Title: Ch. 19 Bacteria and Viruses
1Ch. 19 Bacteria and Viruses
2Ch. 19 Outline
- 19-1 Bacteria
- Classifying prokaryotes
- Identifying Prokaryotes
- Metabolic Diversity
- Growth and Reproduction
- Importance of Bacteria
3Bacteria
- Once microscopes were invented, scientists
discovered a world of microorganisms. - The smallest and most common microorganisms are
the prokaryotes, which are single-celled
organisms that lack a nucleus - The word bacteria is so familiar, that we will
use it as a common term to describe prokaryotes
4Ch. 19 Outline
- 19-2 Viruses
- What is a virus?
- Viral Infection
- Retroviruses
- Viruses and Living Cells
- 19-3 Diseases caused by bacteria and viruses
- Bacterial Diseases in Humans
- Controlling Bacteria
- Viral Diseases
- Viroids and Prions
5Bacteria
- Prokaryotes range in size from 1 to 5 micrometers
in diameter. There are exceptions to this rule.
The Epulopiscium fisheloni is about 500
micrometers long.
6Classifying Prokaryotes
- All prokaryotes were once classified in a single
Kingdom named Monera. - Two Kingdoms of bacteria Eubacteria,
Archaebacteria - Some scientists think that the Eubacteria and
Archaebacteria should be classified as Domains.
7Classifying Prokaryotes
- Eubacteria the larger of the two kingdoms
- Some live in fresh water, salt water, land, on
and within the human body. They can infect large
animals - Eubacteria cell walls protects the cell from
injury and determines its shape - Eubacteria cell walls contain peptidoglycan, a
carbohydrate - Inside the cell wall, a cell membrane protects
the cytoplasm of eubacteria. Some eubacteria
have a second cell membrane outside the cell
membrane
8Classifying Prokaryotes
- Archaebacteria are similar to Eubacteria in that
they are equally small, lack nuclei, and have
cell walls - Archaebacteria do not have peptidoglycan in their
cell walls, plus they have different membrane
lipids - Also, the DNA sequences of key archaebacteria are
more like those of eukaryotes than those of
eubacteria - archaebacteria may possibly be ancestors of
eukaryotes
9tainano.com
10Classifying Prokaryotes
- Many archaebacteria live in harsh environments.
One group of arcaheabacteria is the methanogens,
that produce methane gas. - Methanogens Use only CO2, H and N to produce
energy to live, and as a result give off methane
gas. - Live in swamps, marshes, gut of cattle, termites,
etc. - Methanogens are decomposers
- Other archaebacteria live in
- extremely salty environments or in
- hot springs, mud or digestive tracts
- of animals
www.biology.iupui.edu/.../N100/2k23domain.html
11Classifying Prokaryotes
Bacteria
are classified into the kingdoms of
live in harsh environments such as
include a variety of lifestyles such as
12Classifying Prokaryotes
Bacteria
are classified into the kingdoms of
live in harsh environments such as
include a variety of lifestyles such as
13Identifying Prokaryotes Shapes
- Prokaryotes are identified by
- Their shape
- The chemical nature of cell walls
- The way they move
14Identifying Prokaryotes Shapes
- Rod-shaped prokaryotes are called bacilli
- Spherical shaped prokaryotes are called cocci
- Spiral and corked-shaped prokaryotes are called
spirilla
15Identifying Prokaryotes Cell Walls
- Two different types of cell walls are found in
Eubacteria - A method called Gram staining is used to tell the
two different types of cell walls apart - Violet stain is used to stain the peptidoglycan
cell walls - Alcohol treatment may wash away the violet stain.
If the violet stain remains, then the bacteria
are said to be Gram-positive - These bacteria have thick peptidoglycan cell
walls
16Identifying Prokaryotes Cell Walls
- Gram-negative bacteria have much thinner cell
walls inside an outer lipid layer - Alcohol dissolves the lipid and removes the
violet stain from the cell walls. The
counterstain makes these bacteria appear pink
17Identifying Prokaryotes Cell Walls
- What does the type of cell wall have to do with a
bacteriums resistance to antibiotics? - Gram negative bacterias extra layer outside the
cell wall can make it hard for some antibiotics
to get inside the cell (where they can work). - That makes it important for a doctor to know what
kind of bacteria is causing the infection so that
most effective antibiotic can be used to treat it.
18Identifying Prokaryotes Movement
- How are the ways prokaryotes move?
- Some do not move
- Propelled by flagella
- Lash snake or spiral forward
- Glide
- Which characteristic of prokaryotes illustrates
their diversity best? - By the way they obtain energy
19Identifying Prokaryotes Metabolic Diversity
- Which characteristic of prokaryotes illustrates
their diversity best? - By the way they obtain energy
- Most prokaryotes are heterotrophs, meaning they
get their energy by consuming organic molecules
made by organisms - Other prokaryotes are autotrophs and make their
own food from inorganic molecules
20Identifying Prokaryotes Metabolic Diversity
- Most heterotrophic prokaryotes must take in
organic molecules for both energy and a source of
carbon. These are called chemoheterotrophs. - Humans are also chemoheterotrophs
- If human food is not handled carefully, bacteria
may eat our food and release toxins that cause
food poisoning
21Identifying Prokaryotes Metabolic Diversity
- Photoautotrophs use light energy to convert
carbon dioxide and water to carbon compounds and
oxygen - Photoautotrophs are found where light is
plentiful - The photoautrophs Cyanobacteria contain a bluish
pigment and chlorophyll. They are found
everywhere (land, salt and fresh water) and are
the first to recolonize an area after a natural
disaster.
22Identifying Prokaryotes Metabolic Diversity
- Chemoautotrophs perform chemosynthesis.
-
- They make organic carbon molecules from carbon
dioxide.
23Identifying Prokaryotes Metabolic Diversity
- Chemoautotrophs do not require light as a source
of energy. Instead, they use energy directly
from chemical reactions involving ammonia,
hydrogen sulfide, nitrites, sulfur or iron - Some live deep in the darkness of the ocean
- They use hydrogen sulfide gas that flows from
hydrothermal vents in the ocean
24Identifying Prokaryotes Metabolic Diversity
- Like all organisms, bacteria need a constant
supply of energy. This energy is released by the
process of cellular respiration or photosynthesis
or both - Organisms that require a constant supply of
oxygen to live are called Obligate Aerobes - Obligate Anerobes DO NOT REQUIRE oxygen and may
be killed by it
25Clostridium botulinum
26Clostridium botulinum
- Obligate Anerobe found in soil
- Gram positive
- Rod-shaped
- Grow in can foods that have not been properly
sterilized
27- Faculative Anerobes can live with or without
oxygen - Faculative anerobes can live anywhere because
they can switch between the processes of cellular
respiration or fermentation depending on their
environment
28Escherichia Coli (E. Coli)
29Escherichia Coli (E. Coli)
- Faculative anerobe
- Gram negative
- Rod shaped
- Lives anerobically in large intestine
- Lives aerobically in sewage or contaminated water
30Escherichia Coli (E. Coli)
- Eschericha coli are normal inhabitants of our
digestive tract - A new strain of E. coli (O157H7) has caused
illness and death for people who ate contaminated
hamburger meat.
31Growth and Reproduction
- Bacteria can not grow and divide indefinitely
because of the availability of food and they have
to get rid of wastes - Bacteria grow and divide very rapidly. Their
method of division is called binary fission - Bacteria grow until they double in size, copies
DNA and simply splits into two daughter cells - Binary fission is just asexual reproduction (no
exchange of genetic material)
32Binary Fission
http//www.swt.edu/rr33/
33Growth and Reproduction
- Conjugation A process of exchanging genetic info
in bacteria - A hollow bridge forms between two bacterial cells
and genes move from one cell to the other - Increases genetic diversity of bacteria
34Growth and Reproduction
- When growth conditions become unfavorable, many
bacteria produce spores, which can remain dormant
until there are more favorable growth conditions. - Endospore one type of spore formed when a
bacterium produces a thick internal wall that
encloses its DNA and a portion of its cytoplasm.
35Importance of Bacteria
- We could not survive without bacteria. Some are
producers, others are decomposers, and some are
used by humans for various things.
36Endospores
37Importance of Bacteria
- We could not survive without bacteria. Some are
producers, others are decomposers, and some are
used by humans for various things. - Decomposers
- Bacteria help recycle nutrients in the
environment - Attack and digest dead tissue
- Break down complex compounds in sewage to
simpler ones - Produce purified water
- Produce nitrogen and carbon dioxide gases
- Produce fertilizer compounds
38Importance of Bacteria
- Nitrogen Fixers
- PLANTS NEED NITROGEN TO MAKE AMINO ACIDS which
are used to make PROTEINS - Plants can not use nitrogen gas (N2) directly.
Nitrogen must first be changed chemically to
ammonia (NH3) or other nitrogen compounds. The
process of converting nitrogen gas to a form that
plants can use is called nitrogen fixation. - Many plants have symbiotic relationships with
nitrogen-fixing bacteria. The bacterium
Rhizobium, grows on the roots of soybean plants.
The plant provides nutrients for Rhizobium, and
it converts nitrogen gas in the air to ammonia,
which helps the plant.
39Importance of Bacteria
- Human Uses of Bacteria
- Produce a wide variety of food and beverages
- Industry ? cleaning up oil spills (digest
petroleum) - Mine minerals from the ground
- Remove wastes and poisons from water
- Synthesize drugs and chemicals (genetic
engineering) - Produce vitamins in human intestines
- Produce heat stable enzymes that can be used in
medicine, food production, and industrial
chemistry
40Ch. 19 Outline
- 19-2 Viruses
- What is a virus?
- Viral Infection
- Retroviruses
- Viruses and Living Cells
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42What is a Virus?
- The word virus is derived from the Latin word for
poison - Dmitri Ivanovski identified the cause of tobacco
mosaic disease by extracting juice from an
infected plant - Martinus Beijerinck suggested that tiny particles
in the extracted juice caused tobacco mosaic
disease (called particles viruses) - Wendell Stanley inferred that viruses were not
alive when he obtained crystals of tobacco mosaic
virus
43What is a Virus?
- The word virus is derived from the Latin word for
poison - Viruses particles of nucleic acids, proteins and
in some cases, lipids - Viruses are NON-LIVING, but they do reproduce.
- Viruses can reproduce only by infecting living
cells and once inside, they use the machinery of
the infected cell to produce more viruses
44Viral Structures
A typical virus is composed of a core of DNA or
RNA surrounded by a protein coat.
45What is a Virus?
- The simplest virus may have only a few genes,
whereas the most complex may have more than a
hundred genes - A viruses protein coat is called its capsid. The
capsid includes proteins that enable a virus to
enter a host cell. - The capsid proteins of a typical virus bind to
receptors on the surface of a cell and trick
the cell into allowing it inside.
46What is a Virus?
- Once inside, the viral genes are expressed. The
cell transcribes and translates the viral genetic
information into viral capsid proteins - Sometimes the genetic program causes the host
cell to make copies of the virus, and in the
process the host cell is destroyed.
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48What is a Virus?
- Viruses must bind precisely to proteins on the
cell surface and then use the hosts genetic
system - Viruses that infect bacteria are called
bacteriophages
49Viral Infection
- There are two types of viral infections lytic
and lysogenic - Lytic Infection
- The virus enters the cell, makes copies of
itself, and causes the cell to burst (destroyed) - In a lytic infection, the protein capsid is
activated by contact with a specific host cell - It then injects its DNA directly into the host
cell. - The host cell cannot tell the difference between
its own DNA and the DNA of the virus
50Viral Infection
- Consequently, the cell begins to make messenger
RNA from the genes of the virus - This viral mRNA is translated into viral proteins
that act like a molecular wrecking crew, chopping
up the cell DNA, a process that shuts down the
infected host cell - In this lytic infection, the virus then uses the
materials of the host cell to make thousands of
copies of its own DNA molecule
51Viral Infection
- The viral DNA gets assembled into new virus
particles - Before long, the infected cell lyses or bursts,
and releases hundreds of virus particles that
may go on to infect other cells - Because the host cell is lysed and DESTROYED,
this process is called a lytic infection
52Viral Infection
- Lysogenic Infection
- A host cell makes copies of the virus
indefinitely - A virus incorporates its DNA into the DNA of the
host cell, and the viral genetic information
replicates along with the host cells DNA - Lysogenic viruses do not lyse the host cell
right away. A lysogenic virus remains inactive
for a period of time
53Viral Infection
- The viral DNA that is embedded in the hosts DNA
is called a prophage - The prophage may remain part of the DNA of the
host cell for many generations before it becomes
active. - Eventually, from any number of factors, the DNA
of a prophage will be activated. It will remove
itself from the host cell DNA and direct the
synthesis of new virus particles
54Lytic Vs. Lysogenic
55Retroviruses
- Retroviruses viruses that have RNA as their
genetic material. - When a retroviruses infect a cell, they produce a
DNA copy of their RNA. This DNA, much like a
prophage, is incorporated into the DNA of the
host cell. - There the retrovirus may remain dormant for
varying lengths of time before becoming active
56Retroviruses
- Retroviruses get their name from the fact that
their genetic information is copied backwards,
that is from RNA to DNA instead of from DNA to
RNA. -
- The prefix retro means backwards
- The virus that causes acquired immune deficiency
syndrome (AIDS) is a retrovirus and some cancers
are caused by retroviruses
57Figure 18.9 The structure of HIV, the retrovirus
that causes AIDS
58Figure 18.10 The reproductive cycle of HIV, a
retrovirus
59Viruses and Living Cells
- Viruses must infect a living cell in order to
grow and reproduce - Viruses take advantage of the hosts respiration,
nutrition, and all other functions and are
therefore parasites - Viruses are not alive because they are not made
up of cells and are able to live independently
60Viruses and Living Cells
- Yet viruses can reproduce, regulate gene
expression and even evolve after infecting living
cells - Viruses are at the borderline of living and
non-living things
61Viruses and Living Cells
- Viruses were not probably the first living things
because they are completely dependent on living
things - Viruses may have evolved from the genetic
material of living things
62Ch. 19 Outline
- 19-3 Diseases caused by bacteria and viruses
- Bacterial Diseases in Humans
- Controlling Bacteria
- Viral Diseases
- Viroids and Prions
63Bacterial Diseases in Humans
- Pathogen disease-causing agents
- Disease can be considered a conflict between the
pathogen and the host - Louis Pasteur was the first scientist to show
that bacteria cause a number of human and animal
diseases (The Germ Theory)
64Bacterial Diseases in Humans
- Bacteria produce disease in one of two ways
- Damage the cells and tissue of the infected
organism by directly breaking down the cells for
food - Release toxins (poisons) that travel throughout
the body and interfere with normal activity of
the host.
65- The gram positive bacterium Mycobacterium
tuberculosis is inhaled into the lungs where it
destroys lung tissue - If bacterium enters a blood vessel, it may travel
to new sights and destroy more tissue
66- The Gram positive strain of the Streptococcus
bacterium from Group A causes strep throat by
releasing toxins into the blood stream - This infection can also cause damage to the heart
valves (rheumatic fever) and kidneys (nephritis).
Streptococcal infections can also cause scarlet
fever, tonsillitis, pneumonia, sinusitis and ear
infections.
67- The Gram positive bacterium Corynebacterium
diptheria which causes diptheria infects the
tissues of the throat and releases toxins into
the blood stream - Diptheria can lead to breathing problems, heart
failure, paralysis, and death
68Preventing bacterial disease
- Vaccine preparation of weakened or killed
pathogen - Prompts bodys immune system and promts the body
to produce immunity to the disease - Immunity is the bodys ability to destroy new
pathogens - Antibiotics compounds that block the growth and
reproduction of bacteria
69Antibiotics
- Antibiotic-resistant bacteria bacteria that
have mutated that make them no longer susceptible
to the effects of antibiotics - Genetic mutations for antibiotic resistance
happen spontaneously as a result of errors in DNA
replication - Taking Antibiotics eliminates the susceptible
bacteria from the body and leaves the resistant
bacteria, allowing them to reproduce and pass on
their genetic traits (bacteria reproduce very
rapidly!!!)
70Antibiotics
- Antibiotic misuse
- Usually, if a full course of an Antibiotic is
taken, all the targeted bacteria are killed and
there is no chance for a resistant strain to
evolve - but if the antibiotic is stopped early, the
surviving bacteria will be the ones that were
most resistant to the antibiotic
71Antibiotics
- There are now strains of tuberculosis and S.
aureus that are resistant to multiple drugs
hard to treat! (Multiple Drug Resistant Bacteria) - Widespread use of antibacterial soaps can cause
antibiotic resistant strains of bacteria to evolve
72- Bacillus Anthracis (Anthrax)
- Gram positive
- Forms endospores
- Found in soil or on the fur of animals or in
their digestive tracts - Dangerous to humans and animals
- Lung, intestines, and skin
- Respiratory difficulties, fever, diarrhea, rash
73Food Poisoning
- Staphylococcus aureus
- Gram positive
- causes the most common type of food poisoning
- painful diarrhea and vomiting
74Food Poisoning
- Salmonella bacteria (from unprocessed milk,
pork, poultry, eggs) - Gram negative
- cause vomiting, nausea, and stomach cramps, which
can lead to fever and death (especially in the
very young or very old)
75Bacteria Table
76Preventing bacterial disease
- Controlling Bacteria
- There are various methods used to control
bacterial growth - Sterilization kills pathogenic bacteria with heat
- Disinfectants are chemical solution that kills
pathogenic bacteria - Overuse of disinfectants increase the likelihood
that common bacteria will eventually evolve to
become resistant to them and therefore much
more dangerous and difficult to kill
77Preventing bacterial disease
- Controlling Bacteria
- Food processing allows storage of food in
refrigerators to prevent (delay) spoilage, or
cooking of food at high enough temperatures to
kill pathogens - Canning preserves food for a long time. Food is
heated to a high temperature and placed in
sterile glass jars or metal containers and
sealed. Food that has been properly canned will
last almost indefinitely. - Treating food with everyday chemicals such as
salt (salted meat), vinegar (pickled vegetables),
or sugar (jam) will preserve food.
78Viral Disease in Humans
- Like bacteria, viruses produce disease by
disrupting the bodys normal equilibrium. - Viruses may destroy cells they infect or cause
infected cells to alter their growth and
development - Unlike bacteria, viral diseases cannot be treated
with antibiotics, but there are some vaccines
against viruses. Vaccines should be used before
an infection begins
79Viral Disease in Humans
- Oncogenic or tumor causing viruses may produce
cancer by disrupting the normal controls over
cell growth and division - Rous Sarcoma Virus in chickens
- Human Papilloma Virus genital warts cervical
cancer
80Viral Disease in Humans
- Hepatitis B Virus Liver cancer
- Epstein-Barr Virus (the virus that causes mono
or even chronic fatigue syndrome) Burkitts
lymphoma
81Viral Disease in Plants
- Plant viruses pose a serious threat to the foods
we eat - Viruses have a hard time entering plant cells
because plant cells have a tough cell wall - Viruses enter plants through tears in leaf
tissues, breaks in stems or roots, or
microscopic cell wall damage - Most plant viruses are spread by feeding action
of insects
82Virus Disease Table
83Viroids and Prions
- Scientists have discovered two other virus-like
particles that also cause disease Viroids and
Prions - Viroids cause disease in plants
- Prions cause disease in animals
- Viroids Single-stranded RNA molecules that have
no surrounding capsids - Affect _______ Cells
84Viroids and Prions
- Viroids Single-stranded RNA molecules that have
no surrounding capsids - It is believed that viroids enter an infected
cell and direct the synthesis of new viroids - The viroids then disrupt the metabolism of the
plant cell and stunt the growth of the entire
plant
85Prions
- Prions contain no DNA or RNA only protein
- Disease-causing proteins are folded into the
wrong shape, which does not allow it to function
as it should. - If a normal prion comes into contact with a
disease-causing one, the normal one will also
change its shape so that it is folded wrong and
no longer functions either in this way, the
disease spreads - Diseases such as Scrapie (sheep), mad cow
disease, Creutzfeldt-Jacob disease (in humans)
are all prion diseases that can be distributed by
eating meat that contains the malfolded prion.
86Prions