Survey of filamentous fungi and development of molecular tools for their rapid and accurate identification, in advanced life support systems like the International Space Station

The monitoring of microorganisms in spacecraft aims of saving the integrity of on board equipment as well as the health, protection and performance of the crew members during long-term spaceflights. Due to their ability to grow actively on natural and synthetic materials, Aspergillus, Penicillium and Cladosporium can cause biodeterioration and damage to spaceflight materials such as electronic malfunctioning that occurred on the Mir station. The identification of fungi requires up-to-date knowledge of mycology as well as expertise in the sampling and handling of specific fungi. These manipulations can delay identification and thus postpone cleaning operations and increase the risk of accidental contamination on board. In contrast, molecular tools can quickly obtain a maximum of information on the identity and quantity of microorganisms in the spacecraft, allowing early curative and preventive measures. We selected the real-time PCR technique using the Hybprobe technology with the highly sensible and reproducible LightCycler® system, working faster than the other conventional molecular techniques. Specific primers and probes were developed for the three species most frequently found aboard the International Space Station (ISS): A. flavus, A. niger and A. versicolor. A multiplex reaction that allowed us to distinguish three species of Aspergillus in a single reaction was also optimized. In 2005 and 2006, we benefited from 46 fungal and yeast strains collected on board the ISS during two experimental spaceflights. Most strains belonged to the Aspergillus and Penicillium genera. Our detection tools were validated on these spatial strains that were characterized at the molecular level by AFLP (Amplified Fragment Length Polymorphism) and compared with Earth strains. Differences at the genome level suggest the possible effects of space conditions on DNA integrity with consequences on gene expression as well as morphological, physiological, metabolic modifications and on pathogenicity and aggressiveness.