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We read with great interest the article published in the October 2009 issue of Microbe (p. 440-441) about the "rediscovery" of well-established milestones in microbial ecology. In this article Dr. Gest referred to one of our publications: "Molecular bacterial community analysis of clean rooms where spacecraft are assembled" (C. Moissl et al., FEMS Microbiol. Ecol. 61:509-521, 2007,) as follows: The authors "seized on extremophiles, giving the impression that such microbes have been discovered recently" [. . .] and concluded that "we already have excellent methods" for cleaning and sterilization. Instead of quoting the original article, he referred to a press report in the New York Times (October, 2007). We strongly encourage Dr. Gest and other critics to read the original publication, in which the word "extremophiles" was never mentioned. Nevertheless, we are curious as to whether Dr. Gest is implying that the scientific community currently knows everything there is to know about extremophiles. Is his claim that there is such a wealth of previously published literature that there is no need for further research? In our article, we wrote about the microbial diversity in NASA's spacecraft assembly facilities, which was studied using molecular approaches. We ultimately concluded that the bacterial diversity observed was much broader than expected based on prior culture-based assessments. The bacterial community present included "hardy" microorganisms that had successfully survived routine cleaning and sterilization maintenance procedures in such facilities: "The presence and persistence of microbial contaminants on spacecraft and in their assembly facilities underscores the need for comprehensive cleaning and maintenance protocols and frequent surveys of bacterial communities" (Moissl et al., 2007). In a parallel study, we showed that some microorganisms isolated from spacecraft assembly facilities are capable of tolerating extreme conditions (LaDuc et al., Appl. Environ. Microbiol. 73:2600- 2611, 2007) and sterilization regimes being applied to spacecraft surfaces. Modern spacecraft are very sensitive to sterilization procedures able to eradicate the total bioload (like dry heat). In contrast to the robotic missions of decades ago, space agencies can no longer "bake" the whole spacecraft before sending it to another planet. To meet cleanliness requirements, proper cleaning and sterilization of single components is carried out before assembly and spacecraft are kept as clean as possible during the assembly, testing, and launch preparation periods. The search for the perfect sterilization method still goes on! We hope that this will clarify the whole story behind our publication, and we kindly ask Dr. Gest to peruse the original articles to prevent misquoting us in the future.

Christine Moissl-Eichinger

Universitaet Regensburg

Regensburg, Germany

Kasthuri Venkateswaran

Myron LaDuc

Shariff Osman

Jet Propulsion Laboratory
Pasadena, Calif.