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What is an endospore? (3)
- an inert, resistant form of a bacterium
- endospores have NO metabolism
- only made by gram+ bacteria
- Two genera to know: Bacillus (anthrasis) and Clostridum (botulism or tetnus)
Gram+ Characteristics (3)
- Thick, peptidoglycan cell wall
- teichoic acid in the cell wall
- no outer membrane
Gram- Characteristics (3)
- thin, peptidoglycan walls
- no teichoic acid
- LPS outermembrane
Teichoic acid (3)
- only in gram+ cell walls
- lends stability to the cell wall
- (Also known as endotoxin)
- Three parts:
- Lipid A to anchor is to the outer membrane. TOXIC part.
- Core polysaccharide (similar across gram- bacteria)
- O-polysaccharide (O-antigen) confers sereotype specificity; different for each bacteria.
What is the structure of peptidoglycan? (3)
- Long polymers of two, alternating disaccharides called NAG and NAM which make up the spiral backbone
- Peptides branch off of NAM (L, G, D, L, L)
- To form crosslink, a tetrapeptide is formed by dropping an L (Alanine), connects two NAMs
- B-lactams (antibiotic family) block cross linking, weakening the cell wall.
Bacterial Growth Curve (4)
- Lag (population remains stable)
- Log (exponential growth)
- Stationary (population holds constant; growth = death)
- Death (pop declines)
- bacteria grow to a certain density.
- Once the density is reached, they communicate with each other through "quorum sensing" which signals the bacteria to work as a community rather than as individuals.
- bacteria produce a polysaccharide that glues them together
- holds population at stationary growth
- antibiotics can't get into biofilms.
- rise in nutrients
- increase in combined metabolism of aerobic bacteria
- Oxygen depletion
- kills obligate aerobes
What are extremophiles? (5)
microorganisms that can survive extreme conditions
- a category of extremophile
- adapted to survive in cold temps
- more fluid, unsaturated lipis in cell wall and altered proteins that work in cold.
- prefer middle, normal temperatures
- Pathogens are mesophiles
- optimum around 37 degrees
- heat loving; grow at elevated temps
- altered lipid make up to withstand high temps. Cross linked or saturated lipids.
- Most thermophiles fall into Archea
heat killing bacteria
What are the parts of a virus? (6/11)
- capsule (protects genome)
- enveloped viruses: membrane comes from last host. Not all viruses have an envelope.
Steps of a typical virus life cycle (6/11)
- Uncoating (sheds capsid to release genetic info)
- Replication of genome
- Release (often lyses)
What are the four deoxynucleotides? (7)
How do DNA strands base-pair with each other? (7)
DNA replication enzymes
- Helicase unzips helix
- Primase lays down primer
- DNA polymerase lays down DNA
- RNase H removes RNA primer laid down by primase
- DNA ligase rezips strands
- RNA polymerase makes complimentary RNA strand
- Sigma factor directs to the right gene.
- Promoter recognized by sigma factor.
- RNA made from gene is mRNA
- 70 s Ribosome
- takes mRNA and synthesizes a protein.
- tRNA brings animo acids
What antibiotics affect protein synthesis? (8)
- the transfer of DNA through plasmids
- horizontal gene transfer
- the uptake of free DNA
- horizontal gene transfer
- transfer of genetic data via bacteriophage
- horizontal gene transfer
- the partial breakdown of organic food without net electron transfer to an inorganic terminal electron acceptor.
- NO ETC
- substrate level phosphorylation
- complete breakdown of organic molecules with electron transfer to a terminal electron acceptor such as O2
- Uses ETC
- oxidative phosphorylation
How do aerobic and anaerobic respiration differ?
- Anaerobic respiration has an inorganic final electron acceptor other than oxygen
- Aerobic respiration has a final electron acceptor of oxygen
What is a proton motive force and how is it made?
- A difference in charges across a membrane
- made by pumping out cations (H+) using ETC
a reduced form of some inorganic molecule is used to start this ETC
ETC is energized by loght with electrons donated by a chlorophyll
- energy carrying molecule
- energy can be used pretty much anywhere in the cell
- carries 2-3 times more energy than ATP
- used in redox reactions
- NAD+ to NADH
Embden-Meyerhoff-Parnas (EMP) Pathway
- Net gain: 2 ATP, 2 NADH
- more evolutionarily advanced
Entner-Doudoroff (ED) Pathway
- net gain: 1 ATP, 1 NADH, 1 NADPH
- most common in the GI tract
induces immune response
is bound by antibody
- has memory
- two types: humoral and cell-mediated
Basic antibody structure
- immunoglobulin or IgG
- 4 protein chains; (2 identical heavy chains and 2 identical light chains). If you pulled out two, the tail end would most likely be the same or CONSTANT which is why it’s called Fc. The top half is the variable region or Fab (fragment with antigen binding)
Primary vs Secondary Response
- IgG will respond immediately and more will be produced during the secondary immune response.
- B cell is activated
- differentiates into plasma cells (secrete antibodies) and memory cells.
Humoral immune response
- Needs an antigen presenting cell with MHC-II.
- Needs a helper T cell with CD4 and a TCR (t-cell receptor) on its surface. CD4 recognizes the MHC-II and the TCR binds the antigen. Helper t secretes cytokines.
- Needs a B cell which must bind the antigen (has antibody on surface) and undergo clonal selection.
- A microbe is always present in a diseased host, but absent in a healthy subject.
- Grow microbe in pure culture
- Introduce pure microbe to health host, and host gets sick.
- Same microbe re-isolated from now-sick individual.
Means of spreading infection: Direct Contact
- come into direct contact with diseased individual
- sneezing, touching
Means of spreading infection: Indirect Contact
- fomites (innanimate objects)
- vectors (such as blood sucking insects)
allow pathogen to adhere to surface without pili
Classes of Bacterial Endotoxins
- membrane disruptors
- protein synthesis inhibitors
- signaling pathway disrupters
survives in stomach using urease to protect itself from acid
- infects soft tissue/skin
- nosocomial pathogen know for antibiotic resistence (MRSA)
- virulence factors: afimbrial adhesins and toxins (see below)
- alpha toxin (a membrane disruptor)
- exoliatin protease (a protease)
- TSST (super antigen)
- Staph enterotoxin (superantigen)
- infects respiratory tract; causes whooping cough.
- Afimbrial adhesins (pertactin)
- Toxins (pertussis toxin kills ciliated cells; a messenger disrupter)
- Vaccine protects against pertactin and pertussis toxin.
- infects GI tract; causes dysentery and can lead to kidney failure.
- VF: Uses type III secreteion system to invade cells.
- VF: Shiga toxin kills cells (protein synthesis inhibitor)
Enterotoxogenic E. coli (ETEC)
- Colonizes GI tract; causes travelers diarrhea
- VF: pili (fimbrial adhesin)
- VF: ST (heat stable enterotoxin; a secondary messenger pathway disruptor)
Uropathogenic E. coli
- colonizes urethra, then the bladder, then the kidney
- reservior is yourself
- VF: pili
- STD; syphilis
- human reservior
- three stages: Primary, secondary, and tertiary. Chancres, rash, autoimmunity.
- STD, can lead to sterility
- VF: Afimbrial adhesins.
- Adhensins are always changed, so no vaccine.
- Bubonic plague: localized infection
- Septicemic plague: systemic infection
- Lung infection: pneumonic plague
- reservior is mammals/rats.
- Flea vector (or directly for pneumonic)
- spirochete with three stages
- Stage 1: bull's eye rash
- Stage 2: joint muscle nerve pain
- Stage 3: arthritis
- animal reservoir (deer/mice)
- deer tick vector
Types of Vaccine
- whole cell killed
- subunit (purified)
- conjugated (virulence factors linked to immunogen)