Chapter 6: The Breadth and Limits of Life on Earth.

Scientific ideas about the potential existence of life elsewhere in the universe are predominantly informed by knowledge about life on Earth. Over the past ∼4 billion years, life on Earth has evolved into millions of unique species. Life now inhabits nearly every environmental niche on Earth that has been explored.

Chapter 1: The Astrobiology Primer 3.0.

The Astrobiology Primer 3.0 (ABP3.0) is a concise introduction to the field of astrobiology for students and others who are new to the field of astrobiology.

Characterizing the Piezosphere: The Effects of Decompression on Microbial Growth Dynamics.

The extent to which the full diversity of the subsurface microbiome can be captured cultivation is likely hindered by the inevitable loss of cellular viability from decompression during sampling, enrichment, and isolation. Furthermore, the pressure tolerance of previously isolated strains that span surface and subsurface ecosystems can shed light into microbial activity and pressure adaptation in these transition zones. However, assessments of the effects of elevated pressure on the physiology of piezotolerant and piezosensitive species may be biased by high-pressure enrichment techniques.

Rate and Extent of Growth of a Model Extremophile, , Under High Hydrostatic Pressures.

High hydrostatic pressure (HHP) batch cultivation of a model extremophile, type strain VC-16, was performed to explore how elevated pressures might affect microbial growth and physiology in the deep marine biosphere. Though commonly identified in high-temperature and high-pressure marine environments (up to 2-5 km below sea level, 20-50 MPa pressures), growth at elevated pressure has not been characterized previously. Here, exponential growth of was observed up to 60 MPa when supported by the heterotrophic metabolism of lactate oxidation coupled to sulfate reduction, and up to 40 MPa for autotrophic CO fixation coupled to thiosulfate reduction via H.