Bacteria, Viruses and Immunity Flashcards
Explain the mechanism of action of complement proteins 5-9.
What pathogens are they specific for?
C5b, C6 and C7 bind. The complex then binds the cell membrane via C7. C8 binds this complex and inserts into cell membrane. C9 binds and 10 to 16 molecules polymerise, forming a pore in the bacteria. It’s cytosol is then in continuum with the exterior and it undergoes osmotic lysis.
neisseria gonorrhoeae and neisseria meningitidis
List three enveloped DNA viruses
Hepatitis B
Herpes
Smallpox
What colour would a gram positive bacteria stain?
Purple
What colour would a gram negative bacteria stain?
Pink
Describe the method of gram staining:
Stain with crystal violet - it binds with negatively charged cell components.
Add iodine - forms complexes with crystal violet.
Extract the complexes with acetone or methanol - cannot be extracted through peptidoglycan cell wall.
Stain with red dye.
What can you deduce about a gram positive bacteria?
It has a peptidoglycan cell wall.
What is the structure of the cell wall of a gram negative bacteria?
Plasma membrane, then a thin peptidoglycan cell wall, then an outer membrane consisting of phospholipid and lipopolysaccharide
What is the consequence of a bacteria having a lipopolysaccharide component to its outer cell membrane?
LPS is toxic and causes sepsis, even when the bacteria are dead.
What is the microbiome?
10^14 bacteria that are normally resident on and in the human body.
What would you use an acid fast stain for?
Identify mycobacterium tuberculosis and mycobacterium leprae- bacterial causes of tuberculosis and leprosy.
What name is given to bacteria that are observed as clumps of round cells?
Staphylococci
What name is given to the shape of bacteria that appear as strings of round cells?
Streptococci
What is the name given to bacteria that have an elongated shape?
Rods or bacilli
What name is given to bacteria that appear as clumps of two cells?
Diplococci
What are the external structures that may be observed on a bacteria?
Pili, including fimbriae
Flagella
Capsule
What internal structures may be noted?
Spores, inclusion granules.
What cell envelope types cannot be visualised with a gram stain?
Mycobacterium
Bacteria that are too small - chlamydia, treponemes(syphilis), rickettsia
Mycoplasmas - no peptidoglyca
What stains can be used to identify mycobacterium?
PAS, auramine - fluorescent, Ziehl-Neelsen - bright field
What is the structure of the cell wall of mycobacterium, and what implication does this have for treatment?
Plasma membrane, then a peptidoglycan cell wall, then arabinogalactan which holds together the peptidoglycan and the mycolic acid (hydrophobic 90 carbon lipid).
On the surface are glycolipids
Lipoarabinomannan is also present.
Hardy cell wall, therefore difficult to treat.
What antibiotics can be used to treat a gram positive bacteria?
Penicillins and cephalosporins, glycopeptides.
What would you treat tuberculosis with?
Isoniazid.
By what means do bacteria replicate?
Binary fission
What are the three phases of growth of bacteria in broth?
Lag, exponential and stationary.
What can form on implanted medical devices, and what is the implication?
Biofilms - device must be removed.