Basics of Microbio: Bacteria Flashcards
- vs + Cell Walls:
+ have ______
- have _____
both have _____
+ have Lipoteichoic Acids, THICK cell wall
- have Thin cell wall, periplasm, and outter membrane
both have cell membranes
Major structural component of bacterial cell walls ___ which is made up of ___ that are cross linked by peptide cross bridges attached to ___
Bonus: two antibiotics with this site of action
Peptidoglycan, Sugars: • N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM), NAM
antibiotics: Penicillin, cephalosporins
Examples of Unique Cell Walls
1.
2.
3.
Mycoplasma
No cell wall
Does not gram stain
Cell membrane has sterols for extra stability
Mycobacteria
Cell wall has mycolic acid
Does not gram stain well
Special stains used (Ziehl-Neelsen)
Chlamydia
Lacks muramic acid
Cell Membrane present in:
Present in gram (+) and gram (-) bacteria
acts like human mitos,- Electron transport and oxidative phosphorylation
unique feature of Gram Positive Bacteria__ which induces & binds __
lipoteichoic acid (LTA), • Induces cytokine release, • Binds antibodies → activates complement cascade
Unique features of Gram Negative Bacteria:
- )
- )
- )
1.) Periplasm:
Space between cell membrane and outer membrane
Contains many enzymes like B-lactamase → inactivates antibiotics
2.) Outer Membrane
Contains outer layer of lipopolysaccharide (LPS) • Major*** immune ***trigger for gram (-) bacteria!!!!!
Components of Lipopolysaccharide:
Polysaccharide
**Lipid A - Highly toxic (Triggers cytokine release)
O antigen (Target for antibodies)
Different major surface antigens trigger the immune system in gram (+) and gram (-) bacteria
Gram + bacteria • Cell wall and membrane • Lipoteichoic acid (LTA)
Gram - bacteria • Outer membrane • Lipopolysaccharide (LPS)
Capsules help __ & protect against _
mostly made of _ except:
Helps attach to host cells • Protects against phagocytosis
water with some polysaccharide
Special exception:
Bacillus anthracis (anthrax)
Capsule is protein (d-glutamate) • Major virulence factor • Allows unimpeded growth
Quellung Reaction is
examples of positive reaction: (7)
historical, used to detect if capsule is present. swelling = encapsulated
Strep pneumonia
Group B strep (agalactiae)
H. influenza
N. meningitidis
E. Coli
Salmonella
Klebsiella
how bodies have evolved to protect against encapsulated organisms:
B-cells secrete capsular antibodies (IgG) which bind capsule
& then Phagocytosis consume bacteria Via Fc receptors on antibody
Antibodies bind complement which leads to Formation of MAC → cell death & Formation C3b → opsonin
basis for many vaccines:
Capsular polysaccharides
weakly immunogenic tho therefore “Conjugated” to n immune stimulator protein like : diphtheria toxoid, tetanus toxoid, meningococcal outer membrane protein, mutant diphtheria protein
3 examples of conjugated vaccines for encapsulated bacteria
Neisseria meningitides •
Streptococcus pneumonia •
Haemophilus influenzae type b
key bacteria to think of for Pili and Fimbria:
• Neisseria Gonorrhea (antigenic variation)
Ribosomes: two subunits:
different than ours therefore can be antibiotic targets examples : (2)
Two subunits: 50S and 30S, different than ours
therefore can be Site of action of antibiotics:
Tetracyclines: Bind to 30S subunit
Aminoglycosides: Interferes with 30S protein synthesis
