1. Why isn't the Gram stain used on acid-fast bacteria? Explain your answer
A gram stain is a group of water based dyes which will readily stain the features of certain types of organisms with a typical peptidoglycan cell wall. The problem with acid fast bacteria is that they possess a very thick waxy lipid engrained into their cell wall that won't absorb any of the gram stain colors. Because the is little to no absorption of dye it would be very hard to see under the microscope.
2. Assume that after washing your hands, you leave ten bacteria cells on a new bar of soap. You then decide to do a plate count of the soap after it was left in the soap dish for 24 hours. You dilute 1g of the soap 1:106 and plate it on standard plate count agar. After 24 hours of incubation, ...view middle of the document...
I assumed that the soap was not antibacterial soap thereby even being able to survive on the bar I also assumed that the bacterial growth would occur every two hours since the majority of bacteria go through binary fission every 1-3 hours. I made a table as listed below and filled it out as such.
Hour of Incubation number of bacteria hours of incubation number of bacteria
total cells after 48 hrs
Which is pretty close to the 168 colonies X 10^ 6 found on the agar plate. The total bacteria on the soap after the initial 24 hour period was 40960 cells mathematically. With the table I made above it seems like the bacteria came from the original ten cells you left on the bar of soap which had doubled every two hours and yielded such a fantastic number. Of course the could and would be some cross contamination even though the soap was new I am sure the counter or soap dish had bacteria on it, in it, or around it. It is also possible that bacterial floating in the air could have landed on the bar also leading to such a high number of cells per gram.
In my future career as a nurse I feel that the knowledge gained from this past section really helps me understand how fast bacteria can get out of control and really cause systemic problems for a host. It also reminds me why there is so much push for washing your hands well and often. I will remember this data anytime I have a patient with a pathogenic organism I will also remember how easy it would be to spread organism especially in a hospital environment.