The problem is growing leafy plants like lettuce and spinach in space can come with a side dish of bacteria, according to a new study from a team at the University of Delaware. In tests on plants grown in simulated microgravity, they were shown to actually be more susceptible than normal to the Salmonella enterica pathogen.
TL;DR:
Isn’t biofilm a problem in general? From what I’ve heard, Mir was covered in grime at the end and the ISS isn’t looking much better now.