Cordyceps

[Klayboxx]

It'd be neat if the biodome, or that upcoming underground lava base had a mushroom enemy that when killed bursts spores out, and anyone not in a bio-suit will get infected and start growing fruiting bodies all over, causing toxic damage until they die, or are treated. If left untreated, the dude will gib and leave a couple of the mushroom mobs (or burst into spores and infect everyone around him).