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Microbes and Society
Brief Introduction to Microbes
Prokaryotes vs. Eukaryotes
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Prokaryotes have no membrane bound nucleus
or organelles. They have a single closed loop of
DNA. Most of the prokaryotes reproduce by
fission.
Eukaryotes have both membrane bound nuclei
and organelles. They have DNA that are formed
into chromosomes. Some reproduce through
fission but most reproduce sexually.
Typical Prokaryotic Cell
Typical Eukaryotic Cell
Nomenclature
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“Living” Organisms have both a common and a
scientific name
Genus name is always capitalized while species
name is not. Both are italicized or underlined.
For example, the black-legged tick (common
name) has a scientific name of Ixodes
scapularis.
Virus only have common names as they are not
considered “living” organisms.
Examples of Prokaryotes
Borrelia
Ehrlichia
Staphylococcus
Morphology of Bacteria
Coccus or Round
More Shapes
Bacilli or Rods
Spirochete
Gram-Negative vs. Gram Positive
Bacteria
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An easy way to categorize
2 “types” of bacteria.
Dye bacteria using crystal violet and iodine.
Gram-positives “soak” up the purple dye, gram
negatives don’t. Then rinse in alcohol and
counter stain with safranin. Gram-negatives
stain orange-red while gram-positives stay
purple.
So, what good is this?
Functions of Bacteria
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Commensals
Photosynthesis
Nitrogen fixation
Pathogens
Medicine (Recombinant)
Research
Others!!!!
Types of Virus
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They are simple, very small, and utilize others
for help in reproduction.
Shapes include:
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Helical, e.g. bacteriophage M13
Polyhedral/cubic, e.g. poliovirus
Enveloped - may have poyhedral (e.g. herpes
simplex) or helical (e.g. influenzavirus) capsids
Complex, e.g. poxviruses
Other way to categorize Virus using
nucleic acid
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Some virus have double stranded DNA
(like us)
Others have single stranded RNA (for
example HIV)
Viral Replication
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There are 5 major steps in the replication
cycle of all viruses:
Attachment
Penetration
Nucleic acid and protein synthesis
Assembly of virions
Release/egress
Functions of Virus
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Pathogens
Can be the cause of certain cancers
Utilized in research- may be used to cure
diseases through gene therapy
http://www.edu365.cat/aulanet/comsoc/L
ab_bio/simulacions/GeneTherapy/GeneThe
rapy.htm
Protists
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Eukaryotic, these include protozoa, certain
types of algae and a few others
Four types of protozoans
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Amoebas
Flagellates
Ciliates
Apicomplexans.
Amoebas
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They can change their shape and move by
sending out pseudopodia. Water-borne
amoebas cause amoebic dysentery.
Flagellates
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Move using flagella, this group causes
diseases such as African sleeping sickness,
common venereal disease- Trichimonas,
and Giardia (or beaver fever)
Trichomonad of cattle
Ciliates
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Tiny hairlike projections all over the
surface beat in networks along the cell
which allows the organisms to move
forward, backwards and rotate. They
are also capable of sexual recombination.
There is only 1 ciliate spp. Pathogenic to
humans.
Apicomplexans
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Many are intracellular in parts of their life
cycle, they have organelles that allows
them to gain access into cells.
Malaria-up to 2 million/year die
Toxoplasma- dangerous for
immunocompromised/preganant women
Pneumocystis carinii- one of the leading
causes of death in AIDS patients
Fungi
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Yeasts- lots of positive uses including
fermentation that leads to bread rising, and
alcohol production.
Some yeasts can cause infection (thrush or
yeast infections)
Molds- Decomposers that are sometimes
compacted together known as a mushroom
Lichens-part fungus part other (cyanobacteria)
Ringworm