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***Sample collection***  Samples were collected from built environment surfaces throughout the United States on cotton swabs (Puritan 25-806 2PC) and mailed (usually overnight) to the University of California Davis where they were transferred to lysogeny broth (LB) plates. Colonies were chosen for further examination based on maximizing morphological variation. Each chosen colony was double-dilution streaked (two rounds of streak plates)  and then the identity determined by direct PCR and Sanger sequencing using the 27F (5'-AGAGTTTGATCMTGGCTCAG-3') and 1391R (5'-GACGGGCGGTGTGTRCA-3') primers (see \cite{26020012} for details). Sanger sequences were trimmed and aligned using Geneious \cite{22543367}. The resulting consensus sequence was identified through a combination of BLAST \cite{2231712} and building phylogenetic trees using the Ribosomal Database Project (RDP) website \cite{24288368}. The 48 candidates for spaceflight were chosen on the basis of biosafety level (BSL-1 only), taxonomic variety, and human interest. In the absence of international standards, the biosafety level of each organism was determined by searching the [American Biological Safety Association (ABSA)](https://my.absa.org/tiki-index.php?page=Riskgroups) risk group database, the [American Tissue Culture Collection (ATCC)](http://www.atcc.org/), the [Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ)](https://www.dsmz.de/), and other public databases. An organism was removed from consideration if it was listed as BSL-2 or higher in any country or collection in the world. ***Growth Experiment***