Thursday, 17 April 2014

Microbiology practicals

This was my first Microbiology practical. As it was the first practical, all we did was just practising the different techniques.

Demonstrating the need for aseptic techniques.

Everything must be sterile; the medium and the instruments used.  Important things to make sure to do is to flame the neck before and after using glass bottles and to never put the lid down. 
  • I made four agar plates, one plate was open for 10 minutes (to see what was in the air), the second I placed my fingers on the agar surface (to see whats naturally on my hands), the third a small sprinkle of soil was placed on the agar (to see whats in soil) and the final one was left closed as the control. 
  • Then I made 3 tubes of sterile nutrient broth, one with E.coli in, the second with soil and the third was left sterile and was the control.
(Incubation: 37 degrees Celsius for 48 hours).

Streak Plates

I prepared two malt extract agar plates which I left in the fridge to cool so that I had a really solid surface.  The inoculum is spread and diluted over the medium so that single isolated colonies can be seen. This is good if you have a mixed culture as you can then get  a pure culture from it.

Inoculation: A loop is used to spread the culture. The loop is flamed until red hot before and left to cool.  This is so that it is then sterile before used. A loop of culture is removed and then spread over a segment of the dish. The loop i flamed again and left to cool and a little of the previous segment is used for the next segment. this is repeated for another two times. this dilutes the culture so that single colonies can be seen.

(Incubation: 37 degrees Celsius for 48 hours).

Agar Slopes and Agar Butts

These are used as it provides a large surface area for microbial growth. it also means that they are easy to handle and store.

  • Slopes: To prepare them I got two molten nutrient agar tubes and left them to cool in an inclined position. After they were cooled I put a loopful of culture on each slope, one with E.coli and the other with M. leutus. The loop is drawn gently from the bottom to the top of a slope in a serpentine pattern.
  • Butts: A small amount of inoculum on the tip of an inoculating needle is thrust through the centre to the bass of the agar butt.  One was E.coli and the other was M. leutus. this is used to see if bacteria is able to grow in anaerobic conditions

(Incubation: 37 degrees Celsius for 48 hours).

(Above: the top two are the E.coli, the one to the left is best as there are single colonies near the bottom of the petri dish which is what you want. the one in the bottom left is soil and there are things growing on it even though its hard to see. the last one on the bottom right is my fingers... You can see my four finger spots. There is bacteria on almost everyones hand and skin all of the time. The most common is Staphlococcus (a genus of bacteria of which most are harmless and live on the human skin). This is a good thing to have as this protects against pathogens from getting through the skin.) 

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