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.
Slide 4
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
Slide 5
Shapes and Configurations
Slide 6
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
Slide 7
Cell Membrane and Cytoplasm
Slide 8
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.
Slide 9
Slide 10
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.
Slide 11
Gram Positive/Gram Negative Mix
Slide 12
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.
Slide 13
Slide 14
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.
Slide 15
Bacterial Spores
Slide 16
Slide 17
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
Slide 18
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
Slide 19
Glycocalyx
Slide 20
Slide 21
Bacterial Locomotion Flagella - (sing. Flagellum) long strands
of protein that whip about to propel the bacterium. Bacteria are
either motile, non- motile, or motile depending on the
condition.
Slide 22
Bacterial Flagella
Slide 23
Motility Lab negative/positive
Slide 24
Slide 25
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.
Slide 26
Bacterial Pili
Slide 27
Slide 28
B. Bacterial Reproduction and Growth
Slide 29
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!
Slide 30
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.
Slide 31
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.
Slide 32
The Bacterial Growth Curve
Slide 33
Bacteria Temperature Preferences Psychrophiles - live at cold
temperatures: 0 o to 20 o C. medianMesophiles - live at median
temperatures: 20 o to 40 o C. Most bacteria are mesophiles. Many
infectious bacteria live at 37 o C (body temperature). Thermophiles
- live at hot temperatures: 40 o C and up. Compost and hot
springs.
Slide 34
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.
Slide 35
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.
Slide 36
Be prepared for the Chapter 4 test Due to the amount of
material in chapter 4, the test will be over chapter 4 only!!