As a biology student, doing experiments everyday is my habit already. However there are many instruments that needs to be prepared carefully beforehand, such as autoclave centrifuge tubes and flasks both big and small, pipette tips for different quantities, scraper, and of course preparing Marine Nutrient Agar and Distilled Nutrient Agar on Petri dish.
Some of you that read this post might know how to prepare it already... I mean, it is easy, who won't know how to prepare it? Even a psychologist can do so! But I still want to blog about it.. I want to tell my experience of doing it!!!!!!!!!!!!!
Well, lets start with the quantity of liquid and powder to prepare. To make 1 litre of nutrient agar solution, we need 20g of nutrient agar powder, for both MNA and DNA (Distilled Nutrient Agar). Use Schott bottle 1 litre to do this. After adding the right amount of agar powder and liquid, the mixture should be shake and then put into autoclave machine to 'cook' it. Make sure to not tighten the cover of the Schott Bottle too much cause if it is totally tightened then it will caused high pressure in the bottle then explosion in the autoclave machine will happen.
When put into autoclave machine, set the machine into agar mode or liquid mode, if there are any other kind of liquid autoclave together. After that, get 40 autoclave Petri dishes ready for 1 litre of nutrient agar is able to divide into 40 Petri dishes.
Put all the Petri dishes into a clean laminar flow. Get ready to pour the hot agar into the Petri dish, which is the hardest part.
You might ask me what is hard about pouring it. Well, I can tell you that the agar liquid is really hot for it is over 100 degree Celsius after it is out from the autoclave machine. Imagine holding it for 15-30 minutes with your hand that only been covered with plastic glove.
It is hard to pour the agar if the Petri dish been placed in a very low 'altitude'. So you need to put them high and that makes it easier for you to pour it. The higher the better. After pouring each of it you need to put it aside and let it get hard. Do not cover it as it will not allow the agar to dry properly.
The agar usually does not take more than 10 minutes to get hard. One need to make sure that the bench for the agar to get hard is not shaky but still as shaking can cause the surface of the agar to be not smooth. It is hard to do experiment involving streaking on the surface of the agar as the agar will tear easily.
Just like making milk for the baby to drink, you need to always shake well so that the agar powder can mixed properly with the hot water even after it is 'cooked' in the high temperature in the autoclave machine. This is also to avoid the agar solution to get hard in the bottle itself.
Depends on the demand of the kind of the experiment that is going to perform, sometimes you can see other Biology student make more than 120 plates at once and that require alot of skills to put all the plates into one laminar flow. Usually you will arrange them one level above the other, in this way each of the plate will get the chance to be exposed to the air around and thus get hard faster.
After finishing with pouring of agar, it is good to let the agar to cool down for a longer time and at the same time switch on the UV light in the laminar flow to reduce the chance to get contaminated.
It is not always easy to do things that you don't get familiar with but as you do it often you will turn it into a habit, like me now. Preparing agar is already a habit, or rather than, a hobby for me.
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