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Viruses and Bacteria
Chapter 18
Remember the requirements of
living things
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Made of Cells
Reproduce
Use energy, Grow and Develop
Homeostasis
Heredity/Pass of Traits
Adapt to Environment/Evolve
Interdependence
Not Alive?
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Not made of cells
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Segment of nucleic acid in a protein coat
No respiration, growth and development
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Viruses – Latin for
“poison”
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Very small
Cause disease –
pathogens
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Infect cell and use
it to reproduce
Discovered in 1835
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Variety of shapes
Naming Viruses
1. After disease they cause
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Rabies viruses
Poliovirus
2. After organ or tissue they infect
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Adenovirus = adenoids
3. Most now have genus ending in “virus”
4. Code numbers for similar viruses
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Escherichia coli has T1 to T7 (T = type)
5. If infects bacteria = bacteriophage or
phage
Structure
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Protein coat (capsid)
may contain RNA or
DNA but not both
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RNA – AIDS, Flu,
Rabies
DNA – Warts,
Chickenpox,
Mononucleosis
May have a
membrane (envelope)
surrounding capsid to
help it enter cells
Attachment is Specific
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Virus must attach
before it can infect
Protein coat of virus
attaches to protein
on host cells surface
Attachment protein
for each virus is very
specific
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Polio virus only
infects intestine
and nerve cells
Smallpox only
infects humans
Viral Reproduction
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Have to use host cells for replication
May enter plant cells through points of
injury and animals by endocytosis
Lytic Cycle
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Viral infection, replication and cell
destruction
Lysogenic Cycle
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No new viruses made
Provirus – viral gene inserted in host
chromosome with copies made when cell
divides
Change in environment may cause lytic
cycle to start
Symptoms of Proviruses
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Because lysogenic in
reproduction it can
remain in cells until a
flare up
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Herpes simplex I =
coldsores
Herpes Simplex II =
genital herpes
Hepatitis B =
hepatitis B
Chicken Pox virus can
later cause shingles
(painful infection of
some nerve cells)
Retroviruses
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Only have RNA, no DNA
Makes DNA from RNA using reverse
transcriptase it carries
DNA placed into host DNA and becomes provirus
If person has reverse transcriptase in them it
means they have been infected with a retrovirus
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HIV
How HIV Infects Cells
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Attachment
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Virus surface studded
with glycoproteins
Fits human cell
receptor CD4
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Humans have CD4 on
immune system cells
called lymphocytes
and macrophages
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Entry into Macrophages
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Matches both the CD4 and CCR5 so can enter
Lymphocytes do not have CCR5 so can’t enter until
later
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Replication
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Inside the capsid
comes apart and
releases RNA
Reverse
transcriptase in
virus makes a DNA
version of the RNA
(lots of mistakes so
lots of mutations)
Viral DNA inserts
into host DNA and
makes copies of
itself
New viruses bud
out without killing
cell
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AIDS
 Continues to replicate
and mutate for years
 Eventually recognize
glycoprotein on
lymphocyte called T cells
 T cells are destroyed
 T cells are important in
immune system, without
them you can’t fight off
other diseases
 Spread through semen
or vaginal fluid not
casual contact
Other Viral Diseases
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Influenza – Flu Virus
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Upper respiratory infection
1918 – 1919 22 million Americans and Europeans
die
36,000 per year estimate now
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Cancer
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Hepatitis B = liver
cancer
Epstein-Barr =
Burkitt’s lymphoma
Human Papilloma
Virus = cervical
cancer
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Smallpox
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variola virus
Humans only natural host
Prolonged face-to-face contact, bodily fluids,
air in enclosed spaces, contaminated objects
Fever, red spots on tongue, rash to bumps
that have a belly button look to feeling like
BB pellets under skin
30% die; survivors may go blind and have
scars
Vaccines led to eradication
 Last natural case = 1977
 Lab acquired case = 1978
Emerging Diseases
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1999 – West Nile
Virus
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Spread by mosquito
mild flu-like symptoms
In elderly possible
inflammation of brain
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Hanta Virus
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Southwest United States
38% death rate
Prions and Viroids
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Prion
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Folded proteins but no
nucleic acids
Mad Cow Disease
Creutzfeldt-Jakob Disease
Viroids
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Single strand of RNA with no
capsid
Hepatitis D
18.2 Archaebacteria and Eubacteria
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Prokaryotes
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No Internal Compartmentalization – no
nucleus or organelles
Cell size generally smaller
All are single celled
Single circular strand of DNA
Reproduce by binary fission
Simpler flagella than eukaryotes
More metabolic diversity – can survive without
oxygen
Structure & Reproduction of
Bacteria
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Cell wall keeps it from bursting
May Reproduce by Binary Fission
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Simple asexual reproduction by dividing in two
May happen every 20 minutes
May Reproduce by Conjugation
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Form of sexual reproduction where 1 bacterium
transfers all or some of its genetic material to another
New genetic combination
Bacterial Cell
Shapes
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Bacillus - rod
Coccus - round
Spirillum - spiral
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Strepto – form
strands
Staphylo - clusters
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Strep Throat
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group A
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Initial symptoms
streptococcus
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Other symptoms
after 3 days
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Fever, stomach pain, and
red, swollen tonsils
Red and white patches in
throat, difficulty
swallowing, headache
Rapid test
If positive 10-days
antibiotics
If untreated more
sever sickness may
occur
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Gram-staining – dye
reacts with cell wall
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Gram positive or Gram
negative
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Antibiotics –
interfere with life
processes of
bacteria
Chapter 19 Protists
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Protist
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Uni- or multicellular
Microscopic or very large
Heterotrophic or autotrophic
All Eukaryotes – have membrane bound
organelles
Can cause diseases like malaria or sleeping
sickness
Protozoa 19.1
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Animal-like so heterotrophs
All unicellular
Protozoa: Amoebas
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Use pseudopodia for
movement and
feeding
No cell wall
Asexual Reproduction
Protozoa: Flagellates
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Have one or more
flagella
Harmful and
beneficial
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African sleeping
sickness
Termite symbiosis
Protozoa: Ciliates
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Use cilia to move
Asexual or like
conjugation
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Paramecium
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Protozoa: Sporozoans
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Most reproduce using
spores
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Reproductive cells
develop without
fertilization
All are parasites
Malaria
Algae 19.2
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Plant-like autotrophs using photosynthesis
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No roots, stems, or leaves
Unicellular (a.k.a. phytoplankton) or
multicellular
Fungus-like Protists 19.3
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Decompose organisms
Can move and contain no chitin in cell wall