Stains, Reagents & Indicators

Microbiological work involves the growth of microorganisms in the media in a laboratory environment. Often, such work revolves around identification of certain specific types of microorganisms among a mixed group growing in a culture. A laboratory routinely uses several reagents to grow and identify microbes in a culture. Microbiological stains are used for this purpose. Most of these stains interact with either acidic, basic or neutral species and stain specific strains of microbes or organelles with a color or aid in microscopy. Wrights stain and Giemsa Stains are used for microscopy. Stains like Crystal violet, Gentian Violet, malachite green are used to differentiate between microbial strains. It is essential to maintain the media properties, such as pH, to ensure the optimum growth of the microbes. Several pH indicators are used in the laboratory for this very purpose. Some commonly used pH indicators in microbiological media include bromothymol blue, phenol red, eosin methylene blue and neutral red. These indicators give a change in the color of the media based on the pH. pH in media could change due to various reasons such as the evolution of gases, production of some secondary metabolites etc., and this serves as an indication of growth parameters of the microbe.