> For the complete documentation index, see [llms.txt](https://help.sbtinstruments.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.sbtinstruments.com/troubleshooting/faq/how-do-i-differentiate-dead-and-alive-cells.md).

# How do I differentiate dead and alive cells?

## Live cells grow

The best way to know if a culture is alive is to [track its growth](/mpd/workflows/track-growth-curve.md). A growing cell is an alive cell.

Of course this means tracking cell growth *over time*. In other words, it doesn't apply to a *single* sample.

{% hint style="info" %}

### BactoBox® (using [BacTotal](/advanced/measurements-explained/gating/bactotal.md)) counts every whole cell in a sample

Examples:

* A whole cell that has stopped dividing counts towards cells/mL
* A whole cell that no longer forms a colony counts towards cells/mL
* A whole cell that takes up [propidium iodide](https://en.wikipedia.org/wiki/Propidium_iodide) counts towards cells/mL

The one thing that removes a cell from the cells/mL count is full [lysis](https://en.wikipedia.org/wiki/Lysis). Because a cell that has come apart is no longer there.
{% endhint %}

## Legacy approach via gating

In the past, we offered [custom gating settings](/advanced/measurements-explained/gating.md) to differentiate dead and alive cells. While this worked in some use cases, the approach is too brittle for general use. There are simply too many combinations of bacterial species, sample preparation, media types, culture conditions, etc.

{% hint style="info" %}

## Advanced feature 🧩

This is an advanced feature. We only support advanced features through a [custom solution](/advanced/what-is-a-custom-solution.md). Contact SBT for details.
{% endhint %}


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