Download Chapter 1: The Microbial World and You

Microbiology:
Chapter 1: The Microbial
World and You
The study of microorganisms.
Microorganisms : Small living organisms that
generally can not be seen with the naked eye.
Include:
uBacteria
uFungi (yeasts and molds)
uProtozoa
uAlgae
uMulticellular parasites
Also include nonliving infectious agents:
♦Viruses
♦ Prions
Microbes are Essential for Life on
Earth: Have many important and beneficial
biological functions:
u Photosynthesis: Algae and some bacteria
capture energy from sunlight and convert it to
food, forming the basis of the food chain.
u Decomposers: Many microbes break down
dead and decaying matter and recycle nutrients
that can be used by other organisms.
u Nitrogen Fixation: Some bacteria can take
nitrogen from air and incorporate it into soil.
I mportant and beneficial biological
I mportant and beneficial biological
functions of Microbes:
u Digestion: Animals have microorganisms in
their digestive tract, that are essential for
digestion and vitamin synthesis.
u Cellulose digestion by ruminants (cows, rabbits, etc.)
u Vitamin K and B synthesis in humans.
u Medicine: Many antibiotics and other drugs
are naturally synthesized by microbes.
u Penicillin is made by a mold.
I mportant and beneficial biological
functions of Microbes:
functions of Microbes:
u Food Industry: Many important foods and
beverages are made with microbes:
u Genetic Engineering: Recent advances in gene
splicing allow us to design recombinant
microbes that produce important products:
u Alcoholic beverages (Wine, beer, rum, whiskey)
u Bread
u Vinegar
u Soy sauce
u Cheese
u Pickles, olives, sauerkraut
u Yogurt
u Buttermilk
u Sour cream
u Coffee
u Chocolate
u Hams, sausages
u Human growth hormone (Dwarfism)
u Insulin (Diabetes)
u Blood clotting factor (Hemophilia)
u Recombinant vaccines
uHepatitis A and B vaccines
u Human hemoglobin (Emergency blood substitute)
u Taxol (Breast and ovarian cancer)
u Erythropoietin (Anemia)
u Monoclonal antibodies (Disease diagnosis and
prevention).
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I mportant and beneficial biological
functions of Microbes:
u Medical Research: Microbes are well suited
for biological and medical research for several
reasons:
u Relatively simple and small structures, easy to study.
u Genetic material is easily manipulated.
u Can grow a large number of cells very quickly and at
low cost.
uShort generation times make them very useful to
study genetic changes.
Microbes and Disease: Most microbes are
either beneficial or harmless to humans.
u Less than 1% of microbes cause disease.
u In 1962, the surgeon general of the United
States stated: “The war against infectious
diseases has been won”.
uToday it is clear that this was overly optimistic:
u Emerging diseases: New diseases like AIDS,
hantavirus, Ebola fever, Lyme disease, Hepatitis C,
and others that did not exist a few years ago.
u Antibiotic and Drug Resistance: Many old diseases
are becoming resistant to traditional therapies:
Tuberculosis, gonorrhea, malaria, etc.
u Today infectious diseases cause 50% of the
52 million worldwide deaths per year.
Infectious Diseases Causing Most
Deaths Worldwide in 1998
Disease
Cause
Deaths/year
Acute Respiratory*Bacterial or viral 4,400,000
Diarrheal diseases Bacterial or viral 3,200,000
Tuberculosis
Bacterial
3,100,000
Malaria
Protozoan
3,100,000
Hepatitis B
Viral
2,000,000
Measles
Viral
1,500,000
AIDS
Viral
1,000,000
Neonatal Tetanus Bacterial
600,000
*: Pneumonia, bronchitis, influenza, etc.
Neonatal tetanus kills over 600,000 infants every year.
Source: Tropical Medicine and Parasitology, 1997.
Microbes and Disease in Human
History
4 Bubonic Plague (Black death): Several
devastating epidemics throughout history.
• High mortality: Up to 80% of those infected die.
• 1347-1351: Over 75 million died in Europe,
Asia, and Africa.
• Over 25% of population of Europe died.
• Cause was unknown for over 500 years, leading
to superstition, persecution, and hysteria.
• Bacterial disease transmitted by rat fleas.
• Rare today but still occurs:
• 10-15 cases/year in U.S.
• Last epidemic occurred in India in 1994.
Left: Swollen lymph nodes in bubonic plague infection.
Right: Infected flea bite with eschar and carbuncle.
Source: Tropical Medicine and Parasitology, 1997.
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Worldwide Distribution of Plague
4 Smallpox: One of deadliest human
infectious diseases throughout history.
• Caused by smallpox virus.
• First known case in 1175 B.C.: Egyptian
pharaoh Ramses V died from smallpox.
• Several hundred million deaths through history.
• Up to 90% of Native American population was
killed by smallpox and other diseases (measles
and plague) introduced during European
conquests.
++: Frequent transmission
+/-: Infrequent transmission.
Source: Tropical Medicine and Parasitology, 1997.
• Native population of Central and South America dropped
from 130 million to about 1.6 million over several decades.
• Smallpox was used as a biological weapon by British
colonists in North America.
• 600,000 deaths/year in Europe from 1500-1700.
4 Smallpox (Continued)
• 75% of survivors were severely scarred and/or
blinded.
• An effective vaccine was developed in 1870s by
Edward Jenner, using a related virus (cowpox).
• Smallpox was the first and only viral disease to
be completely eradicated (1977).
• Worldwide immunization campaign in 1960s.
• Only infects humans.
Smallpox infection in a small child.
Disease was eradicated worldwide by immunization in 1977.
Source: Microbiology Perspectives, 1999.
4Tuberculosis (TB): Caused by a bacterium
that mainly infects lungs but may spread to other
parts of body.
• Leading killer of world’s infectious diseases:
• 3 million die worldwide every year.
• Over 1 million killed in U.S. between 1930 -49.
• One out of three people infected worldwide.
• In U.S. 10 million people are presently infected, but only
5% will develop active disease.
• Most healthy individuals can contain infection.
• Treatment: Antibiotics for up to one year.
• After introduction of antibiotics, TB declined from 1950s
to 80s, and then started to increase again.
• Low patient compliance with treatment has caused
antibiotic resistant TB .
• AIDS epidemic has caused an increase in cases.
Tuberculosis is leading killer among infectious diseases
worldwide. Patient with lymph node necrosis.
Photo by Dr. I. Small
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4 Childbirth Fever: Common nosocomial
(hospital acquired) infection.
• Bacterial infection of the uterus as a result of
childbirth or abortion.
• Transmitted by hands and instruments of
physicians and midwives.
• Extremely common before the 1900s.
• About 1 in 17 women who gave birth would become
infected (fever, chills, delirium, and death).
• Cause was unknown.
• Austrian doctor Semmelweiss showed that washing
hands and instruments with a disinfectant solution
greatly reduced cases.
• Today common in women who have illegal
abortions, especially in third world countries.
African AIDS patient with slim disease
Source: Tropical Medicine and Parasitology, 1997
Extensive symmetric tumor lesions of Kaposis’s sarcoma in an
AIDS patient.
Source: AIDS, 1997
4 AIDS: Acquired Immune Deficiency
Syndrome.
• First cases reported in 1981 at UCLA.
• Cause: Human Immunodeficiency Virus (HIV)
• Transmitted by sexual contact, blood transfusions,
mother-to-child, and infected needles.
• Destroys an individual’s immune system, making
them susceptible to many infectious diseases and
cancer.
• Number of cases has grown rapidly during the last
two decades. As of 2001:
• Over 900,000 infected individuals in the U.S.
• Over 40 million deaths worldwide.
Endemic Kaposi’s Sarcoma, nodular form in an AIDS patient.
Source: AIDS, 1997.
Oral candidiasis (yeast infection) in an AIDS patient
Source: Atlas of Clinical Oral Pathology, 1999
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History of Microbiology
Early Studies
History of Microbiology
Spontaneous Generation vs Biogenesis
Before 17th century, study of microbiology was
hampered by the lack of appropriate tools to
observe microbes.
u Robert Hooke: In 1665 built a compound light
microscope and used it to observe thin slices of
cork. Coined the word cell.
u Anton van Leeuwenhoeck : In 1673 was the first
person to observe live microorganisms which he
called “ animalcules” (bacteria, protozoa), using
single-lens microscopes that he designed.
u Before 1860s many scientists believed in
History of Microbiology
Spontaneous Generation vs Biogenesis
History of Microbiology
Spontaneous Generation vs Biogenesis
Spontaneous generation, i.e.: That living
organisms could arise spontaneously from
nonliving matter:
u Mice come from rags in a basket.
u Maggots come from rotting meat.
u Ants come from honey.
u Microbes come from spoiled broth.
4 Theory of Biogenesis: Belief that living cells can
Debate was finally settled by Pasteur.
only arise from other living cells.
u Francesco Redi : In 1668 proved that maggots do
not arise spontaneously from decaying meat.
u Lazaro Spallanzani: In 1765 found that nutrient
broth that had been heated in a sealed flask would
not become contaminated with microbes.
u Louis Pasteur: In 1861 finally disproved
u Some proponents of spontaneous generation argued that
boiling had destroyed the “life force” of air in flask.
u Others argued that microbes were different from other life
forms.
History of Microbiology
Golden Age: 1857-1914
Rapid advances led to the development of
microbiology as a science.
Pasteur’s Contributions to Microbiology:
u Fermentation: Pasteur found that yeasts were
responsible for converting sugar into alcohol in
the absence of air.
u Souring and spoilage were caused by bacterial
contamination of beverages.
spontaneous generation when he demonstrated
that microorganisms in the environment were
responsible for microbial growth in nutrient broth.
u Designed swan neck flasks that allowed air in, but
trapped microbes in neck.
u Developed aseptic technique: Practices that prevent
contamination by unwanted microorganisms.
History of Microbiology
Golden Age: 1857-1914
Pasteur’s Contributions:
u Pasteurization: Developed a process in which
liquids are heated (at 65 o C) to kill most bacteria
responsible for spoilage.
u Disease Causes: Identified three different
microbes that caused silkworm diseases.
u Vaccine: Developed a vaccine for rabies from
dried spinal cords of infected rabbits.
u Directed Pasteur Institute until his death in 1895.
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History of Microbiology
Golden Age: 1857-1914
History of Microbiology
Golden Age: 1857-1914
Germ Theory of Disease: Belief that microbes
cause diseases. Before, most people believed
diseases were caused by divine punishment,
poisonous vapors, curses, witchcraft, etc.
Germ Theory of Disease:
u Agostino Bassi (1835): Found that a fungus was
u Robert Koch (1876): First person to conclusively
responsible for a silkworm disease.
u Ignaz Semmelweis (1840s): Demonstrated that
childbirth fever was transmitted from one patient
to another, by physicians who didn’t disinfect their
hands. He was ostracized by colleagues.
History of Microbiology
Modern Microbiology: After 1914
u Joseph Lister (1860): Used disinfectant to treat
surgical wounds, greatly reducing infection rates.
Considered the father of antiseptic surgery.
prove that a specific bacterium caused a disease.
u Germ Theory: One microbe causes one specific
disease.
u Proved that Bacillus anthracis causes anthrax in cattle.
u Later identified bacterium that causes tuberculosis.
History of Microbiology
Modern Microbiology: After 1914
Chemotherapy: Treatment of a disease by using a
chemical substance. Chemical must be more
poisonous to microbe than host.
u Paul Ehrlich (1910): Search for “magic bullet”.
u Quinine: First known chemical to treat a disease
u Alexander Fleming (1928): Discovered that
(malaria). Used by Spanish conquistadors.
u Synthetic Drugs: Made in the laboratory.
u Antibiotics: Produced naturally by fungi and
bacteria.
u Discovered salvarsan, an arsenic derivative, was
effective against syphilis.
penicillin produced by the mold Penicillium
notatum was able to prevent microbial growth.
u Penicillin was not mass produced until the 1940s.
u Rene Dubos (1939): Discovered two antibiotics
(gramidin and tyrocidine) produced by bacterium
(Bacillus brevis).
History of Microbiology
Modern Microbiology: After 1914
Diversity of Microorganisms
I. Bacteria (Sing. Bacterium)
Problems with Chemotherapy:
u Small, single-celled (unicellular) organisms.
u Toxicity
u Procaryotes: “Before nucleus”.
u Drug resistant microbes
Lack the following structures:
u Nuclear membrane around DNA
u Membrane bound organelles
uMitochondria
uChloroplasts
uGolgi apparatus
uEndoplasmic reticulum
uLysosomes
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Kingdom Prokaryotae: Bacteria lack
nucleus and membrane bound organelles
Diversity of Microorganisms
I. Bacteria (Sing. Bacterium)
u Include two groups:
u Eubacteria: Peptidoglycan cell walls.
u Archaebacteria: Lack peptidoglycan cell walls.
u Shapes: Several forms:
u Bacilli : Rod like. (Sing. Bacillus)
u Cocci: Spherical. (Sing. Coccus)
u Spiral: Corkscrew or curved
u Square
u Star shaped
Diversity of Microorganisms
I. Bacteria (Sing. Bacterium)
u Divide by binary fission (not mitosis).
u Source of nutrients varies:
u Heterotrophs : Consume organic chemicals.
u Autotrophs : Make their own food. Include
photosynthetic bacteria.
u Motility: Many can “swim” by using moving
appendages:
u Cilia: Small hair like structures
u Flagella: Large whip like structures.
u Distinguish between motility and Brownian
motion.
Diversity of Microorganisms
II. Fungi (Sing. Fungus)
u Source of nutrients varies:
u Saprotrophs : Decomposers that feed on dead and
decaying matter. Most fungi are decomposers.
u Parasites: Obtain nourishment by parasitizing live
animals and plants.
Diversity of Microorganisms
II. Fungi (Sing. Fungus)
u Eucaryotes: “True nucleus”
u DNA is surrounded by nuclear membrane.
u Cells have membrane bound organelles:
Mitochondria, endoplasmic reticulum, etc.
u Cells are larger than those of procaryotes.
u May be unicellular or multicellular:
u Unicellular: Yeasts
u Multicellular: Molds, mushrooms
u Do not carry out photosynthesis.
u Must absorb organic nutrients from their
environment.
Diversity of Microorganisms
III. Protozoa (Sing. Protozoan)
u Eucaryotes: “True nucleus”
u DNA is surrounded by nuclear membrane.
u Cells have membrane bound organelles and are larger
than those of procaryotes.
u Unicellular
u Cell wall made of chitin.
u Kingdom Protista
u May reproduce sexually or asexually.
u Sexual or asexual reproduction
u Classified based on locomotion:
u Pseudopods : “False feet”. Cytoplasmic extensions.
uExample: Amoeba
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Protozoa Belong to Kingdom Protista:
Eucaryotic Unicellular or Simple
Multicellular Organisms
Diversity of Microorganisms
III. Protozoa (Sing. Protozoan)
u Classified based on locomotion:
u Flagella: Long whip like appendages.
uExample: Trichomonas vaginalis, causes trichominiasis, a
sexually transmitted disease.
u Cilia: Small hair like appendages
u Nonmotile: Do not move in their mature forms.
uExample: Plasmodium spp., causative agent of malaria.
Diversity of Microorganisms
IV. Algae (Sing. Alga)
u Eucaryotes: “True nucleus”
u Photosynthetic: Important part of food chain
because produce oxygen and carbohydrates used
by animals.
u Unicellular or multicellular
u Kingdom Protista
u Sexual or asexual reproduction
u Cell walls composed of cellulose
u Found in aquatic environments (oceans, lakes,
rivers), soil, and in association with plants.
Comparison of Cells and Viruses
Diversity of Microorganisms
V. Viruses
u Acellular infectious agents, not considered
living because they lack cells.
u Obligate intracellular parasites: Viruses can
only reproduce by using the cellular machinery of
other organisms.
u Simple structure :
u Protein coat (capsid) with either DNA or RNA, but not
both.
u May also have a lipid envelope.
Diversity of Microorganisms
VI. Multicellular Animal Parasites
u Eucaryotes: “True nucleus”
u Multicellular animals, usually are visible to the
naked eye.
u Microscopic during some stages of life cycle.
u Spend part or all of their lives inside an animal
host.
u Helminths include:
u Flatworms (Platyhelminths ): E.g. Tapeworm
u Roundworms (Nematodes): E.g. Ascaris, pinworm.
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