Flashcards in L3_ Bacterial Structure and Function 1 Deck (23)
How do bacteria reproduce?
Describe Bacterial genome
DNA, No introns, Polycistronic, singular circular chromosome, Nucleoid (no membrane)
What kind of ribosomes do bacteria have?
What are bacterial cell walls made of?
How big are bacteria? Compared to viruses and to eukaryotic cells
0.5-5um. 10-100x smaller than eukaryotic, 500-1000x larger than viruses
Are bacteria visible by light microscope with contrast and staining?
What are the three major shapes of bacteria?
Cocci (round), Rods (oval), Spirochetes (corkscrew)
What are 3 characteristic clumping patterns of Cocci?
Clumps (staph), Chains (strep), Diplococci (Neisseria)
Name the Five steps of Gram Staining
1 Fix the bacteria to microscope slide with heat
2 Stain with crystal violet (all turn purple)
3 Iodine Treatment (Gram + permanently purple)
4 Decolorize with Alcohol (Removes CV form Gram -)
5 Couterstain (Safarin re-stains Gram - light pink)
Describe the membrane and cell wall structure of GRAM (-) bacteria
Thin wall with 1 layer of peptidoglycan. Stains pink in GRAM staining. Interior membrane plus exterior membrane with LPS(septic Shock) and Porins which allow for selective permeability.
Describe the membrane and cell wall structure of GRAM (+) bacteria.
Thick wall with 3 layers of peptidoglycan. Stains purple in GRAM staining. Only interior membrane. Teichoic Acid are equivalent of LPS but much less frequently cause shock.
What purpose does the cell wall serve for bacteria.
Gives rigidity and helps resist osmotic forces.
What are some vulnerabilities of cell walls?
They are target by host cell and many antibiotics. Antibiotics will prevent synthesis, lysozyme will cleave wall.
Can you vaccinate against LPS?
NO! it is immunogenic and vaccinating against it would only increase it virulence
What are the two main components of the glycocalyx layer? What are these layers rich in?
Slime Layer and Capsule. Carbohydrate rich
What does the slime layer do?
Formation of biofilms (antibiotic resistance)
What does the Capsule do for bacteria?
What are the purpose of pili/fimbrae and how do they differ between GRAM neg and pos bacteria?
Used for attachment and often a virulence factor. Gram pos were only recently discovered and are simple repeating subunits. Gram neg come in many types and are complex, some have evolved into propulsion systems or secretion molecules that are virulence factors in their own right.
What causes gram - to resist CV stain?
How do Acid Fast bacteria stain and why?
Mycolic acid layer resists both CV and counterstain...need to use acid fast procedure
Is LPS and endo or exotoxin?
What type of GRAM neg pili are used for attachment? propulsion? secretion?
Type1 for attachment, type 4 for propulsion, type 3 and 4 for secretion.