Presentation on theme: "Introduction to Lab 6: Ex. Preparation of Culture Media"— Presentation transcript:
1 Introduction to Lab 6: Ex. Preparation of Culture Media Media factsPreparationSterilizationAseptic technique
2 Introduction to Lab 7: Ex. Preparation of Culture Media The purpose of this exercise is to introduce the concept of growingmicroorganisms in the lab in order to be able to study them.Culture is the term given to microorganisms that are cultivated inthe lab for the purpose of studying them.Medium is the term given to the combination of ingredients thatwill support the growth and cultivation of microorganisms byproviding all the essential nutrients required for the growth(that is, multiplication) in order to cultivate thesemicroorganisms in large numbers to study them.
3 Among the different kinds of microorganisms the two groups that can be grown in cultures are bacteria and fungi.Algae and protozoa require many different nutrients in minutequantities that are difficult to anticipate and prepare in the lab.These organisms have different nutritional requirements andthus various kinds of culture media have been developed.Primary ingredients required by all living organisms include:a carbon source, water, minerals, and a nitrogen source.
4 Living cells need nutrients required for their structure (biosynthesis) as well as nutrients to provide them with energy to perform allof their various life processes.Nutrients are acquired from the environment in which they live intheir natural habitat.Most of these nutrients are then processed within the cell through avariety of metabolic pathways to be incorporated in differentways.The process of building complex structures from simple buildingblocks is called anabolism.The process of breaking up complex materials to harvest the energyin them is called catabolism.The ability to use particular compounds is dependent upon thegenetic makeup (DNA) that the cells have.
5 Since there are different kinds of organisms that can be grown in culture media with varying needs, culture media have alsobeen formulated with different ingredients.Culture media may be found in one of three states:liquid (called broth)semi-solidsolid.Media are solidified by the addition of solidifying agents such asagar (inert compound).Varying the concentration of agar will yield varying degreesof solidification.
6 Culture media may be classified as: Synthetic media (Defined) Complex (Non-synthetic) mediaSynthetic media contain only ingredients for which a completechemical formula is known.Complex media contain at least one ingredient for which a chemicalformula is not known (such as milk, egg, malt, animal tissues)Culture media can also be classified based on the function theyperform in determining various characteristics of organismthat are able to grow on/in theme.g. Differential, Selective media.
8 The ingredients in a medium will affect the chemical nature of the This is important because organisms vary in theirrequirement for different environments.One such property is:pH (which is a measure of the amount of hydrogen ions ina particular medium).This has to be monitored during the preparation of media since thiswill influence the kind of organisms that are able to grow in theThe pH of the medium will thus determine which organisms areable to grow on the medium.For example, fungi prefer acidic media for their growth while bacteriagrow on neutral pH media.
9 The primary function of culture media is to be able to grow particular organisms on/in them.It is important that these media are devoid of any other livingorganisms.This is possible through the process of sterilization(a process by which all living organisms and their spore formsare killed and the medium is made sterile)Culture media are most commonly sterilized through the process ofautoclaving (using high temperatures that will kill all livingorganisms under increased pressure for specified periods of time –in an appliance called the autoclave)
11 -3 different culture media will be prepared in the class. -They will be sterilized in an autoclave and poured into Petri dishes.-These will then be used for the next exercise to be done in the lab.The 3 media that are to be prepared are:Dextrose Starch Agar (DSA)Malt Agar (MA)Nutrient Agar (NA)Be able to assign functions to each of the ingredients for any culturemedium – that is identify the source of:carbon, nitrogen, mineralsand any other specific function they may perform(such as solidification)Most common sources:- carbon are sugars (carbohydrates)- nitrogen are proteins (partially degraded – peptone)- animal tissue extracts as a source for minerals
12 For example:Nutrient Agar:Gelysate peptone- 5.0g (source of carbon and nitrogen);Beef extract g (secondary source of carbon and nitrogen andprimary source of minerals),Agar g (solidifying agent – if this were not addedmedium would be a broth)Aseptic Technique:These are various techniques that are used tominimize the introduction of microorganisms into mediaespecially during transfer processes, such as –pouring of media into Petri dishes,inoculation of culturesThese techniques include:cleaning the bench top work areas with disinfectant solutionwashing hands before starting workother specific techniques that will be demonstrated in the lab.