microbiology (finished) Flashcards
(33 cards)
what are the shapes of bacteria?
- cocci (round shaped)
- bracilli (rod-shaped)
- spirilli (spiral shaped)
how can bacteria be distinguished?
shape, size, staining characteristics and metabolic, antigenic and genetic features
what determines the shape of bacteria?
the rigid cell wall which has a unique structure
what is the bacterial cell wall composed of?
composed of peptidoglycan
- cross-linking provides a strong, but flexible framework to protect cell contents and cells from lysis
what are the properties of gram-positive bacteria?
thicker peptidoglycan walls and the cell walls lack lipopolysaccharide
what are the properties of gram-negative bacteria?
thinner cell walls (less peptidoglycan) and supplemented by large molecules of lipopolysaccharide
what are the staining characteristics of gram-positive bacteria?
retain crystal violet stain/iodine complex = purple (after washing with alcohol)
- more susceptible to antibiotics and lysozyme
what are the staining characteristics of gram negative bacteria?
- stained red by counterstain safranin
- not impacted by lysozyme and resistant to penicillin
what is the function of the cell wall in bacteria?
to prevent osmotic lysis
what is the procedure for Gram stain?
- Heat fix a smear of bacteria
- Stain using crystal violet stain
- Fix the stain with iodine
- Decolourise with alcohol
- Counterstain with safranin.
what is the purpose of a Bunsen burner being present whilst culturing micro-organisms?
creates an updraft to reduce the no. of micro-organism falling on the petri dish
what is sterilisation?
the removal or killing of ALL micro-organisms on an object or in any material
what does using the aseptic technique prevent?
- contamination of the environment by the microbes being handles
- contamination of microbial cultured by unwanted microbes from the environment
what does storing bacteria at 25 degrees or below do?
prevents pathogenic bacteria growing
who will touch ur knees
ammarah ;)
what is microbial metabolism?
the means by which a microbe obtains the energy and nutrients it needs to live and reproduce
how is the microbe’s ecological niche determined?
by looking at the specific metabolic properties of a microbe
what are the metabolic features of obligate aerobes?
requires oxygen for metabolism
what is the metabolic features facultative anaerobes?
they can respire anaerobically if they need to (if there is little/no oxygen available)
what are the metabolic features of obligate anaerobes?
- can only survive in the absence of oxygen
- oxygen is toxic to them
where are antigens found?
they are proteins that are found on the surface of bacteria and are unique to that bacterium
what is vertical transmission?
when genes are transferred down generations, ie from parent to offspring as a result of sexual or asexual reproduction
what is horizontal transmission?
when genes are transferred across from an individual to others in the same generation. This does not occur due to reproduction.
what does agar contain?
a carbon source, nitrogen source, water, vitamins and mineral salts
