scholarly journals Extant Earthly Microbial Mats and Microbialites as Models for Exploration of Life in Extraterrestrial Mat Worlds

Life ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 883
Author(s):  
Bopaiah Biddanda ◽  
Anthony Weinke ◽  
Ian Stone ◽  
Scott Kendall ◽  
Phil Hartmeyer ◽  
...  
Keyword(s):  
Microbial Mats ◽  
Life Forms ◽  
Microbial Mat ◽  
Lake Huron ◽  
Low Oxygen ◽  
Extraterrestrial Life ◽  
Microbial Life ◽  
High Carbonate ◽  
Sulfur Oxidizing ◽  
Bodies Of Water

As we expand the search for life beyond Earth, a water-dominated planet, we turn our eyes to other aquatic worlds. Microbial life found in Earth’s many extreme habitats are considered useful analogs to life forms we are likely to find in extraterrestrial bodies of water. Modern-day benthic microbial mats inhabiting the low-oxygen, high-sulfur submerged sinkholes of temperate Lake Huron (Michigan, USA) and microbialites inhabiting the shallow, high-carbonate waters of subtropical Laguna Bacalar (Yucatan Peninsula, Mexico) serve as potential working models for exploration of extraterrestrial life. In Lake Huron, delicate mats comprising motile filaments of purple-pigmented cyanobacteria capable of oxygenic and anoxygenic photosynthesis and pigment-free chemosynthetic sulfur-oxidizing bacteria lie atop soft, organic-rich sediments. In Laguna Bacalar, lithification by cyanobacteria forms massive carbonate reef structures along the shoreline. Herein, we document studies of these two distinct earthly microbial mat ecosystems and ponder how similar or modified methods of study (e.g., robotics) would be applicable to prospective mat worlds in other planets and their moons (e.g., subsurface Mars and under-ice oceans of Europa). Further studies of modern-day microbial mat and microbialite ecosystems can add to the knowledge of Earth’s biodiversity and guide the search for life in extraterrestrial hydrospheres.

scholarly journals Sterol preservation in hypersaline microbial mats

2020 ◽  
Vol 17 (3) ◽  
pp. 649-666
Author(s):  
Yan Shen ◽  
Volker Thiel ◽  
Pablo Suarez-Gonzalez ◽  
Sebastiaan W. Rampen ◽  
Joachim Reitner
Keyword(s):  
Microbial Mats ◽  
Abiotic Factors ◽  
Total Sterol ◽  
Microbial Transformation ◽  
Microbial Mat ◽  
Hypersaline Lake ◽  
Central Pacific ◽  
Significant Drop ◽  
Subaerial Exposure ◽  
Benthic Ecosystems

Abstract. Microbial mats are self-sustaining benthic ecosystems composed of highly diverse microbial communities. It has been proposed that microbial mats were widespread in Proterozoic marine environments, prior to the emergence of bioturbating organisms at the Precambrian–Cambrian transition. One characteristic feature of Precambrian biomarker records is that steranes are typically absent or occur in very low concentrations. This has been explained by low eukaryotic source inputs, or degradation of primary produced sterols in benthic microbial mats (“mat-seal effect”). To better understand the preservational pathways of sterols in microbial mats, we analyzed freely extractable and carbonate-bound lipid fractions as well as decalcified extraction residues in different layers of a recent calcifying mat (∼1500 years) from the hypersaline Lake 2 on the island of Kiritimati, central Pacific. A variety of C27–C29 sterols and distinctive C31 4α-methylsterols (4α-methylgorgosterol and 4α-methylgorgostanol, biomarkers for dinoflagellates) were detected in freely extractable and carbonate-bound lipid pools. These sterols most likely originated from organisms living in the water column and the upper mat layers. This autochthonous biomass experienced progressive microbial transformation and degradation in the microbial mat, as reflected by a significant drop in total sterol concentrations, up to 98 %, in the deeper layers, and a concomitant decrease in total organic carbon. Carbonate-bound sterols were generally low in abundance compared to the freely extractable portion, suggesting that incorporation into the mineral matrix does not play a major role in the preservation of eukaryotic sterols in this mat. Likewise, pyrolysis of extraction residues suggested that sequestration of steroid carbon skeletons into insoluble organic matter was low compared to hopanoids. Taken together, our findings argue for a major mat-seal effect affecting the distribution and preservation of steroids in the mat studied. This result markedly differs from recent findings made for another microbial mat growing in the nearby hypersaline Lake 22 on the same island, where sterols showed no systematic decrease with depth. The observed discrepancies in the taphonomic pathways of sterols in microbial mats from Kiritimati may be linked to multiple biotic and abiotic factors including salinity and periods of subaerial exposure, implying that caution has to be exercised in the interpretation of sterol distributions in modern and ancient microbial mat settings.

The Quest for Extraterrestrial Intelligence

2020 ◽  
pp. 290-299
Author(s):  
Hui Chieh Teoh ◽  
Katrina Pui Yee Shak
Keyword(s):  
Science Fiction ◽  
Outer Space ◽  
Life Forms ◽  
Technological Advancement ◽  
Extraterrestrial Life ◽  
Extraterrestrial Intelligence ◽  
For Profit ◽  
Not For Profit ◽  
Human Desire ◽  
Substantial Effort

The constant depictions of contact with extraterrestrial life and their constant basic presence in science fiction shows the deep human desire for connection and transcendence with other life forms. In reality, continuous efforts on the search for aliens are being made by renown not-for-profit research organization such as the Search for Extraterrestrial Intelligence (SETI) since 1984. Over the years, plenty of detected signals were dismissed as noise from transmitters on Earth or orbiting satellites but one – the “Wow!” signal. However, artificial signals from extraterrestrial sources could be the key to detecting extraterrestrial intelligence. Apart from passively searching, some are doing active SETI, or known as METI (Messaging Extraterrestrial Intelligence), where humans create and transmit interstellar messages to aliens instead of waiting for theirs. Substantial effort in many areas – awareness, time, technological advancement, techniques – would be necessary to increase the probability of locating outer space intelligence.

Cage aquaculture and water-quality changes in the LaCloche Channel, Lake Huron, Canada: a paleolimnological assessment

2004 ◽  
Vol 61 (9) ◽  
pp. 1691-1701 ◽  
Author(s):  
Saloni Clerk ◽  
Daniel T Selbie ◽  
John P Smol
Keyword(s):  
Water Quality ◽  
Nutrient Loading ◽  
Fish Farming ◽  
Lake Huron ◽  
Quality Changes ◽  
Low Oxygen ◽  
Hypolimnetic Oxygen ◽  
Cage Aquaculture ◽  
Relative Abundances ◽  
Area Of Concern

Lake eutrophication due to cage aquaculture is an area of concern in Ontario; however, without knowledge of pre-impact conditions, it is difficult to determine the extent and magnitude of environmental change. Paleolimnological techniques were used to estimate water-quality conditions prior to, during, and briefly following aquaculture operation in the LaCloche Channel, Lake Huron. Past oxygen and nutrient levels were inferred from assemblages of chironomids and diatoms, respectively, to determine whether recent low-oxygen and nutrient-rich conditions were related to cage aquaculture in operation from 1989 to 1998. Chironomid assemblages exhibited trends consistent with decreased hypolimnetic oxygen levels, with reductions in oxic-type profundal taxa and increased relative abundances of littoral communities. Diatom assemblages reflected a period of nutrient enrichment by increased relative abundances of meso-eutrophic taxa. Improvements in water quality are inferred from assemblages of diatoms in surface sediments, which may correspond to the cessation of fish-farming activities in 1998. In contrast, no sign of deep-water oxygen recovery is recorded by chironomids. These trends are consistent with eutrophication, and suggest that the LaCloche Channel was sensitive to nutrient loading from the cage-aquaculture operation. This study demonstrates the potential of using paleolimnological techniques to track water-quality changes associated with cage farming.

scholarly journals Responses of a Thermophilic Synechococcus Isolate from the Microbial Mat of Octopus Spring to Light

2007 ◽  
Vol 73 (13) ◽  
pp. 4268-4278 ◽  
Author(s):  
Oliver Kilian ◽  
Anne-Soisig Steunou ◽  
Fariba Fazeli ◽  
Shaun Bailey ◽  
Devaki Bhaya ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Microbial Mats ◽  
Carbon Fixation ◽  
Fluorescence Emission ◽  
Transcript Abundance ◽  
High Light ◽  
Microbial Mat ◽  
Fluorescence Emission Spectra ◽  
Thermophilic Cyanobacteria ◽  
Genes Encoding

ABSTRACT Thermophilic cyanobacteria of the genus Synechococcus are major contributors to photosynthetic carbon fixation in the photic zone of microbial mats in Octopus Spring, Yellowstone National Park. Synechococcus OS-B′ was characterized with regard to the ability to acclimate to a range of different light irradiances; it grows well at 25 to 200 μmol photons m−2 s−1 but dies when the irradiance is increased to 400 μmol photons m−2 s−1. At 200 μmol photons m−2 s−1 (high light [HL]), we noted several responses that had previously been associated with HL acclimation of cyanobacteria, including cell bleaching, reduced levels of phycobilisomes and chlorophyll, and elevated levels of a specific carotenoid. Synechococcus OS-B′ synthesizes the carotenoids zeaxanthin and β,β-carotene and a novel myxol-anhydrohexoside. Interestingly, 77-K fluorescence emission spectra suggest that Synechococcus OS-B′ accumulates very small amounts of photosystem II relative to that of photosystem I. This ratio further decreased at higher growth irradiances, which may reflect potential photodamage following exposure to HL. We also noted that HL caused reduced levels of transcripts encoding phycobilisome components, particularly that for CpcH, a 20.5-kDa rod linker polypeptide. There was enhanced transcript abundance of genes encoding terminal oxidases, superoxide dismutase, tocopherol cyclase, and phytoene desaturase. Genes encoding the photosystem II D1:1 and D1:2 isoforms (psbAI and psbAII/psbAIII, respectively) were also regulated according to the light regimen. The results are discussed in the context of how Synechococcus OS-B′ may cope with high light irradiances in the high-temperature environment of the microbial mat.

scholarly journals Microfossils from the Lower Devonian Rhynie Chert with suggested affinities to the peronosporomycetes

2012 ◽  
Vol 86 (2) ◽  
pp. 358-367 ◽  
Author(s):  
Michael Krings ◽  
Thomas N. Taylor ◽  
Edith L. Taylor ◽  
Hans Kerp ◽  
Hagen Hass ◽  
...  
Keyword(s):  
Lower Devonian ◽  
Microbial Mats ◽  
Plant Litter ◽  
Microbial Life ◽  
Opaque Material ◽  
New Information ◽  
Single Form ◽  
Rhynie Chert ◽  
Thin Walled ◽  
Size And Morphology

A conspicuous silicified microfossil, Frankbaronia polyspora n. gen. n. sp., occurs in plant litter and as an inhabitant of microbial mats from the Lower Devonian Rhynie chert, Aberdeenshire, Scotland. Specimens are elongate-cylindrical, oval, or spherical, thin-walled, and may possess conical or column-like surface projections. Most specimens occur isolated, some are arranged in pairs or short chains. Each specimen contains several small spheres, each in turn with a (sub)centric opaque inclusion. Immature specimens indicate that ontogenesis in this fossil includes the formation of a single centric body of opaque material that subsequently is apportioned among the developing small spheres. Frankbaronia polyspora is quite similar in size and morphology to the oogonia containing oospores seen in certain extant members of the Peronosporomycetes. The Rhynie chert is known to contain the oldest fossil evidence of the Peronosporomycetes but only a single form (Hassiella monospora) has previously been documented. The discovery of a second putative representative of this group of organisms proves that this paleoecosystem is still an important source of new information on the paleodiversity of microbial life.

Possible evidence for panspermia: the labelled release experiment

2007 ◽  
Vol 6 (2) ◽  
pp. 95-108 ◽  
Author(s):  
Gilbert V. Levin
Keyword(s):  
Active Agent ◽  
Life Forms ◽  
Current Data ◽  
Release Experiment ◽  
Microbial Life ◽  
Martian Soil ◽  
Life On Mars ◽  
Biological Interpretation ◽  
Life Question ◽  
Chiral Specificity

Abstract30 years after the Viking Mission landed on Mars (20 July 1976) to search for life, despite the positive findings of the Labelled Release (LR) experiment, the issue remains unresolved. The controversial history, following the immediate dismissal of the LR’s evidence for microbial activity in the Martian soil, and the later claim to its having found living microorganisms are reviewed. The bearing of post-Viking-to-current data on the issue is discussed in the context of the scientific community’s growing interest in the long-dismissed possibility of microbial life on Mars. Objections raised over the years to the biological interpretation of the Mars LR, those currently maintained, and their rebuttals are reviewed. A case is presented that enough evidence now exists for an objective review by astrobiologists to resolve this key issue, a review, surprisingly, not yet held. The results could greatly influence NASA’s currently shifting plans for Mars exploration. A variation of the LR experiment to test for chiral specificity in the metabolism of substrates by the active agent found in the Martian soil, and thus having the capability of obtaining an unambiguous answer to the life question, is proposed. Confirmation of life on Mars by this experiment can also determine whether Martian and Earth life forms share a common heritage. Together with mounting evidence for the viable transfer of microorganisms between the two planets, this would be evidence for panspermia, and establish the presence of a common biosphere in which the two planets participate. Should Martian microorganisms show a different chiral specificity than that of Earth life then this would indicate separate origins of the two neighbouring life forms, thereby strongly implying that life occurs widely throughout the cosmos. Any one of these possible outcomes would be a paradigm-breaking event.

Some implications of crustal movement in engineering planning

1970 ◽  
Vol 7 (2) ◽  
pp. 628-633 ◽  
Author(s):  
R. H. Clark ◽  
N. P. Persoage
Keyword(s):  
Great Lakes ◽  
Lake Ontario ◽  
Water Levels ◽  
Crustal Movement ◽  
Earth’S Crust ◽  
Lake Huron ◽  
Great Lakes Basin ◽  
Lake Outlet ◽  
Earth's Crust ◽  
Bodies Of Water

Movements of the earth's crust causing progressive changes in the levels of large bodies of water relative to their shorelines may influence the formulation of water resource projects and/or their continuing effectiveness with time. In the Great Lakes basin there is evidence of an uplift of the earth's crust, of about 1 ft per 100 y, in the northeasterly part of the basin relative to that in the southwest. This results in a corresponding lowering of water levels along the northeasterly shorelines and a rise in water levels along the southwest shores. In at least two of the lakes, Lake Huron and Lake Ontario, the average depth of water will change with time. In Lake Huron, it will gradually decrease because the bed underlying the lake is rising with respect to the lake outlet. In Lake Ontario, the depth of water will increase since the lake outlet is rising with respect to the remainder of the lake. This paper reviews some of the engineering implications of the relative rates of crustal movement in the Great Lakes region on long-term management of the water levels of the Great Lakes.

scholarly journals [FeFe] Hydrogenase Genetic Diversity Provides Insight into Molecular Adaptation in a Saline Microbial Mat Community

2009 ◽  
Vol 75 (13) ◽  
pp. 4620-4623 ◽  
Author(s):  
Eric S. Boyd ◽  
John R. Spear ◽  
John W. Peters
Keyword(s):  
Genetic Diversity ◽  
Environmental Conditions ◽  
Microbial Mats ◽  
Microbial Mat ◽  
Molecular Adaptation ◽  
Degenerate Primers ◽  
Insight Into

ABSTRACT Degenerate primers for the [FeFe] hydrogenase (hydA) were developed and used in PCRs to examine hydA in microbial mats that inhabit saltern evaporative ponds in Guerrero Negro (GN), Mexico. A diversity of deduced HydA was discovered that revealed unique variants, which may reflect adaptation to the environmental conditions present in GN.

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