Inoculation – Definition and Types of Media Used for Inoculation

Microbiology is a branch of science that deals and focuses on microorganisms. Microbiology deals with the study of bacteria, unicellular organisms and viruses. We learn many new terms while studying microbiology such as inoculation. Inoculation meaning in microbiology is that transfer from culture for their growth. It is the direct transfer from the culture of microorganisms to inoculation needle.

inoculation meaning

Meaning of Inoculate in Microbiology

In microbiology, the definition of inoculation is different from common terms such as health, vaccines, and immunology. Inoculation is the study of introducing microorganisms into environments where they will grow and reproduce. In other words, we can say that inoculation means introducing a certain substance into another substance.

For example, inoculation is adding a certain type of nutrient or chemical into a suspension of bacteria. We can say that inoculating a suspension with a particular nutrient or chemical.

This definition is in use in laboratory and researches in which scientists study the growth of microorganisms in a specific environment, study certain species and strains of microorganisms. There is a similarity in the definition of inoculation in microbiology and in immunology.

For example, a vaccine is a method of injection of pathogens into a person’s body where they grow and from our immune system. Thus, in this way, vaccines are able to protect us from pathogens that harm our body they weaken the foreign pathogens before they grow in our body.

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Types of Media Used for Inoculation

  • Agar Plates
  • Broth Culture
  • Slant culture
  • Plate culture
  • Stab culture

Agar Plates

Agar plates are some of the most common media which are in use for growing bacteria and other microorganisms. A mixture of agar and nutrients necessary for bacterial growth. This is then poured into circular Petri dishes where the agar solution solidifies. After this, inoculation of a solution-containing microorganism onto these plates with the help of streaking.

A small streaking loop is a dip into a solution, which contains bacterial cells that are used to streak onto the plates with the bacteria. These plates are stored at the proper temperature for bacterial growth for further study. We can also inoculate liquid media suspensions of bacteria to grow and reproduce.

A single culture of microorganism added to a small solution to form a mixture and pipette into liquid media. For Bacterial growth, we need media in which the mixture of microorganism and solution contain nutrients, compounds, and other necessary molecules.

Broth Culture

An inoculation needle used in inoculating a sterile broth culture. Flaming the open end of the broth will keep it sterile. The broth moved up to the needle so that the tip of the needle is submerged while maintaining the original position of the needle.

Swirling of the needle carefully can help the inoculation of the microorganism from the needle to the sterile broth. The inoculated broth culture then removed from the needle. With the help of the Aseptic technique which is applied to the open end of the broth culture so as to prevent contaminants, and the needle is flamed for sterilization.

Slant Culture

To inoculate a slant culture in a fishtail inoculation technique we use inoculation needle. After transferring the microorganisms from the original microbial culture to the inoculation needle the sterile slant culture is uncapped. The open end of the uncapped slant culture is then flamed.

The position of the slant is such that it moves the needle up until the tip of the inoculation needle comes in contact with the base surface of the sterile media. A zigzag pattern is formed on the agar surface when the inoculation needle inoculates the sterilize agar by the manipulation of the media. To remove the inoculation needle, we use an aseptic technique.

Plate Culture

Inoculation of a plate culture uses a streaking technique to make a streak plate. The inoculation needle streaked across the plate in controlled directions, after lifting the lid so that it hovers above the sterile agar plate. Microbial aerosols created from the hitting of the inoculation tip to the sides of the agar plate. The inoculation needle removed from the inoculated agar plate culture and flamed.

Stab Culture

In inoculating a stab culture, an inoculation needle is an essential tool. Removal of a sterile stab culture cap is completed and the open end of the needle is flamed. The needle tip and length of the needle is pushed into the stab media until the needle reaches 0.5 inches away from the bottom of the stab media. The inoculation needle is removed from the media in the same direction and path that it was pushed into the stab media to prevent the wobbling effect that may disturb the culture. We can sterilize the needle with the help of a flame.

Solved Questions on Inoculate in Microbiology

Q. What do you mean by Inoculation Needle?

Ans: An inoculation needle is laboratory equipment that is useful in the field of microbiology to transfer and inoculate living microorganisms. It is one of the most common tools in a  biological laboratory. It is of two types disposable or re-usable. A reusable inoculation needle made up of nichrome or platinum wire attached to a metallic handle whereas disposable inoculation needle made up of plastic resin.

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