Friday, May 15, 2009


A) KW20, RecJ-, ExoI-, dprA- transformations with MAP7 DNA
Got unexpected numbers for the dilutions. Since the dilutions are 1 in 10, you'd expect 10 times less colonies as you move down. Not the case. Most plates decreased cell count by 2 times. Weird. Again, we found that transformation frequency was not as high as usual (for the WT). Plan is to make MIV-competent cells next week and start from the top.

B) Remaking RecJ-&ExoI- double mutants
Numbers on the plain plates were good (i.e. decreasing by 10X), but overall transformation frequency was low because I didn't get any colonies on the kan-tet plates! Which means the cells didn't transform well, or there weren't enough cells that survived to transform. Redo!

C) Getting to know H.influenzae
This was just an experiment to get myself acquainted with how H.influenzae grows, because some bacteria grow slowly and others very quickly. The aim was to give me a better background knowledge of this little guy. Every hour, I'd take a sample from a growing culture of cells and check it's optical density (OD) with a spectrophotometer. Optical density (cloudiness) is an indicator of how many cells are in the medium because the medium gets foggier as the cells grow. Then I took the same sample from the culture and diluted and plated it. Why? Just because the culture is at a certain OD, doesn't mean that all the cells are alive. Plating lets us determine the cfu (colony-forming units) per mL, which is basically the number of cells in 1 mL that are healthy enough to form colonies. I've collected my data and will learn how to make proper graphs next week.

(Unrelated but kind of related to point C: When we went down to the Invitrogen event yesterday, we saw an electronic cell-counter. You just put a sample on a slide, put it in, and it counts the cells. :O)

Long weekend!

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