Explain why the following steps are essential during subculturing -Flaming the inoculating instrument prior to and after each inoculation
To maintain sterility
Explain why the following steps are essential during subculturing: Holding the test tube caps in the hand to form a V
There are bacteria and contamination on our hands, and we don't want to contaminate the caps or tubes
Explain why the following steps are essential during subculturing: Cooling the inoculating instrument prior to obtaining the inoculum
excess heat can fixate the samples or kill the organisms
Explain why the following steps are essential during subculturing: Flaming the neck of the tubes immediately after uncapping and before recapping
If there are microbes on the neck of the tube, you don't want to accidently bring those into the nutrient base, also you don't want to spread the microbe you were incubating by spreading it through the neck
Purposes of the subculturing procedure
To separate microbes in order to do tests on them. Also, it can be used to prepare and maintain stock cultures. The procedure is done aseptically in order to reduce the risk of contamination
Explain why a straight inoculating needle is used to inoculate an agar deep tube.
the inoculum needs to be drawn out from the bottom of the tube in a straight line, along the line of insertion
There is a lack of orange-red pigmentation in some of the growth on your agar slant labeled S. marcescens. Does this necessarily indicate the presence of a contaminant? Explain.
No it doesn't mean that there is contamination. It could just meant that you failed to inoculate a bacteria. Also, it could mean that the environment was wrong for the bacteria to grow.
Upon observation of the nutrient agar slant culture, you strongly suspect that the culture is contaminated. Outline the method you would follow to ascertain whether your suspicion is justified.
You could grow the culture more to see if cultures of unknown stuff grows.
Can a pure culture be prepared from a mixed-broth or a mixed-agar-slant culture? Explain.
Yes, the components from the mixed culture just need to be separate first. This can be done by doing a streak plate or diluting the mixture and using a spread-plate technique. Then when you have individual colonies you can grow them as a pure culture.
Observation of a streak-plate culture shows more growth in Quadrant 4 than in Quadrant 3. Account for this observation.
This could be due to human error, no properly sterilizing the inoculating loop or spreading some of quadrant 1 into quadrant 4. This can also be due to the fact that a wider streak is used, so if the microbe is not diluted enough, it can grow more
Why is a needle used to isolate individual colonies from a spread plate or streak plate.
With a needle less microbes are picked up. This limits to possibility of getting two different microorganisms by accident.
How can you determine if the colony that you chose to isolate is a pure culture?
The cultures that grow should all look the same, they should have the same cultural characteristics.
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