Notes – Bacteria and Viruses
Viruses
What is a Virus??  Non-living particles that can’t reproduce; contain nucleic acids (DNA or
RNA) and is enclosed in a protein coat
*Smaller than the smallest bacterium and must have a host; do replicate on their own
*Don’t carry out respiration, develop or grow
*Found soil, air, water
*Can mutate to become more dangerous
*Bacteriophages infect bacterial cells
*All living organisms can contract viruses
*Some are species specific – HIV only affects humans
~~~~~~Bacteriophage that infects Bacteria:
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Viral Replication Cycles:
Lytic Cycle: A virus takes over a host’s genetic material, uses its structures and energy to
replicate many viruses and the cell bursts (Lysis) and viruses spread
Bacteriophage Attack on a bacterial Cell
Step
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Summary
The lytic bacteriophage virus attaches itself to the bacterial cell.
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The virus injects the nucleic acid into the cell.
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When all the nucleic acid is injected they begin to replicate, and the
useless original capsid and tail are detaches from the cell.
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The viruses grow using the nutrients of the bacterial cell.
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When viruses are mature, they come out of the cell, destroying it, and
start to infect other cells.
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Lysogenic Cycle: The virus’s nucleic acid (DNA/RNA) is integrated into the host cell’s
chromosome, the cell is then called a provirus, the virus lay “dormant” as the cell reproduces
itself. Below after a virus has injected its nucleic acid:
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Cancer and Viruses Viruses linked to cancer disrupt mitosis. HPV is the most common
(Human Papilloma Virus) causes genital warts and accounts for about 76% of cervical cancers.
Bacteria
*Archaebacteria – The extremist; Oldest; salt-loving; heat-loving
*Eubacteria --Some are photosynthetic (undergo photosynthesis)
*Some undergo chemosynthesis – break down surrounding organic compounds for food
*Some are heterotrophs – “eat” their own food
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Bacteria Adaptations Endospore forms around bacteria during harsh conditions, cells grow
and reproduce, can produce toxins; Botulism (food poisoning), anthrax (lives in soil). Bacteria
can mutate quickly to environmental change and become more dangerous and resistant to
antibiotics
Helpful bacteriaNitrogen fixation (plant root convert nitrogen gas into usable nitrogen for the
plant), return nutrients to soil, produce oxygen, production of cheese, yogurt and pickles. E. coli
in the intestines aids in digestion. Used in farming, medicine and food industry.
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