BIOLOGY 11: UNIT 2: Microbiology
Chapters 1, 7, 8
UNIT 2 OBJECTIVES:
VIRUSES: MOLECULES
1. Describe the basic structure of a virus.
2. Evaluate the evidence used to classify viruses as living or nonliving.
3. Compare and contrast the lytic and lysogenic cycles.
4. Describe the body's basic lines of defense against a viral attack.
5. Give examples of ways to reduce the chance of contracting a viral
disease.
6. Define and give examples of viral specificity.
7. Evaluate the effects of virulence on human health.
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KINGDOM MONERA: BACTERIA
1. Describe the basic structure of the prokaryotic cell.
2. Examine members of the Kingdom Monera and describe characteristics
that unify them.
3. Use examples to illustrate moneran diversity with respect to the
following: form, distribution, motility, ecological role, nutrition, and
human diseases.
4. Differentiate among fermentation, aerobic respiration, and
photosynthesis in bacteria.
5. Contrast the ways in which bacterial decomposers and parasites obtain
food.
6. Demonstrate sterile technique while preparing a streak plate.
7. Demonstrate the correct use of a compound microscope.
8. Evaluate the effectiveness of various antibiotics, disinfectants, and
antiseptics on bacteria cultures.
9. Explain processes by which bacteria adapt to become resistant to
antibiotics.
10. Give examples of the beneficial roles of bacteria.
KINGDOM PROTISTA: PROTISTS
1. Examine members of the Kingdom Protista and describe characteristics
that unify them.
2. Prepare wet-mount slides.
3. Differentiate between phytoplankton and zooplankton by observing
living protists.
4. Compare and contrast a prokaryotic cell (moneran) and a eukaryotic cell
(protist).
5. Demonstrate how knowledge of a pathogenic protist's life cycle can be
used to control its spread.
6. Relate the structural adaptations of protists to their diverse roles in the
food chain.
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VIRUSES:
Is a virus classified as living or nonliving?
Viruses do not fit into the 5 Kingdom system of classification
They are biological microscopic particles that are technically not considered to be
living organisms. They are only capable of reproducing within living cells.
The nature of viruses:
What is a virus? Virus is the Latin word for poison. Since the beginning of time,
people have been plagued with viruses. A virus is a clump of DNA contained
within a protein coating. They can only become active inside a live host.
Viruses are smaller than bacteria and go dormant, to reappear later causing
worse symptoms with each outbreak. Examples of viruses are rhinovirus
(common cold), hepatitis, Epstein-bar, Ebola, HIV, influenza (flu), SARS, West
Nile, small pox, and cold sores. Oncogenic viruses cause cancer by adding
specific genes to an infected cell, making a cancer cell. Viruses have a large
range of shapes some are spherical, elongated, or geometric. Viruses are
specific to their hosts, so that the virus protein must match the protein of
the host in order to be able to infect the host. This property is called viral
specificity.
Timing seems to be very important in treating viruses. They go through several
stages, including the dormant stage, and can morph into stronger strains with
each generation. They are difficult to diagnose and are a challenge to fight.
Phylogeny of the Virus:, p. 204
There is no fossil evidence to support the evolutionary history of viruses.
1) At one time viral ancestors were cellular organisms that lived as parasites on
other cells. Due to their parasitic lifestyle, they gradually lost their own cellular
components and became reduced to their parent form.
2) Viral ancestors were once free-living, precellular forms that later became
parasites of cellular organisms.
3) Viruses arose from detached fragments of genetic material of cellular
organisms. *currently this is the most widely accepted explanation.
Classification of Viruses: Living or Nonliving?
Viruses are lifeless chemicals and carry out no life functions on their own. The
virus must invade a living cell in order to reproduce. Viruses are positioned
between nonliving & living matter. Some biologists currently see the virus as a
nonliving infectious particle. Other biologists disagree and suggest they are alive
because of what happens inside the host cell.
3
Bacteriophages:, p. 200
Viruses that are known as "bacteria killers" are called bacteriophages.
Enterobacteria phage T4 is a bacteriophage that infects E. coli bacteria. Its
DNA is held in an icosahedral head. T4 is a large phage, at ~ 90 nm wide and
200 nm long. Its tail fibers allow attachment to a host cell, and the tail is hollow so
that it can pass its nucleic acid to the cell it is infecting during attachment.
Describe the basic structure of phage viruses
Chemical Composition: All viruses are composed of nucleic acid and protein.
Depending upon the phage, the nucleic acid can be either DNA or RNA but not
both. The simplest phages only have enough nucleic acid to code for 3-5
average size gene products while the more complex phages may code for over
100 gene products. One or more proteins create the head or capsid.
Structural Composition:
The bacteriophage virus consists of 2 regions: the head and the tail
regions.
1) Head or Capsid Region: All phages contain a head structure which can vary
in size and shape. Some are icosahedral (20 sides) others are filamentous. The
head or capsid is composed of many copies of one or more different proteins.
Inside the head is found the nucleic acid DNA for bacteriophage. The head acts
as the protective covering for the nucleic acid.
2) Tail: Many but not all phages have tails attached to the phage head. The tail is
a hollow tube through which the nucleic acid passes during infection. The size of
the tail can vary and some phages do not even have a tail structure. In the more
complex phages like T4 the tail is surrounded by a contractile sheath which
contracts during infection of the bacterium.
The basic structure of phage viruses called bacteriophage
4
VIRAL REPLICATION:There are two types of viral replication:
In viral replication the viral DNA is duplicated before a cell divides. Two of the
ways viral replication can occur are the lytic cycle and the lysogenic cycle.
Both cycles involve the same basic steps of replication but the outcomes differ.
Lytic Cycle: Lysis involves virulent phage because the virulent bacteriophage
invades and destroys the bacterium by causing the cell to burst and die.
Lysogenic Cycle:The lysogenic cycle involves temperate phage because the
temperate bacteriophage invades the bacterial cell and may coexist with the
bacterial cell. The temperate phage does not kill the bacterium. A prophage
forms when a temperate phage infects a bacterial cell. A prophage is formed
when the nucleic acid of a temperate phage is combined with the bacterial
chromosome and the viral nucleic acid acts as another set of genes.
5
Describe the body’s
basic lines of defense
against a viral attack:
The human body constantly
faces attack from foreign
invaders that can cause
infection and disease. These
invaders range from living
microbes, such as bacteria,
fungi, parasites, to nonliving
viruses, toxins, chemicals, and
drugs. Fortunately, the body
has a number of external and
internal safeguards that prevent
most dangerous invaders from
entering and causing harm.
The human body has several
lines of defense against
infection, which work to
prevent germs from invading
the body or to destroy them
once they find their way in.
DNA viruses cause chicken pox, small pox, RNA viruses cause polio, colds,
rabies, flu. The cold virus is endemic (it is with us all the time). When a disease
spreads very quickly it is called an epidemic. Viral infections are difficult to treat
and are not destroyed by antibiotics. Some viruses remain dormant in the body
for years before disease symptoms appear.
1. Non-Specific Defences: First Line of Defence:
The physical barriers that keep them at bay commonly are referred to as
the body's first line of defence. 1) Skin, forms a protective layer that
completely wraps around the body. When cuts or tears in the surface of the skin
provide an entrance for infective agents, glands beneath the skin produce an
enzyme that helps kill bacteria. 2) Mucus membranes, the moist linings of the
respiratory system, trap irritants that enter through the nose. 3) Cilia: tiny hairs,
line the body's airways and constantly wave foreign particles and mucus away
from the lungs to where they can be swallowed safely. 4) Stomach acid, most
harmful microbes that make it to the stomach are destroyed by HCl. In addition,
tears and saliva both contain enzymes that destroy invaders. 5) Brain-blood
barrier, a specialized "filter" that surrounds the brain and spinal cord and acts as
a physical barrier to keep out proteins, toxins, and most microbes, while letting in
glucose, the source of the brain's nutrients.
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2. Specific Defences: Second Line of Defence:
A second line of defence is housed the immune system that recognizes
and destroys foreign substances and organisms that enter the body. The
immune system can distinguish between the body's own tissues and outside
substances called antigens. This allows cells of the immune army to identify and
destroy only those enemy antigens. The ability to identify an antigen also permits
the immune system to "remember" antigens the body has been exposed to in the
past so that the body can mount a better and faster immune response the next
time any of these antigens appear.
Immunity is the condition of being protected against an infectious disease.
Immunity often develops after a germ is introduced to the body. One type
of immunity occurs when the body makes special protein molecules called
antibodies to fight the disease-causing germ. The next time that germ enters
the body the antibodies quickly attack it, usually preventing the germ from
causing disease.
Lymphocytes, white blood cells that develop in bone marrow and circulate
throughout the body in the lymphatic system, are a vital part of the immune
system. Lymphocytes can be divided into two subgroups: B lymphocytes
and T lymphocytes. B lymphocytes (or B cells) produce antibodies. These
protein molecules attach themselves to specific antigens and work with another
type of white blood cell, called phagocytes: scavenger cells that surround and
digest infected cells or microorganisms to destroy the invaders. T lymphocytes
(or T cells) help control the immune response and destroy foreign antigens
directly.
In some cases, people have permanent immunity to a disease; for example,
people who contract chicken pox usually will not have it again or, if they do, they
will have a much more mild case.
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In some instances, people receive antibodies from another person to help
their own immunity. This is known as passive immunity. Infants are born
with immature immune systems and receive antibodies from their mothers, both
during pregnancy (across the placenta) and after birth from breast milk. These
antibodies usually disappear within 6 to 12 months, but until then they help
protect the infant against a range of infections, including pneumonia, bronchitis,
influenza, and ear infection. Active immunity exists when weakened strains
of pathogens are injected into a person. Doctors can give people gamma
globulin, an antibody preparation that offers temporary immunity to patients who
might need this protection. When a person gets an immunization or vaccine the
body's immune system learns to recognize that particular bacteria or virus.
Vaccines are solutions prepared from viral components or inactivated
viruses. Vaccines prevent polio and small pox. When people are vaccinated, the
body reacts to the vaccine as if it was a real virus and produces antibodies. If,
sometime later, the person is exposed to the germ again, the body can fight it off
and not come down with the disease.
<Homework - Review Questions, p. 205 (7-14)>
CASE STUDY: VACCINES: THE NEEDLE OF HOPE, p. 206-209
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PRINCIPLES OF TAXONOMY:
What is taxonomy?
Taxonomy is a branch of biology that names and groups organisms according to
their characteristics and evolutionary history. Taxonomy is the science of
classifying organisms.
Aristotle (384-322 B.C.) was the first to classify living organisms. This Greek
philosopher grouped animals into two categories. The particular organism was
classified as either plant or animal origin.
As time progressed, modern science and rapid research identified many new
organisms. Aristotle’s classification was not sufficient.
The Swedish naturalist Carolus Linnaeus (1707-1778) realized that such a
system was not conducive for modern biology. Linnaeus made two main
contributions to taxonomy. Linnaeus developed a classification system of
organizing organisms into hierarchal categories. He did this be using the physical
appearances of organisms to group them. He was also instrumental in
developing the binomial nomenclature.
Biological classification systems have 2 main purposes: identifying organisms
and providing a basis for recognizing natural groupings of living things.
Binomial Nomenclature:
Biologists give each living thing a binomial or two part name. For example Homo
sapiens is the Binomial name for humans. The first word is the Genus and the
second is the species. These are universal among biologist to avoid confusion.
Linnaeus realized that common names caused a problem as they varied from
region to region. Binomial nomenclature: is the method for naming
organisms by using a two-part Latin name, called the scientific name: the
genus & species name.
Scientific name:
Homo sapiens
Castor canadensis
Acer rubrum
Musca domestica
Common name:
human
Canadian beaver
red maple
housefly
Hierarchal Classification:
This includes seven different levels of
organization. Kingdom, Phyla, Classes,
Orders, Families, Genera, and species are
included in the seven. Kingdom is less
specific and species is more specific.
9
Kings Play Calgary On Friday Gretzky scores.
For many years, most biologists favoured a Five-Kingdom system consisting of
Kingdoms Monera, Protista, Fungi, Plantae, and Animalia. They were placed into
categories by their type of cell (prokaryotic or eukaryotic), level of organization
(unicellular or multicellular), and how they acquire their nutrition. It is suggested
that Protists evolved from the Monerans who are the simplest organism. Fungus,
Plants and Animals evolved from the Protists in three separate evolutionary lines.
The five kingdom system of classification is based on structural differences and
also on modes of nutrition among the eukaryotes.
The 5 Kingdoms: 1) Monera, 2) Protista, 3) Fungi, 4) Plantae, 5) Animalia
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A New Proposal: The Three Domains of Life
In the 1970’s scientists began to find evidence for a previously unknown group of
prokaryotic organisms. These organisms lived in extreme environments such as
the Dead Sea, acid lakes, and salt evaporation ponds. These are environments
that scientists never suspected of maintaining any life. Because they appeared
prokaryotic, they were considered bacteria and named "archaebacteria" ('ancient'
bacteria). However, it became obvious from biochemical characteristics and DNA
sequence analysis that there were numerous differences between these
archaebacteria and other bacteria. Before long, it was realized that these
archaebacteria were more closely related to the eukaryotes than to bacteria.
Today, these bacteria have been renamed Archaea. From this work scientists
proposed that there should be a new category of classification of life,
called the Domain. The Domain is a classification category above Kingdom.
The traditional 5 Kingdom system says nothing about how organisms within
Kingdoms or between kingdoms may be related to each other via evolutionary
relationships among the kingdoms.
A New Proposal is the Three Domains of Life. The three domains are
Bacteria, Archaea, and Eukarya. The three-domain system of classification is
based on biochemical differences that show they are three vastly different groups
of organisms.
Phylogenetic tree: scientists use a diagram to represent evolutionary
relationships between organisms.
<Homework - Review Questions, p.199 (1-6)>
11
KINGDOM MONERA: PROCARYOTES Chapters 7, 8
The Importance of Microorganisms:
Most people only are aware of microorganisms when they get sick, such as the
diphtheria bacteria that caused the Black Death and altered the course of human
history. Most microorganisms are harmless, and many are helpful. Microbes
decompose dead plants & animals.
Microbiology: is the study of microorganisms. Microbiology has contributed
greatly to advancements in applied science & technology (development of certain
antibiotics & manufacturing of dairy products, etc.). Most microbes are
unicellular, but unlike viruses and cells of multicellular organisms,
microbes are capable of independent life.
Kingdom Monera, p. 215
Monerans are the oldest and most abundant living organisms known to date.
Monerans are single-celled organsims and include all bacteria & some simple
photosynthetic and chemosynthetic organisms. Photosynthetic cyanobacteria,
blue-green algae, appear in the fossil record as early as 3.5 billion years ago.
Describe the basic structure of a prokaryotic cell
Structure of Bacteria:
Bacteria are prokaryotic and are found in the Kingdom Monera. Prokaryotes are
very distinctive cells as they lack a nucleus and are very primitive cells.
Prokaryotic cells contain a plasma membrane, which is usually surrounded by a
cell wall and often a capsule. There are no cell organelles other than ribosomes.
Cells that do contain a nucleus are known as Eukaryotic cells and are advanced
cells.
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Bacteria exist in three different shapes:
1) Bacilla (rods)
2) coccus (spheres)
3) spirilla (spirals)
After dividing, many bacteria form groups or clusters, **colonies, or chains
(filaments) of cells. **colonies of bacteria are not multicellular
What do the members of Kingdom Monera have in common?
Bacteria are very small, and with the exception of ribosomes, do not contain
cellular organelles. They do have a chromosome, but it is contained in a
nucleoid, which has no nuclear envelope. Because of this, bacteria are said to
lack a nucleus. Bacteria are called prokaryotes because they lack a nucleus.
Many bacteria have rings of DNA called plasmids, which are often used to carry
foreign DNA into other bacteria for recombinant DNA engineering.
13
Bacterial
Structure
Function
Plasmid
Ring of DNA
Capsule
Protective covering made up of polysaccharides (complex sugars).
Keeps the bacteria from drying out and protect it from being engulfed
Cell Wall
Gives cell its shape and surrounds the cytoplasm protecting it.
Plasma
Membrane
A layer of phospholipids and proteins, which allows certain materials
in and out of the cell
Ribosomes
Only type of cell organelle found in bacteria. Small factories that
translate the genetic code into proteins.
Fimbriae
Small hair like projections that emerge from the cell membrane.
These help the bacteria attach to their host.
Cytoplasm
Or protoplasm. This is where the functions of cell growth, cellular
metabolism and replication are carried out. It is a gel like material
that is composed of water, enzymes, nutrients, wastes, and gases
and contains cell structures such as the ribosomes, chromosomes,
and plasmids.
Nucleoid
A region of the cytoplasm where the chromosomal DNA is located.
Flagella
Hair like structures that provide locomotion. Not all bacteria have
flagella.
Endospores: Some times, under unfavourable environmental conditions, some
bacteria form endospores. An endospore occurs when a portion of the cytoplasm
plus the chromosome dehydrates. The rest of the bacterial cell deteriorates. This
endospore is then highly resistant to the unfavourable conditions; conditions such
as high temperatures, harsh chemicals and drying out. When good conditions
occur, the spore then absorbs water and returns the cell to the typical stage.
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Reproduction of Bacteria:
1) Asexual Reproduction: Binary Fission:
Bacteria reproduce by a way of asexual reproduction called binary fission. In one
bacterium, the single circular chromosome duplicates. Then, the two resulting
chromosomes attach to the inside of the plasma membrane. The cell elongates
and separates into two strands. Finally, the cell membrane grows inward, the cell
wall forms separating two daughter cells each with a chromosome.
2) Sexual Reproduction: Exchange of genetic material
Bacteria reproduce with the exchange of DNA. When bacteria exchange DNA, it
has a similar effect to sexual reproduction, because there is a blending of genes
between two organisms. There are three ways in which bacteria exchange DNA.
Conjugation: donor cell passes DNA to recipient cell by a conjugation tube (sex
pilus).
.
Transformation: bacterium takes up DNA released by dead bacteria.
Transduction: bacteriophages carry DNA from one cell to another.
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Bacterial Metabolism:
Bacteria have three different ways to metabolize nutrients to produce energy:
aerobic respiration, photosynthesis, and fermentation.
What are the differences among fermentation, aerobic respiration, and
photosynthesis in Monerans?
1) Obligate aerobes: Aerobic Respiration
Most bacteria are obligate aerobes. These bacteria require oxygen to survive.
These bacteria will utilize cellular respiration to produce energy.
Cellular Respiration is the breakdown of sugar molecules with the use of oxygen
to release energy.
C6H12O6 + 6O2 --------> 6 H2O + 6 CO2 + Energy
2) Obligate anaerobe: Anaerobic Respiration
Some bacteria are called obligate anaerobes. Obligate anaerobes are unable
to grow in the presence of oxygen and must use photosynthesis or
fermentation to release energy.
Photosynthesis is the use of light energy to produce sugar molecules from
carbon dioxide and water with the use of chlorophyll. Oxygen is the waste
product. Cyanobacteria is an example of a photosynthetic bacteria.
6 CO2+ 6 H2O -----light------>C6H12O6 + 6 O2
Fermentation is the breakdown of sugar molecules without the use of oxygen to
release energy. Fermentation is 19 times less efficient than aerobic cellular
respiration. In fermentation of sugar, the products are ethanol & carbon dioxide.
Some bacteria produce acetone, acetic acid & methane by fermentation. Bacteria
will ferment by one of these two equations.
Pyruvic Acid + NADH ---------->Lactic Acid + NAD+ (also used by animals)
Pyruvic Acid + NADH ---------->Alcohol + CO2 + NAD+ (also used by plants)
3) Facultative anaerobe
Other bacteria are facultative anaerobes. Facultative anaerobes are able to
grow in the presence or absence of oxygen. These bacteria will use cellular
respiration if oxygen is present and fermentation if oxygen is not present.
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Bacterial Nutrition:
Bacteria use all modes of nutrition except heterotrophism by ingestion. Some
bacteria are autotrophic (able to produce their own energy) by
photosynthesis or by chemosynthesis. Cyanobacteria which photosynthesize
in the same manner as plants also give off oxygen. Other bacteria are
autotrophic by chemosynthesis. They oxidize inorganic compounds to obtain
their energy. These bacteria are very important to recycle the nitrogen in our
ecosystem.
Most types of bacteria however, are heterotrophic by absorption. Bacteria
that carry out external digestion of organic matter from dead material and
absorb the nutrients are called saprophytes. Others absorb nutrients from
other living things. When bacteria are absorbing nutrients from living things
they are known as parasites. Saprophytic bacteria are able to feed on more
food sources and contain a greater variety of enzymes used to digest different
foods. Parasitic bacteria are limited in the number of enzymes designed to digest
specific tissues in their host.
Bacteria are called decomposers because they break down organic
material and have a role in digesting sewage and oil, production of alcohol,
vitamins, antibiotics, and genetic engineering.
Symbiotic Bacteria:
When bacteria live in association with other organisms they are known as
symbiotic bacteria. There are three types of symbiosis, and different groups of
bacteria employ all three.
1) In mutualistic symbiotic relationships, both the organisms benefit from
the relationship. For example, nitrogen fixing bacteria live in nodules of
legumes. They provide the plant with nitrogen, and the plant supplies the
bacteria with other nutrients.
2) In a commensalistic relationship, one organism will benefit, and the
other is unaffected. Bacteria live on human skin and do not harm us, but
benefit from the warm moist environment.
3) A parasitic relationship means that one organism is benefiting while the
other is being harmed. Parasitic bacteria harm the host and cause disease
in plants and animals. Because some parasitic bacteria use a human host,
the study of bacteria is of great importance to human beings.
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Antibiotics:
Alexander Flemming discovered in 1928 the first antibiotic accidentally when he
had a moldy Petri dish that would not grow bacteria. The mold in the Petri dish
was producing the antibiotic penicillin. Flemming could not convert the antibiotic
to a usable form, but his work was later continued by other scientists to produce
the variety of antibiotics today.
How do bacteria adapt to become resistant to antibiotics?
Antibiotics are commonly used in an attempt to control bacterial disease. An
antibiotic is a non-specific poison taken in a large enough amount to kill the
parasite without harming the host. They are taken over a period of time to ensure
that all of the parasites in the host will be killed. Because some bacteria are
stronger than the others, they will require more exposure to the antibiotic before
they are killed. However, because people will often feel they have overcome their
parasite while a few still remain, the strongest of the original strain will reproduce
creating a more resilient strain. With the antibiotic creating a selection
pressure for strength, new strains of bacteria are stronger than the last,
and eventually they are referred to as having an antibiotic resistance.
What is sterilization?
The process known as sterilization refers to the process in which all living cells,
spores, and viruses are completely destroyed or removed from an object or
environment. Once something is sterilized, it will remain sterile if properly sealed.
Sterilization is performed on surgical equipment, needles, and certain lab
equipment in order to prevent the spread of microorganisms. Methods used to
sterilize objects involve the use of heat, radiation, filtration, and/or chemical
means. Autoclaves are devices which use hot steam under high pressure to
sterilize objects.
What is disinfection?
The process known as disinfection is the killing, inhibition, or removal of
microorganisms that cause disease. Disinfection may not necessarily eliminate
spores or all of the microorganisms from an object or environment. While
disinfection is not as extreme as sterilization, it is considered to be an adequate
level of cleanliness for most situations.
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What is the difference between an antiseptic and a disinfectant?
Disinfectants are chemical agents used to disinfect inanimate objects and
surfaces. Examples of disinfectants include iodine solution, copper sulfate,
ozone, and chlorine gas.
Antiseptics are chemical agents applied to living tissues to prevent infection.
Antiseptics are generally less toxic than disinfectants because they must
not cause too much damage to the host living tissue. Examples of
antiseptics include iodine, 70% ethanol and 3% hydrogen peroxide.
The concentration of a chemical agent can determine if it can be used as a
disinfectant or an antiseptic.
Roles Of Bacteria: Beneficial & Harmful:
Examples of beneficial effects of bacteria
ORGANISMS
BENEFICIAL EFFECTS
Clostridia
Production of butanol & acetone from molasses
Acetobacter
Production of vinegar from alcohol
Intestinal bacteria
Synthesizes vitamins in humans
Lactobacilli
Production of lactic acid from sugar
Azotobacter, Nitrobacter
Fixation of nitrogen in soils
Steptococci, Lactobacilli
Cheese production
Streptomyces group
Source of antibiotics (neomycin, streptomycin,
erythromycin & terramycin)
Examples of harmful effects of bacteria
ORGANISMS
DISEASE/DESTRUCTION
Bacillus anthracis
Anthrax (a disease of domestic animals)
Clostridium botulinum
Botulism; other clostridia cause tetanus,
gangrene & lockjaw
Streptococci
Strep throat & scarlet fever
Staphylococci
Boils, food poisoning, & skin infections
Lactobacilli
Souring of milk
Pseudomonads
Gasoline spoilage
Bacilli
Destruction of silkworms
Staphylococci &
Food spoilage
Pseudomonads
Coliform bacteria
Pollution of water sources; causes soft rot in
plants, gastroenteritis , & dysentery
Spirilla
Cholera & syphilis
<Homework - Review Questions, p. 219 (1 - 7)>
CASE STUDY: FOLLOWING AN INFECTION, p. 220
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Human Diseases:
Pathogens are any type of virus or organism that causes disease.
Pathogens cause disease symptoms in a variety of ways.
1) Number of pathogens: this places such a tremendous burden on the host's
tissues that they interfere with normal function.
2) Destroying cells & tissues:
3) Producing toxins: these are poisons produced by bacteria.
Bacteria cause some of the worst human diseases.
Infectious Diseases Spread in a Variety of Ways:
Moisture droplets in air, dust, direct contact, fecal contamination, animal bites &
wounds, (cuts & scratches). Usually protection from disease is provided by the
body's own defense mechanisms. Other methods include sterilization,
disinfection and use of antiseptics, extermination of animals that carry disease,
immunization and administration of antibiotics.
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Frontiers of technology: bacteria & sewage treatment
Bacteria and other microbes decompose the remains of dead organisms, and
enable the chemicals of life to be recycled. These microbes and bacteria are now
being used in the sewage disposal process.
Sewage: water that carries organic wastes from humans & industry (toilets,
sinks, dishwashers, washing machines, & various types of industrial equipment).
Sewage Treatment Involves 3 Steps:
1) Primary Sewage Treatment: Mechanical process in which solids settle out
as sludge, but the liquid contains tiny particles & dissolved chemicals.
2) Secondary Sewage Treatment: biological process that uses aerobic
bacteria. Filters remove 90% of biodegradable wastes and are broken down
by aerobic bacteria. The remaining 10% is filtered & further broken down by
anaerobic bacteria, disposed of by incineration and dumped into landfills,
oceans, or used as fertilizers.
3) Advanced Sewage Treatment: Specialized chemical & physical processes
are used to lower the quantity of specific pollutants before the sewage is
released into the rivers or lakes. (Chlorination, ozone, hydrogen peroxide &
UV light may also be used).
<Homework - Review Questions, p. 223 (8-10, 12-15)>
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KINGDOM PROTISTA: PROTISTS Chapter 8
Protists first appeared in the fossil record about 1.5 billion years ago. They are
more advanced than monerans.
Characteristics of protists, p. 226
1) Eukaryotes with membrane-bound nuclei & generally unicellular.
2) Cytoplasm contains organelles, such as ribosomes, mitochondria, and
lysosomes.
3) Organelles help provide a more efficient way of using available nutrients &
carrying out metabolic activities.
4) Protists are microscopic and found in moist habitats.
3 Groups of Protists: Plantlike, Animal-Like and Fungi-like
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Plantlike Protists: EUGLENA
They are plant-like, photosynthetic autotrophs, such as phytoplankton, and
produce a significant portion of oxygen supply in the earth's atmosphere.
Euglena Anatomy
Phylum Euglenophyta (Euglena), p. 227
Found mainly in fresh water, ponds & lakes and abundant in stagnant water and
obtain food by photosynthesis, but in the dark they become heterotrophic
Characteristics of Euglena
1) Possesses a bright red eyespot with a photoreceptor (detects light)
2) Flagellum moves in a whip-like fashion, propelling it through the water.
3) Pellicle
surrounds the
cell, it is a thick
flexible covering
4) Autotrophs - use
photosynthesis
by chloroplasts
5) Vacuoles collect
& remove excess
water
6) Starch granules
is where food is
stored
7) Reproduction is
by longitudinal
fission
The euglena is unique because it is sort of like a plant and also like an
animal. The euglena is able to make its own food like a plant when it is in the
sunlight. When it is in darkness, it can get food like an animal. It ingests tiny
plants and animals much like the amoeba and paramecium.
The euglena reproduces by longitudinal fission, splitting lengthwise in two. The
flagellum goes with one part and the other part grows a new flagellum.
When it is too hot or cold for a euglena, it forms a protective casing called a cyst
around its body that protects it until conditions outside the cyst become better.
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ANIMAL-LIKE PROTISTS: (PROTOZOA), p. 228
AMOEBA, PARAMECIUM, AND SPOROZOAN
They live in moist habitats and are more abundant than bacteria. Reproduction is
usually asexual, by fission. In harsh conditions they can form cysts.
All protozoa are heterotrophs, they must move to obtain food.
Amoeba Anatomy
Phylum Sarcodina (Amoeba), p. 227
Found mainly in fresh water and ponds, parasitic species are found in animal
intestines. When they enter the bloodstream, they can cause liver and brain
impairment that can be fatal.
Characteristics of Amoeba
1) Movement is due to cytoplasmic
extensions & retraction of
pseudopods called false feet,
they are fingerlike projections
used for getting food.
2) Cytoplasm has 2 layers:
ectoplasm (thin, semi-rigid layer
under the plasma membrane) &
endoplasm (a more fluid part
that fills the inside of the cell).
3) It feeds by phagocytosis
(pseudopods flow around & engulf food particles & form a food vacuole).
4) Contractile vacuole = water vacuole- collects water within the organism.
As the vacuole fills, it contracts and water is discharged through a pore in
the plasma membrane.
5) Reproduction is asexual, by binary fission. Once the amoeba splits, the 2
organisms grow to full size and may split again.
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Paramecium Anatomy
Phylum Ciliophora (cilliated protozoans) (Paramecium), p. 227
Live in both fresh & marine habitats. They are the most advanced protozoans.
Characteristics of Paramecia
1) Hairlike cilia are short & numerous & used for swimming.
2) Most common protozoan,"slipper animal"
3) The oral groove, mouth leads to a gullet, a cavity where food enters a food
vacuole, then food is digested wastes are expelled through the anal pore.
4) Contractile vacuole collects excess water & expels it.
5) There are two nuclei, a macronucleus (controls most cell activities) & a
micronucleus (controls reproduction). The macronucleus is the typical
nucleus or "brain" of the cell. The micronucleus however is involved in
conjugation (a primitive form of sexual reproduction).
6) Trichocysts (harpoons) with
poisonous barbs to capture prey or
drive away predators.These spearlike threads are positioned inside
the cell membrane and are
released upon stimulation to impale
a threat or potential food.
7) Reproduction is usually asexual,
but on occasion it will exchange the
micronucleus with another
Paramecium. This exchange is a
primitive form of sexual
reproduction called conjugation. It
is considered sexual because there
is an exchange of genetic material,
but it is primitive because it is not a complete exchange.
Conjugation between two different Paramecia
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Sporozoan Anatomy
Phylum Sporozoa (Sporozoan)
These are the most simple parasitic forms of protozoans.
Characteristics of Sporozoan
1) Non-motile. At some point in their life cycle they become spores
2) Some of these sporozoans have complex life cycles involving more than
one host. The life cycle of this protozoan is dependent upon having
mosquito and human hosts.
The study of this life cycle has been used in attempt to control the parasite;
however, Plasmodium vivax developed a resistance to many of the
antimalarial drugs. Mosquito populations have been attempted to be controlled
by use of insecticides. Because the mosquito reproduces quickly in large
numbers as well, it has developed a resistance to many insecticides. Wide
spread DDT use has developed DDT resistant mosquitoes, so the only lasting
effects of the spread are to the other animals in the environment that are higher
in the food chain. Because DDT takes a long time to break down, these animals
will be affected for a long time.
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FUNGILIKE PROTISTS: SLIME MOLD, p. 232
All fungilike protists are in the Phylum Gymnomycota, called slime molds.
Slime Mold Anatomy
Phylum Gymnomycota (Slime Mold)
They prefer cool, shady, moist places and are found under fallen leaves or on
rotting logs
Characteristics of Slime Molds
1) During a stage of their life cycle, slime molds resemble protozoans &
become amoeba-like or have flagella and at other times
2) They produce spores similar to fungi.
3) It feeds on fungi, bacteria, protozoa, other micro-organisms, and decaying
organic matter.
<Homework - Review Questions, p. 232 (17 - 25)>
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