Faculty Opinions recommendation of Biogeochemistry of microbial mats under Precambrian environmental conditions: a modelling study.

2005 ◽  
Author(s):  
Michael Kühl
Keyword(s):  
Environmental Conditions ◽  
Microbial Mats ◽  
Modelling Study

scholarly journals In-Situ Metatranscriptomic Analyses Reveal the Metabolic Flexibility of the Thermophilic Anoxygenic Photosynthetic Bacterium Chloroflexusaggregans in a Hot Spring Cyanobacteria-Dominated Microbial Mat

2021 ◽  
Vol 9 (3) ◽  
pp. 652
Author(s):  
Shigeru Kawai ◽  
Joval N. Martinez ◽  
Mads Lichtenberg ◽  
Erik Trampe ◽  
Michael Kühl ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Environmental Conditions ◽  
Microbial Mats ◽  
Carbon Fixation ◽  
Hot Springs ◽  
Hot Spring ◽  
Photosynthetic Bacterium ◽  
Early Morning ◽  
Metabolic Flexibility

Chloroflexus aggregans is a metabolically versatile, thermophilic, anoxygenic phototrophic member of the phylum Chloroflexota (formerly Chloroflexi), which can grow photoheterotrophically, photoautotrophically, chemoheterotrophically, and chemoautotrophically. In hot spring-associated microbial mats, C. aggregans co-exists with oxygenic cyanobacteria under dynamic micro-environmental conditions. To elucidate the predominant growth modes of C. aggregans, relative transcription levels of energy metabolism- and CO2 fixation-related genes were studied in Nakabusa Hot Springs microbial mats over a diel cycle and correlated with microscale in situ measurements of O2 and light. Metatranscriptomic analyses indicated two periods with different modes of energy metabolism of C. aggregans: (1) phototrophy around midday and (2) chemotrophy in the early morning hours. During midday, C. aggregans mainly employed photoheterotrophy when the microbial mats were hyperoxic (400–800 µmol L−1 O2). In the early morning hours, relative transcription peaks of genes encoding uptake hydrogenase, key enzymes for carbon fixation, respiratory complexes as well as enzymes for TCA cycle and acetate uptake suggest an aerobic chemomixotrophic lifestyle. This is the first in situ study of the versatile energy metabolism of C. aggregans based on gene transcription patterns. The results provide novel insights into the metabolic flexibility of these filamentous anoxygenic phototrophs that thrive under dynamic environmental conditions.

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 Uncovering chemical signatures of salinity gradients through compositional analysis of protein sequences

2020 ◽  
Vol 17 (23) ◽  
pp. 6145-6162
Author(s):  
Jeffrey M. Dick ◽  
Miao Yu ◽  
Jingqiang Tan
Keyword(s):  
Environmental Conditions ◽  
Microbial Mats ◽  
Compositional Analysis ◽  
Protein Sequences ◽  
Hyperosmotic Stress ◽  
Chemical Compositions ◽  
Salinity Gradients ◽  
Gene And Protein Expression ◽  
The Baltic ◽  
The Impact

Abstract. Prediction of the direction of change of a system under specified environmental conditions is one reason for the widespread utility of thermodynamic models in geochemistry. However, thermodynamic influences on the chemical compositions of proteins in nature have remained enigmatic despite much work that demonstrates the impact of environmental conditions on amino acid frequencies. Here, we present evidence that the dehydrating effect of salinity is detectable as chemical differences in protein sequences inferred from (1) metagenomes and metatranscriptomes in regional salinity gradients and (2) differential gene and protein expression in microbial cells under hyperosmotic stress. The stoichiometric hydration state (nH2O), derived from the number of water molecules in theoretical reactions to form proteins from a particular set of basis species (glutamine, glutamic acid, cysteine, O2, H2O), decreases along salinity gradients, including the Baltic Sea and Amazon River and ocean plume, and decreases in particle-associated compared to free-living fractions. However, the proposed metric does not respond as expected for hypersaline environments. Analysis of data compiled for hyperosmotic stress experiments under controlled laboratory conditions shows that differentially expressed proteins are on average shifted toward lower nH2O. Notably, the dehydration effect is stronger for most organic solutes compared to NaCl. This new method of compositional analysis can be used to identify possible thermodynamic effects in the distribution of proteins along chemical gradients at a range of scales from microbial mats to oceans.

Environmental conditions during freezing, and response of microbial mats in ponds of the McMurdo Ice Shelf, Antarctica

1999 ◽  
Vol 11 (2) ◽  
pp. 198-208 ◽  
Author(s):  
I. Hawes ◽  
R. Smith ◽  
C. Howard-Williams ◽  
A-M. Schwarz
Keyword(s):  
Environmental Conditions ◽  
Microbial Mats ◽  
Freezing Point ◽  
Light Limitation ◽  
Ice Shelf ◽  
Freeze Concentration ◽  
Air Temperatures ◽  
Bottom Waters ◽  
Harvesting Efficiency ◽  
Photosynthesis And Respiration

Environmental conditions, both external to and within three shallow ponds of the McMurdo Ice Shelf, were measured over an annual cycle between January 1997 and January 1998. We combined this with a study of the response of the benthic microbial mat communities to the transition from summer conditions to winter freezing. Over the study period air temperature was above 0°C for a few days during summer. At this time pond temperatures were higher than air temperatures, with evidence of thermo-haline stratification. The shallow areas of ponds froze between late February and early March, with bottom waters in the deepest pond remaining unfrozen until early June. Minimum winter air temperatures were below −40°C. There was little evidence of freezing point depression due to freeze-concentration of solutes, except at the very bottom of ponds. In the most conductive pond investigated, the temperature of basal freezing was −4°C and conductivity did not exceed approximately 60 mS cm−1 immediately prior to freezing. Microbial mats remained photosynthetically active up to conductivities between 40 and 80 mS cm−1, and were able to acclimate to lowered irradiance associated with ice formation. Although photosynthesis and respiration were reduced by 11% and 40% respectively at temperatures of −2°C compared to 1°C, there was no difference in light harvesting efficiency. Results from this study suggest that light limitation of photosynthesis, or freezing, determine the growth season for the microbial communities, depending on depth.

Living and fossil microbialites in Laguna de Los Cisnes (Southernmost Chile): A duel between biotic and abiotic processes

2021 ◽  
Author(s):  
Clément Pollier ◽  
Daniel Ariztegui ◽  
Alejandro Nuñez Guerrero ◽  
Jorge Rabassa
Keyword(s):  
Environmental Conditions ◽  
Microbial Mats ◽  
Wide Spectrum ◽  
Temporal Distribution ◽  
Depositional Environments ◽  
Tierra Del Fuego ◽  
Oxygenic Photosynthesis ◽  
Simultaneous Occurrence ◽  
The Bahamas ◽  
Temporal Dimension

<div> <div> <div> <p>Appeared more than 3.5 billion years ago, microbialites represent one of the oldest ecosystems on Earth. These architects of oxygenic photosynthesis dominate the fossil record for nearly 80% of Earth's history, having influenced the evolution of the planet notably by changing the properties of the atmosphere. Despite a dramatic decline in their abundance from the start of the Phanerozoic, they still develop today in a wide spectrum of depositional environments (The Bahamas, Australia, Brazil, etc.). The spatio-temporal distribution of microbialites therefore make them a valuable archive of both life and Earth evolution. However, after nearly 100 years of research, their origin as well as their environmental significance is still a matter of debate. Little is known about microbialite formation, in particular the relative roles of microbial versus environmental factors ruling their growth. Laguna de Los Cisnes located at 53 ° 25' S and 70 ° 40' W in Chilean Tierra del Fuego, Patagonia, provides us with a unique site to fill this gap. This basin was formed during the retreat of the ice following the last glaciation about 10,000 years ago. Subsequently, the lake was densely colonized by microbial mats that developed the presently living and fossil carbonate microbialites. We have explored the relative contribution of environmental versus biological factors controlling microbialite morphogenesis across various scales.</p> <p>Macroscopically, these organo-sedimentary deposits have an extension of almost 8 km<sup>2</sup> encompassing several morphologies exceptionally large with maximum heights and widths of 1.5 m and 5.0 m respectively. Crater-like shapes are dominant, displaying a spherical to elongated character most frequently unfilled. Both spatial distribution and temporal succession of morphotypes indicate that the dominant physico-chemical character of the water is critical in the localization as well as in the style of the microbial carbonate factory, which in turn is reflected in the morphological character of the subsequent deposit. The microbialite meso-structure reveals a pattern of three lithological distinctive stacked layers. This fabric reflects a multiphase history of formation, linked with the ecological succession of specific bacterial communities throughout time that are still strongly influenced by the prevailing environmental conditions. Interestingly, the simultaneous occurrence of various living bacterial mats provides insights regarding the microscale interactions between the different compounds of the bacterial ecosystem (cyanobacteria, sulfate-reducing bacteria, green algae and diatoms) and their relative roles in the calcification processes.</p> </div> </div> Finally, the presence of extraordinary well-preserved fossil outcrops along with living microbialites gives a temporal dimension to this study, laying the foundation for the development of a new formation model. By applying the latter to other microbialites outcropping at different geographical and temporal scales, the microbial carbonates of Laguna de Los Cisnes can provide critical information to better reconstruct the dominant environmental conditions during the early evolution of life on Earth.</div>

scholarly journals Environmental controls and habitat connectivity of phototrophic microbial mats and bacterioplankton communities in an Antarctic freshwater system

2020 ◽  
Author(s):  
J. Ramoneda ◽  
I. Hawes ◽  
A. Pascual-García ◽  
T.J. Mackey ◽  
D.Y. Sumner ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Microbial Mats ◽  
Environmental Filtering ◽  
Freshwater Ecosystems ◽  
Habitat Conditions ◽  
Environmental Controls ◽  
Rrna Sequencing ◽  
Freshwater System ◽  
Halogenated Aromatic Compounds ◽  
Planktonic Communities

AbstractFreshwater ecosystems are considered hotspots of biodiversity in Antarctic polar deserts. Anticipated warming is expected to change the hydrology of these systems due to increased meltwater and reduction of ice cover, with implications for environmental conditions and physical connectivity between habitats. Using 16S rRNA sequencing, we evaluated the structure of microbial mat and planktonic communities within a connected watershed in the McMurdo Wright Valley, Antarctica to determine the roles of connectivity and habitat conditions in controlling microbial assemblage composition. We examined benthic and planktonic samples from glacial Lake Brownworth, the perennially ice-covered Lake Vanda, and the Onyx River, which connects the two. In Lake Vanda, we found distinct microbial assemblages occupying sub-habitats at different lake depths, while the communities from Lake Brownworth and Onyx River were structurally similar between them. Despite the higher connectivity between bacterial communities in the shallow parts of the system, environmental filtering dominated over dispersal in driving bacterial community structure. Functional metagenomics predictions identified genes related to degradation of halogenated aromatic compounds in surface microbial mats exposed to changes in water regimes, which progressively disappeared with increasing depth. Shifting environmental conditions due to increasing connectivity, rather than dispersal, may become the dominant drivers of bacterial diversity and functioning in Antarctic freshwater ecosystems.

Petrography and genesis of spicular and columnar geyserite from the Whakarewarewa and Orakeikorako geothermal areas, North Island, New Zealand

2003 ◽  
Vol 40 (11) ◽  
pp. 1585-1610 ◽  
Author(s):  
Brian Jones ◽  
Robin W Renaut
Keyword(s):  
New Zealand ◽  
Environmental Conditions ◽  
Microbial Mats ◽  
Three Dimensional ◽  
Geothermal Area ◽  
Microbial Structure ◽  
The Core

Domal masses of geyserite, which surround many geyser vents in the Whakarewarewa geothermal area, are formed largely of spicules, spicule columns, and shrub columns. The non-branching spicules and the branches of branching spicules, individually up to 3 cm high and 1 mm diameter, have a laminated core encased by siliceous cortex. Silicified microbes are rare in the core but common in the cortex. Silicified microbial mats and pseudodendrites are found in the crevices between neighbouring spicules. Shrub columns, up to 5 cm high and 1.5 cm in diameter, are formed of opal-A that was precipitated around a three-dimensional, branching, shrub-like microbial (?) structure. The shrub branches, which are hollow with scalloped walls, do not contain any evidence of the original microbes or minerals that formed them. Silicified microbial mats are present between the columns. Microbial boring and etching by acidic steam led to local diagenetic degradation of these columns. In the geyserite mounds at Whakarewarewa, spicules and spicule columns are common, whereas shrub columns are rare. Interbedding and intercalation of spicular geyserite with shrub columnar geyserite indicate, however, that these different morphologic entities probably formed under similar environmental conditions on the mounds around the geyser vents. Petrographic evidence shows that the spicules, spicule columns, and shrub columns grew through a combination of biotic and abiotic processes.

Vibration Isolator System for Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 182-183
Author(s):  
K. Ohi ◽  
M. Mizuno ◽  
T. Kasai ◽  
Y. Ohkura ◽  
K. Mizuno ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Magnetic Fields ◽  
Environmental Conditions ◽  
Vibration Isolator ◽  
Air Conditioners ◽  
Vibration Isolators ◽  
Large Size ◽  
Electron Microscopes

In recent years, with electron microscopes coming into wider use, their installation environments do not necessarily give their performance full play. Their environmental conditions include air-conditioners, magnetic fields, and vibrations. We report a jointly developed entirely new vibration isolator which is effective against the vibrations transmitted from the floor.Conventionally, large-sized vibration isolators which need the digging of a pit have been used. These vibration isolators, however, are large present problems of installation and maintenance because of their large-size.Thus, we intended to make a vibration isolator which1) eliminates the need for changing the installation room2) eliminates the need of maintenance and3) are compact in size and easily installable.

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