Bacillus cereus · Confirmation
Protein Toxin Crystal Stain – separating B. cereus from B. thuringiensis
Protein Toxin Crystal Stain is a staining solution for the detection of protein toxin crystals in sporulated Bacillus cultures. It is used to separate Bacillus thuringiensis, which forms crystals, from Bacillus cereus, which does not.
- Stains spores and protein crystals
- Differentiates B. thuringiensis from B. cereus
- Ready-to-use solution
How Protein Toxin Crystal Stain works
A smear from a sporulated culture is heat-fixed and stained. Under oil immersion, free spores and the diamond-shaped protein crystals of B. thuringiensis appear deep red, while B. cereus shows spores without crystals.
Typical results
| Organism | Result |
| Bacillus thuringiensis | Spores and protein crystals stained deep red |
| Bacillus cereus | Spores stained, no crystals |
Technical data
| Storage | Room temperature, protected from light |
| Shelf life | 2 years |
Applications and practical notes
Bacillus cereus forms heat-resistant spores and toxins and is counted in rice, starchy foods, dairy products, spices and ready meals according to ISO 7932 and the FDA BAM Chapter 14. Typical applications include:
- Cooked rice, pasta and starchy foods
- Milk powders, dairy products and infant foods
- Spices, herbs and dried ingredients
- Ready meals and catering samples
Working with Protein Toxin Crystal Stain: Use cultures that have sporulated for several days, so that free spores and crystals are present in the smear.
Good practice with media and supplements: keep the bottle tightly closed in a cool, dry place, weigh the powder quickly to avoid moisture uptake, and use fresh distilled or deionised water. Check the pH of each new batch after preparation and before use, and label prepared media with the date. Performance of each lot can be verified with reference strains according to ISO 11133, the standard for the preparation, production, storage and performance testing of culture media.
About the Bacillus cereus method: presumptive Bacillus cereus is counted according to ISO 7932 on Mannitol Egg Yolk Polymyxin (MYP) Agar: typical colonies are pink (mannitol not fermented) and surrounded by a precipitate of hydrolysed lecithin. Selected colonies are confirmed by haemolysis on blood agar. The FDA BAM Chapter 14 adds tests that separate B. cereus from B. thuringiensis by its toxin crystals. COLO.Science offers media, supplements, identification kits and QC strains for the whole procedure.
Complete sets from one supplier: COLO.Science supplies culture media, supplements, rapid tests, identification kits and QC strains as complete sets for the method you follow. Send us your sample types and standards, and we will prepare an offer with the matching products and documentation.
Protein Toxin Crystal Stain is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Protein Toxin Crystal Stain, please send us a request. With every delivery of Protein Toxin Crystal Stain you receive the lot number and expiry date, and on request we send the available documentation for Protein Toxin Crystal Stain.
Where Protein Toxin Crystal Stain fits in Bacillus cereus testing
- Sample preparation – dilution in Buffered Peptone Water or peptone saline
- Plate count – MYP Agar with polymyxin B and egg yolk, 30 °C, 18–48 h
- Alternative isolation – Chromogenic Bacillus cereus Agar or Bacillus cereus Count Plate
- Confirmation – haemolysis, biochemical identification, protein crystal stain; QC strains for each run
See all Bacillus cereus products in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Protein Toxin Crystal Stain | PRO7649 | 10 mL |
Product notice: preparation, storage conditions and shelf life are given on the label. Technical data on this page are for orientation; the label and the lot documentation apply. B2B prices are quoted net, excluding VAT.
Sales and technical support
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Quotations and technical support for culture media and microbiology products across our international sales territory. B2B prices are net, excluding VAT.
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Need the complete set for your method?
Send the sample type, target organism and the standard you follow. COLO.Science will put together the media, supplements, QC strains and confirmation tests for the whole procedure.
