BR5497 was a Tallon Metroid being kept in stasis in the Research Lab Aether room of the Glacier One Space Pirate base in the Phendrana Drifts, in Metroid Prime. It was terminated by Samus Aran during her invasion of the facility. She could either release it by destroying the Xenome Containment Unit holding it with a Missile or by scanning it, which would then make it break out on its own.
Interestingly, it is kept in a containment unit very similar to that of the Metroid hatchling.
"Phazon Infusion, Stage 6. Subject Metroid BR5497. Subject's mass at 180% of previous Phazon cycle. Increasing dosage by 4%."