STREAK-PLATE METHOD - ISOLATION OF PURE CULTURES

Question 1

What is a pure culture and why is it imperative that each species should be isolated in it?

Answer 1

pure culture consists of only type of microorganism

Question 2

What are the three dilution methods commonly used for the isolation of bacteria?

Answer 2

streak plate, spread plate, and the pour plate

Question 3

What is the streak-plate technique?

Answer 3

it provides a simple procedure, it is essentially a dilution technique that spreads a loopful of culture over the surface of an agar plate

Question 4

Describe the colonies that appear on the plates for E.coli, S. Epidermidis, & Mixed culture

Answer 4

E.coli & Mixed - lobulated margins around and mostly circular irregular

Staphylococcus epidermidis - wrinkled and filamentous

Question 5

What is the description and morphology of each colonies/bacterial cells in streak plate method?

Answer 5

S.E - round, raised, shiny gray & non motile, gram +ve, cocci, arranged in clusters

E.C- rough, irregular & rod shaped, gram -ve, nonsporing

Mixture - irregular, undulate & clusters in groups, round

Question 6

Why do we flame the loop between streaking? What is the purpose of a streak plate?

Answer 6

allows you to effectively dilute on the plate and obtain isolated colonies by spreading the inoculum thinner and more evenly

Question 7

What are some reasons for not getting well isolated colonies from a streak plate?

Answer 7

the person streaked the plate in a non-sterile environment