Lab Notes Jan 21

E. Coli lab Jan 21

Can E. Coli become resistant to T4 phages?

e.coli are bacteria (very small, live)
T4 phages – virus that kills e. coli

Falsifiable hypothesis: E. Coli will not become resistant to T4 phages. (null hypothesis)
Only have to see one e. coli become resistant to falsify hypothesis.

IF FALSIFIED: If e coli do become resistant, we have to ask: why?
Why: Hypothesis: It’s random which e. coli are t4 resistant – no reason. (no relationship between resistance and exposure. (null hypothesis)
Why: H: It’s not random. E. Coli become resistant because they were exposed to the t4 phages. (acquired immunity) (Being exposed to t4 phages makes E. Coli resistant)

Tues – Rich chose colony of bacteria.
Used E. Coli colony to inoculate flask of broth – is now cloudy (which means e. coli grew well in broth – divided and divided – all clones of original bacteria) – & to inoculate test tube of T4 phages and sterile broth. No ecolli grew in test tube of t4 phages. We know original colony of E. Coli can grow and that they are killed by t4 phages.

Made dilution of flask of broth inoculated with e. coli.
Started with 1 colony of E. coli – all bateria in colony are clones of 1 original bacteria.
Took small sample (10 microliters) from broth full of E. Coli and added it to 200 mL beaker of sterile broth (1/50,000 dulution)
Used this sample to inoculate 100 test tubes which already had 5 ml of sterile broth in them
Used .5mL of 1/50k dulution of broth culture
Inoculated flask which had a total volume 500 mL sterile broth – inoculated with 50 mL of diluted broth
Have same total volume and concentration in test tubes and flask

Bacteria in flask and test tubes are going to be exposed to t4 phages
Petri plates that have viruses over entire plates – using fire and hockeysticks
Add bacteria to virus plates – fire and hockeysticks
30 plates to a group – label with group name (JKL) , today’s date (1/21)
20 plates write t4 – pipet .2 mL of t4 broth and hockey stick on all 20 plates
label 10: tube 1, tube 2, …. tube 10 (tubes have bacteria in them)
label 10: flask (has bacteria in it) (flask was shaken)
10 plates write no t4
make serial dilution of one tube and flask and plate .1 mL samples onto “no t4” plates

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