Because of this, better methods are needed for determining microbial populations on surfaces that have a very low density of individual microbes. In this study, the researchers became the first to take the microbial census using so-called pyrosequencing studies. Pyrosequencing is a recent method of sequencing DNA from entire microbial communities that is much faster and simpler than other methods, and extremely thorough.
Further findings in the study pointed up the value of pyrosequencing in demonstrating where vigilance in sterilizing equipment is needed. Of most import, certain archaeal sequences, notably from the ammonia-oxidizing genus, Nitrososphaeraceae of the recently proposed phylum, Thaumarchaeota, appeared in ground support equipment samples, both before and after cleaning. Archaea of this phylum can survive on ammonia or urea, or other inorganic chemicals, enhancing their ability to survive extreme conditions, according to the report, so prevention of their transfer to the spacecraft is key.
"Methanobacteriaceae sequences were also observed in the spacecraft hardware samples," the researchers write. "This is particularly relevant for astrobiological issues, since members of this family have been reported to be obligate anaerobic, hydrogenotrophic, and methanogenic organisms and capable of utilizing carbon dioxide as their sole carbon source." The challenge for the JPL's spacecraft team is to ensure that the DNA sequences only arise from dead Methanobacteriaceae, and not from live ones.
(M.T. La Duc, P. Vaishampayan, H.R. Nilsson, T. Torok, and K. Venkateswaran, 2012. Pyrosequencing-derived bacterial, archaeal, and fungal diversity of spacecraft hardware destined for Mars. Appl. Environ. Microbiol. 78:5912-5922.)
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New Evidence for Polyomavirus B
|Contact: Jim Sliwa|
American Society for Microbiology