Dear researchgate community,
I noticed some abnormalities in my recent bacteria growth curves. The strain is DH5a, growing under inducer of heavy protein expression. Even with this stress, previously all my growth curves appear smooth, as in the blue curve in the uploaded figure. But recently, since I opened a new stock of LB media, the growth curves becomes very un-smooth. As the grey curve in the uploaded figure, OD measurement appears jumps a lot and bacteria seems struggling to grow. There also appears a growth phase transition after around OD 0.2, as in the yellow curve.
Since I started new LB stock, I am not sure whether this is the reason. I used LB premix powder, usually even somewhat degrade in the powder will not result in such weird growth behaviors. I wonder if anyone has experience in similar issues.
Thanks in advance and best regards.
Have you tried a growth curve with a control strain (not induced or not expressing protein or empty plasmid) to see if the effect remains true or if it really is a stress effect.
You might also be having some issues with your instrument, insufficient shaking so the cells are clumping or some measurement variability. Try some controls to be sure you get consistent readings from the instrument.
Thanks Michael for the reply. I tried the empty plasmids. The curves are smoother so I am sure it is to do with the expressing protein or stress effect. Previously I could definitely got smooth growth curves even under the stress effect, so I thought may be it is the media quality. But you are right shaking may affect as well.
Media quality might affect overall growth rate or the final density, but I can't think of any reason why media would give you this sort of uneven curve. What is the time course shown?
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