What is agar primarily used for in laboratory settings?

Agar is primarily utilized in laboratory settings as a culture medium to encourage bacterial growth. This gelatinous substance, derived from red algae, provides an optimal environment for microorganisms by supplying essential nutrients and maintaining a moisture-rich habitat. When mixed with various nutrients and placed in petri dishes or other containers, agar solidifies and forms a stable surface where bacteria can be inoculated. This allows for the isolation and identification of different bacterial species, as well as testing their growth characteristics, antibiotic susceptibility, and biochemical activities.

The incorrect options describe other functions; for instance, while urine specimens may be preserved using other methods, agar is not specifically used for that purpose. The process of staining bacteria typically involves different dyes and procedures not related to agar. Additionally, chemical analysis generally utilizes solid or liquid samples without the need for a gel medium like agar, which focuses on biological cultures.