The agar is a differential test medium that distinguishes bacteria based on their ability to lyse red blood cells. The EMB test produced green metallic colonies, which was a big flag that the bacterium might be Escherichia coli.
However, the researcher felt it was important to perform a battery of tests in order to confidently conclude that the Gram positive unknown was indeed B. Bacteria were among the first life forms on Earth and are present all around from the bottom of the ocean to inside the human body.
The bacterium might not have mixed well with the Glycerol solution, creating an improper answer.
In microbiology class students are asked at the end of the semester to identify unknown bacteria using all the lab techniques they have learned and practiced throughout the semester. The instructor verified this to be correct. This indicates a positive test.