Foodborne botulism has often been from home-canned foods with low acid
content, such as asparagus, green beans, beets and corn. However, outbreaks
of botulism from more unusual sources such as chopped garlic in oil, chile
peppers, tomatoes, improperly handled baked potatoes wrapped in aluminum
foil, and home-canned or fermented fish. Persons who do home canning should
follow strict hygienic procedures to reduce contamination of foods. Oils infused
with garlic or herbs should be refrigerated. Potatoes which have been baked
while wrapped in aluminum foil should be kept hot until served or refrigerated.
Because the botulism toxin is destroyed by high temperatures, persons who eat
home-canned foods should consider boiling the food for 10 minutes before
eating it to ensure safety.
Wound botulism can be prevented by promptly seeking medical care for
infected wounds and by not using injectable street drugs.
Bacillus anthracis
(Anthrax bacillus)
Anthrax is an acute infectious disease caused by the spore-forming
bacterium Bacillus anthracis. Anthrax most commonly occurs in wild and
domestic lower vertebrates (cattle, sheep, goats, camels, antelopes, and
other herbivores), but it can also occur in humans when they are exposed
to infected animals or tissue from infected animals.
Anthrax is most common in agricultural regions where it occurs in animals.
These include South and Central America, Southern and Eastern Europe,
Asia, Africa, the Caribbean, and the Middle East. When anthrax affects
humans, it is usually due to an occupational exposure to infected animals or
their products. Workers who are exposed to dead animals and animal
products from other countries where anthrax is more common may become
infected. Humans can become infected with anthrax by handling products
from infected animals or by inhaling anthrax spores from contaminated
animal products. Anthrax can also be spread by eating undercooked meat
from infected animals. It is rare to find infected animals in the United
States or Canada.
Most (about 95%) anthrax infections occur when the bacterium enters a cut
or abrasion on the skin, such as when handling contaminated wool, hides,
leather or hair products (especially goat hair) of infected animals.
Inhalation anthrax is usually fatal. MORE
In the early 1330s an outbreak of deadly bubonic plague occurred in China.
The bubonic plague mainly affects rodents, but fleas can transmit the disease
to people. Once people are infected, they infect others very rapidly. Plague
causes fever and a painful swelling of the lymph glands called buboes, which is
how it gets its name. The disease also causes spots on the skin that are red
at first and then turn black.
Since China was one of the busiest of the world's trading nations, it was only
a matter of time before the outbreak of plague in China spread to western
Asia and Europe. In October of 1347, several Italian merchant ships returned
from a trip to the Black Sea, one of the key links in trade with China. When
the ships docked in Sicily, many of those on board were already dying of
plague. Within days the disease spread to the city and the surrounding
countryside. An eyewitness tells what happened:
"Realizing what a deadly disaster had come to them, the people quickly drove
the Italians from their city. But the disease remained, and soon death was
everywhere. Fathers abandoned their sick sons. Lawyers refused to come and
make out wills for the dying. Friars and nuns were left to care for the sick,
and monasteries and convents were soon deserted, as they were stricken, too.
Bodies were left in empty houses, and there was no one to give them a burial."
The disease struck and killed people with terrible speed. The Italian writer
Boccaccio said its victims often
"ate lunch with their friends and dinner with their ancestors in paradise."
By the following August, the plague had spread as far north as England,
where people called it "The Black Death" because of the black spots it
produced on the skin. A terrible killer was loose across Europe, and Medieval
medicine had nothing to combat it.
In winter the disease seemed to disappear, but only because fleas--which
were now helping to carry it from person to person--are dormant then. Each
spring, the plague attacked again, killing new victims. After five years 25
million people were dead--one-third of Europe's people.
Gene Splicing – or Recombinant DNA
Bacteria can contain
Plasmids, which are circular
pieces of DNA. (Bacteria
don’t have nuclei.)
Pieces of DNA with desired
characteristics can be obtained. (eg.
DNA which directs the production of
human insulin or frost resistance in
plants etc. etc.)
A plasmid is “cut” using
an enzyme.
Desired DNA is inserted
into the plasmid.
It is “glued” back
The plasmid is inserted
into a host bacteria.
The host bacteria
reproduce and the
offspring contain the
inserted DNA (eg. to
make human insulin etc.)
Some of the areas where Recombinant DNA will have an
•Better Crops (drought & heat resistance)
•Recombinant Vaccines (ie. Hepatitis B)
•Prevention and cure of sickle cell anemia
•Prevention and cure of cystic fibrosis
•Production of clotting factors
•Production of insulin
•Production of recombinant pharmaceuticals
•Plants that produce their own insecticides
•Germ line and somatic gene therapy
Proteins that HAVE BEEN manufactured
using genes from bacteria
Viruses are not living organisms.
Without a host cell, viruses cannot
carry out their life-sustaining
functions or reproduce. They cannot
synthesize proteins, because they
lack ribosomes. They must use the
ribosomes of their host cells.
Viruses cannot generate or store
energy because they lack
mitochondria. They have to derive
their energy from the host cell.
They also parasitize the cell for
basic building materials, such as
amino acids, nucleotides, and lipids
Viruses have a “protein coat” with RNA or
DNA on the inside. No other organelles.
T4 Bacteriophage Infecting a Bacterium
animation of virus infecting bacteria
flash animation of virus infecting
bacteria-choose GIF animation summary
Sometimes during the process of viral replication, mutations occur. If
the mutation is harmful, the new virus particle might no longer be
functional (infectious). However, because a given virus can generate
many,. many copies of itself, even if 200,000 particles are no good,
100 might still be just fine. Further, some mutations don't lead to
harm to the virus, but instead lead to a functional but now brand-new
strain of virus (Influenza virus can do this; consequently, there are
several different strains of this virus which have to be identified each
year in order to make a vaccine against the particular strain which
might cause the "flu").
1 Adsorption
2 Penetration
4 Late Replication
5 Maturation
3 Early Replication
6 Release
The tumor viruses change cells by integrating their
genetic material with the host cell's DNA. This is a
permanent insertion in that the genetic material is never
Several viruses have been linked to certain types of
The Epstein-Barr Virus has been linked with Burkitt's
The Hepatitis B and C viruses have been linked with liver
cancer in people with chronic infections.
HTLV-1, a retrovirus, has been linked to T-cell
Papilloma viruses have been linked with cervical cancer.
Some viruses include:
•Common cold
•Ocular Herpes
•Infant Cytomegalic
•Progressive Multifocal
•Viral gastroenteritis
•Chicken pox
•Acute Appendicitis
•Hepatitis A
•Viral meningitis
•Hepatitis B
•St. Louis
•West Nile fever
•Chronic Hepatitis B
•Rift Valley Fever
•Hepatitis C
•Hand, Foot, &
Mouth Disease
•Chronic Hepatitis C
•Hendra Virus
•Hepatitis D
•Dengue fever
•Hepatitis E
•Yellow fever
•Epstein-Barr virus
•Hepatitis X
•Lassa fever
•Dengue hemorrhagic
•Cold sores
The Polio Virus
Polio, or more properly poliomyelitis, was one of the most
feared and studied diseases of the first half of the 20th
Century. It appeared unpredictably, striking its victims,
mostly children, with a frightening randomness that
resulted in near panic during the epidemics of the 1940s
and 50s. Then, in 1955, a breakthrough occurred when,
after massive field trials involving nearly two-million
children, the Salk vaccine was shown to be effective in
preventing the disease. Today, polio is all-but-forgotten
as it has completely disappeared from developed
countries, and worldwide eradication is predicted by 2005.
However, polio's legacy remains. It is estimated that
there are 600,000 polio survivors living in the United
States, and the number worldwide must be in the tens of
Polio is a highly infectious disease caused
by a virus poliovirus. It invades the
nervous system and can cause total
paralysis in a matter of hours. It can
strike at any age, but affects mainly
children under three. Polio is mainly passed
through person-to-person (i.e., fecal-oral)
contact, and infects persons who do not
have immunity against the disease. There
is no cure for polio, but the disease can be
prevented by immunization with polio
An Influenza (flu) virus.
There are billions of
different flu viruses.
Hepatitus A viruses
Hepatitus B virus
Hepatitus C viruses
Hepatitis A
Hepatitis B
Hepatitis C
How It’s
eating or drinking
contaminated food or
water. The hepatitis virus is
found in faeces. It can be
passed on if even a tiny
amount of faeces from a
person with hepatitis A
comes into contact with
another person's mouth
Unprotected sex
Contaminated needles
Non-sterilized equipment
for tattooing,
acupuncture of body
piercing, From infected
mother to baby, Blood
Unprotected sex
Contaminated needles
Non-sterilized equipment
for tattooing,
acupuncture of body
piercing, From infected
mother to baby, Blood
transfusions sharing
notes used to snort
•a short, mild, flu-like
illness nausea and vomiting
diarrhoea loss of appetite
weight loss jaundice (yellow
skin and whites of eyes,
darker yellow urine and pale
faeces) itchy skin.
Some people may need to
be admitted to hospital.
•a short, mild, flu-like
illness nausea and
vomiting diarrhoea loss
of appetite weight loss
•jaundice (yellow skin and
whites of eyes, darker
yellow urine and pale
faeces) itchy skin.
•a short, mild, flu-like
illness nausea and
vomiting diarrhoea loss of
appetite weight loss
•jaundice (yellow skin and
whites of eyes, darker
yellow urine and pale
faeces) itchy skin.
Infection with hepatitis A
is usually mild, but
occasionally causes severe
inflammation of the liver,
requiring admission to
Most adults fully
recover. If they continue
to be infected: chronic
hepatitis liver cirrhosis
liver cancer.
about 80% will remain
infected and can pass on
the virus to others.
chronic hepatitis liver
cirrhosis liver cancer.
images of many viruses
HIV viruses
Human immunodeficiency virus or HIV is a retrovirus
that causes Acquired Immunodeficiency Syndrome
(AIDS), a condition in which the immune system begins
to fail, leading to life-threatening opportunistic
infections. Spread by unprotected sex and sharing
The Epstein-Barr virus (EBV), also called Human
herpesvirus 4 , is a virus of the herpes family (which
includes Herpes simplex virus and Cytomegalovirus), and
is one of the most common viruses in humans. Most
people become infected with EBV, which is often
asymptomatic but commonly causes infectious
mononucleosis. It is named after Michael Epstein and
Yvonne Barr, who together with Bert Achong
discovered the virus in 1964
Some signs of mononucleosis
•constant fatigue
•sore throat
•loss of appetite
•swollen lymph nodes (also commonly known as glands, located in your
neck, underarms, and groin)
•sore muscles
•larger-than-normal liver and spleen
•skin rash
•abdominal pain
Avian (Bird) Flu
These influenza viruses occur naturally among birds. Wild birds worldwide
carry the viruses in their intestines, but usually do not get sick from them.
However, avian influenza is very contagious among birds and can make some
domesticated birds, including chickens, ducks, and turkeys, very sick and kill
them. The risk from avian influenza is generally low to most people, because
the viruses do not usually infect humans. However, confirmed cases of human
infection from several subtypes of avian influenza infection have been
reported since 1997. Most cases of avian influenza infection in humans have
resulted from contact with infected poultry (e.g., domesticated chicken,
ducks, and turkeys) or surfaces contaminated with secretion/excretions from
infected birds.
Influenza A (H5N1) virus – also called “H5N1 virus” – is an influenza A virus
subtype that occurs mainly in birds, is highly contagious among birds, and can
be deadly to them. H5N1 virus does not usually infect people, but infections
with these viruses have occurred in humans.
Of the few avian influenza viruses that have crossed the species barrier to
infect humans, H5N1 has caused the largest number of detected cases of
severe disease and death in humans. However, it is possible that those cases
in the most severely ill people are more likely to be diagnosed and reported,
while milder cases go unreported.
West Nile Virus
West Nile virus (WNV) is a potentially serious illness. Experts believe WNV is
established as a seasonal epidemic in North America that flares up in the
summer and continues into the fall.
About one in 150 people infected with WNV will develop severe illness. The
severe symptoms can include high fever, headache, neck stiffness, stupor,
disorientation, coma, tremors, convulsions, muscle weakness, vision loss,
numbness and paralysis. These symptoms may last several weeks, and
neurological effects may be permanent.
Milder Symptoms in Some People. Up to 20 percent of the people who become
infected have symptoms such as fever, headache, and body aches, nausea,
vomiting, and sometimes swollen lymph glands or a skin rash on the chest,
stomach and back. Symptoms can last for as short as a few days, though even
healthy people have become sick for several weeks.
No Symptoms in Most People. Approximately 80 percent of people (about 4 out
of 5) who are infected with WNV will not show any symptoms at all.
Most often, WNV is spread by the bite of an infected mosquito. Mosquitoes
become infected when they feed on infected birds. Infected mosquitoes can
then spread WNV to humans and other animals when they bite.
Has not been reported in BC yet, but has in Alberta and other provinces.
Human Papiloma Virus
Genital HPV infection is a sexually transmitted disease (STD) that is caused
by human papillomavirus (HPV). Human papillomavirus is the name of a group
of viruses that includes more than 100 different strains or types.
Approximately 20 million people are currently infected with HPV. At least 50
percent of sexually active men and women acquire genital HPV infection at
some point in their lives. By age 50, at least 80 percent of women will have
acquired genital HPV infection
The types of HPV that infect the genital area are spread primarily through
genital contact. Most HPV infections have no signs or symptoms; therefore,
most infected persons are unaware they are infected, yet they can transmit
the virus to a sex partner
Most women are diagnosed with HPV on the basis of abnormal Pap tests. A
Pap test is the primary cancer-screening tool for cervical cancer or precancerous changes in the cervix, many of which are related to HPV.
A Pap test can detect pre-cancerous and cancerous cells on the cervix.
Regular Pap testing and careful medical follow-up, with treatment if
necessary, can help ensure that pre-cancerous changes in the cervix caused
by HPV infection do not develop into life threatening cervical cancer.