BSL is an organization which studies dangerous creatures from distant planets. Its most famous space station orbited SR-388.
When Samus Aran was attacked by an X Parasite on SR-388, she was transported to Galactic Federation HQ. There, her Power Suit was surgically removed, and transported to the BSL Space Station orbiting SR-388. However, while in the Quarantine Bay, the Power Suit pieces formed together to create the SA-X. The SA-X went on a rampage and murdered all the people aboard the station, and infected all the creatures (except few exceptions who escaped with Samus) aboard with X Parasites. After Samus Aran had defeated the SA-X, she sent the station crashing into the planet, causing the planet to vaporize and the X threat never returning. Naturally, there are many other BSL Stations. Who knows what's going on over there...