What is the primary use of broths in microbiology?

Broths serve as a nutrient-rich liquid medium that provides an optimal environment for the growth of microorganisms. This makes them primarily useful for cultivating microbes, especially when fresh cultures or large populations of cells are needed. The liquid state of broths allows for a higher degree of aeration and mobility for the microbes, facilitating faster growth and replication.

In contexts where a large number of cells are required for experiments or further analysis, such as testing antibiotic efficacy or studying metabolic processes, broths are particularly advantageous. The presence of nutrients in the broth supports rapid growth compared to solid media, making it the preferred choice for initial culturing of new isolates or for generation of dense cultures.

Other options, while related to microbiological practices, do not primarily define the use of broths. For instance, preparing slides for microscopy typically involves solid media or streaking techniques, the preservation of microbial samples generally relies on other methods like freezing or lyophilization, and filtering contaminants is more pertinent to methods like sterilization rather than being associated with the primary purpose of broths. Thus, the use of broths in microbiology is fundamentally centered around growing microbes efficiently and in substantial quantities.