> 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/advanced/measurements-explained/gating/bactotal.md).

# BacTotal

## What BacTotal counts towards cells/mL

BacTotal counts **every whole bacterial cell in a sample** towards cells/mL.

Examples:

* A whole, actively-dividing cell counts towards cells/mL
* 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

### <i class="fa-comment-question">:comment-question:</i> Which bacterial species?

**BacTotal does not distinguish between bacterial species.**

*E. coli*, *Bacillus subtilis*, *S. epidermidis*, etc. all count towards cells/mL.

{% hint style="info" %}

### Legacy strain-specific gating

In the past, we offered [custom gating settings](/advanced/measurements-explained/gating.md) to for specific bacteria species. 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.
{% endhint %}

### <i class="fa-comment-question">:comment-question:</i> Which cell states?

**BacTotal does not distinguish between cell states.**

Alive, [VBNC](https://en.wikipedia.org/wiki/Viable_but_nonculturable), inactivated, etc. cells all count 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.

<div><figure><img src="/files/z88yGLDuobN6EYRg7tfw" alt="" width="188"><figcaption><p>Bacterium with broken membrane.<br>BacTotal does <em>not</em> count these towards cells/mL.</p></figcaption></figure> <figure><img src="/files/Y2LTtIZX7I4m7PbIbDoG" alt="" width="188"><figcaption><p>Bacterium with intact membrane.<br>BacTotal counts these towards cells/mL.</p></figcaption></figure></div>

{% hint style="success" %}

### Live cells grow <a href="#live-cells-grow" id="live-cells-grow"></a>

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

See [How do I differentiate dead and alive cells?](/troubleshooting/faq/how-do-i-differentiate-dead-and-alive-cells.md)
{% endhint %}

#### Cell state table

| Cell state                                                                                              | BacTotal counts it towards cells/mL? |
| ------------------------------------------------------------------------------------------------------- | ------------------------------------ |
| Viable / alive                                                                                          | Yes                                  |
| [VBNC](https://en.wikipedia.org/wiki/Viable_but_nonculturable) (viable but nonculturable) / inactivated | Yes                                  |
| Partially broken membrane / partial [lysis](https://en.wikipedia.org/wiki/Lysis) / permeable membrane   | Yes                                  |
| Fully broken membrane / full [lysis](https://en.wikipedia.org/wiki/Lysis)                               | **No**                               |

#### See also

* [How do I differentiate dead and alive cells?](/troubleshooting/faq/how-do-i-differentiate-dead-and-alive-cells.md)
* [Avoid cell lysis](/advanced/advanced-sample-preparation/break-up-clumps-and-chains/avoid-cell-lysis.md)

### BacTotal design

We designed BacTotal to have [good correlation](/mpd/correlation-and-linearity/correlation-with-plate-counts.md) with CFUs for [active cultures](/mpd/cell-growth/active-cultures.md) across bacterial species.

The latest version is **BacTotal\_v2024-10**. When we just write "BacTotal" or "BacTotal-10", this is what we refer to.

{% hint style="info" %}
When you press <kbd><mark style="background-color:violet;">Measure<mark style="background-color:violet;"></kbd>, BactoBox® uses the BacTotal gating settings by default.
{% endhint %}


---

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