title: Microbial Diversity of Impact-Generated Habitats.
abstract: Impact-generated lithologies have recently been identified as viable and important microbial habitats, especially within cold and arid regions such as the polar deserts on Earth. These unique habitats provide protection from environmental stressors, such as freeze-thaw events, desiccation, and UV radiation, and act to trap aerially deposited detritus within the fissures and pore spaces, providing necessary nutrients for endoliths. This study provides the first culture-independent analysis of the microbial community structure within impact-generated lithologies in a Mars analog environment, involving the analysis of 44,534 16S rRNA sequences from an assemblage of 21 rock samples that comprises three shock metamorphism categories. We find that species diversity increases (H = 2.4-4.6) with exposure to higher shock pressures, which leads to the development of three distinct populations. In each population, Actinobacteria were the most abundant (41%, 65%, and 59%), and the dominant phototrophic taxa came from the Chloroflexi. Calculated porosity (a function of shock metamorphism) for these samples correlates (R2= 0.62) with inverse Simpson indices, accounting for overlap in populations in the higher shock levels. The results of our study show that microbial diversity is tied to the amount of porosity in the target substrate (as a function of shock metamorphism), resulting in the formation of distinct microbial populations. Key Words: Microbial diversity-Endoliths-Impact melt-rocks-Mars-Astrobiology. Astrobiology 16, 775-786.
authors.affiliation: 1 Centre for Planetary Science and Exploration/Department of Earth Sciences, University of Western Ontario , London, Canada .
authors.forename: Alexandra
authors.initials: A
authors.lastname: Pontefract
authors.affiliation: 1 Centre for Planetary Science and Exploration/Department of Earth Sciences, University of Western Ontario , London, Canada .|2 Department of Physics and Astronomy, University of Western Ontario , London, Canada .
authors.forename: Gordon R
authors.initials: GR
authors.lastname: Osinski
authors.affiliation: 3 School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK.
authors.forename: Charles S
authors.initials: CS
authors.lastname: Cockell
authors.affiliation: 4 School of Earth Sciences, University of Queensland , St. Lucia-Brisbane, Australia .
authors.forename: Gordon
authors.initials: G
authors.lastname: Southam
authors.affiliation: 1 Centre for Planetary Science and Exploration/Department of Earth Sciences, University of Western Ontario , London, Canada .
authors.forename: Phil J A
authors.initials: PJ
authors.lastname: McCausland
authors.affiliation: 5 Preclinical Imaging Research Centre, Robarts Research Institute, University of Western Ontario , London, Canada .
authors.forename: Joseph
authors.initials: J
authors.lastname: Umoh
authors.affiliation: 5 Preclinical Imaging Research Centre, Robarts Research Institute, University of Western Ontario , London, Canada .
authors.forename: David W
authors.initials: DW
authors.lastname: Holdsworth
mesh_terms: D039903:Actinobacteria / Q000235:genetics*; D001110:Arctic Regions; D044822:Biodiversity; D003889:Desert Climate; D019015:Geologic Sediments / Q000382:microbiology*; D018535:Mars; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics*; D017423:Sequence Analysis, RNA
chemical_list: D012336:RNA, Ribosomal, 16S