© 2001 by Jones and Bartlett Publishers
A. Anatomy of the Bacteria
Bacterial Shapes and Configurations
• Bacillus - (pl. bacilli) rod shaped
• Coccus - (pl. cocci) sphere shaped
• Spiral - (sing. Spirillum) spiral shaped,
vibrio - comma shaped, spirilla corkscrew shaped, also spirochetes.
Bacterial Configurations
• Diplo - pairs of bacteria. Examples:
diplococcus, diplobacillus
• Strepto - chains of bacteria. Examples:
streptococcus, streptobacillus
• Tetrad - groups of four
• Staphylo - “grapes” cluster of bacteria.
Example: staphylococcus
Shapes and Configurations
Cell Membrane and Cytoplasm
• Bacteria also have cell membranes
composed of a phospholipid bilayer.
• The cytoplasm contains no organelles
and has free-floating ribosomes, the site
of protein synthesis.
• Chromosome - closed loop of DNA.
• Plasmids - small circular pieces of DNA
that can be exchanged between
bacteria. R Factor- genes for resistance
Cell Membrane and Cytoplasm
Cell Wall
• All bacteria have cell walls except the
mycoplasmas.
• Structures composed of peptidoglycan a rigid, carbohydrate that forms a
protective barrier for the bacteria.
• Purpose - allows the bacteria to
withstand high osmotic pressures.
Example: salt content.
Gram Staining
• Gram-positive bacteria have a high
amount of peptidoglycan that holds
crystal violet iodine stain. The bacteria
stains a blue-purple color.
• Gram-negative bacteria have less
peptidoglycan and cannot hold the
stain. The bacteria stain a red color.
Gram Positive/Gram Negative Mix
Antibacterial agents that attack
the cell walls
• Penicillin - used as an antibiotic
because it prevents the construction of
the peptidoglycan layers. As cells try to
under fission, they explode.
• Lysozyme - and enzyme in tears and
saliva that break apart the
peptidoglycan causing the cell to lyse or burst open.
Spores
• Spores - highly resistant structures that
can protect the bacteria in unfavorable
conditions. Clostridium, Bacillus, etc.
• The peptidoglycan can surround the
bacterial DNA and preserve it until
conditions are again favorable for
growth.
• Some can live in boiling water and ethyl
alcohol.
Bacterial Spores
Bacterial Spores
The Glycocalyx
• Glycocalyx - sugars and proteins that
provide a protective layer of slime on
the outside of bacteria.
• Also called a capsule.
• Found in various bacilli and cocci
Biofilms
• Biofilm - where a fluid meets a solid
surface, colonized by bacteria and their
capsules and slime layers.
• Dental cavities
• Urinary tract infections
• Industrial pipelines
• Sewage treatment systems Page 99
Glycocalyx
Bacterial Locomotion
• Flagella - (sing. Flagellum) long
strands of protein that whip about
to propel the bacterium.
• Bacteria are either motile, nonmotile, or motile depending on the
condition.
Bacterial Flagella
Motility Lab – negative/positive
Bacterial Pili
• Pili - (sing. Pilus) short, fibrous bacterial
appendages.
• Sex pili - transfer genetic information
from one bacterium to another.
• Adhesins - proteins on ends of pili to
help them stick to tissues. This can
cause the bacterium to be more
infectious. See page 96.
Bacterial Pili
B. Bacterial Reproduction and
Growth
Bacterial Reproduction
• Bacteria reproduce by means of binary
fission.
• The chromosome duplicates.
• The cell elongates.
• The plasma membrane pinches in.
• The cell wall thickens and expands to
separate the cell.
• A reproducing bacterium never dies!
Bacteria Reproduction cont...
• Generation time - the time it takes for a
bacterium to complete a division.
• E. coli - Only 20 minutes!!
• One E. coli could multiply enough to
cover the earth in 36 hours!
• Not possible because the environment
could not support the growth.
J - Curve Growth
• Optimal growth
conditions of
bacteria represented
by a j-shaped curve.
• If unlimited food and
resources were
available and
minimal cell death
occurred….
The Bacterial Growth Curve
Bacteria Temperature Preferences
• Psychrophiles - live at cold
temperatures: 0o to 20oC.
• Mesophiles - live at median
temperatures: 20o to 40oC. Most
bacteria are mesophiles. Many
infectious bacteria live at 37oC (body
temperature).
• Thermophiles - live at hot temperatures:
40oC and up. Compost and hot springs.
Bacterial Oxygen Requirements
• Aerobic bacteria - Need oxygen to
survive.
• Anaerobic bacteria - do not need
oxygen to survive. In fact, oxygen is
fatal to some anaerobic bacteria.
Examples: tetanus and clostridium.
Page 114.
• Facultative bacteria - Can survive in
oxygen or reduced oxygen-staph, strep.
pH of Bacterial Environments
• Most bacteria prefer a neutral pH - 7.
• Acid tolerant bacteria are called
Acidophiles. Useful in the food and
dairy industry. Lactobacillus and
Streptococcus produce the acid in sour
cream and buttermilk. Also found in
yogurt (contains live active cultures).
• Most bacteria do not live in acidic
conditions well: stomach, citrus fruits.
Be prepared for the Chapter 4 test
Due to the amount of material in
chapter 4, the test will be over
chapter 4 only!!