Blog...................

This week in class we preformed dessication and radiation experiments on our organisms. For dessication testing we placed a drop of organism into the appropriate trays and placed them in less than 5% humidity chambers. They will remain there for approximately 42 days and will be rehydrated every seven days. For the radiation experiment we placed a colony from each plate into four liquid suspensions of the same media. The samples were exposed to 0 kGy, 3kGy, 6kGy, and finally 16 kGy. We are testing for both dessication and radiation resistance because it is thought that dessication may have helped some organisms to acquire radiation resistance. At home after class on Monday I began to wonder if there were any organisms that were sensitive to radiation until exposure to a dessicated environment. Dr. Rainey said yes it has been seen in organisms that were radiation resistant after dessication, yet when placed in liquid media lost their resistance and became sensitive to radiation. In class we also counted our unirradiated soil dilution plates and chose 10 colonies from these plates that were possibly the organisms of interest and streaked them onto new media. We chose pink, red, and peach colonies from our 10-2 1/100 PCA plate and our 10-3 1/10 PCA plates. We observed no growth at 10-6, two colonies on 1/100 PCA at 10-5, slight growth on all plates at 10-4, moderate growth at 10-3, and significant growth and 10-2 and 10-1. We had the most growth on 1/100PCA at all dilutions, followed by 1/10 PCA. We had the least growth on MA at all dilutions. We took pictures of all of our 10-1 plates and then showed the decrease in growth on 1/10 PCA through 10-6. As a class we also calculated the colony forming unites per gram of soil for our samples. The final thing we did this week was streak our cultures on to starch media to test for the hydrolysis of starch. Because there was not enough media we were unable to streak all the strains and will finish next week. These will be incubated for 20 days and tested for hydrolysis with iodine. My favorite thing we did in class this week was take pictures. On our 1/100 PCA we observed very cool, very pretty snowflake-like organisms.

Microbial snowflakes!