# OTU taxonomic asssignment
**URL:** https://forum.qiime2.org/t/otu-taxonomic-asssignment/4186
**Category:** User Support
**Created:** [May 17, 2018, 2:56pm UTC](https://forum.qiime2.org/t/otu-taxonomic-asssignment/4186 "2018-05-17T14:56:10Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Jen\_S](https://forum.qiime2.org/u/Jen_S)
#### Post date: [May 17, 2018, 2:56pm UTC](https://forum.qiime2.org/t/otu-taxonomic-asssignment/4186/1 "2018-05-17T14:56:10Z")
Hello All,
Can someone remind me the meaning and difference again between different OTUs assigned like the following:
k\_\_Bacteria; p\_\_Actinobacteria; c\_\_Actinobacteria; o\_\_Bifidobacteriales; f\_\_Bifidobacteriaceae
k\_\_Bacteria; p\_\_Actinobacteria; c\_\_Actinobacteria; o\_\_Bifidobacteriales; f\_\_Bifidobacteriaceae; g\_\_; s\_\_
k\_\_Bacteria; p\_\_Bacteroidetes; c\_\_Bacteroidia; o\_\_Bacteroidales; f\_\_Bacteroidaceae; g\_\_Bacteroides
k\_\_Bacteria; p\_\_Bacteroidetes; c\_\_Bacteroidia; o\_\_Bacteroidales; f\_\_Bacteroidaceae; g\_\_Bacteroides; s\_\_
k\_\_Bacteria; p\_\_Bacteroidetes; c\_\_Bacteroidia; o\_\_Bacteroidales; f\_\_Porphyromonadaceae; g\_\_Parabacteroides
k\_\_Bacteria; p\_\_Bacteroidetes; c\_\_Bacteroidia; o\_\_Bacteroidales; f\_\_Porphyromonadaceae; g\_\_Parabacteroides; s\_\_
k\_\_Bacteria; p\_\_Bacteroidetes; c\_\_Bacteroidia; o\_\_Bacteroidales; f\_\_Rikenellaceae
k\_\_Bacteria; p\_\_Bacteroidetes; c\_\_Bacteroidia; o\_\_Bacteroidales; f\_\_Rikenellaceae; g\_\_; s\_\_
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### Author:  [@ebolyen](https://forum.qiime2.org/u/ebolyen)
#### Post date: [May 17, 2018, 2:56pm UTC](https://forum.qiime2.org/t/otu-taxonomic-asssignment/4186/2 "2018-05-17T14:56:37Z")
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### Author:  [@ebolyen](https://forum.qiime2.org/u/ebolyen)
#### Post date: [May 17, 2018, 3:02pm UTC](https://forum.qiime2.org/t/otu-taxonomic-asssignment/4186/3 "2018-05-17T15:02:57Z")
Hey @Jen_S,
The two forms of taxonomy strings you are seeing are technically unrelated.
The taxa with trailing `; __` are Greengenes OTUs which are specific enough to be considered a "species" or "genus" or whatever, but for which no one has an actual name for. For example:
k\_\_Bacteria; p\_\_Actinobacteria; c\_\_Actinobacteria; o\_\_Bifidobacteriales; f\_\_Bifidobacteriaceae; g\_\_; s\_\_
represents _some kind_ of species of bacteria, but we don't have a taxonomic name for it.
The second form, where there is no trailing prefix, happens when you perform assignment via feature-classifier. It will stop classifying at a confidence threshold that you can configure, so it may only have a classification up to family or genus, and so it stops there.
So in that same example, the feature classifier is confident that your ASV is a member of that GG OTU, and so you receive the "full" taxonomic string (which just so happens to not really have a name for genus and species).
Hope that helps!
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### Author:  [@ebolyen](https://forum.qiime2.org/u/ebolyen)
#### Post date: [May 17, 2018, 3:03pm UTC](https://forum.qiime2.org/t/otu-taxonomic-asssignment/4186/4 "2018-05-17T15:03:00Z")
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### Author:  [@system](https://forum.qiime2.org/u/system)
#### Post date: [June 17, 2018, 9:08pm UTC](https://forum.qiime2.org/t/otu-taxonomic-asssignment/4186/5 "2018-06-17T21:08:08Z")
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