Tube, Culture Media

Quick Answer: The Tube, Culture Media is a test-tube-style vessel into which culture medium is dispensed and sterilised to make broths, agar slants and agar deeps. A culture media tube holds a small volume of medium that dries out and becomes contaminated less readily than a Petri dish.

Making Slants, Deeps and Broths

Media tubes are filled while the medium is still liquid, typically to a third or less of their height for slants and higher for deeps, closed with plugs or caps and sterilised together. For a slant, the tubes are laid at an angle while the agar sets, giving a long sloping surface for streaking; for a deep, they cool upright so an organism can be stabbed into the depth of the agar. Broth tubes simply stay liquid. Each format serves a purpose: slants keep stock cultures, deeps test motility and oxygen use, and broths grow organisms for further tests.

Tubes have practical advantages over plates. The narrow mouth limits airborne contamination and evaporation, so a slant can keep an organism alive in a refrigerator for weeks, and tubes stack in racks rather than taking up bench space. Many identification tests, from triple sugar iron agar to citrate and urease media, are run as slants or deeps in tubes of this type.

The listing gives no material, size, rim style or closure, and it describes the tube rather than any medium, so media must be prepared separately. Screw-thread tubes are listed as disposable screw thread culture tubes for longer storage.

Specifications

Applications

• Preparing nutrient agar slants for maintaining stock cultures
• Semi-solid agar deeps for motility tests
• Biochemical identification media such as triple sugar iron, citrate and urease tests
• Broth tubes for growing inocula and for serial dilutions

Preparing and Cleaning Media Tubes

• Loosen caps or use cotton plugs during autoclaving so steam can penetrate and pressure can equalise.
• Let slants set undisturbed at an angle, then cool them fully before tightening caps to avoid condensation.
• Autoclave used culture media tubes before emptying and washing.
• Store prepared tubes in the refrigerator, labelled with medium and date, and discard any that dry out or show contamination.

Why Choose LabEquip

Microbiology labs in colleges, hospitals and food testing units prepare their own media tubes every week, so they order tubes to match their racks and closures. LabEquip lists them in Biology Lab Products; tell us the size and closure you need through the contact page.

Frequently Asked Questions

What is the difference between a slant and a deep?

A slant is set at an angle to give a large sloping surface for streaking growth. A deep sets upright to give a column of agar into which an organism is stabbed with a needle.

Why keep stock cultures in tubes rather than plates?

Tubes have a small opening, so the medium dries out and becomes contaminated much more slowly. A slant in the refrigerator can keep an organism viable for weeks.

How much medium goes into each tube?

For slants the tube is usually filled to around a third of its height, and for deeps to about half or more. Exact volumes depend on the tube size and the test method.

Does the tube come with medium inside?

The listing is for the tube itself, so culture media are prepared and dispensed separately. If you need prepared media as well, mention it when you contact us.

Which closure should be used?

Cotton plugs allow air exchange and suit aerobic growth, slip-on caps are quick to handle, and screw caps give the tightest seal for long storage. Loosen any cap during autoclaving.

What size are the tubes?

Media tubes come in several diameters and lengths to fit standard racks. The listing does not state the size, so confirm it when you enquire.

Last Updated: September 2026