I am now doing research on purifying bacteria causing ice-ice disease on seaweeds. I used methylene blue to stain the bacterial cells to observe the morphology so that I know whether I have gotten a single bacterium or not. The cells that I got are of coccus shaped; from one isolate, I got a single coccus-shaped, clusters of cocci (streptococcus) and even chain of cocci (staphyloccus). Do we have to take into account not only the shape (coccus, rod,or vibrio) but the arrangement of cells (for coccus there are diplococci, streptococcus, micrococcus) as well to verify the isolates we got are pure or not?
Thank you very much for your time.
Hello colleague,
I’m not specialized in environmental bacteriology, but it seems you have a mixture of bacteria. As to question No. 1, the answer is yes, we have to take into account not only the shape but also the arrangement of bacterial cells. .Generally speaking, bacterial morphology is useful mainly as a step for genus identification. For bacterial purification of a mixed culture, simply touch the culture with a loop and streak (spread) well on medium plates to obtain one colony. Pick only one colony and examine the morphology.
As to question No. 2, there are many different staining methods for bacterial morphology examination depending on the type of bacteria you are working on. You can easily find suitable methods in any general bacteriology bench book. If I can be of further help, feel free to ask.
One more important issue. As far as I have just known, ice-ice disease is caused by Gram negative rods either straight or curved (vibrios). What do cocci that you found have to do with the disease?
You can try Gram staining technique. If your culture is pure, you will get same colour as indication. But if your culture is mixed or contaminated with other types of bacteria which are might contain gram +ve or gram-ve bacteria, you will know..
On the other hand, if you just use methylene blue, it is quite difficult to differentiate the type just by looking at the cell shape and arrangements.
Good luck!
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