Thursday, 27 November 2014

Organisation and time management in experimental Science Short version

The first step in developing a robust system for the production of recombinant GFP, requires knowledge of the growth characteristics of the host organism; in our case Escherichia coli. The standard approach to obtaining this information is to measure the rate of growth of the organism under defined conditions. It may also be useful to determine to what extent factors such as temperature, growth medium composition and pH, vessel configuration, aeration rates etc., influence the yield of cells. The method we shall use, and indeed you have developed yourselves (with a little bit of help), is to monitor growth over time using a spectrophotometer to accurately measure the turbidity (cloudiness) of a liquid culture at a set of well defined time points.

The starting point and the end point of the experiment should be considered in planning your schedule. This is where you need to think carefully about managing your time and organising materials and equipment. I wont give away the method completely, but you might want to think about the following elements of the experiment.

1. What volume of culture should I use? Why?
2. What is the best inoculum to use (loop or defined volume) and how could I determine this empirically?
3. What is the likely time taken for sufficient numbers of cells to populate the culture tube making detection possible. (Hint, you already have your own data on plate and broth cultures). Discuss this with your colleagues.
4. What sample volume is ideal for recording time points?
5. What solution should I use as a "blank"
6. Why did I suggest placing your first sample on ice today?
7. Are there any consequences of depleting the culture during the experiment?
8. What are the growth characteristics of bacterial cultures that have been described in class or on the Internet (e.g. Wikipedia)
9. Should I make single, duplicate or triplicate  measurements, or maybe team up with colleagues? Pros and cons?
10. How should I record and plot my data?
11. What should I do after plotting my data?
12. What do other students' data look like and can I rationalise the results?

Key words Growth curve, E.coli, temperature, pH, aeration, spectrophotometry, blanks, culture, medium, planning, time management, organisation

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