What is the reason why there are multiple OTU identifiers in the same species? - Taxonomy assignments in QIIME

Hello

Can I have your help TT?

What is the reason why there are multiple OTU identifiers in the same species? - Taxonomy assignments in QIIME

After I use Taxonomy assignments, I got the sample results about OTU identifiers (below)

There are lots of OTU identifiers in QIIME.

But I don't know What is the reason why there are multiple OTU identifiers in the same species.

pacificensis - New.CleanUp.ReferenceOTU102261 - 1
zeae - 751601, OTU590290, OTU662875 - 3
zavarinii - 1056070 - 1
yabuuchiae - so many!

Some of them has just one OTU identifier. But In yabuuchiae's case has a lot of OTU identifier

I really wanna know What is the meaning that has many OTU identifier !!TT

Plz help~!

Good evening,

Great question! The basic answer is that OTU clustering happens first, then taxonomy assignment happens second. During the initial OTU clustering process, all OTU representative sequences must be >3% different from each other (or if you used dada2 or deblur, they might be only a few base pairs different from each other!) After clustering OTUs, the best possible taxonomy is assigned to each OTU, and the best match might happen to be to the same microbe in the taxonomy database. So while the OTUs should all be a little different, it’s possible for the taxonomy to be the same.

Does that help answer your question?

Colin

P.S. It looks like this data set was made with Qiime 1. Qiime 2 offers newer (and better!) ways of clustering OTUs and assigning taxonomy, so you could consider using Qiime 2 to improve your results.

1 Like

Thank you for great answer!!

I totally understand about that!!

I am trying to use QIIME2.

Have a nice day!!

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