Microbial identification in complex matrices by LC-MS/MS isn't new. I know people within an hour of my house that have published papers on this going back 10 or 15 years (APG, FTW!)
However -- it never seems to make it into routine usage. Part of it might be the technical aspects, but part of it might be that you need to really understand your matrix and what you're looking for. This great new study provides an awesome twist on microbial ID and a way that I could envision LC-MS/MS really going into daily use!
What's the twist? There are bacteria that we do want around -- particularly in food preparation. But when you've got large populations of bacteria making yogurt or cheese for you it can be hard to tell those from the ones you don't want.
By clever selection of peptides from the extremely well characterized organisms of interest that should never exist in your starting material (or, presumably, in the bacteria you don't want) you can use either untargeted or targeted nLC-QE methods to identify good vs bad microbes.
The reason I'm thinking this is a great example of one that we can adapt to routine analysis is that the signal for these peptides is off the charts -- the XICs on the nanoLC allow you to see even the M+4, maybe even the M+5 isotope on these peptides! You're only getting that when you've got TONS of signal. If you can make out an M+4 at 200nL/min nLC -- this is an ion that you can EASILY find 3 isotopes for using analytical level flow rates (200uL/min)!!!
Yes, I've been pretty hard on the ElfSeverers this week. Good science still ends up there, though, right now and this is one example.
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