I met the Duggarts yesterday in free speech alley with all 17 kids...

On 2/16/09 we did plate counts for the radiated soil samples that were plated on the various media.. We used these counts to calculate the colony forming units per gram of soil. Also, we compared our data from the unradiated soil samples and calculated the percent survival.

Percent Survival= (Unradiated cfu/g / Radiated cfu/g) x 100
MA=6.87%
PCA=41.78%
1/100 PCA=227.6%
1/10 PCA=74.8%
*MA had the largest reduction
*1/100 PCA is a freak of nature (no, not really! I explain it below)

We photographed the one of the -1 dilution plates from each media and one plate from each dilution of 1/10 PCA. Most of the data from the three soil samples (Golbi-1, LRH, and N97-2) agreed with our hypothesis that radiation would lower the plate counts. However, the Golbi-1 radiated soil sample differed from this pattern. Although the cfu/g from the radiated soil sample descreased on PCA and 1/10 PCA, the % survival was higher compared to the other groups with 41.8% and 74.8% respectively. On the other hand, the cfu/g from the radiated soil sample on the 1/100 PCA differed greatly from the results of the other media and soil samples. Our cfu/g increased over 100% as compared to the unradiated soil sample. At first, I assumed that we must have made a mistake. However, upon a little research and brainstorming I have formed a couple of hypothesis to explain this mysterious data. One possibility that I shared in class is that a competitor with the radiation resistant strains was eliminated upon radiation; therefore, the cfu/g would increase. Another possible explaination that I recently came across comes from an article in Nature. In this article, it talks about the advantages of high intracellular manganese and low intracellular iron in radiation resistant organisms. The high intracellular manganese reacts with free radicals produced during a cells metabolisms. Therefore, the bacteria cell is healthier overall. This hypothesis was tested by lowering the intracellular manganese in radiation resistant organisms in which they became more sensitive to DNA damage and cell death. This research is not only beneficial to our study on radiation resistant microorganisms, but it could also be a great tool in minimizes radiation damage to healthy tissue in cancer patients. By increasing the healthy tissues intracellular manganese and not adjusting the concentration in the target cancer cells, side effects from radiation could be greatly reduced. Anyways, back to bacteria!
Our 78 strains were also streaked on starch containing media. The plate was streaked in order to make somewhat of a lawn of cells so that we can clearly visualize clearings if the cells do in fact metabolize the starch. Someone comment on this and tell me if I’m right in saying that we are testing for amylase production? If not, what enzyme are we testing for? The culture were incubated at 25 C.
Next, we recorded the growth in the liquid culture of our 26 stains which were inoculated in the broth on 1/26/09. We measured this growth by vortex the broth and visualizing the turbidity. All of our strains grew in the liquid media. However, some had more growth than others. I am e-mailing a table of the data we recorded from this experiment. Strain #68 was not done because it was not inoculated on 1/26/09 due to contamination. We made a liquid broth and inoculated it with strain #68 on Monday, 2/16/09, and will check it in 20 days. The growth was rate on a scale of 1-4 with 4 being the greatest amount of growth and 1 being little growth.
Dilution plates (-1, -2, -3) were made of the radiated strains. 10 ul were streaked on each plate. Only one plate was streaked per dilution.
From the plate counts on the radiated soil samples, 10 colonies were selected as possible Modestobacter suspects. They are denoted GB11-GB20. I am really excited because we actually got a black colony. I am adding these new isolates to the Modestobacter suspect chart I made from the unradiated soil sample.
Wednesday was a hectic day. We recorded the growth from the temperature and [NaCl] plates. This should have been fairly simple, but it ended up being a really big headache because we miss placed some of the plates. Our observations of these plates is including in the spread sheet on airset. I noticed that not only does temperature and [NaCl] affect colony growth, but it also affects the color. The color is also recorded in the spreadsheet on airset. Our data is recorded using a scale of (0-4+) with zero being no growth and 4+ being the most growth. We have finally overcome the great strain #56 anomaly. #56 hates MA! Why on earth we thought that it grew best on that on our first day of class is beyond me. #56 grows best on PCA. For now on MA and 56 will have nothing to do with each other. Anyhow, 59 and 69 had to be restreaked for the temperature plates and observations will be recorded at a later date. This is due to contamination on their temperature plates. Also, 68 was not originally done on both the temperature and salt plates because the original culture was contaminated. Sean Michael made new plates for temperature and salts for 68. Today was a disaster.

Irradiated Golbi -1 dilution 1/100 PCA plate: