26.(10 points) What are you trying to demonstrate by using the following growth
ID: 141370 • Letter: 2
Question
26.(10 points) What are you trying to demonstrate by using the following growth conditions? What results are you looking for, and what do they mean?-Plating out an unknown organism on solid medium containing egg yolk? 26.(10 points) What are you trying to demonstrate by using the following growth conditions? What results are you looking for, and what do they mean?
-Plating out an unknown organism on solid medium containing egg yolk? 26.(10 points) What are you trying to demonstrate by using the following growth conditions? What results are you looking for, and what do they mean?
-Plating out an unknown organism on solid medium containing egg yolk?
Explanation / Answer
When there is egg yolk present on a solid medium, we try to grow the unknown organisms and try to differentiate it based on the production of the lecithinase and lipase along with presence of proteolytic activity by the organism. Lecithin is a normal component present in the egg yolk and when we grow the micro-organisms we are majorly trying to look for organisms which are mostly bacterial lecithinases. The lecithinases is an enzyme which is released by the bacteria and has the ability to break down lecithin present in the egg yolk component. The egg yolk agar is a enriched and differential medium which is used for isolation of the species which have the ability to break down the lecithinase and also undergo proteolytic activity. The egg yolk present on the solid media helps in the detection of the lecithinase and lipase activity of the micro-organisms.
Results and Its Meaning
On growing unknown species on a solid medium that consists of egg yolk, the results we expect is that if the micro-organisms is able to produce lecithinase, it will break the enzyme lecithin present in the egg yolk. The bacterial lecithinases break down the lecithin component to an insoluble diglycerides and this can be easily seen through formation of opaque halo. This surrounds the colony when the microbes producing lecithinase grows on the egg yolk agar medium. The precipitate occurs as white halo and this is created due to the release of the free fat during the breakdown.
The lipase enzyme produced by the microbes tend to hydrolyze the fats present within the egg yolk and this results in formation of the opaque precipitate around the bacterial colonies. If the microbes produce lipase enzymes, it tends to hydrolyze the fats present within the yolk of the egg and it gives a slightly shiny colonies. The proteolysis enzymes leads to proteolysis which leads to clearing of the medium around the growth of the colonies. The presence of the opaque halo zones represent that the unknown microbe produces lecithinase which has degraded the lecithin present in the egg yolk.
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