> 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/mini-course/dense-culture.md). # Measure a dense culture This is the [Measure a dense culture](/tutorials/measure-overnight-culture.md) tutorial, summarized to its key steps. First growing, and later using a dense *E. coli* culture grown overnight, we disaggregate, dilute 1:10,000 in two steps, and read a concentration off BactoBox®.

Where you start: a Vitroids™ disc dropped into LB medium for an overnight culture.

*** {% stepper %} {% step %} ### Start an overnight culture In the afternoon, drop a Vitroids™ disc (or 50 µL of an in-house *E. coli* glycerol stock) into 50 mL autoclaved LB in a baffled shake flask. Incubate 16 hours at 37 °C, 200 RPM. {% endstep %} {% step %} ### Sample and disaggregate Swirl the flask, aspirate 2 mL into a centrifuge vial, and vortex 1 minute at maximum speed.

Take a 2 mL sample of the overnight culture.

{% endstep %} {% step %} ### Dilute 1:100 Transfer 101 µL of the sample into the 1:100 vial, suspend ×10 to rinse the tip, and vortex 10 seconds.

{% hint style="warning" %} **Vortex properly between dilution steps** Form a visible cyclone in the vial. Allow enough time for the liquid to homogenize. Hold the vial cap gently while vortexing. {% endhint %} {% endstep %} {% step %} ### Dilute 1:10,000 Transfer 101 µL of the 1:100 vial into the 1:10,000 vial, suspend ×10, and vortex 10 seconds. Two 1:100 steps give a 1:10,000 dilution.

Second 1:100 step lands you at 1:10,000.

{% endstep %} {% step %} ### Measure Move the tubing kit to the 1:10,000 vial and press Measure. The dense sample triggers *fast results*. Write down the *cells/mL* and *total/mL*.

{% endstep %} {% step %} ### Clean Move the tubing kit to the disinfection vial and press Clean. Always clean after a measurement.

{% endstep %} {% endstepper %} Multiply the reading by the dilution factor to get the concentration of your undiluted culture. *** ## Do it yourself That is the whole loop. The full tutorial covers the overnight culture, the two-step dilution, and the calculation, step by step. {% content-ref url="/pages/OY34hwi0CQzLh3AKkLyT" %} [Measure a dense culture](/tutorials/measure-overnight-culture.md) {% endcontent-ref %} --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://help.sbtinstruments.com/mini-course/dense-culture.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.