Chapter 19
Viruses and Bacteria
Viruses
• Viruses are NOT cells!
• A virus is made up of:
1.Nucleic acid
(RNA or DNA)
2. Protein coat
What is a virus?
• Made of nucleic acid
(DNA OR RNA),
protein coat (capsid)
and sometimes lipids
• MUST enter living cells
in order to reproduce
• Very small
• Range from a few to
100s of genes
Bacteriophage = virus that
infects bacteria
Viruses: Living or Non-living?
• No cell membrane or other living cell
components
• Host cells required for reproduction
• Do not metabolize or respond to stimuli
• BUT, they do have genetic info and can
change over time
Virus Infection:
Lytic vs. Lysogenic Cycles
• Lytic Cycle:
virus enters cell,
makes copies of
itself, and causes
the cell to “lyse”
or burst
• Lysogenic Cycle:
virus integrates into
host cell DNA and
viral genetic info is
copied along with
host cell’s DNA
Lytic Cycle
The viral infection that
rapidly kills the host cell is
the lytic cycle.
Lytic Cycle of a
Cold or Influenza
Virus
The cold or flu virus
infects cells lining of
the nose and throat,
reproducing more
cold viruses and
destroying body
cells.
Review Lytic and Lysogenic Cycles…
• Handouts from book!
Retrovirus
• A virus that contains
RNA instead of DNA
• Human
Immunodeficiency
Virus (HIV) is a
retrovirus
• HIV causes AIDS
ENVELOPE
RNA
CAPSID
HIV Virus and Immune System
The thymus gland by
the heart and the bone
marrow produce the
white blood cells that
protect us from
infection.
HIV attacks the T cell
of the immune system.
Retroviruses
• When enter cells, produce
DNA copy of RNA then
integrate into host cell
• Can remain dormant until
replicate and burst open
cell
• “Retro” because genetic
info is copied backwards
RNA => DNA
• Destroys helper T cells
–Makes getting other diseases
really easy
• Transmitted by blood,
breast feeding, sexually, and
other bodily fluids
• Can happen to anyone!
Mouth sores common to AIDS patients
Viruses as Parasites
• Take advantage of
host cell’s
respiration, nutrition
and other cellular
functions
• Depends entirely on
another organism for
its existence
Types of Viral Diseases
• Must know
– Names
– Symptoms
– Transmission
West Nile
• Symptoms
– Fever
– Headache
– Body ache
• Transmitted by
– infected mosquitoes
Chicken Pox
• Symptoms
– Fever and weakness
– Red, itchy rash
• Transmitted by
– Direct contact
– Droplet inhalation
Common Cold
• Symptoms
– Sneezing
– Sore throat
– Fever
– Muscle and headaches
• Transmitted by
– Direct contact
– Droplet inhalation
Warts/HPV
• Symptoms
– Noncancerous growths on
skin; can become
cancerous
• Transmitted by
– Direct contact
– Sex
Hepatitis
• Symptoms
– Jaundice
– Fatigue
– Abdominal pain
– Diarrhea and nausea
• Transmitted by
– Human waste, contaminated
food and water (Hep A)
– Contact w/ bodily fluids (B & C)
Herpes
• Symptoms
– Blister like sores (can
actually be on any part of the
body)
– Fever
– Fatigue
• Transmitted by
– Direct contact
– Sex
Measles
• Symptoms
– High fever
– Sore throat
– Rash
– Swollen eyelids
• Transmitted by
– Droplet inhalation
Polio
• Symptoms
– Fever
– Headache
– Muscle weakness
– Difficulty swallowing
• Transmitted by
– Droplet inhalation
Smallpox
• Symptoms
– High fever
– Fatigue
– Rash
• Transmitted by
– Contact
– Droplet inhalation
Virus Prevention
(No treatments!)
• Vaccination
– Injection of weakened or dead pathogen
• Hygiene
– Wash your hands!
• Safe sex
– Use condoms or other
prophylactic contraceptives
• Abstinence
– Only method that is 100% effective against
transmission of sexually transmitted viruses
Bacteria
Bacteria are small
PROKARYOTIC
cells.
They have a cell
wall and DNA.
Some bacteria are
beneficial and
some are
pathogenic.
*Pathogenic = disease causing
Bacteria
• Used as a common
name to describe
prokaryotes
• Usually range from
1-5 micrometers!
• Divided into two
kingdoms:
eubacteria and
archaebacteria
Staphylococcus epidermidis
Eubacteria
• Largest bacterial Kingdom
• Wide range; many lifestyles,
live almost anywhere
• Usually have cell wall for
shape and protection - cell
wall contains peptidoglycan
• Have cell membranesometimes an extra
membrane outside of it as
well
Escherichia coli
Archaebacteria
• Look similar to eubacteria under
microscope but chemically different
• No peptidoglycan & different membrane
lipids
• DNA more like eukaryotes (Share a
more recent common ancestor)
• Live in extreme/harsh environments
How Are Bacteria Identified?
Identified by:
– Shape
– Movement techniques
– Way of obtaining energy
– Oxygen Needs
– Mode of Reproduction
Shape
• Rod-shape:
Bacilli
• Spherical
shape:
Cocci
• Spiral and
corkscrew:
Spirilla
Movement
• Not all prokaryotes can move
• Ones that move
– Propelled by flagella (whiplike structures for
movement)
– Lash, snake or spiral
– Glide along layer of slime
Escherichia coli
Start taking notes here:
Metabolic Diversity:
Heterotrophs vs. Autotrophs
• Most are heterotrophic!
• If autotrophic:
– Some are photoautotrophs (similar to plants)
– Some are chemoautotrophs (make organic molecules
from CO2
• If heterotrophic:
– Most are chemoheterotrophs (Take in organic
molecules for energy and carbon supply)
– Humans are chemoheterotrophs, too!
– Some are photoheterorophs (photosynthetic but need
organic compounds for carbon source)
Oxygen Needs
• Facultative anaerobes
– Can survive with or without oxygen
• Obligate anaerobes
– Must live in the absence of oxygen
• Obligate aerobes
– Require constant supply of oxygen to live
Growth and Reproduction
• Conjugation
– Asexual Reproduction
– Hollow bridge forms
between two cells and
genes move from one
cell to the other;
increases genetic
diversity
– IS a sexual process
(NOT
REPRODUCTION –
does not produce
gametes)
Binary Fission
• Asexual Reproduction
– Grows to where it doubles in size then
replicates DNA and divides in half
– New bacteria gentically identical
The Role of Microorganisms in
Maintaining Equilibrium in the
Environment
Importance of bacteria
Bacteria are vital to maintaining the living
world!
Not all are pathogenic!!!
Helpful Bacteria
• Decomposers break down dead organic material
• Biotechnology - inserting helpful genes into a
plasmid
• Bioremediation - bacteria eat up oil spills
• Food production
• Nitrogen fixation – convert atmospheric nitrogen
into a usable form the plant can take in from the
soil
• Aid in digestion
Importance of bacteria
Some are producers that capture
energy by photosynthesis.
Importance of bacteria
Others are decomposers breaking down
nutrients in dead matter.
Bacteria breakdown dead and decaying
organisms.
Help to recycle nutrients – which helps to
maintain equilibrium in the environment.
Bacteria also help perform critical steps in
sewage treatment.
Importance of bacteria
Bacteria convert nitrogen gas into a form
plants can use, this is called nitrogen
fixation.
Nitrogen fixation allows nitrogen atoms
to continually cycle through the
biosphere.
Nitrogen fixing bacteria
in the nodules of roots
Importance of bacteria
Bacteria are also used to make some
foods such as:
-pickles!
-ice cream!
-yogurt!
Bacteria’s Importance
• Producers
• Nitrogen Fixation
• Human Uses
–
–
–
–
–
–
Food and beverage production
Industry
Drug and chemical production
Live in our intestines; provide vitamins
Biotechnology
Clean up oil spills
• Decomposers
– Recycle nutrients in ecosystem
– Sewage treatment
Pathogenic Bacteria
Two ways bacteria causes diseases:
1. Break down organism’s cells for food
2. Release toxins that affect the
organism’s body
Examples of Bacterial Diseases
• Streptococcus
– Symptoms – fever, sore throat, swollen
glands
• Diphtheria
– Symptoms – sore throat, low grade fever
**Both cause disease by releasing TOXINS!!
Circulatory System
Bacteria can
infect the heart
valves and the
lining of the
ventricles.
Left
ventricle
The circulatory
system brings
oxygen and
nutrients to all
body cells.
Beneficial Bacteria in the
Digestive System
Bacteria like E. coli
make digestive
enzymes and
vitamin K in the
large intestine.
Brain
Spinal
cord
Spinal&
peripheral
nerves
Nervous System
The nervous
system responds
to changes in the
external and
internal
environment. It is
“the
communicator”.
Nervous System Infections
Both bacteria
and viruses can
infect the brain
causing such
diseases as
meningitis and
encephalitis.
Nerve cells or
Neurons
Controlling Bacteria
• Food storage and processing
• Disinfectants
– Chemical solutions that kill bacteria
• Sterilization
– Method to control growth of bacteria by heat
• Vaccines – Prevention!
– Weakened or killed pathogens
– Sometimes prompts body to produce immunity
• Antibiotics – Treatment!
– Block growth of bacteria
Comparing VIRUSES and
BACTERIA
A.
B.
1. Which is a virus?
2. Which is a bacteria?
3. Which is living?
4. Which is non-living?