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Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Jan 22, 2016

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Page 1: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

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Page 2: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Ch 18

Microbial Models: Genetics

of Viruses and

Bacteria

Page 3: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.
Page 4: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.
Page 5: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.
Page 6: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

VirusVirus-

*biological particle (not a cell)*composed of nucleic

acid (RNA or DNA)

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VirusVirus-

*surrounded by capsid

(protein coat) and sometimes a

viral envelope (membrane surrounding)

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Page 9: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

The head of a dress-maker's pin

can provide seating accommodation for

five hundred million

rhinoviruses (cause of the common cold)

!

Page 10: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Why not alive?•Lacks: nucleus, cytoplasm, organelles, cell membrane

Page 11: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

•Why not alive? •No reproduction by mitosis No meiosis

(require a host cell in order to reproduce)

obligate intracellular parasites

Page 12: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

•Why not alive? •Resistant to Resistant to alcoholalcohol

resistant to dehydration by

osmosisobligateobligate

intracellularintracellular parasitesparasites

Page 13: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

•Why not alive? •virus virus crystallizationcrystallization

cells cannot form crystals

obligateobligate intracellularintracellular

parasitesparasites

Page 14: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.
Page 15: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lytic Lytic CycleCycle

Page 16: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lytic Cycle

“lock & key”

Page 17: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lytic Cyclephage injects DNA

(hopefully, for the virus, it is resistant to the restriction nucleases!)

Page 18: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lytic Cyclephage DNA hydrolysises bacterial DNA via. enzymes

Page 19: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lytic Cyclephage proteins are produced, phage DNA reproduced

Page 20: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lytic Cyclehost cell provides: nucleotides, ribosomes, tRNA etc.

Page 21: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lytic CycleLysozyme produced and bacterial wall is digested

Page 22: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lytic Cycle

Page 23: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lytic Cycle

Page 24: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lysogenic Lysogenic CycleCycle

Page 25: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lysogenic Cycletemperate temperate virusesviruses

Page 26: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

““phage” phage” inserts inserts DNA; via. DNA; via. “lock & “lock & key”key”

Lysogenic Cycle

Page 27: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

encorporatencorporate into e into bacterial bacterial DNA via. DNA via. crossing crossing overover

Lysogenic Cycle

Page 28: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

cellular cellular division division

w/ a w/ a “friend” “friend”

--replicatereplicates along s along with with

bacterial bacterial DNADNA))

Lysogenic Cycle

Page 29: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

at some at some point, point, exits the exits the chromosomechromosome, & , & initiates initiates a LYTIC a LYTIC cyclecycle

Lysogenic Cycle

Page 30: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Lysogenic Cycle

Phages Phages manufacturmanufactureded

Page 31: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

virulent

latent/ tempera

te

Page 32: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Why haven’t phages exterminated all

bacteria?• Restriction Enzymes in bacteria– Methylation of bacterial DNA prevents the restriction enzyme from attacking its own self

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Why haven’t phages exterminated all

bacteria?• Natural Selection favors the mutant bacteria w/ protein receptors that have an altered shape– no longer recognizable by phage

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Why haven’t phages exterminated all

bacteria?• LYSOGENY

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Viruses are Classified as:

1. DNA viruses

2. RNA viruses

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1. membranous envelope

presentpresent 2. membranous

envelope absentabsent

Viruses are Classified as:

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Reproduce in nucleusReproduce in nucleus

Envelope derived from Envelope derived from nuclear membranenuclear membrane

Typically, leave some Typically, leave some DNA behind in nerve DNA behind in nerve cellscells

ex.ex. of enveloped =of enveloped = herpes virusherpes virus

Page 39: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

ex. Herpes Simplex Type 1 (cold sore)

Page 40: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Herpes Viruses•Use nuclear membrane to

derive new envelope.•Viral DNA integrated into Host DNA as a provirus.

•Shows both lytic and lysogenic life cycles.

Page 41: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.
Page 42: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

RETROVIRUS ex. HIV

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human immunodificiency

virus

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`

host is a WBC called a T-cell

Page 46: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

HIV needs to connect to TWO protein types on the outside of the

Immune System’s Helper T Cells

Page 47: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

HIV needs to connect to TWO protein types on the outside of the

Immune System’s Helper T Cells (WBC)

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LAST KIND

• DNA

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DNA VirusesDNA Viruses1.Insert their DNA into host/ the host produces mRNA compliment

2.2.Production of new viral proteins, or join with the DNA of the host cell

3.Directs production of new viruses

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Viral Viral DiseasesDiseases MeaslesMeasles

PolioPolio SmallpoxSmallpox InfluenzaInfluenza S.A.R.S.S.A.R.S. Bird fluBird flu

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“The single biggest threat to man's continued dominance on the planet is

the virus!”

-Joshua Lederberg, Ph.D, Nobel laureate 1969

(won prize with Beadle and Tatum)

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Actually, he won the prize for discovering that bacteria can exchange genes… but what a great quote!

Page 53: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

EMERGING VIRUSES: HOW? HOW?HOW? HOW?

Mutations of existing virus

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Dissemination from

a small, isolated

population

Increasing viral traffic

ie. new roads can allow

virus to spread between

previously isolated areas

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Mutated form

spread from

animals

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How to How to combate combate Virus?Virus?VACCINES VACCINES - -- -**variants of variants of pathogen pathogen

*stimulates the *stimulates the immune immune system to “arm” system to “arm” and and “defend”“defend”

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Note: Can Note: Can preventprevent some some viral viral illnesses, illnesses, Cannot Cannot curecure the the viral infectionviral infection

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Some viruses cause

Page 59: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

Human papilloma virusHuman papilloma virus

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Viral nucleic acid becomes integrated

into the hosts DNA

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Proto-oncogenes code for proteins that affect the cell cycle.

Page 62: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

•ViroidViroid-- “naked” RNA

*disrupt metabolism of plants stunts growth

Page 63: Ch 18 Microbial Models: Genetics of Viruses and Bacteria.

•ViroidViroid--

BIG NEWS b/c *molecules* can be an infectious agent and spread

disease!

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•Prions- infectious *present in brain

cells *misfolded proteins *converts “regular” proteins to prion version Mad cow disease

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