What Are the Advantages and Disadvantages of Agar Slants?

The advantages of agar slants include providing bacterial storage over extended periods with a minimal risk of contamination or desiccation while disadvantages involve the organisms being less observable and accessible than those in petri dishes. Agar slants also lend themselves to the identification of bacteria by characteristic patterns of movement.

The process of creating agar slants consists of pouring heated nutrient media into sterile test tubes and tipping the tubes until the media solidifies. The increased depth of the agar and the existence of water suspended in the gelled material provides moisture to maintain a viable bacterial growth environment. Tightly capping the tubes prevents evaporation of the media or contamination of the culture.

The slanted agar provides a larger surface area to support bacteria than does an upright test tube. Static organisms display a growth pattern following the inoculation streak along the agar slant. Mobile bacteria cover the surface of the agar slant or show uneven borders or lobes based on the organism’s level of mobility. The growth pattern offers clues to the type of the bacteria being grown.

In some instances, the preferred method of culturing is a mixture of agar slant and plate techniques. A substantial inoculation in a petri dish provides rapid bacterial growth. The next step is to transfer the bacteria from the original culture to multiple test tubes prepared with agar slant cultures and stored in a refrigerator for later analysis. Transfer back to a petri dish may be necessary for the final assay.