MMBL day 6.
Today, we started by checking the results of our agar plates inoculations, to see what our bacteria eats. First, we checked the results of our starch hydrolysis test. Starch and iodine react to make a bluish substance. So, if the bacteria grows in starch, it will have digested the starch in our agar plate. So, around the bacteria, there should be no starch left, and therefore nothing for the iodine to react with near the bacteria. To determine this, we put iodine over our starch sample. We observed no clear zones around our bacteria. Rather, the iodine reacted with everything on the plate (our side, anyway), turning it a dark blue. Therefore, our bacteria must not feed off of starch.
Next, we tried the casein hydrolysis test. Similar to the starch, some bacteria can secrete enzymes that hydrolyze casein. So, if our bacteria feeds off of casein, there will be a clear zone around the bacteria. Once again, our bacteria showed no such clear zone. Obviously not tempted by casein.
We then looked to the tributyrin agar plate. If our bacteria was partial to lipids, then it would secrete lipase and digest it, similar to the last two. If the lipase breaks down the lipid, there will be a clear zone. Just like the last two, ours showed no clear zone. We have ourselves a picky little bacterium. Three down, one more to go for the agar plates.
For the DNA agar plate, some bacteria will secrete DNase enzyme that will hydrolyze many of the linkages between nucleotides in the DNA, leaving small DNA fragments. To us, this should look like a clear zone around our bacteria. Once again… nada. Nothing. Negative.
Perhaps the Gelatin? If our bacteria hydrolyzes gelatin, then it will be liquid in our tube. Not that we had our hopes up at this point, but this test proved negative as well. Just to make sure, however, we decided to incubate it longer.
So… we have failed to satisfy our bacterium with our limited menu. Perhaps it likes Litmus milk, but we won’t know until tomorrow because we forgot to do that sample (I know, I know… but give us a break! There’s a big long list of similar looking tubes and agar plates to inoculate! It seems a reasonable mistake). So, we inoculated the Litmus milk and stuck it in the incubator.
Well, perhaps we’ll have a little more luck with the fermentation. If our bacteria does ferment, it will produce an acid and gases. So, we looked for growth of the bacteria, for a change in color (to yellow), and for gas bubbles.
We tested positive for sucrose, maltose, lactose, and glucose. So, ours is picky when it comes to food, but doesn’t mess around when it comes to fermentation.
We then looked at the triple sugar test. This slant contained lactose and sucrose at 1% concentration, but glucose at only 0.1%. If the butt of the tube is yellow, then we’re positive for sucrose or lactose. Our entire tube was yellow, so we know it fermented either sucrose or lactose.
After that, we looked at the petri dish with the virus. Only the area where we put the virus (a little peace sign on ours) was left clear. Everywhere else on the dish, the bacteria had grown. When we applied the virus to our bacteria, the bacteriophages from the virus injected their DNA into the nearby bacteria, multiplied inside the cell, and caused the lytic cycle, destroying the bacteria around the virus inoculation.
Also, because we had forgotten our Thioglycolate test two days ago, we looked at the results of the one we inoculated yesterday. There was growth throughout the tube, showing clearly that our bacteria was facultative.
The last result we looked at was our GasPak Anaerobic System. Unfortunately, for the second time, the indicator strip remained blue. So, there must have been another leak. But, we did notice that our bacteria grew a lot, while others did not. This is further evidence for our bacteria being facultative, because there was neither a lack of oxygen nor an abundance of it in the locked system.
In preparation for tomorrow, we inoculated Tryptophan, Urea, Citrate, Nitrate, and MR-VP, to see which amino acids our bacteria is capable of breaking down.
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