Bacteria
Bacteria on
the tip of a
pin
Prokaryotes
Identified by their
• Shapes
• Chemical nature
of their cell walls
• The ways they
move
• The ways they
obtain energy
Basic Structure
Cell wall – protects the cell & gives it shape.
Outer membrane – protects the cell against
some anibiotics (only present in gramnegative)
Cell membrane – regulates movement of
materials into & out of the cell; contains
enzymes important to cellular respiration.
Plasmid – circular piece of DNA that
contains some genes obtained through
genetic recombination.
Capsule & Slime layer – protect the cell &
assist in attaching the cell to other surfaces.
3 basic shapes
Bacillus
Coccus
Spirilla
• Cell Arrangements
– Diplo – cells are paired
– Staphylo – cells are in
grape-like clusters
– Strepto – cells are in
long chains
Cell Wall
• Two different types of cell walls
are found in eubacteria
• Gram staining helps to tell them
apart using two different types of
dye
– Violet - primary stain
– Red - counterstain
• Gram positive
– Bacteria cells containing
peptidoglycan absorb only
the violet dye
– Appear purple in the microscope
• Gram negative
– Bacteria with a second(outer) layer
of lipid and carbohydrate molecules
– Extra layer absorbs only the red stain
– Appear pink in the microscope
Gram Staining Bacteria
• Gram Positive – stains purple
• Gram Negative – stains pink
http://www.uphs.upenn.edu/bugdrug/antibiotic_manual/Gram3.htm
Growth and Reproduction
• Binary Fission: bacterium
doubles in size, it
replicates its DNA and
divides in half.
• Is this sexual or asexual
reproduction?
Growth & Reproduction- Conjugation
• the process by which two living bacteria
bind together and one bacterium transfers
genetic information to the other.
Sex pili
Growth and Reproduction…
• Endospore – protects the cell against harsh
environmental conditions, such as heat and
drought.
• May allow the bacterium to survive for
thousands of years.
Bacillus cereus
Bacillus cereus
– (found in soil)
• straight rods, arranged singly or in pairs
• cells stain Gram-positive (blue-violet)
Aquaspirillum serpens
Aquaspirillum serpens
– (found in fresh water)
• -spiral shaped, arranged singly
• -cells stain Gram-negative (red)
E. Coli
Escherichia coli
– (digest food in your intestines)
• straight rods, arranged singly or in pairs
• cells stain Gram-negative (pink)
Staphylococcus Epidermidis
Staphylococcus Epidermidis
– epidermis (found normally on skin)
• spherical shape
• cells stain Gram-positive (blue-violet)