A review of the mechanisms of mineral-based metabolism in early Earth analog rock-hosted hydrothermal ecosystems

Geologic legacy spanning >90 years explains unique Yellowstone hot spring geochemistry and biodiversity

“…Input of deeply circulating HO waters between 1998 and 2004 delivered alkalinity in the form of HCO 3 − that could consume remnant H + and slowly raise the pH of the spring towards the pKa of HCO 3 − [~6.4 at 80°C (Amend and Shock, )], while also delivering Cl − , allowing it to reach levels similar to the parent hydrothermal reservoir of ~310 mg L −1 (McKenzie and Truesdell, ). The increase in the pH of EP also promoted the stability of compounds like S 2 O 3 2− and S x 2− , given that they are both thermodynamically unstable at more acidic pH (reviewed in Amenabar and Boyd, ). The increase to moderately acidic pH also promoted shifts in the microbial activities taking place in the spring that may have included SO 4 2− reduction (SR), an activity that is generally favoured in more moderate (pH 5 to 9) conditions (Postgate, ).…”

“…S° is chemically stable at temperatures <100°C (Nordstrom et al ., ), a characteristic that can lead to its accumulation in acidic springs where it can serve as an electron donor, acceptor, or both donor and acceptor (e.g., disproportionation) in microbial metabolism (Amenabar and Boyd, ). Moreover, acidic springs sourced by vapour phase gases are also likely to be enriched in volatiles such as H 2 S, hydrogen (H 2 ) and methane (CH 4 ) (Lindsay et al ., ) and have higher total sulphur contents, including solid phase S° and its oxidation product SO 4 2− , relative to alkaline springs (Nordstrom et al ., ; Amenabar and Boyd, ).…”

Closure of Earth’s Biosphere: Evolution and Current State

“…To propose a possible solution to this paradox, let us consider the history of the origin of the terrestrial biosphere. Very many published studies have been devoted to reconstructions of the history of Earth's biosphere based on existing geological and paleontological data (Lazcano, Miller, 1996;Russell et al, 2010;Lane et al, 2010;Dibrova et al, 2012;Sousa et al, 2013;Weiss et al, 2016;Lanier, Williams, 2017;Russell, Hall, 2006;Wächtershäuser, 2006;Kitadai, Maruyama, 2018;Amenabar, Boyd, 2019), and there is no sense in restating them here. One of the more interesting studies (Judson, 2017) In what follows, all factual material without references will be taken from the previously mentioned work (Judson, 2017).…”

“…The very first question is as follows: When did the biosphere appear, not as a place where living organisms exist, but rather as a system of interacting organisms, populations, and ecosystems? Most experts are inclined to believe that life on Earth originated under anaerobic conditions around the hydrothermal sources that supply energy for chemoautotrophic synthesis (Lazcano, Miller, 1996;Judson, 2017;Russell, Hall, 2006;Amenabar, Boyd, 2019). An alternative hypothesis, suggesting the heterotrophic nature of the first organisms, encounters a number of objections.…”

“…The scenario of chemoautotrophic generation of life (Lazcano, Miller, 1996;Judson, 2017;Russell, Hall, 2006;Amenabar, Boyd, 2019) suggests isolated oases of life around hydrothermal springs. There was virtually no interaction between them because of the limited availability of resources.…”