Has this happened to anyone else? I Had my first lab practical in microbiology the other day, and I studied so hard for it, we were allowed to use our lab manuals and I felt very prepared, so we have to do a gram stain on a unknown bacteria and then identify if it is gram + or gram- and write down the morphology of the colonies. I thought this would be a piece of cake. Turns out I couldn't find anything on my slide and I did two seperate slides. I was mortified! I felt like such a failure I wanted to cry, I was the last one to leave that night with nothing to see on my slide. I know I did the stain right, Ive done them before, but the other times. the teacher would come over and find it for you by adjusting your microscope. Does anyone have any sure fire tips to prevent this from happening again?Thanks to anyone who has any pointers!
Oct 28, '05
You were using oil immersion microscopy, right? On the highest power? With the stage up all the way and the slide just touching the magnifier? Just making sure those steps were done...then I have always found that I have to SLOWLY turn the fine adjustment knob towards me a few rotations before I see anything. I have had the same sense of " oh god there's nothing there" fear before..but then a few more turns..walla.
Also when I place my slide on the stage I always make sure that it's centered over the light source on an area I can tell is stained...and that the light source is all the way up.
I'm so sorry you had such a rough go of it. I know all microscopes are different..ours are brand new and were VERY expensive...the ones I used in A+P were no where near as good as the ones I am using in Micro.
Oct 28, '05
I always made sure to put a lot of the specimen on the slide. It would take longer to dry, but then I would have no trouble finding it once everything was complete. The teacher would tell us to smear it really thin on the slide (which I did), but I had so much extra on it that it made it easy to find.
Oct 29, '05
Thanks for responding! I'm thinking that when I put the smecimen on the slide I didnt need to put a small drop of deionized water first since the bacteria was already in a liquid form, this is not the usual case, normally we would take a small amount with a loop off a petri dish. Thats the only thing I can guess messed me up. Yes I did use oil immersion, and slowly turned the fine adjustment towards me but all I saw was a black and white blob, the oil. Hopefully I'll have many more chances to practice.
Oct 29, '05
Yes that could be it. When using a broth/liquid culture you don't need the drop of water.
Oct 30, '05
The most important thing to remember when attempting to locate a specimen on a slide is first find the specimen under Low Power (10X). If you find it under low power all you need to do is add oil immersion, move to the oil immerssion lens and I guarantee you that your specimen will be there.
If you can't find the specimen under low power, it isn't there. Another recommendation I have for you is to draw a circle on the slide with a wax pencil, place your specimen within that circle, then look for that circle mark under low power, then gradually go in towards the specimen.
Hope this helps.
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