ASVs versus OTUs, is conversion possible

I am new to bioinformatics and I am trying to expand my knowledge in this field. Being that I am new to this area, can someone explain the difference between OTUs and ASVs? Also, if you have OTU data (from say 4 years ago) can that data be converted to ASVs?

Thank you in advance!

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Hi @cmctw6,
Welcome to the forum and the field!
This is a great first topic to begin with as well. I would recommend by reading this paper first which does a nice job of explaining both. In brief, amplicon sequence variants (ASVs) are, in their simplest form, a higher resolution version of OTUs, or 100% OTUs. That is to say the difference of a single nt will lead to designation of new ASV whereas with OTUs, reads are typically clustered at some % identity (most commonly 97%). Note that you can create ASVs then cluster them down to get OTUs, but you cannot go the reverse because once you have clusters there is no way of knowing what the original composition of those reads was. If you have raw data (.fastq) from which those OTUs were created from you can certainly re-analyse and start with ASVs.