During the Great Exodus, Optimus Prime have rallied all remaining pockets of Autobots left on Cybertron and ordered them to build the Ark which will allow them to leave their dying world and search for a new home to live.
After departing Cybertron, the Ark was under attack by The Nemesis which broke out into a space naval battle. Many crew members of the Ark were killed, wounded or went overboard in the intense fight.
When the black hole sucked the Ark and the Nemesis in, the two ships were sent to different locations and started searching for the Allspark. Some time later, a small group from the crew managed to make their way to Earth . The fate of the rest of the crew is unknown so far.