Some media are considered general all-purpose media and support growth of a large variety of organisms. A prime example of an all-purpose medium is tryptic soy broth TSB.
Specialized media are used in the identification of bacteria and are supplemented with dyes, pH indicators, or antibiotics. One type, enriched media , contains growth factors, vitamins, and other essential nutrients to promote the growth of fastidious organisms , organisms that cannot make certain nutrients and require them to be added to the medium.
When the complete chemical composition of a medium is known, it is called a chemically defined medium. For example, in EZ medium , all individual chemical components are identified and the exact amounts of each is known. In complex media , which contain extracts and digests of yeasts, meat, or plants, the precise chemical composition of the medium is not known.
Amounts of individual components are undetermined and variable. Nutrient broth, tryptic soy broth, and brain heart infusion , are all examples of complex media.
Figure 1. On this MacConkey agar plate, the lactose-fermenter E. Serratia marcescens, which does not ferment lactose, forms a cream-colored streak on the tan medium.
Media that inhibit the growth of unwanted microorganisms and support the growth of the organism of interest by supplying nutrients and reducing competition are called selective media.
An example of a selective medium is MacConkey agar. It contains bile salts and crystal violet, which interfere with the growth of many gram-positive bacteria and favor the growth of gram-negative bacteria , particularly the Enterobacteriaceae.
These species are commonly named enterics, reside in the intestine, and are adapted to the presence of bile salts. The enrichment cultures foster the preferential growth of a desired microorganism that represents a fraction of the organisms present in an inoculum. For example, if we want to isolate bacteria that break down crude oil, hydrocarbonoclastic bacteria , sequential subculturing in a medium that supplies carbon only in the form of crude oil will enrich the cultures with oil-eating bacteria.
The differential media make it easy to distinguish colonies of different bacteria by a change in the color of the colonies or the color of the medium. Color changes are the result of end products created by interaction of bacterial enzymes with differential substrates in the medium or, in the case of hemolytic reactions, the lysis of red blood cells in the medium.
In Figure 1, the differential fermentation of lactose can be observed on MacConkey agar. The lactose fermenters produce acid, which turns the medium and the colonies of strong fermenters hot pink. The medium is supplemented with the pH indicator neutral red, which turns to hot pink at low pH. Selective and differential media can be combined and play an important role in the identification of bacteria by biochemical methods. The microbiology department is celebrating the end of the school year in May by holding its traditional picnic on the green.
The speeches drag on for a couple of hours, but finally all the faculty and students can dig into the food: chicken salad, tomatoes, onions, salad, and custard pie. By evening, the whole department, except for two vegetarian students who did not eat the chicken salad, is stricken with nausea, vomiting, retching, and abdominal cramping. Several individuals complain of diarrhea. Also this is a recipe for growing mushrooms. This would be a ph balanced substrate and it would be loaded with a blend of complex polysaccharides, omega-3, the immunological benefits of the bees pollen.
Once you pour the dishes let it cool as this instruction says. You need to Pasteurize though, do not sterilize. The reason is because you kill all good and all bad microbes. When you pasteurize you kill the bad and leave the good. This from my understanding is a master mix for agar. Anyone can make this at home. Hope to see the research on medicinal mushrooms continuing to expand or health, or longevity, our nerves, please get a hold of some research about Chaga, Reishe, Lions Mane, or Gametes Trametes better know as the turkey tail.
Also look into the Studies being down in Oakland on the Psilocybe mushrooms as the new law that decriminalized mushrooms and other plants.
The time for research is now! And Remember!! Peace and blessings. May your consciousness be ever hungry for growth! If possible could you add me to the group? I am an aspiring Microbiologist and hope to get more insight or even help in the field and my studies. Thank you, Good morning, pls am interested in joining the whatsapp group for microbiologist. Agar are come from huge agar plant know as kelps.
Are you kidding Ritesh Sharma 0. I dont know about that but you can add a broad spectrum antibiotic to avoid griwth of bacteria in your plates. Whats the basic defferences between all culture media And which culture media would use for which???? Sir I have used nutrient agar for fungus culture…. Before i use PDA for culture it was gud…. But i found lots of bacterial contamination in my Nutrient agar culture….
Does the composition of beef extract hampers the groeth of fungus and favours bacteria instead. Hello I have a question. If a leg wound is cultured and it is put on a nutrient agar, Selective agar and Differential Agar what are expected to show? I streaked out from sweet potato steep water and I had both red colonies and white colonies that turned nutrient agar kind of green. Please what kind of organisms are these. They areboth staining gram positive. Basal media 2. Enriched media 3.
Nutrient Agar. Contents 1 Composition of Nutrient Agar 1. Un-inoculated Nutrient Agar. About Acharya Tankeshwar Articles. Hello, thank you for visiting my blog. I am Tankeshwar Acharya.
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