Bacteria Notes
Basic Definition
karyo Organisms
• Bacteria: Pro
Prokaryotic
– Pro: Primitive or “prior to”
– Karyon: Nucleus or “kernel”
– Single-celled organisms without a nucleus
– Has circular DNA
– Often has “plasmid” DNA that helps codes for genes to
increase fitness (ex. Antibiotic resistance)
– Bacteria can be measured in micrometers
• 0.000001m or 10-6
What are the two
groups of bacteria?
1. Bacteria
Cell walls with peptidoglycan
Made up of types of peptide and sugar bonds
2. Archaebacteria
•
•
Cell walls lack peptidoglycan
Adapted to extreme environments:
 Extremely hot and cold, salty, without oxygen, etc.
What are the basic shapes
of bacteria?
– Rod-shaped (Bacilli)
Bacillus anthracis (Anthrax),
Yersinia pestis (Bubonic plague)
– Comma-shaped (Vibrios)
Vibrio cholerae
– Spherical (Cocci)
Streptococcus, Staphylococcus
– Spiral (Spirilla)
Treponema pallidum (Syphillis)
Bacterial Staining
• Gram-positive: Retains the crystals of violet dye in the
peptidoglycan of the cell wall.
• Only has an inner layer of plasma membrane
• Infection by this type can be treated by antibiotics such as
penicillin, which attacks the peptidoglycan of the cell wall.
Bacterial Staining
• Gram-negative: Will not pick up much the violet dye
because the cell wall is covered by an additional outer
membrane, and instead appears pink.
• Infection by this type must be treated by a broadspectrum antibiotic such as ciprofloxacin that enters
bacteria and disrupts protein synthesis
Outer membrane
Peptidoglycan
Inner membrane
What is a plasmid?
• Plasmids are circles of DNA that can replicate
separately from the main bacterial DNA.
• Plasmids may carry genes that allow bacteria
to survive exposure to antibiotics.
Bacterial Growth and Reproduction
• Binary Fission: (video)
-Asexual division
-DNA replicates and cytoplasm divides
-Creates two genetically identical cells from one parent cell
• Conjugation: (video)
-Not true sexual reproduction
-Sex pilus extends between bacteria
-Plasmid DNA is transferred from one bacterium to another to
introduce genetic diversity
• Spore Formation:
-Occurs when growth conditions are unfavorable
-An endospore is a “spore” with a thick internal wall of membrane
that encloses and protects its DNA