Transcript Bacteria, Viruses, Protists, and Prions

Bacteria
Bacteria
• Unicellular
• Prokaryotes
• Cells walls containing peptidoglycan
Bacteria
• Extremely Abundant
– Cover nearly every square centimeter of Earth
Bacterial Shapes
• Bacilli: rod shaped
– Bass-ill-eye
• Cocci: spherical
– Cox-eye
• Spirilla: spiral, corkscrew
– Spy-rill-uh
What are the differences
between eubacteria and
archaebacteria?
Eubacteria versus Archaebacteria
• Cell walls of Eubacteria have lots
peptidoglycans (mesh of sugar and amino
acids)
– Archaebacteria do not
• Archaebacteria often live in very extreme
environments (hot springs, digestive
tracts, Great Salt Lake, etc.)
Cell Walls
Gram staining is a diagnostic tool used to
classify bacteria
• Gram positive: stain violet
– due to thick peptidoglycan walls
– Eubacteria or archaebacteria?
• Gram negative: stain pink/red
– No peptidoglycans in cell
walls
Metabolism
• Bacteria can be heterotrophic or
autotrophic
– Remember: autotrophs are not ALL
photosynthesizers!
– Some are chemosynthesizers (convert carbon
into organic compounds)
How Bacteria Reproduce:
Binary Fission
• When a bacterium
has doubled in size,
it replicates its DNA
and divides in half
• Sexual or asexual?
• Identical or different
daughter cells?
If bacteria are identical, how do
they evolve?
Where does genetic variety
come from (besides natural
mutation rate)?
Genetic Variety in Bacteria
• Conjugation: cell-to-cell contact
• Transformation: bacterium takes up
foreign DNA from surrounding
environment
• Transduction: DNA is transferred from one
bacterial cell to another by a virus
Conjugation
• A hollow bridge (pilus) forms between two
bacteria and genes move from one cell to
the other
• Increases genetic diversity of a population
Conjugation
Transformation
• Bacteria take in
foreign DNA from
surroundings and
incorporate it into
their own DNA
*Remember Griffith’s
experiment
Transduction
• DNA is transferred from one bacterium to
another by a virus
• When new bacteriophages are made, they
may contain a small amount of the host
cell’s DNA
Benefits of Bacteria
• Some are producers that undergo
photosynthesis
• Some are decomposers that break down
dead matter to recycle the nutrients
• Some convert nitrogen gas to a form that
can be used by plants (nitrogen fixation)
What are some dangers of
bacteria?
Dangers of Bacteria
• Break down cells and tissues for food
Example: Tuberculosis (destroys lung
tissue)
• Release toxins (poisons) that travel
through the body
Example: Streptococcus releases toxins
into the blood stream causes strep throat
and scarlet fever
Viruses
• A virus is a core of DNA or RNA
surrounded by a protein coat (capsid)
Viruses
• They can only reproduce by infecting living
cells
• They enter a cell and use its cell
machinery to produce more viruses
Retroviruses
• Contain RNA as genetic information
instead of DNA
Would you consider viruses
living?
Are Viruses Living?
• Cannot reproduce alone, must have a host
cell
• Do not undergo growth or development
• Do not obtain or use energy
• Evolve
Prions
• Diseases such as Scrapie (in sheep) and
Mad Cow Disease are not caused by
bacteria or viruses. What could cause
them?
Prions
• Contain only protein
• Cause disease by forming protein clumps
which then induce normal proteins to
become Prions
• The build up eventually damages nerve
tissue
Protists
• Domain?
• Kingdom?
• Prokaryotic or Eukaryotic?
Protists
• Domain: Eukarya
• Kingdom: Protists
• Eukaryotic
Protists
• Protists are defined by what they are not.
Protists are eukaryotes that are not animals,
plants, or fungi.
They were the first eukaryotic organisms on
earth.
Types of Protists
• Animal-Like Protists: heterotrophs
• Plant-Like Protists: produce food through
photosynthesis
• Fungus-Like Protists: obtain food by
external digestion
Animal-Like Protists
• Heterotrophs
cilliate
sporozoan
zooflagellate
Sarcodine
(amoeba)
Animal-Like Protists
• Malaria
• African Sleeping Sickness
Plant-Like Protists
• Carry out photosynthesis
Fungus-Like Protists
• Grow in damp, nutrient rich environments
• Absorb food through cell membranes
Review!