Biosphere frontiers of subsurface life in the sedimented hydrothermal system of Guaymas Basin

Abstract

Temperature is one of the key constraints on the spatial extent, physiological and phylogenetic diversity, and biogeochemical function of subsurface life. A model system to explore these interrelationships should offer a suitable range of geochemical regimes, carbon substrates and temperature gradients under which microbial life can generate energy and sustain itself. In this theory and hypothesis article, we make the case for the hydrothermally heated sediments of Guaymas Basin in the Gulf of California as a suitable model system where extensive temperature and geochemical gradients create distinct niches for active microbial populations in the hydrothermally influenced sedimentary subsurface that in turn intercept and process hydrothermally generated carbon sources. We synthesize the evidence for high-temperature microbial methane cycling and sulfate reduction at Guaymas Basin – with an eye on sulfate-dependent oxidation of abundant alkanes – and demonstrate the energetic feasibility of these latter types of deep subsurface life in previously drilled Guaymas Basin locations of Deep-Sea Drilling Project 64.

Subsurface hydrothermal processes and the bioenergetics of chemolithoautotrophy at the shallow-sea vents off Panarea Island (Italy)

“…This type of thermodynamic analysis of potential microbial metabolisms has been successfully conducted in many environments, including several submarine Amend and Shock, 2001;Hernandez-Sanchez et al, 2014;LaRowe and Amend, 2014;LaRowe et al, 2008;McCollom, 2000;McCollom, 2007;McCollom and Shock, 1997; A C C E P T E D M A N U S C R I P T 6 2004; Shock et al, 1995;Teske et al, 2014), and terrestrial hydrothermal systems Inskeep and McDermott, 2005;Shock et al, 2010;Spear et al, 2005;Vick et al, 2010;Windman, 2010). Unfortunately, energetic profiles of shallowsea hydrothermal systems are rare, despite the fact that their diverse geochemistry accounts for a large number of potential catabolic strategies.…”

Abyssivirga alkaniphila gen. nov., sp. nov., an alkane-degrading, anaerobic bacterium from a deep-sea hydrothermal vent system, and emended descriptions of Natranaerovirga pectinivora and Natranaerovirga hydrolytica

“…Oil reservoirs have naturally been widely studied as a source of hydrocarbon-degrading organisms (Cheng et al, 2014;Jones et al, 2008;Larter et al, 2005), but other environments such as deep-sea hydrothermal vents also offer suitable habitats (He et al, 2013;Kleindienst et al, 2012;Rueter et al, 1994;Simoneit, 1990;Teske et al, 2014). In this study, a hydrocarbon-degrading bacterium, strain L81…”

The energetics of anabolism in natural settings

“…Because the Gibbs energy of all chemical reactions is a function of temperature, pressure and composition, determining the energetic limits of anabolism will differ depending on these environmental variables (for example, Shock, 1998, 2000;McCollom and Amend, 2005;LaRowe and Regnier, 2008;Amend and McCollom, 2009;Amend et al, 2011Amend et al, , 2013LaRowe and Amend, 2014;Osburn et al, 2014;Teske et al, 2014;Price et al, 2015). In addition, the amount of energy that it takes to produce and sustain a given number of microorganisms depends on the mass of cells and the relative proportion of biomolecule types that make up these cells.…”