Something inspired by http://www.nature.com/nature/journal/v488/n7413/full/488690a.html and http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1866175/?tool=pmcentrez Most space habitat eco-engineers spend much time worrying about fungal ecology. Fungi are adaptable, ubiquitous and quite able to grow where they are not intended. From the cruft behind panels on ordinary spacecraft to subversive mycelial networks under the parkland in the greatest O'Neills, if the fungi get out of control the ecosystem suffers. The Fall led to a few cases when things truly got out of hand, like the Waarheid fungus. Waarheid Habitat was a HEO habitat operated by Roodewal-Orchid. During the Fall all contact was lost, with final transmissions suggesting widespread internal fighting against subverted defense automation. Being potentially infested with TITANs or still active defensebots it was never high on any salvage list, but in AF 9 a crew from Myrmecos visited. They discovered that the habitat had survived after a fashion. The defence systems had killed all inhabitants and then gone permanently dormant. The habitat had closed up the solar windows and then slowly rotted. As the vegetation died the ecosystem was taken over by fungi and detritivores. Over time most organic material became food for the growing fungi, converting everything into a web of hyphae, with rhizomorphs stretching deep into the soil and walls hunting for nutrients, and bizarre fruiting bodies adapted for microgravity. Evolutionary competition and a high mutation rate had made the fungi extremely adept at absorbing nutrients. As the Myrmecos crew discovered, this was a real problem. Some species really loved the energy- and nutrient-rich environment of their spacecraft, despite sensible post-mission sterilisation. They suffered explosive mold growth in the kitchen. One species apparently had found a way of breaking down the pseudo-proteins used in smart clothing. Worst, one species had a liking for biomorps. The Waarheid fungus usually infects via the lungs, where it colonizes the mucus. Then it begins to expand as filaments into the tissue, causing brown cough. If left untreated it leads to death in much the same way as pneumonia. The dead body becomes a massive breeding ground for the fungus, erupting fruiting bodies from all available orifices, spreading the spores for a new cycle. The most worrying aspect of the fungus is that it is quite resistant to normal antifungals and medichines: it has evolved some unknown protection against them, perhaps as a side effect from evolving in a fullerene-rich environment. A healing vat can handle the early stages of infection fairly well by dismantling the infected tissue and building new lungs, but the problem is that the spores are small and very persistent: if you get it on a ship it takes a complete sterilization of every spot to get rid of them all.