Intro Flashcards
What is medical microbiology?
the study of the dynamic interaction between microbes and the human host. This interaction (or symbiosis) involves commensalism, mutualism and parasitism
What is meant by the term “normal flora”?
commensal or mutual symbionts adapted to the special conditions found in various body locations. Normal flora tend to avoid injuring the host, and are often beneficial to the host.
What is meant by the term pathogen?
any microorganism that has the capability to cause disease.
What is meant by the term virulence?
The ability of a microorganism to cause disease.
What is a virulence factor?
factors (e.g. toxins) produced by organisms that enable it to infect, cause disease, and/or kill the host.
How big are viruses?
(0.03- 0.3 µm)
How big are bacteria?
0.1- 10 µm
How big are fungi?
4- 10 µm
What are unicellular fungi called? Multicellular?
Uni = yeast
Muti = mold
True or false: parasites are strictly multicellular?
False
What is the cell walls composed of in bacteria?
peptidoglycan
What is the cell walls composed of in fungi?
Chitin
Which cell walls contain sterols: those of bacteria or of fungi?
Fungi
What are the ribosomes that are present within eukaryotes? Prokaryotes?
Eukaryotes = 60 + 40 = 80
Pro = 50+ 30 = 70s
Where does cellular respiration occur in eukaryotes? Prokaryotes?
Eu = mito
Pro = cell membrane
What is brightfield microscopy?
Normal microsopy
What is darkfield microscopy? What is it better for?
Inverted background d/t light condenser scattering light
better for small bacteria
What is phase-contrast microscopy? What is is used for?
Parallel beams of light are passed through objects of different densities.
Enables the internal details of microbes to be examined
What is fluoresenct microscopy?
Staining microorganisms with fluorescent dyes
What is electrion microscopy?
Uses magnets rather than light to get higher resolution
How can bacterial antigens be detected?
microsopy, through antibody detection, DNA sequencing, (ELISA, pcr, etc)
What are the four different types of media used to grow bacteria?
(1) enriched nonselective media
(2) selective media
(3) differential media
(4) specialized media
What are the five ways that bacteria are classified?
- Visible features
- Nutrition
- End products
- Surface molecules
- Nucleic acid analysis
What is the shape of cocci bacteria?
Disc
What is the shape of bacilli?
Rod
What is the shape of spirochetes?
Spirals
What are the two different apendages found in bacteria?
Pili, flagella
Which type of bacteria have an outer cell membrane: gram positive or negative?
negative
Which type of bacteria have a thick peptidoglycan layer: gram positive or negative?
positive
Which type of bacteria have LPS: gram positive or negative?
gram negative
Which type of bacteria are able to form spores: gram positive or negative?
Gram positive
Which type of bacteria are able to have capsules: gram positive or negative?
Both
Which type of bacteria are resistant to lysozyme: gram positive or negative?
Gram-negative
Which type of bacteria have a periplasmic space: gram positive or negative?
Gram negative
Which type of bacteria produce endotoxin: gram positive or negative?
Both
What are acid-fast bacteria?
Gram positive bacteria that have a wax-like lipid coating of mycolic acid
True or false: both gram positive and negative bacteria have a peptidoglycan layer
True
What are the four steps of gram staining?
- Add crystal violet
- Add gram iodine
- Decolorize with EtOH/acetone
- Safarnin red
What is more complex, a gram positive of gram negative cell wall?
Gram negative
What are the layers to a gram positive cell wall?
Peptidoglycan layer, followed by a membrane
What are the layers of a gram negative cell wall?
Cell membrane, peptidoglycan layer, space, cell membrane
What are the two sugars that comprise peptidoglycan?
NAG
NAM (N-acetylmuramic acid)
What is the link between the NAG and NAM that is a target of lysozyme?
beta 1,4, cross links
What are the proinflammatory effects of peptidoglycan?
Fixes complement
Binds to PRPs
Triggers TNF
What is the stain used to identify acid fast bacteria like mycobacteria? What does this bind to?
Carbol fuchsin. which binds to mycolic acid
Is peptidoglycan necessary for cell survivial?
Yes, but more important/more expressed when inside a host
What is the purpose of the safranin that is added when gram staining?
To counter-stain other cells red
What are the three components of LPS?
O antigen
Core polysaccharide
Lipid A
What is the function of Lipid A in LPS?
Anchors the entire molecule to the cell membrane
Which of the three parts of LPS is responsible for the endotoxin activity?
Lipid A
What is the core polysaccharide part of LPS made of?
9-12 sugars
What is the O-antigen part of LPS made of?
O antigen is attached to the core and extends away from the bacteria. It is a long linear polysaccharide consisting of 50 to 100 repeating saccharide units of 4 to 7 sugars per unit.
What basic structure of LPS is identical for related bacteria and is similar for all gram-negative Enterobacteriaceae
Lipid A
How can the O-antigen be used to identify a bacteria line?
The O antigen distinguishes serotypes (strains) of a bacterial species.
What does LPS cause?
Shock via TNF
How many sex pilli are found on bacteria?
One
What is the function of common pilli?
attachment to epithelial cells
Sex pili are encoded on a/an (blank) and are also referred to as (blank)
Sex pili are encoded on an F plasmid and are also referred to as F pili
What are the rotating helical structures attached to the plasma membrane and involved in locomotion
Flagella (H antigen)
What is the major function of a bacterial capsule?
Prevent phagocytosis
What is a biofilm?
an organized community of bacterial cells that has a capsule/slime layer surrounding the entire community
What is the Quellung test?
A test is used to identify bacterial capsules; treating with anti-capsular antibodies results in a visible “swelling” of the capsule
True or false: both gram positive and negative bacteria can form endospores
False–only some gram positive can. NEVER gram negative
How long can spores exist for?
Long time (centuries)
What do endospores contain? (3) What are the layers of an endospore?
- a complete copy of the chromosome,
- the bare minimum concentrations of essential proteins and ribosomes,
- a high concentration of calcium bound to dipicolinic acid.
The spore has an inner membrane, two peptidoglycan layers and an outer keratin-like protein coat.
What is in the periplasmic space of gram negative bacteria?
Peptidoglycan
What is teichoic acid?
Lipid found in gram positive bacteria peptidoglycan layer.
This promotes the attachment of the bacteria to others
What is the function of the outer membrane of gram negative bacteria?
Maintain structure, is a permeability barrier
What are the proteins embedded in the outer membrane of the gram negative bacteria that allos diffusion of hydrophilic molecules?
Porins
What are the main components of the inner layer of gram negative cell membrane? Outer?
Inner = phospholipids Outer = LPS
What does LPS bind to that causes shock?
CD 14 and TLR4 on phagocytes.
What is the function of the mycolic acid in the outer membrane of bacteria?
Impeded entry of chemicals/lysosomal enzymes
What are the two components of the acid fast structure, besides mycolic acid?
Lipoarabinomannan (like LPS)
Arabinoalactans (brached poly saccharide)
What are pili made of?
Protein subunits called pilin
Endospoes are made only by which bacteria type: gram positive or negative?
Only gram positive