# What is false contaminant in negative control?

**URL:** https://forum.qiime2.org/t/what-is-false-contaminant-in-negative-control/22838
**Category:** Other Bioinformatics Tools
**Created:** [April 21, 2022, 10:15am UTC](https://forum.qiime2.org/t/what-is-false-contaminant-in-negative-control/22838 "2022-04-21T10:15:18Z")
**Posts on this page:** 1
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### Author: ![colinbrislawn](https://forum.qiime2.org/user_avatar/forum.qiime2.org/colinbrislawn/32/6221_2.png) [@colinbrislawn](https://forum.qiime2.org/u/colinbrislawn)
#### Post date: [April 21, 2022, 12:37pm UTC](https://forum.qiime2.org/t/what-is-false-contaminant-in-negative-control/22838/2 "2022-04-21T12:37:28Z")

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Hello @Diki,

In general, we recommend that folks do not cross-post questions, as it's mostly the same people on the Qiime2 GitHub and the Qiime2 forums and we will see it either way.

> [@Diki](#):
>
> What are these taxa inside the negative control?

Did you know that the Illumina platform has a barcode-hopping problem (that Illumina wrote a paper about 🙃 )?

> **[index-hopping-white-paper-770-2017-004.pdf](https://www.illumina.com/content/dam/illumina-marketing/documents/products/whitepapers/index-hopping-white-paper-770-2017-004.pdf)**
>
> 331.32 KB

Those taxa in your NTC could be the most common taxa in your real samples, that were misassigned to your NTC through barcode hopping / crosstalk. This is part of the reason that removing all taxa found in your NTC from your full study is a [bad idea](https://forum.qiime2.org/t/discussion-methods-for-removing-contaminants-and-cross-talk/5626/)!

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