Types of Media in Microbiology & Plating Techniques. (1).pptx

Media used in microbiology.

1. Since humans take foods for energy so why don’t we take foods???

2. Various Types of Media & Plating techniques used in Microbiology

3. Topics to be covered: Cultivation or culture of bacteria Purpose of culturing Culture medium Types of culture medium Culturing method for microbes

4. Cultivation/Culture of Bacteria A microbial culture, is a method of multiplying microorganisms by letting them reproduce in pre-determined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organisms, its abundance in the sample being tested, or broth.

5. Types of culture media: Defined media Complex media A defined media refers to a medium having a known concentration of ingredients, like sugar (glucose or glycerol) and nitrogen source (such as ammonium salt or nitrate as inorganic nitrogen). 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 chocolate agar , are all examples of complex media.

6. Functional types of Media: Supportive media   contain nutrients that will enable a wide variety of most non-fastidious microbes to grow . Media supplemented by blood or other special nutrients ( eg blood agar) to allow growth of organisms that cannot grow on general purpose media. E.g. tryptic soy agar, and brain heart infusion agar. Enriched media is the use of certain growth media to favor the growth of a particular microorganism over others , enriching a sample for the microorganism of interest. Enrichment cultures are used to increase a small number of desired organisms to detectable levels. E.g. Blood agar, Chocolate agar, Loeffler's serum, MacConkey agar, Lowenstein-Jensen media. Selective media generally selects for the growth of a desired organism, stopping the growth of or altogether killing non-desired organisms. Differential media takes advantage of biochemical properties of target organisms, often leading to a visible change when growth of target organisms are present. MacConkey agar is both selective & differential media since it have lactose and neutral red dye bacteria's catabolize and release an acidic pigment of red colour on pink media.

7. Important components present in all types media: Protein sources : Peptones. Carbon / Nitrogen / Vitamin sources : Yeast extract. Indicators : Eosin, Methylene blue, Crystal Violet… etc.,

8. Purpose of culturing: Isolation To create antigens for laboratory use Estimate viable counts Maintain stock cultures Long term storage of cultures

9. What is a culture medium???? The food material or substances required for growing microorganisms in-vitro (outside the body) is called culture medium.

10. Types of culture media: Classification based on physical state Solid medium Semi-solid medium Liquid medium Classification based on ingredients Simple medium Complex medium Synthetic or defined medium Special medium

11. Classification based on physical state Solid medium : Agar is the most commonly used solidifying agent. Semi-solid medium : Such media are soft and are useful in demonstrating bacterial motility and separating motile from non-motile strains. Liquid medium : are sometimes referred as broth.

12. Classification based on ingredients Simple media : Nutrient agar, nutrient broth Complex media : It has ingredients that exact chemical composition is unknown. Synthetic or defined media : Prepared from pure chemical substances for research purpose and every chemical composition is known. Special media : a) Enriched media b) Selective media c) Differential media d) Transport media e) Anaerobic media

13. What is agar and why its being used in media?? Agar, also called agar-agar, gelatin-like product made primarily from the  red algae Gelidium and Gracilaria  (division Rhodophyta). Extracted from seaweed, it is a plant-based gelatin . The addition of agar-agar (a complex carbohydrate extracted from seaweed) results in a solid medium.  Agar is an ideal solidifying agent for microbiological media because of its melting properties and because it has no nutritive value for the vast majority of bacteria . Agar media is  essential for the study of microorganisms and molecular biology  and is widely used in the culture and detection of pathogens from contaminated food and water. It’s a good hardening agent since microbes cannot degrade it . In addition, due to its porous 3D framework , agar is frequently used in biomolecular separation and purification – Agarose Gel Electrophoresis.

14. CULTURING METHODS OF MICROBES

15. STROKE CULTURE Stroke culture is made in tubes containing agar slope or slant. Uses: Provide a pure growth of bacterium for slide agglutination and other diagnostic tests .

16. Stab culture Prepared by puncturing with a long straight, charged wire in a suitable medium such as nutrient gelatin or glucose agar. Uses : a) Demonstration of gelatin liquefaction. b) Oxygen requirements of the bacterium under study. c) Maintenance of stock cultures.

17. Another method for Anaerobes cultivation via GasPak tool kit

18. The pour plate and spread plate culture Pour plate method In this method the diluted microbial sample is taken in petri dish and culture media was added in which the agar is in melted state. It is pored over the bacterial sample, which is then mixed into the medium by gentle agitation of the plate. It gives an estimate of the viable bacterial count in a suspension. Spread plate method Small volume of diluted mixture containing approximately 30-300 cells is transferred Spread evenly over surface with a sterile bent rod The pour plate approach allows for more sensitivity, so is ideal for samples with lower bacterial numbers .

19. Diagrammatic representation of pour plate and spread plate POUR PLATE SPREAD PLATE

20. STREAK CULTURE Used for the isolation of bacteria in pure culture from clinical specimens. One loop full of the specimen is transferred onto the surface of a well dried plate. Spread over a small area at the periphery. The inoculum is then distributed thinly over a plate by streaking it with a loop in a series of parallel lines in different segments of the plate. On incubation, separated colonies are obtained over the last series of streaks.

21. Diagrammatic representation of streak culture

22. Bacterial colony morphology and its importance?? Colony morphology is  the visual culture characteristics of a bacterial colony on an agar plate . Observing colony morphology is an important skill used in the microbiology laboratory to identify microorganisms.

23. LIQUID CULTURE Inoculated by touching with a charged loop or by adding the inoculum with pipettes or syringes. Method employed for blood culture and for sterility tests. Preferable for inoculum containing antibiotics and other antibacterial substances. Preferred when large yields are desired. Liquid culture is more suitable than agar when working in the absence of a laminar flow hood .

24. Some important questions from mechanism of action of medias……

25. Growth curve of bacteria….

26. Thank you Everyone

27. Questions