Spock is an appropriate reference here. Recall that when they found his torpedo casing coffin in the third movie it was covered by the microbes present when fired off the Enterprise at the end of the second movie. The microbes had been heavily evolved by the effects of the Genesis Planet.
Consider that the Space Shuttles that assembled most of the ISS were launched from Cape Canaveral. Which is a coastal environment. All jokes about John Kerry in a blue bunnysuit aside, there certainly were contaminants on the shuttles when they launched. Having seen Discover up close a number of times at NASM I was struck by how a lot of her exterior is covered in cloth blankets and not metal or tile. A good wind from yye sea could certainly attack plankton to her exterior. Which would then be carried into space.
Attach, not attack