It’s an agar-based medium that is used to isolate microorganisms in labs. Selective media: This media allows the growth of certain microbes while inhibiting the growth of others.gonorrhea while blood agar (which is prepared by adding 5-10% blood by volume to a blood agar base) is used to identify hemolytic bacteria. It’s used to grow fastidious microorganisms as they require additional nutrients and growth-promoting substances.Įxamples are chocolate agar, blood agar, and Loeffler’s serum slope. Enriched media: This media is prepared by adding additional substances like blood, serum, or egg yolk in the basal medium.Examples are nutrient broth, nutrient agar, and peptone water. They are generally used to isolate microorganisms in labs or in sub-culturing processes. The basal media do not require enrichment sources for the growth of non-fastidious bacteria and are suitable for growing Staphylococcus and Enterobacteriaceae. They are also known as general-purpose media and are considered non-selective media. Basal media: These are routinely used simple media having carbon and nitrogen sources that boost the growth of many microorganisms.Examples include Tryptic soy broth, phenol red carbohydrate broth, MR-VP broth, and nutrient broth. The media is used for the profuse growth of microorganisms and fermentation studies. Liquid media are also called broths, they allow for uniform and turbid growth of bacterial strains when incubated at 37✬ for 24hrs. Liquid media: These media do not contain any traces of solidifying agents, such as agar or gelatin, and large growth of bacterial colonies can be observed in the media.It’s mainly used to study the motility of microorganisms, distinguish between motile and non-motile bacterial strains (through U-tube and Cragie’s tube), and cultivate microaerophilic bacteria – bacteria on this media appear as a thick line.Įxamples of semi-solid media are: Hugh and Leifson’s oxidation fermentation medium, Stuart’s and Amies media, and Mannitol motility media. Semisolid media: This media has 0.2-0.5% agar concentration, and due to the reduced agar concentration, it appears as a soft, jelly-like substance.Įxamples of solid media are blood agar, nutrient agar, McConkey agar, and chocolate agar. The media is not hydrolyzed by microorganisms and is free from growth-inhibiting substances. The bacterial growth on solid media varies in appearance as mucoid, round, smooth, rough, filamentous, irregular, and punctiform. Solid media are used to grow microorganisms in their full physical form, prepare bacterial pure cultures, or isolate bacteria to study colony characteristics. Sometimes, in the place of agar, some other inert solidifying agents are used, such as gellan gum. The agar-containing media solidifies at 37 ✬. Most commonly, 1.3% agar is used to prepare solid media in labs. Solid media: In these media, the agar which is an unbranched long chain of polysaccharides is added in the concentration of 1.5-2.0%.This article will focus on the composition, classification, and types of culture media used in microbiology labs to study a spectrum of microbial forms. įurthermore, it’s also essential for isolating pure cultures, storing culture stock, studying biochemical reactions, testing microbial contamination, checking antimicrobial agents and preservatives effect, testing viable count, and testing antibiotic sensitivity. Ĭulturing microorganisms is essential for diagnosing infectious diseases, obtaining antigens, developing serological assays for vaccines, genetic studies, and identification of microbial species. However, there are also microorganisms that can’t grow on a culture media at all in any condition – these are called obligate parasites. Microorganisms have varying nature, characteristics, habitat, and even nutritional requirements, thus it is impossible to culture them with one type of culture media.
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