Hypolithic Photosynthesis in Hydrothermal Areas and Implications for Cryptic Oxygen Oases on Archean Continental Surfaces

Havig, J. R.; Hamilton, Trinity L.

doi:10.3389/feart.2019.00015

Cited by 11 publications

(13 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We do agree that mineral gels could have played a protective and structural role for the first protocell populations arising in hot spring pools, just as they do within microbial mats growing in Yellowstone National Park or Rotorua in New Zealand today. Silica gels also form hard mineral sinters that have harbored and preserved evidence for life throughout the fossil record (Handley et al, 2008;Campbell et al, 2015;Havig and Hamilton, 2019). The alternative offered here is that microscopic membranous compartments, rather than minerals, served as a primary organizing matrix to initiate the first steps along the pathway to the origin of life.…”

Section: Figmentioning

confidence: 99%

“…However, early life was also continuously exposed to sunlight and could develop photosynthesis utilizing primitive pigments such as PAHs as an energy source (Deamer, 1992;Summers and Rodoni, 2015). Dry land exposure to damaging ultraviolet radiation would have been mitigated through hypolithic lifestyles (Havig and Hamilton, 2019) and might also have promoted key prebiotic reactions (Sutherland, 2017). Although salty seawater would have been an extreme environment for relatively fragile freshwater life, as microbial populations dispersed downhill toward the sea, they evolved cell walls with ion pumps to keep salt ions from disrupting intracellular metabolism.…”

Section: Evolutionary Implications Of the Hypothesismentioning

confidence: 99%

See 1 more Smart Citation

The Hot Spring Hypothesis for an Origin of Life

2020

View full text Add to dashboard Cite

We present a testable hypothesis related to an origin of life on land in which fluctuating volcanic hot spring pools play a central role. The hypothesis is based on experimental evidence that lipid-encapsulated polymers can be synthesized by cycles of hydration and dehydration to form protocells. Drawing on metaphors from the bootstrapping of a simple computer operating system, we show how protocells cycling through wet, dry, and moist phases will subject polymers to combinatorial selection and draw structural and catalytic functions out of initially random sequences, including structural stabilization, pore formation, and primitive metabolic activity. We propose that protocells aggregating into a hydrogel in the intermediate moist phase of wet-dry cycles represent a primitive progenote system. Progenote populations can undergo selection and distribution, construct niches in new environments, and enable a sharing network effect that can collectively evolve them into the first microbial communities. Laboratory and field experiments testing the first steps of the scenario are summarized. The scenario is then placed in a geological setting on the early Earth to suggest a plausible pathway from life's origin in chemically optimal freshwater hot spring pools to the emergence of microbial communities tolerant to more extreme conditions in dilute lakes and salty conditions in marine environments. A continuity is observed for biogenesis beginning with simple protocell aggregates, through the transitional form of the progenote, to robust microbial mats that leave the fossil imprints of stromatolites so representative in the rock record. A roadmap to future testing of the hypothesis is presented. We compare the oceanic vent with land-based pool scenarios for an origin of life and explore their implications for subsequent evolution to multicellular life such as plants. We conclude by utilizing the hypothesis to posit where life might also have emerged in habitats such as Mars or Saturn's icy moon Enceladus. Key Words: Origin of life-Prebiotic chemistry-Hydrothermal systems-Protocells-Progenotes-Microbial communities. Astrobiology 20, 429-452. ''To postulate one fortuitously catalyzed reaction, perhaps catalyzed by a metal ion, might be reasonable, but to postulate a suite of them is to appeal to magic.''

show abstract

Section: Figmentioning

confidence: 99%

Section: Evolutionary Implications Of the Hypothesismentioning

confidence: 99%

The Hot Spring Hypothesis for an Origin of Life

2020

View full text Add to dashboard Cite

show abstract

“…If UV conditions on the early Earth were indeed harmful to life, silica precipitated from hydrothermal environments could have provided some protection from harmful UV while allowing the benefits of surface life [15]. By being able to precipitate silica through wet-dry cycling (hypothesized as being crucial for increasing complexity in prebiotic chemistry [1]), the simulation chamber we present here may be valuable in testing hypotheses regarding the ability of surface hot springs to shield from harmful UV radiation [15].…”

Section: Silica and Its Possible Role In The Origin Of Lifementioning

confidence: 98%

“…The exact UV conditions throughout early Earth are still debated, and it is not yet known whether or not surface UV was hostile to life, or whether life may have exhibited some kind of defense against harmful UV, or instead dwelled in non-surface environments which would have been more shielded from UV [20,21]. If UV conditions on the early Earth were indeed harmful to life, silica precipitated from hydrothermal environments could have provided some protection from harmful UV while allowing the benefits of surface life [15]. By being able to precipitate silica through wet-dry cycling (hypothesized as being crucial for increasing complexity in prebiotic chemistry [1]), the simulation chamber we present here may be valuable in testing hypotheses regarding the ability of surface hot springs to shield from harmful UV radiation [15].…”

Section: Silica and Its Possible Role In The Origin Of Lifementioning

confidence: 99%

“…This silica precipitate can entomb and preserve microbial life [8], but can also be observed to be intimately associated with extant microbes (Figure 1) through silica-coatings [9][10][11]. While the exact functions/benefits of these coatings are not completely understood, they may provide some degree of UV protection as silica can shield from intense UV due to a high radiation absorbance [12], a similar strategy employed by many microbial communities in hot spring systems which thrive as endolithic (within-rock) communities boring into the surface of siliceous sinter [13,14], or as hypolithic (under-rock) communities living under millimeters of loose siliceous sinter [15].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Silica Precipitation in a Wet–Dry Cycling Hot Spring Simulation Chamber

Gangidine

Havig

Hannon

et al. 2020

Life

Self Cite

View full text Add to dashboard Cite

Terrestrial hot springs have emerged as strong contenders for sites that could have facilitated the origin of life. Cycling between wet and dry conditions is a key feature of these systems, which can produce both structural and chemical complexity within protocellular material. Silica precipitation is a common phenomenon in terrestrial hot springs and is closely associated with life in modern systems. Not only does silica preserve evidence of hot spring life, it also can help it survive during life through UV protection, a factor which would be especially relevant on the early Earth. Determining which physical and chemical components of hot springs are the result of life vs. non-life in modern hot spring systems is a difficult task, however, since life is so prevalent in these environments. Using a model hot spring simulation chamber, we demonstrate a simple yet effective way to precipitate silica with or without the presence of life. This system may be valuable in further investigating the plausible role of silica precipitation in ancient terrestrial hot spring environments even before life arose, as well as its potential role in providing protection from the high surface UV conditions which may have been present on early Earth.

show abstract