The beginning of our experimental work end

Hi All:

As usual, how hard was our last session! Wasn´t it!!

Figure 1:Lucia and Mónica starting their bacterial dilution series.

Why was it so hard?

Because…

First of all, we were discussing during almost two hours what we performed until 18th of January of 2016 in our Project: Studying uv effect on bacterial growth… .Since the first experiment: how many bacteria are in a single colony?  To the final one: determine which is our basal mutation frequency.

Second: We discussed what the number of colonies in the plates means. And as a consequence we ‘ve found out what we are doing with

-Dilutions of cultures,

-plating,

-volumes…

And as I mention previously, we are counting bacterial colonies!!!.

 Figure 2: Cristina and Alba counting…

We estimated the división rate of our bacteria at… Paula’s home and Laboratory (28ºC) conditions.

Remember:

2n = Nº of Total bacteria; then, n is… (see your notebooks!!!).

And we also performed the following table:

Table 1: Colonies number to determine the mutation frequency (dilutions 0 and -1 corresponds to number of colonies in Sacarose 5% plates; dilutions -5 and -6 with TY plates).

And confirm we are in agreement with previous results in last PIIISA Project (see here) 

And Finally we planify our first uv treatment experiment!!!.

Based on literature and what we expected we performed the following experiment:

Two bacteria (3I, series 1-3;  and 3G, series 4-6).

Three uv stress conditions: 0 (no stress), 15 and 30 seconds.

In order to get all the numbering data we decided to make the corresponding dilutions of the following manner:     

a)  For the Control plates (0 uv treatment; series plates 1 and 4). The dilutions were performed in a similar way to previous one.

b) For the 15 and 30 s uv treatment (series 2-3 and 5-6). We estimated that 90-99% of the bacteria will dead. Then the dilutions performed were: 

  

After several rounds of dilutions, spreading (hopefully) without mistakes, we are waiting for our results. We have two different strains (3G and 3I) to have any data. One (3I) it is incubated at Paula’s home

 Fig. 3: OurPaula’s home incubator.

And the second (3G) in the Lab.

Several critical points in our experiment:

1)      Did we make the calculations properly?? (I think so but… who knows?)
2)      Did we make the dilutions properly?? Everybody should peform the pipetting and tubes and plates properly, without any mistake. (We’ll see….).
3)      The most important one: Is it adecuate the uv treatment performed??  This is, neither great, so we kill too many cells, nor small we didn’t see any mutation rate increase.

Girls, Keep alert!!

Next results will define how far we are in our Project.

Come on!!! we are closer to the End

Francisco Martínez-Abarca

Estación Experimental del Zaidín. CSIC.

Granada