Chapter 2/4: Bacterial Cell Walls Flashcards
What are most bacterial cell walls composed of?
Peptidoglycan
Which two alternating molecules make up petidoglycan?
NAM, NAG
Which peptidoglycan subunit is cross-linked at adjacent layers by peptide bonds?
NAM
Which two amino acids are connected by a single peptide bond in peptidoglycan cross-linking?
DAP, D-Ala
Which two amino acids are connected by a pentaglycine interbridge in peptidoglycan-cross linking?
L-Lys, D-Ala
What type of bacteria use a single peptide bond in peptidoglycan cross-linking?
Gram negative
What type of bacteria use a pentaglycine interbridge in peptidoglycan cross-linking?
Gram positive
What molecule acts as a carrier for NAM in peptidoglycan synthesis?
UDP
What serves as a transport channel across the plasma membrane in peptidoglycan synthesis?
Bactoprenol
What is the name for the space between the plasma membrane and cell wall?
Periplasm
What protein can cleave the bond between NAM-NAG subunits in the peptidoglycan backbone?
Lysozyme
What type of structure forms in Gram positive cells after lysozyme treatment?
Protoplast
What type of structure forms in Gram negative cells after lysozyme treatment?
Spheroplast
What molecule can cleave the peptide interbridge cross-link in certain Staphylococcus species?
Lysostaphin
What type of antibiotics prevent transpeptidation?
Beta-lactam
What is produced in resistance to Beta-lactam antibiotics?
Beta-lactamases
What drug binds to Bactoprenol to prevent subunit synthesis and transport?
Bacitracin
What drug prevents NAM-NAG linkages from forming and transpeptidation?
Vancomycin
What are three types of Beta-lactam antibiotics?
Penicillin, Ampicillin, Cephalosporin
What types of major phenetic group divisions are based on cell wall chemistry differences?
Gram positive vs. Gram negative, Acid fast vs. non acid-fast
What type of bacteria lack a cell wall completely?
Mycoplasma sp.
What color are Gram-negative cells stained?
Pink
What color are Gram-positive cells stained?
Purple
What type of cell walls have a thick outer layer of peptidoglycan and a very narrow periplasmic space?
Gram-positive cell walls
What negatively charged molecules spear through the peptidoglycan layers in Gram-positive cell walls?
Teichoic acids
What function do Teichoic acids serve in Gram-positive cell walls?
Structure
What type of cell walls have a varying width periplasmic space and a thin layer of peptidoglycan?
Gram-negative cell walls
What type of cell walls have an additional outer membrane?
Gram-negative cell walls
What is the outer membrane composed of in Gram-negative cell walls?
Lipopolysaccharide (LPS)
What type of cell walls have a peptidoglycan layer with large pores?
Gram-positive cell walls
What proteins serve in transport in Gram-negative cells?
Porin, TonB
What type of rare transporters allow movement from the periplasm directly to the outside of the cell?
Autotransporters
What type of transporters shuttle materials from the cytoplasm to outside of cell in a single step?
Type III
What primary stain is used in a gram stain?
Crystal violet
What mordant is used in a gram stain to crystallize purple stain?
Gram’s iodine
What decolorizer dissolves lipopolysaccharides and shrinks Gram-positive large pores in a gram stain?
95% ethanol
What counterstain enters only vacant cells in a gram stain?
Safranin
