Tube C Case Study Answers

The aseptically inoculate nutrient broth tubes A and B did not have any microbes inoculated into the tubes so it should not have been cloudy and that was what was seen. Tube C should have been cloudy because it had E. coli inoculated into the nutrient broth and that was also seen. A simple streak was also performed and it looks has if the loop went over previous streaks which should not have been done. A complex streak was also done. No colonies grew towards the end of the streak, this could be due to the inoculation loop being to hot and incinerating the bacteria cells, meaning the loop should have had more time in order to properly cool down. The Brain Heart Infusion plate is a complex medium that does not inhibit the microorganisms, thus
The steaks that were done on this plate seemed to show that E. coli did not have lipases because it did not have clear zones. Staphylococcus aureus seemed to have these clear zones meaning it can secrete lipases. The bacteria Bacillus subtilis did not grow well to see if there was a clearing. After doing some research, it was shown that B. subtilis is lipase positive so there should have also been some clear sones like the Staphylococcus aureus (Watson). The DNAse agar could not have been analyzed because HCl was not available to precipitate the DNA to see if the bacterium had the enzyme DNase. If the test could have been analyzed, Staphylococcus aureus would be positive for DNase and E. coli would have been negative (DNase
When the plate is flooded with iodine, where there is a clearing then that bacteria can secrete amylase. There was a clearing only around Bacillus subtilis on the plate meaning that it can secrete amylase. Staphylococcus aureus and E. coli did not have this clearing meaning they can not secrete amylase. Casein agar is a complex that tests for the ability of a bacterium to secrete a proteinase enzyme that can break down the protein casein, which is found in milk. There was no visual clearing on any of the bacteria. What should have been seen for E. coli was that there should have been no visual clearing (Casein Agar). There should have been visual clearing around Staphylococcus aureus because it breaks down casein (Arvidson, 2009). With Bacillus subtilis, there also should have been visual clearing (Kaiser,