Microbial Biota Research Articles

Nitrogen loss in coastal sediments driven by anaerobic ammonium oxidation coupled to microbial reduction of Mn(IV)-oxide

Coastal sediments play a central role in regulating the amount of land-derived reactive nitrogen (Nr) entering the ocean, and their importance becomes crucial in vulnerable ecosystems threatened by anthropogenic activities. Sedimentary denitrification has been identified as the main sink of Nr in marine environments, while anaerobic ammonium oxidation with nitrite (anammox) has also been pointed out as a key player in controlling the nitrogen pool in these locations. Collected evidence in the present work indicates that the microbial biota in coastal sediments from Baja California (northwestern Mexico) has the potential to drive anaerobic ammonium oxidation linked to Mn(IV) reduction (manganammox). Unamended sediment showed ammonification, but addition of vernadite (δMnO2 with nano-crystal size ∼15 Å) as terminal electron acceptor fueled simultaneous ammonium oxidation (up to ∼400 μM of ammonium removed) and production of Mn(II) with a ratio ∆[Mn(II)]/∆[NH4+] of 1.8, which is very close to the stoichiometric value of manganammox (1.5). Additional incubations spiked with external ammonium also showed concomitant ammonium oxidation and Mn(II) production, accounting for ∼30 % of the oxidized ammonium. Tracer analysis revealed that the nitrogen loss associated with manganammox was 4.2 ± 0.4 μg 30N2/g-day, which is 17-fold higher than that related to the feammox process (anaerobic ammonium oxidation linked to Fe(III) reduction, 0.24 ± 0.02 μg 30N2/g-day). Taxonomic characterization based on 16S rRNA gene sequencing revealed the existence of several clades belonging to Desulfobacterota as potential microorganisms catalyzing the manganammox process. These findings suggest that manganammox has the potential to be an additional Nr sink in coastal environments, whose contribution to total Nr losses remains to be evaluated.

Seasonal Population Trends of Microbial Communities in Oil Tainted Soils in Greater Port Harcourt Area, Nigeria

The utilization of oil in industries has devastating effect to the environment. Industrial effluents and oil spills are continuously contaminating the soil. Further, seasonality influences the distribution of pollutants in soil. Consequently, soil microbial biota and ecological processes are affected. This study assessed the effect of seasonality on soil fungal and bacterial communities in oil contaminated soils in 12 selected sites in Greater Port Harcourt Area. Standard analytical procedures were used to obtain bio-physicochemical data from the soil samples and t test was used to analyse data. The levels of total petroleum hydrocarbons (TPH) were above 5000 ppm (DPR recommended limit). There was significant difference (p ≤ 0.000) between the means of TPH in wet and dry seasons. Seasonality influenced % HUF and % HUB in the soils of urban, industrial and agricultural sites. Generally, the seasonality trends showed that there was a declining population of THB, HUB, TF, and HUF from the wet season to the dry season. However, the results show that there was a stable trend in % HUB as compared to oscillations observed in % HUF in oil tainted soils across a seasonal divide. We recommend characterization of the microorganism to identify the best candidate for bioremediation of oil tainted soils across a seasonal divide.

Impact of fertilization and tillage practices on transformations of carbon, essential plant nutrients and microbial biota composition in soils: a review

Impact of fertilization and tillage practices on transformations of carbon, essential plant nutrients and microbial biota composition in soils: a review

Turmeric and Ginger Extracts Affects the Proximate Composition, Oxidative Stability, Shelf Life and the Microbial Biota of Smoked <i>Clarias gariepinus</i> Fillets

African catfish, Clarias gariepinus of average weight 1.5 kg were filleted and pretreated with extracts of turmeric (TU) and ginger (GI) before hot smoking at 80 °C. The combination levels of TU and GI per treatment were as follows: Treatment 1, T1 (100TU:50GI), T2 (50TU:100GI), T3 (0TU:150GI), T4 (0TU:0GI), and T5 (75TU:75GI). The fillets were immersed into the treatment solution for 20 min and then hot smoked for 36 hours at 80°C. The smoked and dried fillets were stored for 30 days and analyzed for proximate composition, thiobarbituric acid essential substances (TBASR), peroxide value (PV), free fatty acid content, total volatile nitrogen base, and fungal and microbial biota. Protein content increased in the post-treated sample while moisture was reduced and lipid varied with smoking. Thiobarbituric acid reactive substances of the fillets were highest among those subjected to treatment T4, 0.75±0.11mg/100g but lowest for those of T1, 0.38±0.01mg/100g. The free fatty acids of the fillets after treatment, ranged from 1.23±0.07 % oleic acid in fillets treated with T1, to 3.06±0.08% oleic acid in fillet treated with T4. The fillets TVB-N treated with treatment 4 (T4), had the highest 1 TVB-N 19.81±0.04 mg/100g. Fillet treated with T4 had the highest FFA of 3.06±0.08% oleic acid while those treated to T1 had, 1.23±0.07 % oleic acid. Peroxide value was highest for T4, 20.07±0.22 and lowest for those subjected to T1, 10.30±0.03.Treatment 1 was toxic to both bacterial and fungal infestation with no visible growth of Rhizopus spp growth after 3 days of incubation. However, there was high vegetative fungal growth in the T4 experimental group.

Characterization of the Rhizosphere Bacterial Microbiome and Coffee Bean Fermentation in the Castillo-Tambo and Bourbon Varieties in the Popayán-Colombia Plateau

BackgroundThe microbial biodiversity and the role of microorganisms in the fermentation of washed coffee in Colombia were investigated using the Bourbon and Castillo coffee varieties. DNA sequencing was used to evaluate the soil microbial biota and their contribution to fermentation. The potential benefits of these microorganisms were analyzed, including increased productivity and the need to understand the rhizospheric bacterial species to optimize these benefits.MethodsThis study used coffee beans for DNA extraction and 16 S rRNA sequencing. The beans were pulped, samples were stored at 4ºC, and the fermentation process was at 19.5ºC and 24ºC. The fermented mucilage and root-soil samples were collected in duplicate at 0, 12, and 24 h. DNA was extracted from the samples at a concentration of 20 ng/µl per sample, and the data obtained were analyzed using the Mothur platform.ResultsThe study demonstrates that the coffee rhizosphere is a diverse ecosystem composed primarily of microorganisms that cannot be cultured in the laboratory. This suggests that the microbial community may vary depending on the coffee variety and play an essential role in fermentation and overall coffee quality.ConclusionsThe study highlights the importance of understanding and optimizing the microbial diversity in coffee production, which could have implications for the sustainability and success of coffee production. DNA sequencing techniques can help characterize the structure of the soil microbial biota and evaluate its contribution to coffee fermentation. Finally, further research is needed to fully understand the biodiversity of coffee rhizospheric bacteria and their role.

Carbonate diagenesis: A celebration of the work of John Anthony Dawson (Tony) Dickson

Carbonate diagenesis: A celebration of the work of John Anthony Dawson (Tony) Dickson

Diversity of Microbial Communities Associated with Epilithic Macroalgae in Different Coral Reef Conditions and Damselfish Territories of the Gulf of Thailand

Reef degradation and algae-farming fish alter the structures and compositions of coral-algal-microbial communities. We collected epilithic macroalgae in different reef conditions and damselfish territories. The microbial communities were characterized by subjecting the V3-V4 hypervariable region of the 16S rRNA gene to amplicon sequencing. Metagenomic analysis revealed 2 domains, 51 phyla, 112 orders, and 238 families and the dominance of Proteobacteria and Bacteroidota in both fair and degraded reefs inside and outside territories. Chloroflexi on the degraded reef was dominant and its proportion was almost two and a half times compared to the fair reef, whereas Cyanobacteria was low on the degraded reef. Bacteroidota was dominant on the fair reef, whereas Actinobacteriota was scarce on this reef. For the damselfish territories, Chloroflexi was dominant inside the territory, whereas Bacteroidetes were found outside the territory. Differences in the microbial species diversity and richness were not apparent between all sites; however, species evenness was higher on the degraded reef condition and lower outside the territory. Important potential pathogens of reef organisms, such as Vibrio, Photobacterium, and Phormidium, were found on the degraded reef areas inside the damselfish territory. The farming behaviors of damselfish influenced microbial communities by changing the epilithic algal matrix that harbors many microbial communities. This study provides useful information on microbial biota in coral reef habitats which is further applicable to reef conservation and coastal management.

An isolated chemolithoautotrophic ecosystem deduced from environmental isotopes: Ayyalon cave (Israel)

The stable isotopes composition of chemolithoautotrophic cave ecosystems is known to differ from epigenic caves. Here we show that in addition, dead carbon (devoid of 14C), is utilized and transferred throughout this ecosystem, rendering it unsuitable for radiocarbon dating. The connectivity of the Ayyalon Cave ecosystem with the surface is studied, along with its sources of energy and carbon, as well as the interconnections between its constituents. We use isotopic evidence to show that its ancient resilient ecosystem is based on an underground food web depending on rich biomass production by chemolithoautotrophic nutrient supplies, detached from surface photosynthesis. Carbon isotopic values indicate that: (1) the microbial biota use bicarbonate from the groundwater (23.34 pMC [% of modern carbon]) rather than the atmospheric CO2 above the water (71.36 pMC); (2) the depleted 14C signal is transferred through the entire ecosystem, indicating that the ecosystem is well-adapted and based on the cave biofilm which is in turn based on groundwater-dissolved inorganic carbon. Incubation of Ayyalon biofilm with 14C-labelled bicarbonate indicates uptake of the radio-labeled bicarbonate by sulfur-oxidizing proteobacteria Beggiatoa, suggesting that these sulfur-oxidizing microorganisms use the water-dissolved inorganic carbon for chemolithoautotrophic carbon fixation. Organic matter in the cave is much lighter in its stable nitrogen and carbon isotopes compared with respective surface values, as expected in chemolithoautotrophic systems. This evidence may be applicative to subsurface voids of ancient Earth environments and extraterrestrial systems.

Microbiocenosis of Anthropogenically Transformed Soils

A microbiological examination of the soils, polluted with different types of urban wastewater (Tashkent city), aiming determination of the microbial diversity and characterization of the bacterial community was carried out. The examination was conducted with use of classical microbiological methods with cultivation of samples on elective nutrient media. The soil sampling was carried out during winter season and period of plants’ vegetation. As result of examination the qualitative and quantitative characteristics of the bacterial community were determined and the microbial diversity was established. The predominant microorganisms of this community, capable to active functioning at chloride concentrations of the environment for up to 10 % and possessing high remediation potential towards biological and chemical pollutants, have been isolated. Rare strains belonging to the genus Amycolatopsis, which, in contrast to typical representatives of this genus, have the ability to form a water-soluble blue pigment, have been isolated. It was established that typical representatives of microbial biota, such as heterotrophic microorganisms Bacillus, Pseudomonas and actinomycetes, possess significant remediation potential towards biological and chemical pollution. It was determined that pollution of the soil caused by anthropogenic factors at the end of the day leads to decrease in species diversity and changes in composition of the soil microbiocenosis. The results obtained convincingly testify perspectives of biomonitoring and possible use of microorganisms in the processes of soil rehabilitation. The introduction of pollutant-resistant microorganisms, which are capable to degrade them, may become a practical approach for soil cleansing in the future.

Terrestrialization in the Ordovician

Abstract This contribution reviews the evidence for terrestrial organisms during the Ordovician (microbial, land plant, fungal, animal) and for the nature of the terrestrial biota. The evidence regarding the origin and early diversification of land plants combines information from both fossils and living organisms. Extant plants can be utilized in: (1) phylogenetic analyses to provide evidence for the nature of the algal–land plant transition and the characteristics of the most basal land plants; (2) evolutionary developmental biology studies of the characters that enabled the invasion of the land; (3) molecular clock analysis to provide evidence regarding timing of the origin and diversification of land plants. We conclude that the Ordovician was a critical period during the terrestrialization of planet Earth that witnessed the transition from a microbial terrestrial biota to one dominated by a vegetation of the most basal land plants.

Fungi determine increased soil organic carbon more than bacteria through their necromass inputs in conservation tillage croplands

Stover mulching over no-till soil is regarded as a promising practice to increase soil organic carbon (SOC) in croplands against climate change. Microbial necromass is a significant source of SOC stock and unequivocally controlled by the microbial community. Yet, a complete link that spans from agricultural practices to microbial community features, to soil necromass C, and eventually to SOC is poorly understood. Here, we conducted a 10-y corn field experiment with five treatments, which included conventional tillage (CT), no-tillage without stover (NT–0), and no-tillage with low, medium, and high amounts of stover mulching (NT–low, NT–medium, and NT–high) in a Molisol of northeastern China. We investigated the stocks and changes in total SOC and its microbial necromass C along a soil depth down to 40 cm, and we evaluated how SOC dynamics and stabilization processes were associated with microbial community features. We characterized microbial community diversity and structure using 16S rRNA and internal transcribed spacer (ITS) sequencing, and we characterized microbial biomass and necromass using phospholipid fatty acid and amino sugar biomarkers. Compared with conventional tillage, no-tillage with medium and high amounts of stover mulching increased SOC stocks in the upper 0–40 cm of soil by > 0.4% per year. No-tillage treatments (without and with stover) had almost no effect on the proportion of total microbial necromass C to SOC, but greatly modified the ratio of fungal necromass C to bacterial necromass C, which increased in top layers (0–5 cm) and decreased in deep layers (10–40 cm). SOC was governed mainly by fungal necromass C, which was correlated positively with fungal biomass. Fungal necromass C, not bacterial necromass C, was more closely associated with microbial community composition. Our results suggested that no-tillage with medium stover mulching was the optimal treatment to achieve the best trade-off between stover input and SOC storage. Differentiating microbial C pools from total SOC and, notably, separating fungal and bacterial necromass C pools can refine our mechanistic understanding of SOC storage as well as its association with microbial biota.

Role of Microbes in Plant Growth and Food Preservation


 Introduction: Microbes perform better functions for agricultural production by promoting various direct and indirect mechanisms in soil and plants. If agricultural development is to satisfy the needs of an increasing global population, a deeper understanding of soil microbiology is needed. Furthermore, microbial biota such as yeast, bacteria etc., plays a significant role in food preservation by various mechanisms.
 Review results: Despite their pathogenicity, microbes play a substantial role in dispensing an assortment of fermented drinks and foods in the food industry and home. Probiotics, fermented foods and alcoholic beverages are flattering extra popular due to their health benefits and flavour. Furthermore, they increase the yield and growth of plants by improving mineral availability to the plants and by another mechanism.
 Review implementation: This present review also discusses the various organisms used in the agricultural processing of beverages and food and the benefits of using the following microbes in the beverage and food industry.

Evaluation of the production of biohydrogen during the co-digestion of organic wastes in an upflow hybrid anaerobic reactor

The effect of the hydraulic retention time (24, 12, and 6 h) during the co-digestion of organic residues was studied using a novel upflow hybrid anaerobic sludge reactor with a carbon/nitrogen ratio of 30, initial pH of 5.5, temperature of 35 °C, and a granular inoculum. The reactor performance at the tested HRTs followed the order 650 ± 50 (24 h) > 48 ± 4 (12 h) > 20 ± 2 mL BH2 g-1CDO removed (6 h). The content of the metabolites obtained using an HRT of 24 h followed the order acetic acid > isobutyric acid > butyric acid under acetogenic conditions. However, for HRTs of 12 and 6 h, the sequence was butyric acid > valeric acid > propionic acid > acetic acid. Based on molecular analyses, the biohydrogen selectivity was attributed to the presence of the genera Megasphaera, Clostridium, Lactobacillus, and Prevotella, which accounted for 26%, 2%, 12%, and 29% of the microbial biota at 24 h. Additionally, the yield of the upflow hybrid anaerobic reactor was superior to that of an upflow anaerobic reactor (24 h).

Size-dependent adverse effects of microplastics on intestinal microbiota and metabolic homeostasis in the marine medaka (Oryzias melastigma)

Microplastic (MP) is an emerging environmental pollutant and exposure to MPs has been associated with numerous adverse health outcomes in both wild and laboratory animals. The toxicity of MPs depends on concentration, exposure time, chemical composition and size distribution, but the impacts of particle size remain inconclusive yet. In this study, adult marine medaka (Oryzias melastigma) were exposed to different size of polystyrene MPs (PS-MPs) with concentration of 10 mg/L for 60 days and the growth performance, lipid metabolism, immune parameters and gut microbiome were determined. Results indicated that particle size is a dominant factor causing lipid metabolism disorders and hepatic toxicity in PS-MPs-exposed fish. The bodyweight, adipocyte size and hepatic lipid contents were significantly increased in 200 μm PS-MPs-exposed fish, while 2 and 10 μm PS-MPs-exposed fish exhibited liver injury principally manifested asthepresence oflittlefibrosis and inflammation. Given that larger particles could not enter the circulatory system, the impacts of PS-MPs on intestinal microbial biota homeostasis were further investigated. The results not only showed the characterization of gut microbial communities in Oryzias melastigma, but also indicated that microbial diversity and composition were altered in gut of fish exposed to PS-MPs, in particular 200 μm PS-MPs. The differentially abundant bacterial taxa in PS-MPs-exposed fish mainly belonged to the phylum Verrucomicrobia, Firmicutes and Fusobacteria. And furthermore, increased abundance of Verrucomicrobia and Firmicutes/Bacteroidetes ratio and decreased Fusobacteria were correlated with the increased bodyweight. Intestinal microbiome should play a critical role in regulating host lipid metabolism in fish exposed to lager size of PS-MPs.

Lower Triassic (Induan) stromatolites and oolites of the Bernburg Formation revisited – microfacies and palaeoenvironment of lacustrine carbonates in Central Germany

We propose a new facies classification scheme of the cyclic lacustrine carbonates of the Bernburg Formation (Lower Triassic, Induan), with a major focus on the microbial biota and grains. Our data are based on a detailed bed-by-bed outcrop study in Central Germany, within a robust (litho)stratigraphic framework. We concentrate on two intervals of the Bernburg Formation: one around the Calvorde/Bernburg Formation boundary (including the HRZ – „Hauptrogensteinzone“), and a second around the ninth cycle near the upper formation boundary. The textural and mineralogical composition of the two endmember components: skeletal stromatolites and oolites, and the macro-, meso-, and microstructural characteristics (supplemented by μ-XRF-data) allow to classify the carbonates into five lithofacies types. They are interpreted with respect to the development of an ideal lacustrine depositional cycle, embedded between a lake level rise and a lake level fall. The microfacies attributes of the microbialites include various lamination types, shrubs, spherulites, and laminated/clotted/fenestral microfabrics. All sedimentologic (macro-, meso, and microscale) and geochemical data of this study indicate nearshore deposition of the carbonates at marginal shoals in a major endorheic lake (playa lake) with high alkalinity and salinity, and strongly fluctuating lake levels, under arid climates. The lacustrine carbonates are associated with maximum lake expansions, and are laterally interfingering with fan deltas, as indicated by abundant clastic grains in the intercalations of the skeletal stromatolites. The Bernburg Formation microbial buildups reflect changes in lake-level, hydrodynamics and grain supply, and therefore offer insights for the paleoenvironmental interpretation of lacustrine microbialites elsewhere.

A gap in sedimentation in the Silurian section of the Subpolar Urals at the Ludlow-Pridoli boundary

Research subject.The article discusses the results of a new detailed study of a reference section of the Upper Silurian in the Subpolar Urals. This study was undertaken to clarify the existing contradictions concerning the age of the Ludlow-Pridoli boundary deposits and the definition of the Ludlow-Pridoli boundary, which is based on the study of different fauna groups.Materials and methods.The newly collected collections contained more than 100 samples of sedimentary rocks with fossil macro fauna, 22 tests on microfauna, 198 tests on chemical analysis for determining the content of Ba, Sr and δ13C and δ18O isotopes in carbonates. The results of experiments were confirmed by the authors’ bio-sedimentological, paleo-ecological and chemostratigraphic data.Results.The conducted research confirmed the existence of a gap in sedimentation at the end of Ludlow; clarified the thickness of the Sizim stage in the reference section; elucidated its sedimentological and chemostratigraphic characteristics; allowed changes in biodiversity due to a change in the sedimentation regime, paleoecological impact on biota in the late Ludlow and restoration of biota in the early Pridoli to be traced. The study also demonstrated that the time boundaries of the transgressive and regressive stages in the development of the Northern Ural sea basin and the event-stratigraphic boundary of the Ludlow-Pridoli were directly related to the main global events in the Late Silurian (Lau Event, Lower Pridolian Event), the traces of which are preserved in the studied section.Conclusions.The intensification of regressive tendencies across the largest part of the Northern Ural paleobasin in the Late Ludlow, widespread development of microbial biota, cessation of the Silurian reef formation, as well as the extinction of Pentamerida brachiopods – exclusively, indicate a significant ecosystematic restructuring in the late Ludlow. It can be assumed that the absence of a significant positive deviation of the δ13C global Lau Event in this section is associated with the identified gap, the amplitude of which correlates with the Ozarkodina snajdri and Ozarkodina crispa zones located above the Polygnathoides siluricus zone in the conodont sequence of the Upper Ludlow.

First Recorded Account of Arbuscular Mycorrhizal Fungi in Sand Dunes in South Eastern Australia: Biogeography and Species Richness

Hanlon, L.M., 2021. First recorded account of arbuscular mycorrhizal fungi in sand dunes in south eastern Australia: Biogeography and species richness. Journal of Coastal Research, 37(2), 280–290. Coconut Creek (Florida), ISSN 0749-0208.Coastal arbuscular mycorrhizal fungi on incipient foredunes survive in extreme and environmentally stressful ecosystems that are regularly eroded and replaced. These dunes encounter strong, salt-laden winds, sea-water overwash, and low nutrients and are subject to storms of greater magnitude than established foredunes, often being scarped. The species richness of coastal arbuscular mycorrhizal fungi was examined in sand dunes, as well as in the roots of mixed vegetation and grasses growing in the dunes, to elucidate differences in species between the incipient foredune and established foredune gradients and to address the paucity of information on the biogeography of coastal arbuscular mycorrhizal fungi. Seventy-three operational taxonomic units were identified through DNA analyses and classified into 16 arbuscular mycorrhizal species, of which Glomus spp. was dominant in both dune niches. Three species were specific to the established foredune ecosystem, and four discrete species were found in the incipient foredune ecosystem, demonstrating a robustness to disturbance. Additionally, one discrete species of arbuscular mycorrhizal fungus was found in the two incipient foredune grasses. All nucleotide sequences have been accepted and assigned accession numbers by GenBank. The identification of microbial biota in coastal sites is of vital importance in allowing more informed decisions to be made on the restoration and conservation of coastal sand dunes or ecosystem remediation. It is postulated that these results are the first to report the biogeography and species richness of arbuscular mycorrhizal fungi on the southern coast of Australia.

Nutritional and Microbiota Analysis of Fresh Produce in Delhi and National Capital Region

Fresh produce available in an area is the major source of phytonutrients for healthy life. Decrease in the concentration of phytonutrients is directly linked to a range of health issues in terms of increase in the rate of infections. This study conducted on fresh produce available in Delhi and National Capital Region (NCR) on microbiological and nutritional analysis showed a significant increase in microbial load in fruits as they stay over the period of a week to fortnight at room temperature. A total of seven different types of fresh produce were procured for analysis. Out of them, lemon showed the lowest microbial count and sugar content and grapes showed highest microbial count and sugar content. Results were also compared with refrigerated and room temperature stored fruits. It was concluded that fresh fruits have more nutritive value than stored fruits (room and refrigerated). In this study, glucose content was determined by Fehling's titration and Ascorbic Acid by Dichlorophenolindophenol method. The microbial biota was assessed by serial dilution method for determining microbial load of different types of bacteria. Some of the fruits showed decrease in the nutritive value and correspondingly increase in the load of antibiotic resistant microbes during storage rendering them unfit for human consumption.

Multifunctional Periphytic Biofilms: Polyethylene Degradation and Cd2+ and Pb2+ Bioremediation under High Methane Scenario.

Priority pollutants such as polyethylene (PE) microplastic, lead (Pb2+), and cadmium (Cd2+) have attracted the interest of environmentalists due to their ubiquitous nature and toxicity to all forms of life. In this study, periphytic biofilms (epiphyton and epixylon) were used to bioremediate heavy metals (HMs) and to biodegrade PE under high (120,000 ppm) methane (CH4) doses. Both periphytic biofilms were actively involved in methane oxidation, HMs accumulation and PE degradation. Epiphyton and epixylon both completely removed Pb2+ and Cd2+ at concentrations of 2 mg L−1 and 50 mg L−1, respectively, but only partially removed these HMs at a relatively higher concentration (100 mg L−1). Treatment containing 12% 13CH4 proved to be most effective for biodegradation of PE. A synergistic effect of HMs and PE drastically changed microbial biota and methanotrophic communities. High-throughput 16S rRNA gene sequencing revealed that Cyanobacteria was the most abundant class, followed by Gammaproteobacteria and Alphaproteobacteria in all high-methane-dose treatments. DNA stable-isotope probing was used to label 13C in a methanotrophic community. A biomarker for methane-oxidizing bacteria, pmoA gene sequence of a 13C-labeled fraction, revealed that Methylobacter was most abundant in all high-methane-dose treatments compared to near atmospheric methane (NAM) treatment, followed by Methylococcus. Methylomonas, Methylocystis, Methylosinus, and Methylocella were also found to be increased by high doses of methane compared to NAM treatment. Overall, Cd+2 had a more determinantal effect on methanotrophic activity than Pb2+. Epiphyton proved to be more effective than epixylon in HMs removal and PE biodegradation. The findings proved that both epiphyton and epixylon can be used to bioremediate HMs and biodegrade PE as an efficient ecofriendly technique under high methane concentrations.

The Paleoproterozoic Francevillian succession of Gabon and the Lomagundi-Jatuli event

Abstract The Paleoproterozoic Francevillian succession of Gabon has figured prominently in concepts about Earth’s early oxygenation and genesis of a large positive excursion in carbon-isotope values, the Lomagundi-Jatuli event (LJE). Here we present a detailed study of a 139-m-long core of Francevillian rocks marked by carbonate δ13C (δ13Ccarb) values of 5‰–9‰ that decline upsection to near 0‰, a trend inferred by many workers as a fingerprint of the LJE and its termination. However, we show that the shift in δ13Ccarb values coincides with a facies change: shallow-marine facies are marked by the strongly positive values, whereas deeper-marine facies (below storm wave base) are at ∼0‰. The most circumspect interpretation of such facies dependence of δ13Ccarb is that shallow-marine settings record the isotope effects of local physical and biochemical processes driving the ambient dissolved inorganic carbon (DIC) pool to heavier values, and the lighter values (∼0‰) in deeper-water facies track the DIC of the open-marine realm where δ13C was largely unaffected by fractionations occurring in shallow-water settings. Further, a transgressing redoxcline created conditions for precipitation of Mn-bearing minerals and chemotrophic microbial biota, including methane cycling communities evident by organic δ13C (δ13Corg) values of −47‰ and Δδcarb-org values as high as 46‰. Thus, the Francevillian C-isotope profile reflects basin-specific conditions and is not a priori an indicator of global C-cycle disturbances nor of the termination of the LJE.