3.4 - Microbiology Flashcards
What is an agar plate?
A Petri dish containing agar and nutrients used to culture micro-organisms
What are aseptic techniques?
A range of techniques used to culture micro-organisms under sterile conditions in order to minimise contamination
What is an autoclave?
A device used to sterilise equipment under high temperatures
What is crystal violet?
A purple dye used in Gram staining
What is a culture?
The growth of living matter in vitro (outside a living organism) under suitable conditions
Define the term Gram negative
Describes bacteria that have a thin peptidoglycan wall with an outer lipopolysaccharide membrane and a red appearance following gram staining. On treatment with alcohol, the lipopolysaccharide layer is lost and the crystal violet washes away.
Define the term Gram positive
Describes bacteria that have a thick peptidoglycan wall and a purple appearance following gram staining. The thick peptidoglycan wall retains crystal violet when rinsed with alcohol.
What is gram staining?
A technique used to differentiate between Gram negative and Gram positive bacteria
What is a inoculating loop?
A tool used to safely transfer, smear or streak a small sample from a micro-organism culture
What is a nutrient media?
A solid or liquid nutrient-rich medium used in the cultivation of micro-organisms. It contains a carbon source, nitrogen source, water and growth factors (e.g. salts and vitamins)
What is a peptidoglycan?
A polymer consisting of amino acids and sugars that forms a 3D mesh and makes up the cell walls of most bacteria
What is safranin?
A counterstain used in gram staining that dyes Gram negative bacteria red
Explain the term serial dilution
A sequence of dilutions, in which the dilution factor is constant, used to dilute a stock solution.
What is total cell count?
The total number of cells (both living and dead) in a given area or volume
What is total viable count?
An estimate of the total number of living cells in a given area or volume
