What Is the Purpose of Inoculating an Agar Slant?

The purpose of inoculating an agar slant tube is for the long-term maintenance of an isolated culture of microorganisms. Agar is a complex carbohydrate from algae that is infused with water and nutrients so that bacteria and other organisms can grow on its surface.

A slant tube is a test tube prepared by pouring in a melted agar medium while the tube is tilted. This creates a slanted surface on which to inoculate bacteria. Creating a large plug of agar medium and capping the tube prevents desiccation and allows for the long-term storage of living bacterial cultures. It is essential that the tubes and medium are sterile before use. Otherwise, organisms other than the intended culture could grow and contaminate the sample.

Bacteria require several different substances to live including water, a source of energy, carbon, sulfur, nitrogen, phosphorus, vitamins and minerals. They can grow in liquid or solid mediums, but the requirements of some species are quite specific. For particular species, rigid acidity controls, the presence or absence of oxygen, or specific temperatures are required. Solid media usually use agar, which is solid below 113 degrees Fahrenheit, to solidify them. It accomplishes this with a concentration of between 1 percent and 2 percent.