Initial Abundance Research Articles

The initial solar system abundance of 60Fe and early core formation of the first asteroids.

High-precision Ni isotope analyses of the differentiated andesitic meteorite Erg Chech 002 (EC 002), the oldest known crustal fragment of a planetesimal, show that short-lived 60Fe was present in the early solar system with an initial 60Fe/56Fe ratio of (7.71 ± 0.47) × 10-9, which is five times more precise than previous estimates and is proposed to be the reference value for further studies. Using this ratio, the Ni isotopic composition of EC 002 implies that metal segregation in the source of the EC 002 parental melts took place [Formula: see text] million years (Myr) after solar system formation, and similar very early metal-silicate differentiation ages are obtained for 4-Vesta ([Formula: see text] Myr) and the angrite parent body ([Formula: see text] Myr). Such an early age dictates a specific accretion and differentiation history for the EC 002 parent body, with metal segregation occurring at relatively low temperatures (1000° to 1200°C), followed by a high-temperature silicate melting event.

Genome-wide conditional degron libraries for functional genomics.

Functional genomics with libraries of knockout alleles is limited to non-essential genes and convoluted by the potential accumulation of suppressor mutations in knockout backgrounds, which can lead to erroneous functional annotations. To address these limitations, we constructed genome-wide libraries of conditional alleles based on the auxin-inducible degron (AID) system for inducible degradation of AID-tagged proteins in the budding yeast Saccharomyces cerevisiae. First, we determined that N-terminal tagging is at least twice as likely to inadvertently impair protein function across the proteome. We thus constructed two libraries with over 5,600 essential and non-essential proteins fused at the C-terminus with an AID tag and an optional fluorescent protein. Approximately 90% of AID-tagged proteins were degraded in the presence of the auxin analog 5-Ph-IAA, with initial protein abundance and tag accessibility as limiting factors. Genome-wide screens for DNA damage response factors revealed a role for the glucose signaling factor GSF2 in resistance to hydroxyurea, highlighting how the AID libraries extend the yeast genetics toolbox.

Advancing dental biofilm models: the integral role of pH in predicting S. mutans colonization.

Mathematical models can provide insights into complex interactions and dynamics within microbial communities to complement and extend experimental laboratory approaches. For dental biofilms, they can give a basis for evaluating biofilm growth or the transition from health to disease. We have developed mathematical models to simulate the transition toward a cariogenic microbial biofilm, modeled as the overgrowth of Streptococcus mutans within a five-species dental community. This work builds on experimental data from a continuous flow reactor with hydroxyapatite coupons for biofilm growth, in a chemically defined medium with varying concentrations of glucose and lactic acid. The biofilms formed on the coupons were simulated using individual-based models (IbMs), with bacterial growth modeled using experimentally measured kinetic parameters. The IbM assumes that the maximum theoretical growth yield for biomass is dependent on the local concentration of reactants and products, while the growth rates were described using traditional Monod equations. We have simulated all the conditions studied experimentally, considering different initial relative abundance of the five species, and also different initial clustering in the biofilm. The simulation results only reproduced the experimental dominance of S. mutans at high glucose concentration after we considered the species-specific effect of pH on growth rates. This highlights the significance of the aciduric property of S. mutans in the development of caries. Our study demonstrates the potential of combining in vitro and in silico studies to gain a new understanding of the factors that influence dental biofilm dynamics.IMPORTANCEWe have developed in silico models able to reproduce the relative abundance measured in vitro in the synthetic dental biofilm communities growing in a chemically defined medium. The advantage of this combination of in vitro and in silico models is that we can study the influence of one parameter at a time and aim for direct validation. Our work demonstrates the utility of individual-based models for simulating diverse conditions affecting dental biofilm scenarios, such as the frequency of glucose intake, sucrose pulsing, or integration of pathogenic or probiotic species. Although in silico models are reductionist approaches, they have the advantage of not being limited in the scenarios they can test by the ethical consideration of an in vivo system, thus significantly contributing to dental biofilm research.

Gravitational waves from primordial black hole isocurvature: the effect of non-Gaussianities

Ultra-light primordial black holes (PBHs) with masses M PBH < 5 × 108g can dominate transiently the energy budget of the Universe and reheat the Universe through their evaporation taking place before Big Bang Nucleosynthesis. The isocurvature energy density fluctuations associated to the inhomogeneous distribution of a population of such PBHs can induce an abundant production of GWs due to second-order gravitational effects. In this work, we discuss the effect of primordial non-Gaussianity on the clustering properties of PBHs and study the effect of a clustered PBH population on the spectral shape of the aforementioned induced GW signal. In particular, focusing on local-type non-Gaussianity we find a double-peaked GW signal with the amplitude of the low-frequency peak being proportional to the square of the non-Gaussian parameter τ NL. Remarkably, depending on the PBH mass M PBH and the initial abundance of PBHs at formation time, i.e. ΩPNH,f, this double-peaked GW signal can lie well within the frequency bands of forthcoming GW detectors, namely LISA, ET, SKA and BBO, hence rendering this signal falsifiable by GW experiments and promoting it as a novel portal probing the primordial non-Gaussianity.

Oxide-Metal Transition Processes of CuxO Foams during CO2RR Probed by Operando Quick-XAS

Electrochemical CO2 reduction reaction (CO2RR) is a promising alternative for large-scale production of hydrocarbons. However, there are still some challenges including poor product selectivity and highly complex multiple-step reaction mechanisms.[1,2] To enhance the electrochemically active surface area and create more active surface sites, one of the promising approaches is the use of partial or complete (surface) oxidation of nanostructured copper materials. These Cu oxide precursor catalyst materials are not stable during the cathodic potentials applied for CO2RR, but still show an enhanced selectivity for the formation of C2+ products.[3,4] Interestingly, few studies proposed that oxygen can be present under CO2RR conditions in a few nm thick amorphous copper layer, while DFT calculations indicate that no subsurface oxygen remains thermodynamically stable at these highly cathodic potentials.[5-7] So far, only Valesco-Vélez et al. studied the Cu oxidation state changes (Cu2+ and Cu+ to metallic Cu) during CO2RR in CO2-saturated 0.1 M KHCO3 probed by operando X-ray absorption spectroscopy (XAS).[8] However, for pure CuO no reduction to metallic copper or Cu2O even at highly cathodic conditions is found, due to the formation of a copper carbonate passivation layer.[8] Thus, it is still poorly understood how the structure of the Cu/CuxO precursor materials and their simultaneous reduction processes to metallic copper influence the CO2RR product distribution and the overpotential required for hydrocarbon formation. Recently, we have shown the critical potential of oxide-metal transition processes for a Cu oxide foam annealed at 300 °C in air probed by operando XAS, X-ray diffraction (XRD), and Raman spectroscopy techniques.[9,10]Using Cu K-edge Quick-XAS technique, we aim to understand the potential-dependent reduction of different Cu2+:Cu+ ratios to Cu0 for nanoporous CuxO foam precursor catalysts under CO2RR conditions. The CuxO foams were prepared by electrodeposition and subsequent thermal annealing between 100 and 450 °C in air to generate the different Cu2+:Cu+:Cu0 ratios. Initially, from ex-situ XANES, XRD, and XPS analyses, we found that a rise in annealing temperature leads to an increase in the proportion of Cu2+ species and their degree of crystallinity within the CuxO foams. After annealing at 100 °C and 200 °C, the CuO phase/species are amorphous and mainly found at the surface of the foam. Once the annealing temperature reaches 300 °C or higher, the CuO phase is entirely crystalline.With these different chemical states of the precursor catalyst, the Cu oxide-metal transition kinetics during cathodic potential increment (ΔE = 100 mV), step (ΔE > 100 mV), and jump (ΔE > 500 mV) experiments in CO2-saturated 0.5 M KHCO3 were comprehensively investigated using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) and Linear Combination Fit (LCF) analyses of the operando Cu K-edge Quick-XANES data. Our results demonstrate that different oxide-metal transition kinetics were found strongly dependent on the initial abundance of Cu2+ species and precursor structure (ordered vs. amorphous) as well as on the applied potential protocol to the CuxO foam precursor catalysts. More precisely, a high initial population of crystalline CuO, which is found for the CuxO foams annealed at 300 °C and 450 °C, leads to a significant shift of the oxide-metal transition potential towards lower cathodic overpotentials. For example, for the CuxO foam annealed at 450 °C (rich in crystalline CuO phases) the oxide-metal transition potential is shifted to 0 VRHE, while for the foam annealed at 100 °C this transition occurs at – 0.6 VRHE. Furthermore, smaller potential increments increase the formation and accumulation of Cu+ species, thereby slowing down the reduction kinetics. For the CuxO foam annealed at 200 °C, we could observe a full reduction to metallic Cu if jumping from OCP directly to – 0.5 VRHE, whereas no full reduction took place if using incremental potentials before applying – 0.5 VRHE.Overall, we show the substantial influence of crystalline CuOand the applied potential protocol on the reduction of CuxO foam precursor materials to metallic Cu during CO2RR.

The Effect of Grazing on Central Anatolian Steppe Vegetation: A Modeling Approach Using Functional Traits.

Grazing is a major ecological driver that influences vegetation dynamics globally. We investigated the long-term effects of different grazing regimes on the vegetation structure of the Central Anatolian steppes, a region characterized by its unique convergence of biogeographical influences and historical land use. We employed the spatially explicit FATELAND model to simulate vegetation dynamics over a 50-year period under three distinct grazing scenarios: no grazing, moderate grazing, and overgrazing. Our simulations incorporated a range of plant functional traits to predict changes across five different vegetation types in Central Anatolia, including woodland steppes and treeless steppes. The simulations revealed that moderate grazing supports the diversity and abundance of various plant functional groups, excluding resprouter trees, which flourish under no grazing conditions. In contrast, overgrazing leads to significant reductions in the abundance of perennial forbs and both spiny and non-spiny subshrubs, often resulting in a shift toward grassland dominated by resprouter gramineae or an annual herb-dominated grassland, depending on the initial abundance of gramineae. Our findings highlight the critical role of grazing management in maintaining biodiversity and ecological stability in steppe ecosystems. While moderate grazing can enhance plant functional group diversity, overgrazing significantly threatens the ecological integrity of the Central Anatolian steppes. In conclusion, our modeling approach reveals that the grazing regime is a major driver in shaping the vegetation structure of Central Anatolian steppes. Grazing management strategies that are adjusted to the ecological characteristics and historical context of specific regions are required to prevent degradation and promote sustainable grassland vegetation.

Assessing the oral microbiome of head and neck cancer patients before and during radiotherapy.

To characterize the oral microbiome of patients with head and neck squamous cell carcinoma (HNSCC) before and during radiotherapy (RT), compared to healthy individuals. Evaluating the impact of oral microbiome in the clinical outcomes one year following the end of RT. Oral samples were collected from HNSCC patients who underwent RT using the following regimens: no dose received (T0), dose 12-16Gy (T1), dose 30-36Gy (T2) and dose ≥ 60Gy (T3). Samples from healthy individuals were also collected only once as a control group. Regions V1-V2 of the 16S rRNA were sequenced by Illumina and analyzed using Mothur. 49 patients with HNSCC and 25 healthy individuals were included. At T0, HNSCC patients showed a lower abundance of Firmicutes and Streptococcus (p = 0.011, p = 0.002) and a higher abundance of Bacteroidetes (p = 0.005) compared to healthy individuals. During RT, Fusobacterium (p = 0.017) and Porphyromonas (p = 0.0008) decreased, while Streptococcus increased at T1 (p = 0.001). By T3, the differences in Firmicutes, Bacteroidetes, and Streptococcus between the control and HNSCC groups were no longer significant (p > 0.3). Patients with higher initial abundances of Porphyromonas (p = 0.012) and Fusobacterium (p = 0.017) had poorer outcomes, including recurrence, metastasis, and death. In contrast, disease-free patients had a higher abundance of Streptococcus (p = 0.004). Oral microbiome dysbiosis was found in HNSCC patients. By the end of RT, the main initial differences in phylum and genus abundance observed at T0 between the control and HNSCC groups were no longer present. Higher abundances of Fusobacterium and Porphyromonas were associated with poor outcomes.

Complex interactions of deer herbivory, soil chemistry, and competing vegetation explain oak–hickory forest tree regeneration in central Pennsylvania, USA

The root causes of forest tree regeneration failure are difficult to resolve, although numerous studies show ungulate herbivory, soil conditions, and competition from undesirable vegetation as likely contributors. To better understand the relative importance of each issue, we conducted a 7-year manipulative experiment to assess the interactive effects of white-tailed deer ( Odocoileus virginianus) herbivory, soil acidity, and competing vegetation on tree regeneration in oak–hickory forests of central Pennsylvania, USA. Outcomes depended on initial tree seedling abundance, and all three factors had significant interactions. At low initial seedling abundance, fencing resulted in the greatest increase, but all treatments had a positive effect on seedling growth and abundance. At higher initial seedling abundance, abundance failed to recover 7 years after herbicide treatment and soil pH was an important predictor. When soil pH was &gt;4.6 from lime application, seedling growth and abundance in unfenced controls with high initial abundance was comparable to the fenced-only treatment. Competing vegetation, assumed to be a symptom of excessive, long-term deer herbivory, does not seem to be the primary factor limiting tree regeneration in our study area. Ameliorating acid deposition warrants greater consideration as a management action because it could provide long-lasting benefits compared to short-term fence installations.

Metabolic interactions shape emergent biofilm structures in a conceptual model of gut mucosal bacterial communities

The gut microbiome plays a major role in human health; however, little is known about the structural arrangement of microbes and factors governing their distribution. In this work, we present an in silico agent-based model (ABM) to conceptually simulate the dynamics of gut mucosal bacterial communities. We explored how various types of metabolic interactions, including competition, neutralism, commensalism, and mutualism, affect community structure, through nutrient consumption and metabolite exchange. Results showed that, across scenarios with different initial species abundances, cross-feeding promotes species coexistence. Morphologically, competition and neutralism resulted in segregation, while mutualism and commensalism fostered high intermixing. In addition, cooperative relations resulted in community properties with little sensitivity to the selective uptake of metabolites produced by the host. Moreover, metabolic interactions strongly influenced colonization success following the invasion of newcomer species. These results provide important insights into the utility of ABM in deciphering complex microbiome patterns.

The solar beryllium abundance revisited with 3D non-LTE models

The present-day abundance of beryllium in the solar atmosphere provides clues about mixing mechanisms within stellar interiors. However, abundance determinations based on the Be II313.107 nm line are prone to systematic errors due to imperfect model spectra. These errors arise from missing continuous opacity in the UV, a significant unidentified blend at 313.102 nm, departures from local thermodynamic equilibrium (LTE), and microturbulence and macroturbulence fudge parameters associated with one-dimensional (1D) hydrostatic model atmospheres. Although these factors have been discussed in the literature, no study has yet accounted for all of them simultaneously. To address this, we present 3D non-LTE calculations for neutral and ionised beryllium in the Sun. We used these models to derive the present-day solar beryllium abundance, calibrating the missing opacity on high resolution solar irradiance data and the unidentified blend on the centre-to-limb variation. We find a surface abundance of 1.21 ± 0.05 dex, which is significantly lower than the value of 1.38 dex that has been commonly adopted since 2004. Taking the initial abundance via CI chondrites, our result implies that beryllium has been depleted from the surface by an extra 0.11 ± 0.06 dex, or 22 ± 11%, on top of any effects of atomic diffusion. This is in tension with standard solar models, which predict negligible depletion, as well as with contemporary solar models that have extra mixing calibrated on the abundances of helium and lithium, which predict excessive depletion. These discrepancies highlight the need for further improvements to the physics in solar and stellar models.

Recent replenishment of aliphatic organics on Ceres from a large subsurface reservoir.

Ceres hosts notable aliphatic-organic concentrations, ranging from approximately 5 to >30 weight % in specific surface areas. The origins and persistence of these organics are under debate due to the intense aliphatic organic signature and radiation levels in Ceres' orbit, which would typically lead to their destruction, hindering detection. To investigate this, we conducted laboratory experiments to replicate how the signature of the organic-rich regions would degrade due to radiation. Our findings indicate a fast degradation rate, implying the exposure of buried organics within the past few million years. This degradation rate, coupled with observed quantities, implies that the aliphatics must be present in substantial quantities within the shallow subsurface. Our estimates suggest an initial aliphatic abundance 2 to 30 times greater than currently observed, surpassing significantly the levels found in carbonaceous chondrites, indicating either a significant concentration or remarkable purity.

Flow-based Generative Emulation of Grids of Stellar Evolutionary Models

We present a flow-based generative approach to emulate grids of stellar evolutionary models. By interpreting the input parameters and output properties of these models as multidimensional probability distributions, we train conditional normalizing flows to learn and predict the complex relationships between grid inputs and outputs in the form of conditional joint distributions. Leveraging the expressive power and versatility of these flows, we showcase their ability to emulate a variety of evolutionary tracks and isochrones across a continuous range of input parameters. In addition, we describe a simple Bayesian approach for estimating stellar parameters using these flows and demonstrate its application to asteroseismic data sets of red giants observed by the Kepler mission. By applying this approach to red giants in open clusters NGC 6791 and NGC 6819, we illustrate how large age uncertainties can arise when fitting only to global asteroseismic and spectroscopic parameters without prior information on initial helium abundances and mixing length parameter values. We also conduct inference using the flow at a large scale by determining revised estimates of masses and radii for 15,388 field red giants. These estimates show improved agreement with results from existing grid-based modeling, reveal distinct population-level features in the red clump, and suggest that the masses of Kepler red giants previously determined using the corrected asteroseismic scaling relations have been overestimated by 5%–10%.

Negative plant–soil feedback influences a dominant seeded species, Western yarrow (Achillea millefolium), in grassland restoration

Plant community ecology guides restoration of degraded lands, yet seed‐based restorations sometimes fail or result in unpredictable outcomes, necessitating a better understanding of community trajectory and stability. Western yarrow (Achillea millefolium) declined suddenly in two separate restoration projects after initial high relative abundance. To assess the potential role of soil pathogens, we surveyed plant and soil fungal communities in these restorations, and used an 8‐year‐old field experiment that crossed yarrow planted in varying densities with a fungicide treatment. Two greenhouse experiments then evaluated whether the suppressive effect in yarrow soil spread to native species used in restoration. Lower yarrow cover in a restoration project 5 years compared to 3 years after seeding coincided with higher relative abundance of fungal taxa that can cause disease, particularly Crown‐rot fungi (Paraphoma spp.). Paraphoma increased over time in experimental plots and coincided with yarrow decline. Decline onset was density‐dependent, occurring faster in plant communities where yarrow density was higher. Fungicide applications altered fungal pathogen communities and promoted yarrow cover relative to control plots. In the greenhouse, yarrow grew larger with fungicide, consistent with suppression of fungal pathogens. However, biomass of natives grown in yarrow‐conditioned soil was not affected by fungicides, suggesting pathogens did not spread. The rapid establishment and competitive nature of yarrow, followed by pathogen‐induced decline, make it an attractive early transitional “bridge species,” so long as its pathogens are species‐specific. Our results suggest negative plant‐soil feedback can drive rapid decline of individual species, and considering plant–soil feedback could improve restoration predictability.

Evolutionary Dynamics of a Two-Stage Population with Density-Dependent Regulation of the Survival of Reproductive Individuals

The paper studies an evolutionary model of natural selection in a two-stage population with autoregulation of the survival of adult individuals. The population breeds seasonally, and we assume that reproductive potential is determined genetically. The proposed ecological-genetic model is a combination of an ecological model of the dynamics of a stage-structured population and a microevolutionary model of the dynamics of its genetic structure when the adaptive trait of birth rate is controlled by a single diallelic autosomal locus with allelomorphs A and a. We study the proposed model analytically and numerically and determine the parametric regions with different dynamic behaviors. We consider the possibility of changing the dynamic mode due to a variation in the genetic composition of the population. The study shows the genetic composition of the population, namely, whether will it be polymorphic or monomorphic, is mainly determined by the values of the reproductive potentials of heterozygotes and homozygotes. Reduced fitness of the heterozygotes leads to a “bistability trap” when both monomorphic fixed points are attractive, and the initial abundances of stage classes and allele frequencies determine the genotype that will be fixed in the population. However, with density-dependent regulation of the survival of adult individuals, displacement of one of the alleles can lead to the extinction of the population. In general, a change in the direction of evolution may be accompanied by a change in the population dynamics mode.

Population response of eastern wild turkey to removal of wild pigs

AbstractThere is insufficient understanding of interspecific interactions with the eastern wild turkey (Meleagris gallopavo silvestris) and wild pigs (Sus scrofa). Wild pigs compete with wild turkeys and predate nests and adults; however, population‐level effects on wild turkeys are not clear. Using cameras, we assessed responses of wild turkey populations to wild pig removal in central Alabama, USA, from 2018–2021. We compared wild turkey relative abundance and occupancy on 3 large‐scale pig‐removal treatment sites (3,407–5,531 ha) relative to a control site (2,510 ha) during 1 pre‐treatment year and 2 post‐treatment years, with analyses including a covariate expressing the cumulative number of pigs removed from each site standardized by the initial pig abundance on the site. We removed 1,851 wild pigs from the 3 treatment sites over 22 months. Based on N‐mixture modeling, when the number of pigs removed was equal to our baseline population estimates (i.e., 100% removal relative to initial population), there were 1.50 (95% CL = 1.01–2.23) times as many wild turkeys, and detection of wild turkeys was 2.01 (95% CL = 1.49–2.70) times as likely. Additionally, poults were 3.49 (95% CL = 1.12–10.89) times as likely to occupy an area when the number of pigs removed was equal to our baseline population estimates compared with poult occupancy at baseline pig abundance. Our data suggests that reduction of wild pig populations may lead to a localized increase in populations of wild turkeys.

HIDALGO: A FUN object from the earliest epoch of the solar system’s history

Chemical and isotopic measurements of HIDALGO, a stoichiometrically pure hibonite inclusion found in the matrix of the Dar al Gani 027 meteorite, were conducted by secondary ion mass spectrometry to investigate its origin and evolution. HIDALGO is characterized by large mass-dependent isotope fractionations in O, Ca, and Ti, as well as large negative anomalies in neutron-rich 48Ca and 50Ti, making it the newest member of the HAL-type FUN inclusions. The highly fractionated Ca and Ti isotopes but unfractionated Mg isotopes are consistent with HIDALGO being a residue from an extensive evaporation event, during which large fractions of initial Ca and Ti, and essentially all the initial Mg, in the precursor material were lost. HIDALGO appears to have incorporated live 26Al at a higher level than other HAL-type inclusions, but still at a lower amount compared to the Solar System’s initial 26Al abundance typically found in non-FUN CAIs. Interestingly, the inferred 10Be abundance in HIDALGO is comparable to the values observed in the majority of CV3 CAIs but ∼ 2.5 times higher than those in HAL-type samples. HIDALGO’s unusual 26Al/27Al and 10Be/9Be ratios, together with the 48Ca-50Ti anomalies, can be best explained by the formation of its precursor material in the isotopically heterogeneous solar nebula. Finally, large 7Li excesses correlating with Be/Li were found in HIDALGO, a behavior that can be interpreted as due to in-situ decay of live 7Be. Charged particle spallation of initially Li-free HIDALGO can simultaneously account for the inferred 7Be abundance and the measured Li elemental concentration. The consistency between the measurement and spallation calculation results provides support for the prior existence of 7Be in HIDALGO, possibly produced by irradiation close to the Sun.

Single-/Co-Driving of Tetracycline, Triclocarban and Zinc on Microbial Community, Resistome and Function in the Cyanobacteria-Blooming Freshwater Ecosystem.

Environmental concentrations of antimicrobials can inhibit Cyanobacteria, but little is known about their effects on Cyanobacteria-blooming freshwater ecosystem. Here, a 21 days' outdoor freshwater mesocosm experiment was established to study effects of single and combined tetracycline, triclocarban and zinc at environmental concentrations on microbial community, microbial function and antimicrobial resistance using amplicon- and metagenomic-based methods. Results showed that three chemicals reshaped the microbial community with magnified effects by chemical combinations. Relative abundance of Cyanobacteria was decreased in all chemical groups, especially from 74.5 to 0.9% in combination of three chemicals. Microbial community networks were more simplified after exposure. Proteobacteria and Bacteroidetes predominated in Cyanobacteria-degraded ecosystems, and their relative abundances were significantly correlated with antibiotic resistome, suggesting that they might host antibiotic resistance genes. Notably, relative abundance (copy per 16S rRNA gene) of total antibiotic resistome reached five to nine folds higher than the initial abundance in chemical-combined groups. The affected antibiotic resistance genes referred to a wide range of antibiotic classes. However, weak effects were detected on biocide/metal resistance and microbial virulence. Three chemicals posed complicated effects on microbial function, some of which had consistent variations across the groups, while some varied greatly in chemical groups. The findings highlight sensitivity of Cyanobacteria-blooming ecosystem to antimicrobials.

Investigating the response of the butyrate production potential to major fibers in dietary intervention studies

Interventions involving dietary fibers are known to benefit host health. A leading contribution of gut microbiota is commonly recognized with production of short chain fatty acids (SCFA) suspected to play a key role. However, the detailed mechanisms are largely unknown, and apart from a well-described bifidogenic effect of some fibers, results for other bacterial taxa are often incongruent between studies. We performed pooled analyses of 16S rRNA gene data derived from intervention studies (n = 14) based on three fibers, namely, inulin-type fructans (ITF), resistant starch (RS), and arabinoxylan-oligosaccharides (AXOS), harmonizing the bioinformatics workflow to reveal taxa stimulated by those substrates, specifically focusing on the SCFA-production potential. The results showed an increased butyrate production potential after ITF (p < 0.05) and RS (p < 0.1) treatment via an increase in bacteria exhibiting the enzyme butyryl-CoA:acetate CoA-transferase (but) that was governed by Faecalibacterium, Anaerostipes (ITF) and Agathobacter (RS) respectively. AXOS did not promote an increase in butyrate producers, nor were pathways linked to propionate production stimulated by any intervention. A bifidogenic effect was observed for AXOS and ITF, which was only partly associated with the behavior of but-containing bacteria and largely represented a separate response. Low and high Ruminococcus abundances pre-intervention for ITF and RS, respectively, promoted an increase in but-containing taxa (p < 0.05) upon interventions, whereas initial Prevotella abundance was negatively associated with responses of butyrate producers for both fibers. Collectively, our data demonstrate targeted stimulation of specific taxa by individual fibers increasing the potential to synthesize butyrate, where gut microbiota composition pre-intervention strongly controlled outcomes.

Magnesium Isotopes Archive the Initial Carbonate Abundances of Metasedimentary Rocks Prior to Thermal Decarbonation

AbstractInvestigating the carbonate preservation efficiency (CPE) of continental crust is crucial to understand the global carbon cycle, which requires constraints on initial carbonate abundances (ICAs) of crustal rocks. To link Mg isotopes to ICAs, we present elemental and Mg isotopic data for Himalayan carbonate‐bearing and carbonate‐free metasedimentary rocks. Given no evident melt extraction or external‐fluid infiltration, ICAs of these samples can be independently estimated by elemental data. Despite different carbonate species in the protoliths, all the samples show congruent relationship between their δ26Mg and ICAs, owing to the elevated carbonate δ26Mg and Mg/Ca in protoliths of calcite‐rich samples resulting from diagenetic processes. When collated with literature data, we suggest the observed correlation here can be applied to most carbonate‐bearing (meta‐)sedimentary rocks. Based on a steady state box‐model, we constrained the modern net carbonate accretion flux ( Tmol/year) and the average time‐integrated CPE (∼%) for continental crust.

The enrichment of antibiotic resistance genes in swine manure compost was related to the bulking agent types

Composting is a major method to produce organic fertilizers, and the variation in antibiotic resistance genes (ARGs) during composting is crucial for the safe utilization of mature compost. The effects of different bulking agents (cellulose-rich cornstalk and lignin-rich garden waste) on ARGs variations during swine manure composting were investigated. The results showed that composting thermophilic could effectively reduce ARGs (58–61 %), whereas ARGs rebounded and were enriched with decreasing temperature during the maturation stage. Compared to their initial abundance, ARGs were enriched 6.97 times (cornstalk) and 22.27 times (garden waste) during the maturation period. The ARGs enrichment mechanism in swine manure composting differed for cornstalk and garden waste amendments. The cornstalk was used as the bulking agent, the selective pressure of continuous high temperature resulted in the proliferation of spore-forming bacteria (Bacillus, Sporosarcina and Psychrobacillus), which are potential host bacteria of ARGs and cause ARGs enrichment through vertical gene proliferation. In the garden waste treatment, the enriched ARGs in the final compost were related to horizontal gene transfer mediated by mobile genetic elements (intl1), with the primary potential host bacteria being Bacillus, Saccharomonospora, and Caldicoprobacter. The types of enriched ARGs were consistent across different bulking agents composting process, and the risk genes enriched in the final mature compost included ermB, ermF, sul1, sul2, tetO, and tetX.