I have a cryo stock of a gram negative bacteria, which came with the instructions to grow in a highly nutritive media NBRC 802 for activation. However it has been contaminated with a gram positive Bacillus sp. that seems to be outgrowing it in all conditions. Using an M9 has proved unfruitful as either bacteria are too slow growing in it, and as soon as higher nutrition is introduced, the Bacillus completely overgrows the target bacteria. Does anybody have any suggestion of classical or molecular techniques to resolve this issue?
take a lump of your stock and do a serial dilution. Plate multiple dilution and see if you get different types of colonies. Substreak both then do a gram stain or sequence to check for your target. Substreak two additional times to ensure purity then make a new stock. Otherwise, use a gram + specific antibiotic such daptomycin to get rid of the bacillus.
You should visit this link.
https://www.pharmaceutical-journal.com/research/antimicrobial-therapies-for-gram-positive-infections/20203363.article?firstPass=false
1. Try anti-Gram-Positive antibiotics as Asst.Prof.Muthanna H. Hussain posted above.
2. As an alternative to serial dilutions, you could get something close to the same thing by restreaking for single colonies on the plates, and pick single colonies that have the right morphology and analyze them to make sure they are the right thing. Instructions for this: https://en.wikipedia.org/wiki/Streaking_(microbiology)#/media/File:FINAL_mmg_301_honors_option.jpg (but you can do more than just 4 sectors to dilute further).
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