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.

scholarly journals Sterol preservation in hypersaline microbial mats

2019 ◽  
Author(s):  
Yan Shen ◽  
Volker Thiel ◽  
Pablo Suarez-Gonzalez ◽  
Sebastiaan W. Rampen ◽  
Joachim Reitner
Keyword(s):  
Microbial Mats ◽  
Abiotic Factors ◽  
Microbial Transformation ◽  
Microbial Mat ◽  
Hypersaline Lake ◽  
Central Pacific ◽  
Significant Drop ◽  
Subaerial Exposure ◽  
Insoluble Organic Matter ◽  
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 analysed freely extractable and carbonate-bound sterols 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 both 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 sterols concentrations, up to 98 %, in the deeper layers, and a concomitant decrease in total organic carbon. Carbonate-bound sterols were generally low in abundance, suggesting that incorporation into the mineral matrix does not play a major role for the preservation of eukaryotic sterols in this mat. Likewise, pyrolysis revealed that steroids (i.e., including sterenes, steranes and sterols), in contrast to hopanoids, were not sequestered into insoluble organic matter which may give rise to a further bias in the preservation of steroids vs. hopanoids, particularly in the later stages of burial. While these findings argue for a strong 'mat-seal effect' in the mat studied, they markedly differ from recent findings made for another microbial mat growing in the near-by 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 sterols distributions in modern and ancient microbial mat settings.

scholarly journals Phylogenetic Analysis of a Microbialite-Forming Microbial Mat from a Hypersaline Lake of the Kiritimati Atoll, Central Pacific

PLoS ONE ◽  
2013 ◽  
Vol 8 (6) ◽  
pp. e66662 ◽  
Author(s):  
Dominik Schneider ◽  
Gernot Arp ◽  
Andreas Reimer ◽  
Joachim Reitner ◽  
Rolf Daniel
Keyword(s):  
Phylogenetic Analysis ◽  
Microbial Mat ◽  
Hypersaline Lake ◽  
Central Pacific

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 Comparative study of vent and seep macrofaunal communities in the Guaymas Basin

2015 ◽  
Vol 12 (18) ◽  
pp. 5455-5479 ◽  
Author(s):  
M. Portail ◽  
K. Olu ◽  
E. Escobar-Briones ◽  
J. C. Caprais ◽  
L. Menot ◽  
...  
Keyword(s):  
Deep Sea ◽  
Gulf Of California ◽  
Microbial Mats ◽  
Abiotic Factors ◽  
Ecological Processes ◽  
Guaymas Basin ◽  
The Family ◽  
Family Level ◽  
Higher Temperature ◽  
Macrofaunal Community

Abstract. Understanding the ecological processes and connectivity of chemosynthetic deep-sea ecosystems requires comparative studies. In the Guaymas Basin (Gulf of California, Mexico), the presence of seeps and vents in the absence of a biogeographic barrier, and comparable sedimentary settings and depths offers a unique opportunity to assess the role of ecosystem-specific environmental conditions on macrofaunal communities. Six seep and four vent assemblages were studied, three of which were characterised by common major foundation taxa: vesicomyid bivalves, siboglinid tubeworms and microbial mats. Macrofaunal community structure at the family level showed that density, diversity and composition patterns were primarily shaped by seep- and vent-common abiotic factors including methane and hydrogen sulfide concentrations, whereas vent environmental specificities (higher temperature, higher metal concentrations and lower pH) were not significant. The type of substratum and the heterogeneity provided by foundation species were identified as additional structuring factors and their roles were found to vary according to fluid regimes. At the family level, seep and vent similarity reached at least 58 %. All vent families were found at seeps and each seep-specific family displayed low relative abundances (< 5 %). Moreover, 85 % of the identified species among dominant families were shared between seep and vent ecosystems. This study provides further support to the hypothesis of continuity among deep-sea seep and vent ecosystems.

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.

scholarly journals Comparative study of vent and seep macrofaunal communities in the Guaymas Basin

2015 ◽  
Vol 12 (11) ◽  
pp. 8497-8571 ◽  
Author(s):  
M. Portail ◽  
K. Olu ◽  
E. Escobar-Briones ◽  
J. C. Caprais ◽  
L. Menot ◽  
...  
Keyword(s):  
Deep Sea ◽  
Gulf Of California ◽  
Microbial Mats ◽  
Abiotic Factors ◽  
Common Species ◽  
Ecological Processes ◽  
Community Patterns ◽  
Guaymas Basin ◽  
Higher Temperature ◽  
Macrofaunal Community

Abstract. Understanding the ecological processes and connectivity of chemosynthetic deep-sea ecosystems requires comparative studies. In the Guaymas Basin (Gulf of California, Mexico), the presence of seeps and vents in the absence of biogeographic barrier, comparable sedimentary settings and depths offers a unique opportunity to assess the role of ecosystem specific environmental conditions on macrofaunal communities. Six seep and four vent assemblages were studied, three of which were characterised by common major foundation taxa: vesicomyid bivalves, siboglinid tubeworms and microbial mats. Macrofaunal community structure at the family level showed that density, diversity and composition patterns were primarily shaped by seep and vent common abiotic factors including methane and hydrogen sulphide concentrations. The type of substratum and the heterogeneity provided by foundation species were identified as additional structuring factors and their roles were found to vary according to fluid regimes. Surprisingly, the presence of vent environmental specificities, with higher temperature, higher metal concentrations and lower pH was not significant in explaining community patterns. Moreover, Guaymas seep and vent shared an important number of common species suggesting frequent connections between the two ecosystems. Finally, this study provides further support for the hypothesis of continuity among deep-sea seep and vent ecosystems.

scholarly journals Microbial mats as shelter microhabitat for amphipods in an intermittent karstic spring

2018 ◽  
pp. 7 ◽  
Author(s):  
Petar Žutinić ◽  
Ines Petrić ◽  
Sanja Gottstein ◽  
Marija Gligora Udovič ◽  
Koraljka Kralj Borojević ◽  
...  
Keyword(s):  
Microbial Mats ◽  
High Water ◽  
Microbial Mat ◽  
Flow Conditions ◽  
Temporary Stream ◽  
Strong Current ◽  
Cyanobacterial Species ◽  
Animal Activity ◽  
Winter Sample ◽  
Representative Samples

Microbial mats represent complex communities where cyanobacteria and diatoms as key organisms provide shelter for diverse assemblages of aquatic invertebrates, like the small stygophilous amphipod Synurella ambulans. Studies addressing such communities in the karst springs have rarely examined springheads, and have ignored intermittent springs. During high flow conditions the stygophilic crustaceans are flushed to the surface of a temporary stream Krčić where microbial mats prevent their drift and enables their successful retreat into underground in the periods of drought. The objective of this study was to characterize the microbial mat community of the Krčić Spring as a shelter for S. ambulans during strong current and high water level. Representative samples for diatom and cyanobacterial species identification and composition, as well as the fresh mat material for potential animal activity and cyanobacterial phylogenetic analysis were collected. The most dominant diatom was Achnanthidium minutissimum, whilst Fragilaria capucina, Meridion circulare, Navicula cryptocephala and Nitzschia palea had abundance greater than 0.5%. Morphological observations of cyanobacteria revealed that Phormidium favosum was the most dominant, with Hydrocoleum muscicola as a subdominant. Cyanobacterial phylogenetic relationship revealed two distinct clusters: (i) "Phormidium cluster", confirming morphological observations in both winter and spring samples, and (ii) "Wilmottia cluster", a first report for Croatia and found exclusively in the winter sample. Laboratory observations revealed a small stygophilic amphipod S. ambulans, hiding and feeding inside the pockets of fresh microbial mat. The intermittent Krčić Spring as a predator-free and competitor-free ecosystem provides a spatiotemporal conformity between microbial mat and stygophilous amphipod.

scholarly journals Radiocarbon Dating of Recent Intertidal Microbial Mats on Atoll Rims

Radiocarbon ◽  
2013 ◽  
Vol 55 (3) ◽  
pp. 1603-1616 ◽  
Author(s):  
Jean Trichet ◽  
Christine Hatté ◽  
Michel Fontugne
Keyword(s):  
Southern Hemisphere ◽  
Radiocarbon Dating ◽  
Microbial Mats ◽  
French Polynesia ◽  
Microbial Mat ◽  
Accumulation Process ◽  
Reservoir Effect ◽  
Activity Measurements ◽  
Effect Estimation

Microbial mats (koparain Polynesian) that develop in shallow brackish to hypersaline ponds on the rims of atolls were investigated for their accumulation process and rate. Two sequences of ∼30-cm-deep kopara, composed of 7 and 5 layers distinguished by their colors and sedimentological facies were collected in 1996 from the Tetiaroa atoll, French Polynesia. The combination of radiocarbon activity measurements on both organic and carbonate constituents, reservoir effect estimation, and comparison with the Southern Hemisphere atmospheric bomb-peak14C record allowed us to establish a fine chronology of the layer successions documenting the mode of formation, erosion, and restoration of these microbial mat deposits.

scholarly journals CARACTERIZAÇÃO DOS ESTROMATÓLITOS DA FORMAÇÃO CAPIRU (PROTEROZÓICO) NAS REGIÕES DE MORRO AZUL E MORRO GRANDE: LESTE DO PARANÁ

2002 ◽  
Vol 51 ◽  
Author(s):  
Sandra B. Guimarães ◽  
José Manoel Dos Reis Neto ◽  
Rossano B. L. Siqueira
Keyword(s):  
Cross Section ◽  
Microbial Mats ◽  
Microbial Control ◽  
Plane Parallel ◽  
Sedimentary Structures ◽  
Subaerial Exposure ◽  
Proterozoic Age

As regiões de Morro Azul e de Morro Grande no leste do Paraná abrigam exposições de estromatólitos, compostos por formas colunares e esteiras microbianas na Formação Capiru do Grupo Açungui de idade Proterozóica. Estes estromatólitos estão associados a metadolomitos e indicam provável controle microbiano na geração de dois diferentes grupos: a) esteiras microbianas na região de Morro Azul e b) estromatólitos colunares na região de Morro Grande. Os estromatólitos colunares possuem até 35 cm de altura por 15 cm de diâmetro, ocorrem em colunas simples ou ramificadas, geralmente associadas a estruturas sedimentares plano-paralelas e a marcas de onda. Em planta, os estromatólitos são elipsoidais a circulares, onde a laminação interna se apresenta de ondulada a moderadamente convexa. As esteiras microbianas são compostas de uma sucessão de lâminas finas associadas a estruturas características de exposição subaérea como tepees e gretas de contração. As características morfológicas das estruturas estromatolíticas, associadas às estruturas sedimentares observadas nas diferentes litofácies, permitem caracterizar distintos ambientes de plataforma para as duas regiões: para a de Morro Azul, um ambiente de supramaré; enquanto para a de Morro Grande, um ambiente variando de entremarés a inframaré. CHARACTERIZATION OF STROMATOLITES IN THE CAPIRU FORMATION (PROTEROZOIC) IN THE MORRO AZUL AND MORRO GRANDE REGIONS: EASTERN PARANÁ Abstract The Morro Azul (região de Morro Azul) and the Morro Grande (região de Morro Grande) regions in eastern Paraná contain columnar stromatolites and microbial mats in the Capiru Formation of the Açungui Group of Proterozoic age. These structures are associated with metadolomites, indicating probable microbial control in the formation of two different groups of stromatolites: a) columnar stromatolites in região de Morro Grande and b) microbial mats in the região de Morro Azul. Columnar stromatolites reach up to 35 cm in height and 15 cm in diameter as columns or branched generally associated with plane-parallel sedimentary structures and wave marks. In cross-section, the stromatolites are elliptical to circular, and the lamination is wavey to moderately convex. The microbial mats are composed of a succession of fine laminal associated with structures characteristic of subaerial exposure, such as tepees and mud cracks. The morphlogic features of the stromatolites and the observed sedimentary structures in the different lithofacies suggest distinct shelf environments for the two regions: for região de Morro Azul, a supratidal facies, while in the região de Morro Grande, an environment varying from intertidal to infratidal.

scholarly journals Carbon fixation and rhodopsin systems in microbial mats from hypersaline lakes Brava and Tebenquiche, Salar de Atacama, Chile

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0246656
Author(s):  
Daniel Kurth ◽  
Dario Elias ◽  
María Cecilia Rasuk ◽  
Manuel Contreras ◽  
María Eugenia Farías
Keyword(s):  
Molecular Diversity ◽  
Microbial Mats ◽  
Carbon Fixation ◽  
High Salinity ◽  
Environmental Dna ◽  
Taxonomic Diversity ◽  
Mineral Precipitation ◽  
Hypersaline Lakes ◽  
Taxonomic Level ◽  
Benthic Ecosystems

In this work, molecular diversity of two hypersaline microbial mats was compared by Whole Genome Shotgun (WGS) sequencing of environmental DNA from the mats. Brava and Tebenquiche are lakes in the Salar de Atacama, Chile, where microbial communities are growing in extreme conditions, including high salinity, high solar irradiance, and high levels of toxic metals and metaloids. Evaporation creates hypersaline conditions in these lakes and mineral precipitation is a characteristic geomicrobiological feature of these benthic ecosystems. The mat from Brava was more rich and diverse, with a higher number of different taxa and with species more evenly distributed. At the phylum level, Proteobacteria, Cyanobacteria, Chloroflexi, Bacteroidetes and Firmicutes were the most abundant, including ~75% of total sequences. At the genus level, the most abundant sequences were affilitated to anoxygenic phototropic and cyanobacterial genera. In Tebenquiche mats, Proteobacteria and Bacteroidetes covered ~70% of the sequences, and 13% of the sequences were affiliated to Salinibacter genus, thus addressing the lower diversity. Regardless of the differences at the taxonomic level, functionally the two mats were similar. Thus, similar roles could be fulfilled by different organisms. Carbon fixation through the Wood-Ljungdahl pathway was well represented in these datasets, and also in other mats from Andean lakes. In spite of presenting less taxonomic diversity, Tebenquiche mats showed increased abundance and variety of rhodopsin genes. Comparison with other metagenomes allowed identifying xantorhodopsins as hallmark genes not only from Brava and Tebenquiche mats, but also for other mats developing at high altitudes in similar environmental conditions.

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