Transcript Biology\Viruses, Bacteria, & Infectious Diseases

Viruses, Bacteria, & Infectious Diseases
Learning Target Objectives: (I can …)
• Compare and contrast viruses to bacteria: their spread, our
immune response, and the treatments used for each.
• Classify viruses and prokaryotes based on shape, gram-stain
results, etc. describing bacterial and viral structure and
reproduction.
• Evaluate the effects of bacteria on humans, good and bad.
• Predict the significance to health of the different stages of a
viral or bacterial infection.
• Design a controlled experiment using bacteria.
• Research and identify illnesses/diseases and the organisms
that cause them.
• Discuss the importance of the contributions made by
scientists such as Jenner, Sabin, Salk, etc. to health/medicine.
•Explain the body’s immune response to illness.
Vocabulary:
Capsid * reverse transcriptase * retrovirus *
bacteriophage * lytic cycle * lysogenic cycle * Edward
Jenner * Salk & Sabin * Louis Pasteur * monera *
cocci * bacilli * spirilli (spirochete) * diplo- * strepto* staphylo- * archaeo- * anaerobes * halophile *
thermoacidophile * gram negative * gram positive *
plasmids * endospores * saprophyte *
parasite/pathogen * autotroph * obligate anaerobes *
facultative anaerobes * obligate aerobes * binary
fission * conjugation * pili * toxin * endotoxin *
exotoxin * antibiotics * pathogen * Koch’s postulates
* phagocytes * inflammatory response * neutrophils *
macrophages * interferon * arthropods * antigen *
lymphocytes * antibodies * immunity * vaccination *
allergy * histamine * polio * AIDS * cyanophyta
Viruses
• Not classified in any of the 5 kingdoms
• Considered non-living because they cannot reproduce
without a host’s help
• Are sub-cellular agents made of nucleic acid (either RNA
or DNA) surrounded by a protein “coat”
Viral Structure:
1) a piece of nucleic acid
2) capsid – a protein coat which holds the nucleic acid
No nucleus, no organelles.
Must use a host’s organelles to make more viruses.
Viral Spread:
Viruses cannot move on their own. They move by hitching
a ride on dust and water droplets in the air. They can be
spread through food, drink, saliva, blood, or other body
fluids, as well as insect bites.
Viral Invasion:
1) Virus attaches to host cell.
2) Viral nucleic acids are injected into host cell. Capsid
remains outside of cell.
3) Viral nucleic acid “turns off” host cell processes and
redirects the cell to make new viral nucleic acid and
capsids.
4) Viral components join togather
5) Host cell, bursts releasing viruses.
DNA Viruses:
1) May link to host DNA and then make RNA, then protein,
etc. as needed.
OR
2) May start making its own RNA that will direct ribosomes
to make viral protein.
RNA Viruses:
1) The viral RNA may direct protein synthesis directly. (Ex:
polio virus)
OR
2) The RNA may be transcribed in reverse using reverse
transcriptase to make DNA. The DNA makes new RNA
which then directs viral protein synthesis. This type of
virus is called a retrovirus. (Ex: AIDS virus)
Bacteriophage – virus that invades bacteria.
Many bacteria are NOT (as) harmful until infected with viruses that
use the bacteria to make toxins. Ex: diphtheria bacteria and scarlet
fever – when streptococci bacteria are invaded.
Viral Cycles (Stages):
Lytic cycle – virus replicates in host, then breaks it open, spreading
viruses to new cells.
Lysogenic cycle – virus invades host cell, may join with the DNA but
remains inactive (dormant) unless “irritated”.
Common Viral Disorders:
Papillomavirus (warts)
Herpes viruses (chicken pox, shingles, mononucleosis)
Herpes Simplex (cold sores, STD)
Smallpox
Rabies
Polio
Flu or Adenovirus
Encephalitis
Epstein-Barr (mono – it affects B-cells)
Measles
AIDS (affects T-cells)
Mumps
Cancer?
Because viruses live inside our own cells, they are difficult
to kill without killing our cells too. Some treatments
include:
AZT (AIDS)
Acyclovir (a.k.a Zovirax or Valtrex – prevents viral
replication)
Interferon (one of our bodies natural responses)
Vaccination (prevention rather than treatment)
“fever”
Important Scientists:
Edward Jenner – used vaccine made from cowpox to
prevent smallpox
Salk and Sabin - polio vaccines (affected Pres. Franklin
Roosevelt)
Louis Pasteur – rabies vaccine
Bacteria
Kingdom: Monera
• Prokaryotes (no membrane bound organelles or nucleus)
• Single-celled
• Microscopic
3 general shapes of bacteria:
1) spherical (cocci)
2) rod-shaped (bacilli)
3) spiral (spirilli or spirochetes)
Prefixes for bacterial colonies:
Diplo – in pairs
Strepto – in chains
Staphylo – clusters (like grapes)
All 3 shapes can exist as single cells.
Kingdom Monera:
4 Phyla:
1) Phylum Archaebacteria:
Archaeo – ancient
These live in harsh, primitive environments where most
other organisms could NOT survive.
a) methanogens – live in some digestive tracts, at the
bottom of bogs, and in sewage treatment ponds. They
use CO2 and H2 to form methane (CH4) and water.
They are anaerobes – live only in areas where free
oxygen is not found.
b) extreme halophiles –
phile- “lovong” halite – salt
Salt loving bacteria live in high salt areas such as the
Great Salt Lake and the Dead Sea.
c) thermoacidophiles –
thermo – heat
Live in very hot, acidic areas such as the hot springs of Yellowstone
National Park or in other volcanic areas.
2) Phylum Schizophyta:
Contains 4 classes which can be further classified by their reaction to
Gram stain (crystal violet).
a) Gram-negative bacteria – have a protective (peptoglycan) layer which
resists taking on a full stain (stain pink).
* HARD to kill with antibiotics.
b) Gram positive bacteria – don’t have the protective coating. They take
on crystal violet stain (stain purple).
Can be killed fairly easily with antibiotics.
-----------------This phylum has bacteria which cause: diptheria, tuberculosis, typhus,
syphillis, Lyme’s disease,. But some also produce antibiotics.
3) Phylum Cyanophyta:
• Also called blue-green bacteria
• Autotrophs, contain chlorophyll & other pigments but no
chloroplasts.
The Red Sea got its name from occasional large
populations of red pigmented bacteria (blooms).
• Often confused with algae
• Some found in soil will form nodules in legume (peas,
beans, etc) roots to “fix” nitrogen.
4) Phylum Prochlorophyta:
• Live with saltwater organisms. (Some consider this a
sub-group of cyanophyta but these may only contain
chlorophyll, no other pigments.)
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Moneran (bacterial) Structure & Movement
Single chromosome of DNA in a circular shape
May have plasmids (smaller, separate circular DNA pieces)
Have cell walls
Some produce protective capsules around their wall (gram-negative
bacteria)
May produce endopsores – an envelope that allows the bacteria to
become dormant and resist heat, cold, chemicals, etc. until a better
environment returns.
May move by flagella or filaments
Nutrition:
Heterotrophs:
1) Saprophytes – feeds on dead or decaying matter (Help recycle
nutrients)
2) Parasites/pathogens – absorb nutrients from a host, may result in
disease.
Autotrophs: 1) photoautotrophs- use sunlight to make food,
2) chemoautotrophs – use chemical energy to make food
Bacterial Respiration:
Obligate anaerobes – can not survive in environment with
oxygen (Ex: methanogens)
Facultative anaerobes – can live with OR without oxygen
Obligate aerobes – require oxygen (Ex: bacteria that infect
the lung, like tuberculosis)
Reproduction:
• Can divide about every 15 minutes
• Binary fission – asexual, splitting into two.
• Conjugation – a piece of DNA from one bacteria is
transferred to another across a pili bridge. This DNA is
then incorporated into the new bacteria’s existing strand
or as a separate plasmid.
Toxin Production:
Toxin – a poison
Endotoxin – in cell walls of gram-negative bacteria. Cause
fever, weakness, etc.
Exotoxin – bacterial wastes secreted out. VERY potent. Ex:
tetanus exotoxin, diphtheria, botulism.
Many bacteria only begin producing certain toxins if infected
by a virus (bacteriophage)
---------------------Antibiotics – chemicals produced by microorganisms that
inhibit growth of or kill other microorganisms.
Some Bacterial Diseases:
Rickettsia – spread by ticks & lice, causes Rocky Mountain Spotted
fever.
Lyme disease – spread by deer ticks (possibly other ticks). Can cause
paralysis, etc.
Botulism – deadly food poisoning (double vision is a symptom)
Gonorrhea – sexually transmitted disease.
Strep throat/scarlet fever/rheumatic fever – caused by Streptococcus
pyogenes (Note: There are many different strep strains out there.)
Impetigo – usually staphylococcus 9sometimes strep)
Plague (Black Death, Bubonic plague) – spread by rat fleas
Tetanus – causes “lockjaw”
Cholera – spread through water usually
Syphillis – STD
Control Bacterial Spread by:
Heating, drying, preservatives (dehydrate bacteria), freezing
(SLOWS growth & reproduction but doesn’t kill bacteria), antibiotics
(but these also kill the good bacteria
Infectious Diseases
Pathogen – any agent that causes an infectious disease (a disease that
can be spread from 1 host to another). Pathogen Exs: bacteria,
invertebrates (such as worms).
Identifying Pathogens:
Koch’s Postulates are used to identify a pathogen.
1) isolate the suspected organism from its host
2) grow the organism in pure culture in the lab
3) inject the lab grown organism into a healthy host
4) wait to see if the same disease appears. If it does, you’ve found the
pathogen.
Some pathogens produce toxins (harmful chemicals). One of the most
damaging types are neurotoxins. These attack nerve cells and
prevent transmission of nerve impulses. (Ex: botulism – produces a
neurotoxin which causes double vision and possibly death)
Beneficial Bacteria
***(put list on back of your note outline packet)
Used to produce:
Vinegar, Yogurt, Sauerkraut, Pickles, Cheeses,
Vitamin K – made by bacteria in our intestines, used for
normal blood clotting
Insulin – human DNA is inserted in bacteria. The bacteria
“read” the human gene and produce insulin.
Antibiotics – many are produced by bacteria or other
microorganisms.
Disease Transmission (spread):
Microorganisms can be spread from host to host by: air, water,
direct contact, and arthropods (crayfish, spiders, insects, ticks, etc.)
The microorganisms may be transmitted in dormant form as a
spore or a cyst. This protects the organism from damage or death
until it finds a host.
Immune Response: Our reaction to foreign substances.
Nonspecific Defenses:
1) skin, mucous membranes, etc. (our first line of defense) prevent
pathogens from entering the body. Tears, sweat, saliva, and urine
contain chemicals that kill some pathogens.
2) Pathogens that get into our body, past our first line of defense, can
start an infection. This causes an inflammatory response (swelling,
warmth, fever, redness, pain) which brings white blood cells (WBCs)
to the area.
WBCs involved in the inflammatory response include 2
types of phagocytes (Phagocytosis = cell eating by
engulfing particles):
1) neutrophils – small WBCs that surround and eat small
numbers of bacteria.
2) macrophages – large WBCs that ingest large numbers of
bacteria.
(***Note: There are many other types of WBCs.)
A nonspecific immune response to a viral infection involves
the production of a protein known as interferon.
Interferon prevents viruses from reproducing.
Genetic engineering has helped increase the production of
interferon. Interferon is also being studied as a cancer
fighting agent and is used to treat AIDS (however, it’s not
a cure.)
Specific Immune Defenses:
Specific pathogens can be recognized by our immune system.
Antigen – usually proteins found on or produced by pathogens which
cause our immune system to react in a specific way.
Lymphocytes – special WBCs including B-cells (attacked by mono) and
T-cells (attacked by AIDS)
T-cells : (differentiate/mature in the thymus gland) attack antigens
directly by joining with the pathogen.
There are several T-cell types including memory cells which
recognize antigens that have attacked before. Usually memory cells
can kill the pathogen before symptoms arise for the second time.
B-cells : (differentiate/mature in the bone marrow) produce antibodies
(Y-shaped proteins that bind to and destroy antigens.)
Immunity and Immune Disorders:
Immunity – resistance to a specific pathogen.
Vaccination – exposure to a “killed” or “weakened”
(attenuated) virus/pathogen, given as an injection. This
usually gives the person immunity to this pathogen.
Antibiotics – drugs that fight bacterial infections. Ex:
Penicillin (discovered by Sir Alexander Fleming. It is
produced by a mold.
Note: don’t confuse antibiotics with antibodies which are
bodies make.
Allergy – an immune response to a harmless (nonpathogen) antigen. The response may include the
release of histamine, a chemical that causes watery
eyes, runny nose, etc. in an attempt to flush out the
antigen.
AIDS
Acquired Immune Deficiency Syndrome
• caused by HIV (human immunodeficiency virus)
• This is a retrovirus
• Transmitted through sexual contact, contaminated
syringes, infected blood
• Enters T-cells and are unaffected by antibodies
• May remain in a lysogenic state for 10 years or so before
becoming lytic. (This destroys the T-cell leaving the
person susceptible to other illnesses.)