TYPE OF MICROBIOLOGY CULTURE MEDIA

Media is group in to two which are; Liquid media, and solid media.

Liquid media: as the name implied, these types of media are liquid in nature, they are used to culture many micro organism.

The organism growth on these media when they are inoculate into the media, they remain stagnant for sometimes before they will adjust to the environment, after then they found the environment conducive then growth started, these phase is called lag phase. After the lagging phase which also called primary phase, multiplication begin through a binary fission, this phase is called logarithmic phase. Multiplication continues for some time with a series of progression. During these time there come an accumulative of some residue of unusable material, the residue become toxic to the organism which result to the dead of the organism, when this continue their come a time there will be equilibrium between the dead organism and the live one, this phase is called stationary phase. As the accumulation of unusable material persist, dead of micro organism increase to a point that there will be decline of the living organisms, it will reach a point that the dead of the organism will be high than the living, this phase is called decline phase.

When this micro organism growth in a liquid medium, they derived source of their nutrient from the media, often the metabolism of these source derived from the media, they excrete a by-product into the medium. For identification of bacteria, the used of the by-product is necessary. For example some bacteria yield a by-product called indole when they are culture in a medium full of amino acid tryptophan that is free from peptone water, in such case test can be carried out on the media to examine either there is present of indole produce by bacteria or not. One of the important used of liquid culture media is for examination of bacteria either they have the potential of fermenting sugars to free the medium from sugar molecules. For examination of this, there is an indicator to show either acid is present in the medium doe to fermentation of sugar by the micro organism in the medium.

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Solid medium

Solid medium: These mediums are solid in nature, hasn’t potential of moving in the culture plate.

When organism are culture in a liquid media they have the power of moving around the media, but on solid media, they growth on point of inoculation and form a colonies there. The physical appearance of colonies form on the media depends on the type of bacteria cultured. Culture of bacteria carried out on solid media aid in isolation of colonies from a mix culture. In another hand liquid media can be converted to solid media by adding agar or gelatin on it.

Gelatin was the first solidifying agent used for solidification as the discovery goes on, another solidifying media was discovered which is called agar, and the agar is more potential compare to gelatin.

Agar is a polysaccharide obtained from seaweed in several oceans of the world e.g. pacific and Mediterranean Sea. Doe to extraction of agar from seaweed a source from water make it high performance and quality. Primarily when agar was discovered it usually supply in a small pieces, but now they are supply in powder form which is easy to weigh and proliferation. As other substance has it properties, also that is how it is the same with agar, it has a figure of properties. The most usefulness of it is that it has power approximately 1-15% concentration of gel. The substance has melting point of 98ºC and on preparation for used, it set at the range of 35-38ºC. on these range, it permit the incubation of culture media as the way the gel are with soften the gel first, and after sterilization heat labile substance i.e. blood is added to the media without any discomfort to either the media or the added blood, but at least the temperature should be between 20ºC to 51ºC.

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Gelatin was originally gotten from hair, skin, and collagen. They also form gel but the rate of it gel is greater than that of agar, it has a concentration range of approximately 12-15% in the nutrient broth. If the substance is exposed to a temperature at 100ºC for a long time, the temperature will damage their properties setting. They have low melting point compare to agar that is 31 º C. several bacteria enzyme call gelatinase, this enzyme has the power of broken down gelatin into a liquid form these phenomenon aid in grouping of bacteria that remain in the liquid after growth have taken place at 37 ºC or the liquid faction form at room temperature after their growth.

Enriched media

Enriched media: As the name implied, is a media which other substance has been added to it in other to upgrade to it needed requirement. For example when blood is added to basal medium, it permits rapid growth of organism faster compare to that of ordinary basal medium alone.

Substance that enriched that status of media are; blood, serum, carbohydrate, chocolate blood etc.

Enrichment media

Enrichment media: this media is a fluid media but selective. The media is incorporated in such a way that it inhibit the growth of other micro organism other than the one which the media is prepared for, the media is design for specific growth of selected micro bacteria i.e. when the media is design for Coliform bacilli.

It will inhibit the growth of typhoid organism and permit coliform to growth freely and vis visa.

Selective media

Selective media: these media is in solid form, it contains substance that inhibits the growth of one organism and allowed the growth of other for example deoxycholate citrate agar for growth of salmonella and shigella species,

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the substance incorporated could be antibiotic or other chemical, etc.

Differential media

Differential media: these media are sometime called indicator media, the media differentiate one organism from the other on the same culture plate,

these usually occur in the case of mix culture. i.e. MacConkey which is used to differentiate lactose fermental and non lactose fermental micro organism, also blood agar that is used to distinguish organisms by their ability to yield different class of hemolysis.

Auxonographic media

Auxonographic media this is a clear media that lack some nutrient factors, the organism which to be culture is spread on the surface of the media.

Any growth in or around in the sported nutrient on the media show the need of particular factor of nutrient, examination of some certain organism is carried in these way with this media.

Transport media

Transport media: as the name imply, these media is purposely design or produce for transporting cultural specimen from one hospital the other or from one

laboratory to another laboratory. The media in made in a semi liquid form, and it help in preserving the life of micro organism to be culture during transportation. The duration of preservation could be an hour or even a day depending on the type of specimen be transported. The media is always incorporated in a swab stick. Material for dispensation of media for culture of micro organism is dispense into the following apparatus which will be used for culturing, i.e. petris dish, bottle with platic or metal caps with rubber linear tube with cap or with no absorbent cotton wool plugs.

The media is label with date of preparation, name, date of expiring, type of the media, and it specific function, this are the paramount things required for the identification of the media.

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