After this week I knew my life would never be the same! I realized that I would have to read the encyclopedia cover to cover to earn my A! On Monday we completed numerous tasks in lab. First we met in room 347 where we discussed the blogs and the importance of commenting on others' blogs! We were given our list of assignments for the day which included: completing our starch streaks from the previous class, checking the growth from our liquid cultures, vortexing and scoring our liquid cultures, streaking our liquid dilutions, counting the irradiated plates, taking pictures of our selected plates, and choosing ten to restreak. Our first task, which was to complete our starch streaks from the previous class, went fairly well. We had to streak strains: 33, 50, 52, 41, 42, 44, 47, 51 and 43 because the media that it needed to be streaked on was not available last class. We were given "strict" rules to streak the plate straight down, which is what I did. After this we checked the growth from our liquid cultures. To do this we had to vortex the tubes so that the growth which was present predominantly at the bottom of the tube would be suspended throughout the tube. We measured the growth by the amount of turbidity present. There was growth present in every tube! However, strain 50 had the most turbidity, signifying the greatest amount of growth. We then took 10 microliters of the irradiated soil dilutions and streaked it onto plates. Next we counted the irradiated plates and calculated the colony forming unit/ gram (similar to the calculations which were performed last class). The most growth was found on the 1/100 PCA media, and the least growth were found on the PCA media. On marine agar media there was an average of 17.3 colonies which is low. This could be because the organisms from this sample are not very tolerant or salt. As before, as the dilutions increased (-1 to -3) the amount of colonies decreased dramatically After counting the colonies and before doing calculations we chose ten colonies (six black and four pink) from our plates to restreak. We also calculated the percent survival (this week cfu/g divided by last week's cfu/g). The results from these calculations revealed that the not many organisms survived. The greatest percentage survival was found on the 1/100 PCA media. Thorugh this we concluded that radiation reduces population; it selects for different organisms. Those that survived were tolerant to radiation. Also, on radiated plates there are no Streptomyces and less diversity. Mostly orange and pink colonies were present. .
On Wednesday, the task load got a bit lighter. The assignments included rating NaCl and temperature plates and making new stock culture from our control plates (25ºC). The various temperatures included 10, 25, 30, 37, and 42 degrees. The different salt percentages included 1, 3, 6, and 9. For the temperature plates there most growth occurred at 30 ºC, whereas the least amount of growth was mainly at 10 ºC. This experiment has to be performed again because these plates were placed in a faulty incubator, which could account for the low growth rates at this temperature. The 1/10 PCA plates were contaminated, so we was not able to use them. The salt plates showed most growth on 1 percent NaCl and lowest growth at 9 percent NaCl. This may be because these organisms are not salt tolerant.
From the pictures below you can see that as the dilution increased less colonies were found on the plates of the irradiated soil.
LRH -1 dilution tenth strength PCA:
LRH -3 dilution tenth strength PCA:
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