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At least 127 records · Page 7Linked to original sources
USGS2017

Microbially mediated barite dissolution in anoxic brines

Fluids injected into shale formations during hydraulic fracturing of black shale return with extraordinarily high total-dissolved-solids (TDS) and high concentrations of barium (Ba) and radium (Ra). Barite, BaSO 4 , has been implicated as a possible source of Ba as well as a problematic mineral scale that forms on internal well surfaces, often in close association with radiobarite, (Ba,Ra)SO 4 . The dissolution of barite by abiotic processes is well quantified. However, the identification of microbial communities in flowback and produced water necessitates the need to understand barite dissolution in the presence of bacteria. Therefore, we evaluated the rates and mechanisms of abiotic and microbially-mediated barite dissolution under anoxic and hypersaline conditions in the laboratory. Barite dissolution experiments were conducted with bacterial enrichment cultures established from produced water from Marcellus Shale wells located in northcentral Pennsylvania. These cultures were dominated by anaerobic halophilic bacteria from the genus Halanaerobium . Dissolved Ba was determined by ICP-OES and barite surfaces were investigated by SEM and AFM. Our results reveal that: 1) higher amounts of barium (up to ∼5 × ) are released from barite in the presence of Halanaerobium cultures compared to brine controls after 30 days of reaction, 2) etch pits that develop on the barite (001) surface in the presence of Halanaerobium exhibit a morphology that is distinct from those that form during control experiments without bacteria, 3) etch pits that develop in the presence of Halanaerobium exhibit a morphology that is similar to the morphology of etch pits formed in the presence of strong organic chelators, EDTA and DTPA, and 4) experiments using dialysis membranes to separate barite from bacteria suggest that direct contact between the two is not required in order to promote dissolution. These results suggest that Halanaerobium increase the rate of barite dissolution in anoxic and high ionic strength solutions. Additionally, the increase in rate occurs without direct microbe-mineral contact suggesting that metabolites secreted by the bacteria may be responsible for promotion of dissolution. The findings of this study have implications for understanding barium cycling in marine/hypersaline environments, release of barium (and associated radium) from waste solids generated from energy and mining industries, as well as potential for developing new anti-scaling chemicals.

Applied Geochemistry↗
USGS2006

Conservation of Toll-like receptor signaling pathways in teleost fish

In mammals, toll-like receptors (TLR) recognize ligands, including pathogen-associated molecular patterns (PAMPs), and respond with ligand-specific induction of genes. In this study, we establish evolutionary conservation in teleost fish of key components of the TLR-signaling pathway that act as switches for differential gene induction, including MYD88, TIRAP, TRIF, TRAF6, IRF3, and IRF7. We further explore this conservation with a molecular phylogenetic analysis of MYD88. To the extent that current genomic analysis can establish, each vertebrate has one ortholog to each of these genes. For molecular tree construction and phylogeny inference, we demonstrate a methodology for including genes with only partial primary sequences without disrupting the topology provided by the high-confidence full-length sequences. Conservation of the TLR-signaling molecules suggests that the basic program of gene regulation by the TLR-signaling pathway is conserved across vertebrates. To test this hypothesis, leukocytes from a model fish, rainbow trout ( Oncorhynchus mykiss ), were stimulated with known mammalian TLR agonists including: diacylated and triacylated forms of lipoprotein, flagellin, two forms of LPS, synthetic double-stranded RNA, and two imidazoquinoline compounds (loxoribine and R848). Trout leukocytes responded in vitro to a number of these agonists with distinct patterns of cytokine expression that correspond to mammalian responses. Our results support the key prediction from our phylogenetic analyses that strong selective pressure of pathogenic microbes has preserved both TLR recognition and signaling functions during vertebrate evolution.

Comparative Biochemistry and Physiology, Part D: G↗
USGS2004

Mineral stimulation of subsurface microorganisms: release of limiting nutrients from silicates

Microorganisms play an important role in the weathering of silicate minerals in many subsurface environments, but an unanswered question is whether the mineral plays an important role in the microbial ecology. Silicate minerals often contain nutrients necessary for microbial growth, but whether the microbial community benefits from their release during weathering is unclear. In this study, we used field and laboratory approaches to investigate microbial interactions with minerals and glasses containing beneficial nutrients and metals. Field experiments from a petroleum-contaminated aquifer, where silicate weathering is substantially accelerated in the contaminated zone, revealed that phosphorus (P) and iron (Fe)-bearing silicate glasses were preferentially colonized and weathered, while glasses without these elements were typically barren of colonizing microorganisms, corroborating previous studies using feldspars. In laboratory studies, we investigated microbial weathering of silicates and the release of nutrients using a model ligand-promoted pathway. A metal-chelating organic ligand 3,4 dihydroxybenzoic acid (3,4 DHBA) was used as a source of chelated ferric iron, and a carbon source, to investigate mineral weathering rate and microbial metabolism. In the investigated aquifer, we hypothesize that microbes produce organic ligands to chelate metals, particularly Fe, for metabolic processes and also form stable complexes with Al and occasionally with Si. Further, the concentration of these ligands is apparently sufficient near an attached microorganism to destroy the silicate framework while releasing the nutrient of interest. In microcosms containing silicates and glasses with trace phosphate mineral inclusions, microbial biomass increased, indicating that the microbial community can use silicate-bound phosphate inclusions. The addition of a native microbial consortium to microcosms containing silicates or glasses with iron oxide inclusions correlated to accelerated weathering and release of Si into solution as well as the accelerated degradation of the model substrate 3,4 DHBA. We propose that silicate-bound P and Fe inclusions are bioavailable, and microorganisms may use organic ligands to dissolve the silicate matrix and access these otherwise limiting nutrients.

Chemical Geology↗
USGS2008

Microbial and chemical factors influencing methane production in laboratory incubations of low-rank subsurface coals

Lignite and subbituminous coals were investigated for their ability to support microbial methane production in laboratory incubations. Results show that naturally-occurring microorganisms associated with the coals produced substantial quantities of methane, although the factors influencing this process were variable among different samples tested. Methanogenic microbes in two coals from the Powder River Basin, Wyoming, USA, produced 140.5-374.6 mL CH 4 /kg ((4.5-12.0 standard cubic feet (scf)/ton) in response to an amendment of H 2 /CO 2 . The addition of high concentrations (5-10 mM) of acetate did not support substantive methane production under the laboratory conditions. However, acetate accumulated in control incubations where methanogenesis was inhibited, indicating that acetate was produced and consumed during the course of methane production. Acetogenesis from H 2 /CO 2 was evident in these incubations and may serve as a competing metabolic mode influencing the cumulative amount of methane produced in coal. Two low-rank (lignite A) coals from Fort Yukon, Alaska, USA, demonstrated a comparable level of methane production (131.1-284.0 mL CH4/kg (4.2-9.1 scf/ton)) in the presence of an inorganic nutrient amendment, indicating that the source of energy and organic carbon was derived from the coal. The concentration of chloroform-extractable organic matter varied by almost three orders of magnitude among all the coals tested, and appeared to be related to methane production potential. These results indicate that substrate availability within the coal matrix and competition between different groups of microorganisms are two factors that may exert a profound influence on methanogenesis in subsurface coal beds.

International Journal of Coal Geology↗
USGS2008

Molecular sequences derived from Paleocene Fort Union Formation coals vs. associated produced waters: Implications for CBM regeneration

Coalbed methane regeneration is of increasing interest, and is gaining global attention with respect to enhancement of gas recovery. The objective of this study is to determine if there are differences in methanogen nucleic acid sequences associated with low rank coals from the Powder River Basin, Wyoming, in comparison with sequences that can be recovered from coal bed-associated produced waters. Based on results obtained to date, the sequences from the coals appear to be associated with putatively deep-rooted thermophilic autotrophic methanogens, whereas the sequences from the waters are associated with thermophilic autotrophic and heterotrophic methanogens. The recovered sequences associated with coal thus appear to be both phylogenetically and functionally distinct from those that are more closely associated with the produced water. To be able to relate such recovered sequences to organisms that might be present and possibly active in these environments, it is suggested that direct observation, followed by isolation and single cell-based physiological/molecular analyses, be used to characterize methanogenic consortia possibly associated with coals and/or produced waters. It is also important to characterize the microenvironment where these microbes might be found, in both ecological and geological contexts, to be able to develop effective, ecologically relevant coalbed methane regeneration processes.

International Journal of Coal Geology↗
USGS2011

Microbial sulfate reduction and the sulfur budget for a complete section of altered oceanic basalts, IODP Hole 1256D (eastern Pacific)

Sulfide mineralogy and the contents and isotope compositions of sulfur were analyzed in a complete oceanic volcanic section from IODP Hole 1256D in the eastern Pacific, in order to investigate the role of microbes and their effect on the sulfur budget in altered upper oceanic crust. Basalts in the 800m thick volcanic section are affected by a pervasive low-temperature background alteration and have mean sulfur contents of 530ppm, reflecting loss of sulfur relative to fresh glass through degassing during eruption and alteration by seawater. Alteration halos along fractures average 155ppm sulfur and are more oxidized, have high SO 4 /ΣS ratios (0.43), and lost sulfur through oxidation by seawater compared to host rocks. Although sulfur was lost locally, sulfur was subsequently gained through fixation of seawater-derived sulfur in secondary pyrite and marcasite in veins and in concentrations at the boundary between alteration halos and host rocks. Negative δ34S sulfide-S values (down to -30 °) and low temperatures of alteration (down to ~40 °C) point to microbial reduction of seawater sulfate as the process resulting in local additions of sulfide-S. Mass balance calculations indicate that 15-20% of the sulfur in the volcanic section is microbially derived, with the bulk altered volcanic section containing 940ppm S, and with δ34S shifted to -6.0‰) from the mantle value (0 ‰). The bulk volcanic section may have gained or lost sulfur overall. The annual flux of microbial sulfur into oceanic basement based on Hole 1256D is 3-4 X10 10 molSyr-1, within an order of magnitude of the riverine sulfate source and the sedimentary pyrite sink. Results indicate a flux of bacterially derived sulfur that is fixed in upper ocean basement of 7-8 X 10 -8 molcm -2 yr -1 over 15m.y. This is comparable to that in open ocean sediment sites, but is one to two orders of magnitude less than for ocean margin sediments. The global annual subduction of sulfur in altered oceanic basalt lavas based on Hole 1256D is 1.5-2.0 X 10 11 moly -1 , comparable to the subduction of sulfide in sediments, and could contribute to sediment-like sulfur isotope heterogeneities in the mantle.

Earth and Planetary Science Letters↗
USGS2025

Triple-oxygen isotopic evidence of prolonged direct bioleaching of pyrite with O2

Sulfate is often touted as containing atmospheric oxygen whose isotopic signature can constrain redox, environmental conditions, and biological activity. Yet, the amount and isotopic fractionation associated with air-O 2 incorporation during sulfate formation is still debated, making its verification difficult. In this study, we identify a distinct, microbially dominated environment with the potential to preserve maximum signals of air-O 2 in sulfate. We report triple-oxygen isotope data for sulfate produced from pyrite oxidation in microbial and abiotic experiments, and from natural dissolved sulfate from the Rio Tinto, Spain, an acid mine drainage site. The oxygen isotope systematics of sulfate in these environments define a unique kinetic isotope effect associated with initial stage pyrite oxidation by Acidithiobacillus ferrooxidans that preserves >80 % oxygen from air-O 2 in sulfate. Unlike experiments, which evolve toward water-oxygen dominated sulfate on short time scales, Rio Tinto, Spain hosts a microbe rich environment with distinct geochemistry that maintains high O 2 -oxygen in sulfate. Therefore, in addition to containing isotopic records from water and air, sulfates can also contain a biosignature that is promising for understanding conditions on Mars and early Earth.

Earth and Planetary Science Letters↗
USGS2007

S-33 constraints on the seawater sulfate contribution in modern seafloor hydrothermal vent sulfides

Sulfide sulfur in mid-oceanic ridge hydrothermal vents is derived from leaching of basaltic-sulfide and seawater-derived sulfate that is reduced during high temperature water rock interaction. Conventional sulfur isotope studies, however, are inconclusive about the mass-balance between the two sources because 34S/32S ratios of vent fluid H2S and chimney sulfide minerals may reflect not only the mixing ratio but also isotope exchange between sulfate and sulfide. Here, we show that high-precision analysis of S-33 can provide a unique constraint because isotope mixing and isotope exchange result in different ??33S (?????33S-0.515 ??34S) values of up to 0.04??? even if ??34S values are identical. Detection of such small ??33S differences is technically feasible by using the SF6 dual-inlet mass-spectrometry protocol that has been improved to achieve a precision as good as 0.006??? (2??). Sulfide minerals (marcasite, pyrite, chalcopyrite, and sphalerite) and vent H2S collected from four active seafloor hydrothermal vent sites, East Pacific Rise (EPR) 9-10??N, 13??N, and 21??S and Mid-Atlantic Ridge (MAR) 37??N yield ??33S values ranging from -0.002 to 0.033 and ??34S from -0.5??? to 5.3???. The combined ??34S and ??33S systematics reveal that 73 to 89% of vent sulfides are derived from leaching from basaltic sulfide and only 11 to 27% from seawater-derived sulfate. Pyrite from EPR 13??N and marcasite from MAR 37??N are in isotope disequilibrium not only in ??34S but also in ??33S with respect to associated sphalerite and chalcopyrite, suggesting non-equilibrium sulfur isotope exchange between seawater sulfate and sulfide during pyrite precipitation. Seafloor hydrothermal vent sulfides are characterized by low ??33S values compared with biogenic sulfides, suggesting little or no contribution of sulfide from microbial sulfate reduction into hydrothermal sulfides at sediment-free mid-oceanic ridge systems. We conclude that 33S is an effective new tracer for interplay among seawater, oceanic crust and microbes in subseafloor hydrothermal sulfur cycles. ?? 2006 Elsevier Inc. All rights reserved.

Geochimica et Cosmochimica Acta↗
USGS2021

Development of soil radiocarbon profiles in a reactive transport framework

Today, there is a greater appreciation for the importance of the physical protection of carbon (C) through interactions with mineral surfaces, isolation from microbes, and the important role of transport in shaping soil properties and controlling moisture limitations on decomposition. As our paradigm for soil organic carbon (SOC) preservation changes, so too should our representation of the underlying processes in soil models. Reactive transport models (RTMs) provide a framework capable of assessing the interactive influence of soil chemistry and transport processes on the accumulation and turnover of SOC. In this study, we present new developments in the isotopically enabled RTM “CrunchTope,” which is capable of explicitly tracking the three isotopes of carbon ( 12 C, 13 C, and 14 C) and their fractionation between multiple coexisting and interacting solid, liquid and gas phases. This modeling framework opens the door to new applications of depth-resolved RTMs models in application to SOC and deeper subsurface carbon reservoirs. Here, we demonstrate SOC accumulation and radiocarbon aging for long-timescale models of soil development in CrunchTope. Our goal is to assess advantages and limitations of such an approach and to identify the type and complexity of reaction networks that are required to adequately apply this model to SOC dynamics. We assess the behavior of this model relative to a high-resolution dataset of SOC content, stable isotope composition, and radiocarbon ages as well as physical and hydrologic data measured from a chronosequence of soils located near Santa Cruz, California. Starting from a previously published model using a simplified reaction network with a single class of carbon, we sequentially incorporate multiple C reservoirs subject to both reactivity and transport pathways. Our results indicate that multiple SOC pools with different mean ages of C do not inherently emerge as a result of including reactions which are conventionally expected to provide a diversity of transit times, i.e., sorption and complexation of SOC on mineral surfaces. Instead, transit times emerge as a result of the timescales of the reactions represented in the reaction network. For mineral associated C, the RTM framework imposes dynamic equilibrium with the fluid phase dissolved organic C, such that no distinction in radiocarbon ages is achieved between these pools. Aged C can be produced by including a solid-phase C reservoir, with a rate-limited solubilization coefficient. Aging of SOC in this way is more akin to selective preservation than to mineral protection and, while such a mechanism may be at play in many soils, mineral protection is thought to be at least as important. As such, our results indicate that additional parameterization is required to reproduce the heterogeneity of carbon transit times that result from organo-mineral interactions. These efforts show the promise of a modeling approach where the varied transit time of soil C emerges from the dynamic physical and hydrologic properties of the model rather than from the a priori assignment of operationally defined pools.

Geochimica et Cosmochimica Acta↗
USGS2008

Distinguishing black carbon from biogenic humic substances in soil clay fractions

Most models of soil humic substances include a substantial component of aromatic C either as the backbone of humic heteropolymers or as a significant component of supramolecular aggregates of degraded biopolymers. We physically separated coarse (0.2–2.0 μm e.s.d.), medium (0.02–0.2 μm e.s.d.), and fine (> 0.02 μm e.s.d.) clay subfractions from three Midwestern soils and characterized the organic material associated with these subfractions using 13 C-CPMAS-NMR, DTG, SEM-EDX, incubations, and radiocarbon age. Most of the C in the coarse clay subfraction was present as discrete particles (0.2–5 μm as seen in SEM images) of black carbon (BC) and consisted of approximately 60% aromatic C, with the remainder being a mixture of aliphatic, anomeric and carboxylic C. We hypothesize that BC particles were originally charcoal formed during prairie fires. As the BC particles aged in soil their surfaces were oxidized to form carboxylic groups and anomeric and aliphatic C accumulated in the BC particles either by adsorption of dissolved biogenic compounds from the soil solution or by direct deposition of biogenic materials from microbes living within the BC particles. The biogenic soil organic matter was physically separated with the medium and fine clay subfractions and was dominated by aliphatic, anomeric, and carboxylic C. The results indicate that the biogenic humic materials in our soils have little aromatic C, which is inconsistent with the traditional heteropolymer model of humic substances.

Geoderma↗
USGS2012

Photodissolution of soil organic matter

Sunlight has been shown to enhance loss of organic matter from aquatic sediments and terrestrial plant litter, so we tested for similar reactions in mineral soil horizons. Losses of up to a third of particulate organic carbon occurred after continuous exposure to full-strength sunlight for dozens of hours, with similar amounts appearing as photodissolved organic carbon. Nitrogen dissolved similarly, appearing partly as ammonium. Modified experiments with interruption of irradiation to include extended dark incubation periods increased loss of total organic carbon, implying remineralization by some combination of light and microbes. These photodissolution reactions respond strongly to water content, with reaction extent under air-dry to fully wet conditions increasing by a factor of 3–4 fold. Light limitation was explored using lamp intensity and soil depth experiments. Reaction extent varied linearly with lamp intensity. Depth experiments indicate that attenuation of reaction occurs within the top tens to hundreds of micrometers of soil depth. Our data allow only order-of-magnitude extrapolations to field conditions, but suggest that this type of reaction could induce loss of 10–20% of soil organic carbon in the top 10 cm horizon over a century. It may therefore have contributed to historical losses of soil carbon via agriculture, and should be considered in soil management on similar time scales.

Geoderma↗
USGS2020

Coal biomethanation potential of various ranks from Pakistan: A possible alternative energy source

The present study investigated the possibility of microbial transformations of coal to gas (biogasification) as an alternative to conventional coal mining because this approach has the potential to be less expensive, cleaner, and providinge greater access to deeper coal resources. Biogasification is often associated with low rank coal such as lignite and subbituminous coal that hasve produced enough coalbed methane to be commercially viable in the United States and Australia. However, little work has been done to analyze the potential of biogasification in higher rank coal. For this purpose, bioassay using a wetland-derived consortium, and a coal-derived consortium were used to analyze coal samples from Pakistan belonging to different ranks (lignite to semi-anthracite). Among all samples a low volatile bituminous coal produced the maximum methane 34.95 µmol CH4/g coal with the wetland-derived microbial consortium, followed by subbituminous coal (30.18 µmol CH4/g coal). Lower methane levels were recorded with the coal-derived consortium, with subbituminous coal yielding the highest concentration (25.1 µmol CH4/g coal). Methane levels appeared to be increasing on the last measurement indicating the coal-derived consortium was slower than the wetland-derived consortium but could still catalyze biogasification in higher rank coals. Quantitative polymerase chain reaction analysis for mcrA functional genes suggested indicated that the microbial community members that produce methane (methanogens) varied during the incubations. Energy conversion efficiency of different strategies (other biological and underground coal gasification processes) was also compared and discussed. This study was the first to compare bioassay using consortia of microbes non-indigenous and indigenous to coal and indicate the potential of biogasification from many different coalbeds across Pakistan.

Article↗
USGS2014

Integration of stable carbon isotope, microbial community, dissolved hydrogen gas, and 2 H H 2 O tracer data to assess bioaugmentation for chlorinated ethene degradation in fractured rocks

An in situ bioaugmentation (BA) experiment was conducted to understand processes controlling microbial dechlorination of trichloroethene (TCE) in groundwater at the Naval Air Warfare Center (NAWC), West Trenton, NJ. In the BA experiment, an electron donor (emulsified vegetable oil and sodium lactate) and a chloro-respiring microbial consortium were injected into a well in fractured mudstone of Triassic age. Water enriched in 2 H was also injected as a tracer of the BA solution, to monitor advective transport processes. The changes in concentration and the δ 13 C of TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC); the δ 2 H of water; changes in the abundance of the microbial communities; and the concentration of dissolved H2 gas compared to pre- test conditions, provided multiple lines of evidence that enhanced biodegradation occurred in the injection well and in two downgradient wells. For those wells where the biodegradation was stimulated intensively, the sum of the molar chlorinated ethene (CE) concentrations in post-BA water was higher than that of the sum of the pre-BA background molar CE concentrations. The concentration ratios of TCE/(cis-DCE + VC) indicated that the increase in molar CE concentration may result from additional TCE mobilized from the rock matrix in response to the oil injection or due to desorption/diffusion. The stable carbon isotope mass-balance calculations show that the weighted average 13 C isotope of the CEs was enriched for around a year compared to the background value in a two year monitoring period, an effective indication that dechlorination of VC was occurring. Insights gained from this study can be applied to efforts to use BA in other fractured rock systems. The study demonstrates that a BA approach can substantially enhance in situ bioremediation not only in fractures connected to the injection well, but also in the rock matrix around the well due to processes such as diffusion and desorption. Because the effect of the BA was intensive only in wells where an amendment was distributed during injection, it is necessary to adequately distribute the amendments throughout the fractured rock to achieve substantial bioremediation. The slowdown in BA effect after a year is due to some extend to the decrease abundant of appropriate microbes, but more likely the decreased concentration of electron donor.

New Jersey↗
USGS2015

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

Natural hydrate-bearing sediments from the Nankai Trough, offshore Japan, were studied using the Pressure Core Characterization Tools (PCCTs) to obtain geomechanical, hydrological, electrical, and biological properties under in situ pressure, temperature, and restored effective stress conditions. Measurement results, combined with index-property data and analytical physics-based models, provide unique insight into hydrate-bearing sediments in situ. Tested cores contain some silty-sands, but are predominantly sandy- and clayey-silts. Hydrate saturations S h range from 0.15 to 0.74, with significant concentrations in the silty-sands. Wave velocity and flexible-wall permeameter measurements on never-depressurized pressure-core sediments suggest hydrates in the coarser-grained zones, the silty-sands where S h exceeds 0.4, contribute to soil-skeletal stability and are load-bearing. In the sandy- and clayey-silts, where S h < 0.4, the state of effective stress and stress history are significant factors determining sediment stiffness. Controlled depressurization tests show that hydrate dissociation occurs too quickly to maintain thermodynamic equilibrium, and pressure–temperature conditions track the hydrate stability boundary in pure-water, rather than that in seawater, in spite of both the in situ pore water and the water used to maintain specimen pore pressure prior to dissociation being saline. Hydrate dissociation accompanied with fines migration caused up to 2.4% vertical strain contraction. The first-ever direct shear measurements on never-depressurized pressure-core specimens show hydrate-bearing sediments have higher sediment strength and peak friction angle than post-dissociation sediments, but the residual friction angle remains the same in both cases. Permeability measurements made before and after hydrate dissociation demonstrate that water permeability increases after dissociation, but the gain is limited by the transition from hydrate saturation before dissociation to gas saturation after dissociation. In a proof-of-concept study, sediment microbial communities were successfully extracted and stored under high-pressure, anoxic conditions. Depressurized samples of these extractions were incubated in air, where microbes exhibited temperature-dependent growth rates.

Journal of Marine and Petroleum Geology↗
USGS2026

Evidence for a biological origin of uranium-rich carbon masses within the Ediacaran Salt Range Formation of Pakistan

Thucholites are unique organic structures found in igneous and sedimentary rocks composed of a U-C-rich interior enclosed by an organic outer shell. Their formation and occurrence have perplexed scientists for over 100 years. Typically, thucholites are sparse in sedimentary rocks but where found in abundance, they may be the result of rapid paleoecological disruptions, e.g., volcanic ashfall. Here, we evaluated thucholites from the Ediacaran Salt Range Formation of the Indus Basin in Pakistan using field emission scanning electron microscopy (FESEM) and nanoscale secondary ion mass spectroscopy (NanoSIMS) to propose a two-stage mechanism for thucholite development. NanoSIMS results suggest organic matter in thucholite cores formed by biological fractionation (represented by the presence of lighter 13 C/ 12 C and 34 S/ 32 S) while the outer organic mantle formed via radiolysis-induced polymerization. FESEM elemental analysis confirms compositional differences between the two thucholite components (core and mantle), further implying their contrasting origins. Dimensional comparison of thucholite cores and their U-bearing mineral morphologies to ancient and modern U-biomineralized microbes suggests that the thucholite cores formed from metal-biological interactions. The presence of volcanogenic biotite, alkali feldspar, and clay spherules (interpreted as devitrified volcanic glass) with thucholite suggests that the thucholite cores in the Salt Range Formation are biological responses to rapid paleoenvironmental change from volcanic eruption which preserved the fossilized morphologies of Proterozoic microorganisms.

Salt Range↗
USGS2014

Sapronosis: a distinctive type of infectious agent

Sapronotic disease agents have evolutionary and epidemiological properties unlike other infectious organisms. Their essential saprophagic existence prevents coevolution, and no host–parasite virulence trade-off can evolve. However, the host may evolve defenses. Models of pathogens show that sapronoses, lacking a threshold of transmission, cannot regulate host populations, although they can reduce host abundance and even extirpate their hosts. Immunocompromised hosts are relatively susceptible to sapronoses. Some particularly important sapronoses, such as cholera and anthrax, can sustain an epidemic in a host population. However, these microbes ultimately persist as saprophages. One-third of human infectious disease agents are sapronotic, including nearly all fungal diseases. Recognition that an infectious disease is sapronotic illuminates a need for effective environmental control strategies.

Trends in Parasitology↗
USGS2015

Biogeochemical environments of streambed-sediment pore waters with and without arsenic enrichment in a sedimentary rock terrain, New Jersey Piedmont, USA

Release of arsenic (As) from sedimentary rocks has resulted in contamination of groundwater in aquifers of the New Jersey Piedmont Physiographic Province, USA; the contamination also may affect the quality of the region's streamwater to which groundwater discharges. Biogeochemical mechanisms involved in the release process were investigated in the streambeds of Six Mile Run and Pike Run, tributaries to the Millstone River in the Piedmont. At Six Mile Run, streambed pore water and shallow groundwater were low or depleted in oxygen, and contained As at concentrations greater than 20 μg/L. At Pike Run, oxidizing conditions were present in the streambed, and the As concentration in pore water was 2.1 μg/L. The 16S rRNA gene and the As(V) respiratory reductase gene, arrA , were amplified from DNA extracted from streambed pore water at both sites and analyzed, revealing that distinct bacterial communities that corresponded to the redox conditions were present at each site. Anaerobic enrichment cultures were inoculated with pore water from gaining reaches of the streams with acetate and As(V). As(V) was reduced by microbes to As(III) in enrichments with Six Mile Run pore water and groundwater, whereas no reduction occurred in enrichments with Pike Run pore water. Cloning and sequencing of the arrA gene indicated 8 unique operational taxonomic units (OTUs) at Six Mile Run and 11 unique OTUs at Pike Run, which may be representative of the arsenite oxidase gene arxA . Low-oxygen conditions at Six Mile Run have favored microbial As reduction and release, whereas release was inhibited by oxidizing conditions at Pike Run.

New Jersey↗
USGS2017

Virulence and biodegradation potential of dynamic microbial communities associated with decaying Cladophora in Great Lakes

Cladophora mats that accumulate and decompose along shorelines of the Great Lakes create potential threats to the health of humans and wildlife. The decaying algae create a low oxygen and redox potential environment favoring growth and persistence of anaerobic microbial populations, including Clostridium botulinum , the causal agent of botulism in humans, birds, and other wildlife. In addition to the diverse population of microbes, a dynamic chemical environment is generated, which involves production of numerous organic and inorganic substances, many of which are believed to be toxic to the sand and aquatic biotic communities. In this study, we used 16S-rDNA-based-amplicon sequencing and microfluidic-based quantitative PCR approaches to characterize the bacterial community structure and the abundances of human pathogens associated with Cladophora at different stages (up to 90 days) of algal decay in laboratory microcosms. Oxygen levels were largely depleted after a few hours of incubation. As Cladophora decayed, the algal microbial biodiversity decreased within 24 h, and the mat transitioned from an aerobic to anaerobic environment. There were increasing abundances of enteric and pathogenic bacteria during decomposition of Cladophora , including Acinetobacter , Enterobacter , Kluyvera , Cedecea , and others. In contrast, there were no or very few sequences (< 0.07%) assigned to such groups in fresh Cladophora samples. Principal coordinate analysis indicated that the bacterial community structure was dynamic and changed significantly with decay time. Knowledge of microbial communities and chemical composition of decaying algal mats is critical to our further understanding of the role that Cladophora plays in a beach ecosystem's structure and function, including the algal role in trophic interactions. Based on these findings, public and environmental health concerns should be considered when decaying Cladophora mats accumulate Great Lakes shorelines.

Great Lakes↗