In the streak-plate technique, how are microorganisms diluted and spread out to from individual colonies?
The petri dish is divide into four areas. the bacterial mixture is added to one area of the dish with an inoculating loop. the bacteria is then spread over the other three areas in different with flaming the loop in between quadrants. the individual cells are spread out over the dish and give rise to separate colonies.
Which area of a streak plate will contain the greatest amount of growth? The least amount of growth? Explain.
Greatest: Original streak area.
Least: Third (last) streak area.
More streaks dilute and spread out the growth.
Does each discrete colony represent the growth of one cell? Explain your answer. Why can a single colony on a plate be used to start a pure culture.
Yes, each discrete colony represents the growth of one cell because the mixture was being spread out over the dish.
A single colony can start a pure culture because the colony arose from a single cell and divides to create single species.
Why can mannitol salt agar and EMB agar be described as both selective and differential media?
Because they can isolate organisms and partially identify different groups of bacteria
How can a streak plate become contaminated?
By letting too much air in returning loop.
by no using proper aseptic technique and leaving the lid off the plate too long.
How the results of the pour-plate method compare with those obtained using the streak-plate and spread-plate method?
The results should compare favorably with the streak plate and spread plate methods to obtain isolated colonies.