Gram Stains (Ready To Use)

What Is Staining In Microbiology?

If you were to observe a cell or microorganism under a microscope in its natural state it would be difficult to understand what you were looking at. This is because most microbes and cells lack colour and contrast.

Laboratory staff and scientists use different mounting techniques, combined with dyes and microbiology stains to add contrast to specimens and make them easier to observe at a microscopic level and aid with identification.

This is what is known as ‘staining’ in microbiology.

Sample Preparation

In microbiology laboratories, especially clinical settings, light microscopes are most commonly to view specimens. Before a sample can be viewed it needs to be mounted onto a microscope slide.

There are two methods commonly used to mount specimens on to slides making them ready to be viewed under a microscope:

microbiology stains on a microscope slide

Wet mounting – live samples and specimens are fixed to a slide using water, a stain or other liquid. A cover slide is placed over the top and the sample is then ready to view. Fixing the specimen in this way also helps to keep the sample within the field of view once it is under the microscope.

Fixation – the aim is to preserve the shape and structure of a specimen before viewing it under a microscope. There are several different methods to do this, sometimes heat is used to fix a sample, chemicals may be applied to make the specimen accept a dye or stain, other times a stain may be applied directly.

Which Stains And Dyes Are Used?

The stains and dyes used on microscope slides are numerous and the chosen stain will produce a different outcome. Stains are selected based on the type of sample being observed and what organisms or cells need to be observed.

Most commonly, a positive stain is used as the stain is readily absorbed by the cell or organism making it stand out against the background. In some cases, negative stains are more advantageous – negative stains have the opposite effect, staining the background and leaving the cell or organism as a negative silhouette.

Commonly used dyes such as crystal violet, basic fuchsin, malachite green, and methylene blue serve as positive stains. Acidic dyes, such as rose bengal and eosin serve as negative stains as these are repelled by negatively charged cell walls.

Some prepared specimens will only have one stain or dye used on them, this is called simple staining and will usually make all the organisms in a sample the same colour.

Differential staining involves the use of multiple stains to make different organisms’ different colours and therefore, distinguishable from each other.

Often used in clinical laboratories differential staining techniques include acid-fast staining, endospore staining and the very commonly used Gram staining.

Gram staining involves multiple steps and different stains, so Gram staining kits are readily available and convenient for laboratory use.

Pro-Stains™ Microbiology Stains

Here at Pro-Lab Diagnostics, we understand the importance of laboratories being able to access reliable, high-quality microbiological stains. We manufacturer and supply our brand of stains, Pro-Stains™, to ensure our customers have a go-to source for quality stains.

Safranin / Neutral Red Counterstain (1.0L)-0

Manufactured in our purpose-designed laboratories, our stains are available in a range of ready to use and concentrated sizes.

Using the finest quality raw materials, our stains are produced following all current regulatory requirements, and CE labelled. Strict quality controls and filtering techniques ensure every product sent to customers is of high quality.

We also provide a convenient range of Gram, TB and Cryptosporidium staining kits.

Customer service is important at Pro-Lab Diagnostics, so we also offer a custom delivery and preparation service if routine orders don’t work for your laboratory.

For further details, please get in touch.

Tel: 0151 353 1613 Fax: 0151 353 1614 E-mail:

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