Final answer:
Light blue tubes containing sodium citrate are used to study citrate utilization by bacteria. Sodium citrate agar plates containing a pH indicator like bromothymol blue can turn blue when bacteria with citrate utilization enzymes are able to grow on the medium.
Step-by-step explanation:
In biological studies, light blue tubes containing sodium citrate are used to study citrate utilization by bacteria. Some bacteria have enzymes that allow them to transport and metabolize citric acid, and the presence of citric acid in a growth medium can be detected by observing a color change in the medium. Sodium citrate agar plates containing a pH indicator like bromothymol blue can turn blue when bacteria with citrate utilization enzymes are able to grow on the medium.