Intro to Microbial Pathogens (Feldman) Flashcards Preview

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Protein capsid surrounds either RNA or DNA

Some have lipid bilayer "envelope"


Viruses are not cells, they are obligate intracellular parasites. What does this mean?

Computer analogy: a computer virus must be in a computer in order to be destructive

Viruses can't synthesize proteins, can't generate energy, and can't maintain ionic potential across membrane. They need OUR cells' mitochondria, etc. to act


Enveloped Viruses

Lipid bilayer surrounding capsid contains viral attachment proteins

When alcohol, etc sprayed on virus, membrane dissolves and virus has no way of infecting cells

Less stable than non-enveloped

Transmission host-to-host

Ex: HIV (but HIV is resiliant! Conformational masking, etc)


Non-Enveloped Viruses

Tough protein capsid contains viral attachment proteins

Resistant to alcohol, low pH, etc.

More stable than enveloped viruses

Transmission is fecal-oral

Ex: Polio, HepA, HPV



No nucleus

One chromosome (usually circular)

70S Ribosomes

Cell wall


Gram positive cell wall

(Two layers)

Plasma membrane

Thick peptidoglycan cell wall

Teichoic acid on peptidoglycan cell wall

Ex: Streptococcus, staphylococcus


Gram negative cell wall

(Three layers)

Plasma membrane

Thin peptidoglycan layer

Outer membrane

LPS on outer membrane

Ex: Neisseria


Targets of anti-bacterial drugs

Cell wall (because humans don't have one)

Protein synthesis (humans have 80S and bacteria have 70S)

DNA gyrase (humans don't have it)


Viral infection

1) Viral glycoprotein binds specific receptor on cell

2) Virion uncoats

3) Virus replicates by synthesizing nucleic acid and empty capsids

4) Virus inserts viral glycoproteins into cell's membrane

5) Viral egress: capsids full of nucleic acid emerge from cell, picking up envelope and inserted viral glycoproteins on the way out


CD8 T cells

Differentiate to cytotoxic T cells (IL-2 helps) that kill viral infected cells by secreting granzymes


CD4 Th2 cells

Activate B cells to become plasma cells that secrete antibodies to kill/neutralize/opsonize extracellular pathogens or toxins


CD4 Th1 cells

Activate macrophages (engulf) and NK cells (which can activate lysosomes) to kill intracellular pathogens replicating in phagosomes or lysosomes


Pattern Associated Molecular Pattern (PAMP)

Molecule on pathogen that is seen as foreign and activates the immune system

Ex: LPS on gram negative bacteria; Teichoic Acid on gram positive bacteria


Toll-Like Receptor (TLR)

On immune cells, recognize PAMPs on pathogen and trigger immune response


Complement pathways

MB-Lectin Pathway (Innate)

Alternative Pathway (Innate)

Classical Pathway (Adaptive)