© 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

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, non- motile, 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: 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.

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!!