Microbiology Stains & Kits

At Biotium, our specialty is creating fluorescent dyes that simplify and improve your scientific experiments. For Microbiology, we offer a wide range of fluorescent dyes and assays kits to stain bacteria, yeast and fungi, including dyes to assess cell viability and bacterial gram stain type. We have also developed a complete toolkit of reagents for viability PCR, a revolutionary method for determining microbial viability using qPCR.

Also visit our Cellular Stains Table for a comprehensive list of cellular stains with their ability to stain various cell types.

A traditional colorimetric gram staining protocol is laborious, requiring up to 5 different solutions to stain cells, including toxic alcohol and acetone to decolorize the sample, and precise timing. In contrast, Wheat Germ Agglutinin (WGA) has been shown to bind specifically to N-acetylglucosamine in the peptidoglycan layer of the cell wall of gram-positive bacteria, and can be labeled with a number of different fluorescent dyes for one-step fluorescent cell labeling. Our WGA conjugates feature bright and photostable CF® Dyes for rapid and sensitive staining of gram-positive bacteria. The WGA conjugates are available in 13 color options as well as combination kits that include counterstains for viability analysis or all bacteria.

The table below lists the application of several cellular stains for various organisms. A “Yes” indicates the stain is validated for the organism and may be used for reliable analysis. A “No” indicates that we do not recommend this stain for that organism; however some staining may still occur. See our FAQ for more information.

For most of the stains the following cell types were used:
Mammalian cells: HeLa
Yeast: Saccharomyces cerevisiae
Gram+ bacteria: Staphylococcus epidermidis
Gram- bacteria: E. coli

Biotium is the inventor of the original viability PCR dye, PMA, and the new and improved viability PCR dye, PMAxx™. These photoreactive, membrane-impermeant, DNA binding dyes offer superior dead cell selectivity over traditional culture-based methods and the previous EMA (Ethidium Monoazide) v-PCR dye. We have also developed a large range of products and kits for viability PCR.

Learn more about viability PCR and our related products.

Introduction to viability PCR (v-PCR)

Viability PCR is a powerful technology for the sensitive and rapid detection of viable microorganisms. Unlike time-consuming culturing methods, qPCR is a fast and sensitive method of detection. However, normal qPCR does not distinguish between live and dead cells. With v-PCR using PMAxx™ or PMA, you get the speed, sensitivity and specificity of PCR, plus quantifiable viability. And because no culturing is required, you can even detect viable but not culturable (VBNC) bacteria. The v-PCR technology can be applied not only to bacteria but to other organisms like yeast, viruses, eukaryotes, and archaea.

How does v-PCR work?

The infographic below shows the basic mechanism of v-PCR. PMAxx™ and PMA are photoreactive dyes with high affinity for DNA. The dyes intercalate into dsDNA and form a covalent linkage upon exposure to intense visible light. The reaction inhibits PCR amplification of modified DNA templates by a combination of removal of modified DNA during purification and inhibition of template amplification by DNA polymerases. Because the dyes are cell membrane-impermeable, when a sample containing both live and dead bacteria is treated with dye, only dead bacteria with compromised cell membranes are susceptible to DNA modification. In a qPCR reaction, dead cell DNA will show delayed amplification and higher Ct than live cells.

Strain-specific v-PCR kits are designed for selective detection of viable bacteria from a specific strain using PMAxx or PMA dye and real-time PCR. The kits contain PMA dye or PMAxx™ dye, Forget-Me-Not™ EvaGreen® qPCR Master Mix, and validated PCR primers for detection of selected strains of bacteria.