International Space Station Internal Active Thermal Control System: An Initial Assessment of the Microbial Communities within Fluid from Ground Support and Flight Hardware

The Internal Active Thermal Control System (IATCS) aboard the International Space Station (ISS) maintains appropriate ambient cabin temperatures. The microbial community of IATCS fluid was examined using conventional culture-based and advanced molecular techniques including adenosine triphosphate (ATP) and Limulus Amebocyte Lysate (LAL) assays, direct microscopic examination, and restriction fragment length polymorphism (RFLP) analyses of 16S rDNA genes from the community metagenome. About 50% of the samples examined showed populations that are uncultivable but contained viable cells. RFLP analyses identified nine distinct bacterial groups from the 171 clones and eight distinct bacterial groups from the 26 cultivable organisms,indicating significant diversity.