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Bacteria
Bacteria
• Unicellular
• Prokaryotes
• Cells walls containing peptidoglycan
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.)
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