Viruses and Bacteria
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What do these diseases have in
common?
Mumps
http://www.kcom.edu/faculty/chamberlain/Website/lectures/lectu
re/IMAGE/MUMPS.GIF
Hepatitis B
http://www.idph.state.il.us/images/hepatitisb.jpg
Measles
http://www.idph.state.il.us/images/measles.jpg
Polio
http://www.immune.org.nz/site_resources/Prof
essionals/Diseases/Polio/Polio.jpg
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It looks alive, acts alive…
but its not!
• Viruses are not living things. They differ
from living things in several ways:
– They need to be inside a living organism to
reproduce themselves.
– Outside the cell, they have no metabolism.
– They do not have cell parts. (i.e. nucleus,
mitochondria, etc)
– They are composed of only a nucleic acid
(DNA or RNA) inside a protein capsule.
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• Viral Reproduction
– In order to reproduce:
• A virus attaches to a host cell.
• The virus injects the cell with its nucleic acid.
• The viral nucleic acid commands the cell to make more
viral protein and nucleic acid.
• The cell then ruptures, releasing hundreds of new
viruses.
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http://porpax.bio.miami.edu/~cmallery/150/
gene/sf11x1virus.jpg
Retroviruses…No, they aren’t from
the 70’s!
– These are viruses that store their genetic
information as RNA.
– Their genetic information is copied
backward-from DNA to RNA.
• Ex: some types of cancer & AIDS
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http://international.ucla.edu/cms/images/hiv_virus.jpg
How it works……
• They infect their
host cell.
• They produce a
DNA copy of
their RNA.
• It may remain
dormant for
varying lengths
of time.
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http://hiv.buffalo.edu/./images/hiv_virus_in_action.jpg
Your friendly bacteria
• Bacteria are living, unicellular
prokaryotes.
• Divided into two kingdoms:
Eubacteria and Archaebacteria
• Heterotroph or autotroph (most use
chemosynthesis).
• Types of Bacteria are classified
based on their shape, type of cell
wall, and movement.
• Bacteria have three basic shapes:
– Bacilli – rod-shaped
– Cocci – spherical
– Spirilla – spiral
http://fig.cox.miami.edu/~cmallery/150/proceuc/c27x3p
roc_shapes.jpg
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• Eubacteria have peptidoglycan and certain
specialized lipids in their cells walls that are not
present in Archaebacteria.
• Gram staining is used to differentiate types of
Eubacteria.
– Those having thick cell walls will absorb more of the
dye and appear dark purple (Gram positive).
– Those having thinner cell walls will absorb less of
the dye and appear pink (Gram negative).
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http://bioweb.uwlax.edu/bio203/s2008/jaedike_alic/grainpositive.jpg
http://www.asm.org/Division/c/photo/gc1.JPG
http://porpax.bio.miami.edu/~cmallery/150/gene/sf9x3box.jpg
Bacteria Growth and Reproduction
• Bacteria reproduce in two main
ways:
– Binary fission – when a bacteria grows
to double its original size, it copies its
DNA and divides, producing two
identical cells.
– Conjugation – a hollow bridge is
formed between 2 bacteria and genes
are transferred from one cell to the
other.
• This creates genetic diversity within the
population.
– Spore formation – when conditions are
unfavorable (lack of food, drought) that
encloses its DNA and part of its
cytoplasm in a spore.
• When conditions are better, the spore
will germinate, and the bacterium will
continue to grow.
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http://www.emc.maricopa.edu/faculty/farabee/BIOBK/69091a.jpg
They’re not all bad….
• Bacteria are most widely known for causing
diseases such as strep throat, tetanus,
meningitis, and tuberculosis.
• However, most bacteria are very useful:
– E. coli helps us digest our food & make vitamins for
humans.
– Many are important decomposers in our ecosystem.
– Rhizobium provides plants with nitrogen.
– A few bacteria are used to clean up small oil spills in
the ocean.
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• Vaccinations
– A weakened form of the pathogen
(virus/bacteria) is used to
stimulate the production of
antibodies.
– However, bacteria and viruses
have very high reproductive rates,
which result in many mutations.
– Thus, bacteria and viruses evolve
quickly, often requiring a different
vaccine every year.
http://www.biojobblog.com/vaccination%5B1%5D.JPG
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http://www.biojobblog.com/vaccination(5).jpg
• There are two types
of vaccines
(immunities):
• Active – person is
injected with the
actual pathogen,
and immune cells
make their own
antibodies against
the disease,
immunity is
permanent
• Passive – person is
injected with
antibodies that fight
the disease, but
immunity is
temporary
http://www.iavi.org/viewpage.cfm?aid=1682
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