I am attempting to construct a standard curve to determine the concentration of bacteria in lactose broth. I concentrated the starting lactose broth, made serial dilutions, plated each dilution twice and took an initial OD reading. I repeated this a total of 4 times. I did not consider any dilution with an OD>0.6 due to turbidity. My curve yielded a correlation coefficient of about 84%. When I take a random sample from an inoculated lactose broth and take an OD reading, the expected CFU/ml is always greater than the plated CFU/ml, which makes sense since the spec does not distinguish between alive and dead bugs. Can I use this model to predict bacterial concentration in LB on a going forward basis using the standard curve, assuming all conditions remain the same ?
I think you're better off using a colorimeter instead of a spectrophotometer. I just grow my culture in a nephelometric flask and take readings at different time points. You can plate them up as well whilst taking a reading. This is what my understanding is. Now it is up to you what you find most suitable for your work.
Hi Ronny, what is wrong with a correlation coefficient of about 84%.?
I think that is pretty good, and you can adjust it when you are plating the bugs because many of the plated bugs will not grow anyway.
https://info.gbiosciences.com/blog/bacterial-growth-curves-turbidimetric-determination
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