Exam #1: Introduction Flashcards
Define Virulence.
Ability of a microorganism to cause disease
Define Virulence Factor.
Factors produced by organisms that enable it to infect, cause disease, &/or kill the host
What are the distinguishing features of viruses?
- Smallest, 0.03-0.3 um–can be seen w/ EM only
- Obligate intracellular pathogens
What are the distinguishing features of bacteria?
- 0.1-10 um
- Simple
- Unicellular
- Prokaryote (lack membrane-bound organelles)
- Reproduce by asexual division
What are the distinguishing features of fungi?
- 4-10 um
- More complex
- Eukaryotic
- Reproduce sexually & asexually
- Unicellular or multiceullular
What are the distinguishing features of parasites?
- 4um- many meters long (i.e. largest/ longest)
- Most complex microorganisms
What are the general features of prokaryotes?
General= lack membrane-bound organelles
- Contain cell wall
- No sterols in cell membrane
- No nuclear membrane
- Single circular DNA w/out histones
- Haploid
- No membrane bound organelles
- Asexual reproduction
- 70S ribosome
- Respiration via cell membrane
What are the general features of eukaryotes?
General= contain membrane-bound organelles
- Cell wall absent or composed of chitin
- Cell membrane contains sterols
- Classic nuclear membrane
- Multiple strands of DNA w/ histones
- Diploid
- Sexual & asexual reproduction
- 80S ribosome
- Respiration via mitochondria
What are the common methods for identification & classification of bacteria?
1) Microscopy
2) Detection of bacterial antigens
3) Detection of specific bacterial nucleic acids
4) Culture
5) Detection of antibody responses to bacteria
What is the H-antigen associated with?
Flagella
What is the K-antigen associated with?
Capsule
What is the O-antigen associated with?
LPS
What shape are Cocci?
Spherical-shaped
What shape are Bacilli?
Rod-shaped
What shape are Spirochetes?
Spiral-shaped
What are the five ways that bacteria can be classified?
1) Visible features
2) Nutrition
3) End products
4) Surface molecules
5) Nucleic acid analysis
What are the two major categories of bacteria?
Gram-positive & Gram-negative
What are the characteristics of gram-negative bacteria?
- Contain an additional outer membrane
- Thin peptidoglycan layer
- LPS +
- No sporulation
- Pink/ Red
What are the general characteristics of gram-positive bacteria?
- No outer membrane
- Thick peptidoglycan layer
- LPS negative
- Teichoic acid & Lipoteichoic acid positive
- Can form spores
- Purple
What are acid fast bacteria?
- Contain waxlike lipid coat of mycolic acid
Why is peptidoglycan a good drug target?
Essential for bacterial survival & unique to prokaryotes i.e. bacteria
List the steps of Gram stain & the colors associated with each step.
1) Crystal Violet stain, binds gram+ & turns them purple
2) Crystal Violet precipitated with iodine–>remains in + not -
3) Unbound stain removed with decolorizer
4) Safranin counter-stain applied, turns gram- red
Describe the structure of LPS. Where is LPS found?
LPS is found in the outer leaflet of the phospholipid bilayer in gram-negative bacteria. LPSconsists of:
- Lipid A
- Core polysaccharide
- O-antigen
What is Lipid A? Describe how Lipid A interacts with the immune system.
Lipid A is the innermost subunit of LPS that possesses it’s endotoxin activity
- Binds CD14 of TLR4, leading to the production of pro-inflammatory cytokines
- Can induce septic shock
(Anchors LPS to the outer leaflet)
What is the Core protein?
Intermediate subunit of LPS between Lipid A & O-Antigen
What is O-Antigen?
Part of LPS that is used to classify gram-negative bacteria
What are Pili?
Also called fimbrae, are hair-like structures on gram-negative & positive bacteria
What is a common pili?
Hair-like structure involved in bacterial attachment to epithelial cells
What is a sex pili?
- Hair-like structures involved in the exchange of genetic material from on bacteria to another
- Encoded on F plasmid & referred to as F pili
What are flagella?
- Rotating helical structures attached to the plasma membrane & involved in locomotion
- Important virulence factor
What is a Capsule?
- Loose polysaccharide or protein layer surrounding some gram-positive or gram-negative bacteria
- Serves as another important virulence factor
- Antiphagocytic
Biolfim
Organized community of bacterial cells w/ capsule around the entire community
What does a positive Quelling test identify?
Bacterial capsulses
Why are patients’ status post splenectomy more susceptible to infection by capsulated bacteria?
Capsulated bacteria are opsonized & cleared by the spleen
What type of bacteria can make endospores?
Gram-positive
What are tiechoic & lipotiechoic acid? What type of bacteria are they associated with, and what is their function?
Tiechoic & LTA= components of the thick peptidoglycan layer of gram+ bacteria
- Function= facilitate attachment of gram+ bacterial cells to host & other bacteria
What is mycolic acid?
Long, branched chain fatty acids that are covalently attached to peptidoglycan in “acid fast” bacteria
