Phospholipid Fatty Acid Research Articles

Microbial utilization of recently fixed, plant-derived organic carbon in shallow Holocene and Pleistocene aquifers in Bangladesh

The presence of dissolved arsenic in shallow aquifers of Bangladesh is widely accepted to require microbial dissimilatory iron-reduction in anoxic aquifers utilizing organic carbon as an electron donor. However, the various potential sources of this carbon, and whether organic carbon sources vary with sediment age (i.e. < 12 kyr-old Holocene vs older Pleistocene sediments) are still poorly understood. To shed light on these questions, natural abundance radiocarbon signatures of in situ microbial phospholipids fatty acids (PLFA), concentrations of sterol biomarkers, and aqueous [Cl-] and [Br-] were compared in two Bangladesh aquifers; a shallow (11–15 m) aquifer low in dissolved arsenic containing oxidized (orange) Pleistocene sands, Dopar Tek (DT), and a shallow (6–21 m) aquifer high in dissolved arsenic containing reduced (grey) Holocene sands, Desert Island (DI). Radiocarbon signatures of PLFA (Δ14CPLFA = −30 to −63 ‰ and +9 to +25 ‰, respectively) indicate microbial utilization of carbon fixed from the atmosphere within the last several decades, the drawdown of which into the shallow portions of both the Pleistocene Dopar Tek and Holocene Desert Island aquifers was likely enhanced by regional pumping activities. Similar results were previously obtained for two other Holocene aquifers in the same region, but to our knowledge this is the first time modern PLFA has been extracted from Pleistocene sediments. At both sites, high proportions of phytosterols, low sewage contamination indices (SCI < 0.7), and generally low Cl/Br ratios (averaging 434 and 544 at Desert Island and Dopar Tek respectively), are consistent with predominantly plant-derived organic carbon inputs. This contrasts with sewage-derived input inferred from higher sewage contamination index values (>0.7) previously observed at the two other shallow Holocene aquifers in the same region. Overall, our observations show that microbial communities within shallow aquifers, including those of Pleistocene age, utilize very recently fixed organic carbon associated with both plant and/or sewage origin. The microbial utilization of organic carbon fixed within the past several decades, likely derived from plants, in the anaerobic Pleistocene, has not, as of yet, led to iron reduction that would be sufficient to increase arsenic concentrations in groundwater. However, the observed microbial utilization of recently fixed carbon within all Bangladesh aquifers studied to date, indicates that pumping enhanced drawdown represents a potential risk to any systems where it might occur.

Higher n-3 polyunsaturated fatty acid status during early pregnancy is associated with lower risk for depression at 12 months postpartum: The NuPED study

Perinatal depression can negatively affect the health of the mother and her offspring. N-3 polyunsaturated fatty acids (PUFA) may play a role in the aetiology of depression. Therefore, we investigated the association of n-3 PUFA status during early pregnancy with perinatal depression among women living in urban Johannesburg, South Africa. For this prospective analysis, we analysed red blood cell (RBC) total phospholipid fatty acid (FA) composition (% of total FA) of 242 pregnant women at <18 weeks’ gestation. We used the Edinburgh Postnatal Depression Scale (EPDS) to identify women at risk for depression (EPDS score ≥9) at <18, 22 and 36 weeks’ gestation, and at 6 and 12 months postpartum. RBC EPA status was negatively (β=-0.22, p<0.05), and the AA/EPA ratio positively (β=0.24, p<0.05) associated with EPDS scores at 12 months postpartum. Higher RBC DHA and n-3 index were further associated with lower odds (OR=0.56 [95% CI: 0.32-0.91]; OR=0.63 [95% CI: 0.39-0.94]), while higher n-6/n-3 PUFA and AA/EPA ratios early in pregnancy were associated with higher odds for depression at 12 months postpartum ((OR=2.34 [95% CI: 1.12-4.97]; OR=1.02 [95% CI: 1.00-1.05]). Our results suggest that women with a higher RBC n-3 PUFA status during early pregnancy may be at lower risk for depression at 12 months postpartum.

Biogeochemical properties of blue carbon sediments influence the distribution and monomer composition of bacterial polyhydroxyalkanoates (PHA)

Coastal wetlands are highly efficient ‘blue carbon’ sinks which contribute to mitigating climate change through the long-term removal of atmospheric CO2 and capture of carbon (C). Microorganisms are integral to C sequestration in blue carbon sediments and face a myriad of natural and anthropogenic pressures yet their adaptive responses are poorly understood. One such response in bacteria is the alteration of biomass lipids, specifically through the accumulation of polyhydroxyalkanoates (PHAs) and alteration of membrane phospholipid fatty acids (PLFA). PHAs are highly reduced bacterial storage polymers that increase bacterial fitness in changing environments. In this study, we investigated the distribution of microbial PHA, PLFA profiles, community structure and response to changes in sediment geochemistry along an elevation gradient from intertidal to vegetated supratidal sediments. We found highest PHA accumulation, monomer diversity and expression of lipid stress indices in elevated and vegetated sediments where C, nitrogen (N), PAH and heavy metals increased, and pH was significantly lower. This was accompanied by a reduction in bacterial diversity and a shift to higher abundances of microbial community members favouring complex C degradation. Results presented here describe a connection between bacterial PHA accumulation, membrane lipid adaptation, microbial community composition and polluted C rich sediments.Graphical Geochemical, microbiological and polyhydroxyalkanoate (PHA) gradient in a blue carbon zone.

Influence of sediment quality and microbial community on the functioning capacity of a constructed wetland treating alkaline leachate after 5.5 years in operation

Constructed wetlands (CWs) have been demonstrated as a cost-effective alternative to chemical treatment systems for mine waters, with the microbial communities attributed to promoting carbonation and aiding pH neutralization. However, few data are available for the long-term use of CWs treating alkaline leachates nor the activity of microbes within them. To investigate the feasibility of CW to buffer alkaline pH, a pilot-scale wetland was implemented in 2015 to treat alkaline bauxite residue leachate. After 5.5 years, samples of supernatant water and sediment were taken at 0.5 m increments along the 11 m long wetland. Waters were analysed for pH, EC and metal(loid) content, while sediment was subjected to physico-chemical assessment and element fractionation. Microbial biomass and community were assessed by phospholipid fatty acid analysis (PLFA) and functionality by the Rapid Automated Bacterial Impedance Technique (RABIT).Evidence presented demonstrates that the CW operating for 66 months effectively treats bauxite residue leachate, with reduced influent pH from 11.5 to 7.8. Trace element analysis revealed effective reduction in Al (94.9 %), As (86.7 %) and V (57.6 %) with substrate analysis revealing a frontloading of elevated pH and trace element content in the first 5 m of the wetland. Sediment Al, As and V were present mostly (>94 % of total) in recalcitrant forms. Sediment Na was mostly soluble (48–62 %), but soils were not sodic (ESP < 15 %). Investigations into the microbial community revealed greatest biomass was in the first 5 m of the wetland, where pH, EC and metal contents were greatest. Microbial respiration using endemic Phragmites australis as a substrate demonstrates an ability to cycle recalcitrant carbon sources within a CW system. These novel microbial findings highlight the need for further investigation into the microbial communities in alkaline CWs.

Recurring heavy rainfall resulting in degraded-upgraded phases in soil microbial networks that are reflected in soil functioning

• We assess the recovery of microbial networks underneath crust to repeated rainfall.• The network fragmentation after the second heavy rain was milder than at the first one.• Cohesive networks were related to high enzyme activity involved in C, N, and P cycles.• Loose networks were related to high Ca, K, Mg, NH4 and organic N.• The network in dry-crusted soils collapsed after the second heavy rain.Biological soil crusts (BSCs) are an important multi-trophic component of arid ecosystems in the Mediterranean region. In a mesocosm experiment, the authors investigated how the network of interactions among the members of the soil microbial communities in four types of soil sample responded when soils were exposed to two simulated extreme rain events. The four types of soil samples were: covered by Cladonia rangiformis and previously hydrated (+BSC+H), covered by C. rangiformis and dried (+BSC−H), uncovered and hydrated (−BSC+H), uncovered and dried (−BSC−H). Network analysis was based on the co-occurrence patterns of microbes; microbes were assessed by the phospholipid fatty acids analysis. The authors further explored the relations between networks’ metrics and soil functions denoted by enzymatic activity and soil chemical variables. All networks exhibited Small world properties, moderate values of clustering coefficient and eigen centrality, indicating the lack of hub nodes. The networks in −BSC−H soils appeared coherent during the pre-rain phases and they became modular after rains, while those in +BSC−H soils kept their connectivity till the second rain but this then collapsed. The network metrics that were indicative of cohesive networks tended to be related to enzyme activity while those that characterized the loose networks were related to Ca, K, Mg, NH4+ and organic N. In all mesocosms except for +BSC−H, networks’ fragmentation after the second heavy rain was milder than after the first one, supporting the idea of community acclimatization. The response of microbial networks to heavy rains was characterized by the tendency to exhibit degradation-reconstruction phases. The network collapse in the crusted only mesocosms showed that the communities beneath crusts in arid areas were extremely vulnerable to recurring heavy rain events.

Sediment microbial community structure, enzymatic activities and functional gene abundance in the coastal hypersaline habitats

Salt marsh vegetation, mudflat and salt production are common features in worldwide coastal areas; however, their influence on microbial community composition and structure has been poorly studied and rarely compared. In the present study, microbial community composition (phospholipid fatty acid (PLFA) profiling and 16S rRNA gene sequencing (bacterial and archaeal)) and structure, enzymatic activities and abundance of functional genes in the sediments of salt ponds (crystallizer, condenser and reservoir), mudflat and vegetated mudflat were determined. Enzyme activities (β-glucosidase, urease and alkaline phosphatase) were considerably decreased in saltpan sediments because of elevated salinity while sediment of vegetated mudflat sediments showed the highest enzyme activities. Concentrations of total microbial biomarker PLFAs (total bacterial, Gram-positive, Gram-negative, fungal and actinomycetes) were the highest in vegetated mudflat sediments and the lowest in crystallizer sediments. Nonmetric-multidimensional scaling (NMDS) analysis of PLFA data revealed that the microbial community of crystallizer, mudflat and vegetated mudflat was significantly different from each other as well as different from condenser and reservoir. The most predominant phyla within the classified bacterial fractions were Proteobacteria followed by Firmicutes, Bacteroidetes and Planctomycetes, while Euryarchaeota and Crenarchaeota phyla dominated the classified archaeal fraction. Cyanobacterial genotypes were the most dominant in the condenser. Mudflat and vegetated mudflat supported a greater abundance of Bacteroidetes and Actinobacteria, respectively. The results of the present study suggest that salt ponds had significantly decreased the microbial and enzyme activities in comparison to mudflat and vegetated mudflat sediments due to very high salinity, ionic concentrations and devoid of vegetation. The present study expands our understanding of microbial resource utilization and adaptations of microorganisms in a hypersaline environment.

Soil aggregate microstructure and microbial community structure mediate soil organic carbon accumulation: Evidence from one-year field experiment

Soil organic carbon (SOC) accumulation is easily susceptible to tillage managements, which strongly affect soil structure and microbial community structure. Subsoiling is developed for mitigating soil compaction and thus improving soil structure. Coupled with straw residue incorporation, it is expected not only to enhance this improvement but also to promote organic carbon (C) storage in soil. However, how subsoiling tillage managements change soil aggregate microstructure, microbial community structure and SOC fractions, and how soil aggregate microstructure and microbial community structure affect SOC in the topsoil and subsoil layers are equally unknown. An in-situ incubation field experiment was conducted in a Mollisol in northeastern China and included conventional tillage (CT), subsoiling tillage (ST) and subsoiling tillage with straw residue incorporation (ST + S). The methods of synchrotron-based X-ray micro-computed tomography scanning, phospholipid fatty acid and SOC density fractionation were used to analyze aggregate pore characteristics, microbial community structure and SOC fractions, respectively. The results showed that both ST and especially ST + S not only improved soil aggregate microstructure but also enhanced microbial biomass and then favored SOC accrual in the topsoil (0–20 cm). In the subsoil (20–35 cm), ST + S exerted similar positive effects as those in the topsoil. However, ST only improved soil aggregate microstructure but decreased microbial community biomass and SOC in the subsoil. Moreover, soil aggregate structure characteristics explained (solely explained 6 % in the topsoil and 12 % in the subsoil, respectively) a smaller part of the variation in SOC within aggregates than soil microbial characteristics did (solely explained 15 % in the topsoil and 25 % in the subsoil, respectively). Specifically, bacteria explained 26 % and 66 % of the variation in SOC within aggregates in the topsoil and subsoil, respectively. The porosity of macropores (>100 μm) also explained 25 % of the variation in SOC within aggregates in the topsoil, whereas the porosity of micropores (<30 μm) explained more variation (12 %) than that of macropores (3 %) in the subsoil. Notably, the substantially different interaction mechanism-processed of pore characteristics, microbial structure and SOC between topsoil and subsoil was probably traceable for the variation in the influx of organic C, pore size distribution and microbial adaptability in soil layers. These results would provide new insights on tillage managements strategies for improving soil conditions in terms of optimizing soil aggregate microstructure–microbes–SOC interactions in the topsoil and subsoil layers.

The Impacts of Phosphorus-Containing Compounds on Soil Microorganisms of Rice Rhizosphere Contaminated by Lead

The cost effectiveness of using exogenous phosphorus to remediate heavy metals in soil, which would alter the structure of the soil microbial community, had been widely acknowledged. In the present study, phospholipid fatty acid (PLFA) technology was taken as the breakthrough point, and rhizosphere soil microorganisms in different growth stages (jointing stage and maturity stage) of Minghui 86 (MH) and Yangdao No.6 (YD) rice were taken as the research objects. As revealed by the results, the rhizosphere soil microorganisms of MH and YD had distinct sensitivities to exogenous phosphorus and had a certain inhibitory effect on MH and YD enhancement. The sensitivity of rice root soil microorganisms to exogenous phosphorus also varied in different growth stages of rice. Bacteria were the dominant microorganism in the soil microbial community of rice roots, and the gain of exogenous phosphorus had a certain impact on the structure of the two soil microbial communities. Through analysis of the microbial community characteristics of MH rice and YD soil after adding exogenous phosphorus, further understanding was attained with respect to the effect of exogenous phosphorus on the microbial community characteristics of rice rhizosphere soil and the impact thereof on ecological functions.

Rapid biodegradation of atrazine by a novel Paenarthrobacter ureafaciens ZY and its effects on soil native microbial community dynamic.

An atrazine-utilizing bacterium, designated as ZY, was isolated from agricultural soil and identified as Paenarthrobacter ureafaciens. The P. ureafaciens ZY demonstrated a significant degradation capacity of atrazine, with the degradation efficiency of 12.5 mg L-1 h-1 in liquid media (at pH 7, 30°C, and the atrazine level of 100 mg L-1). The P. ureafaciens ZY contained three atrazine-degrading genes (i.e., trzN, atzB, and atzC) could metabolize atrazine to form cyanuric acid, which showed lower biotoxicity than the parent atrazine as predicted by Ecological Structure Activity Relationships model. A laboratory-scale pot experiment was performed to examine the degradation of atrazine by P. ureafaciens ZY inoculation and investigate its effects on the native microbial communities. The results exhibited that the P. ureafaciens ZY was conductive to the degradation of atrazine, increased the total soil phospholipid fatty acids at the atrazine level of 50, 70, and 100 mg kg-1. By using high-throughput sequencing analysis, Frateuria, Dyella, Burkholderia-Caballeronia-Paraburkholderia were considered as the most important indigenous atrazine-degrading microorganisms due to their relative abundances were positively correlated with the atrazine degradation rate. In addition, P. ureafaciens ZY also increased the abundance of atrazine-degrading genus Streptomyces and Bacillus, indicating that there may be a synergic relationship between them in the process of atrazine degradation. Our work provides a new insight between inoculums and native microorganisms on the degradation of atrazine.

Use of phospholipid fatty acid analysis as phenotypic biomarkers for soil health and the influence of management practices

Phospholipid fatty acid analysis (PLFA) provides an easy to use and robust measure of changing soil microbial condition. The method provides data on both the quantity and composition of the soil microbial community- critical knowledge because the community is an important component of soil health. However, it is challenging for new researchers to know how to process data, how to interpret the results, and to know its effectiveness in evaluating soil health management. We set out to address these challenges using the North American Project to Evaluate Soil Health Measurements PLFA dataset. The dataset is comprised of results of over 1800 agricultural soil samples from a range of environmental regions and management practices. Using this dataset, we identified that quantifying soil PLFA biomass through summing the biomarkers from C14:0 to C20:0 yielded greater biomass results than summing specific biomarkers and was almost identical to summing C9:0 to C20:0. We utilized microbial biomass with common and novel biomarker ratios to evaluate the response of the soil microbial community to changes in the environment or changes in management practice. These ratios were based on commonly used genotypic categorization (e.g., Gram-positive to Gram-negative) or based on chemical structure with chemical ratios of either universal characteristics (e.g., unsaturated to saturated) or targeted phenotypic biomarkers known to shift with changing growth conditions (e.g., a15:0 and a17:0 to i15:0 and i17:0). One novel phenotypic ratio, the adaptation response ratio (ARR), significantly correlated with mean annual temperature and soil pH across grassland reference plots, a wheat climate transect, an intensive vegetable agricultural dataset, and a wheat-corn dataset from Mexico. Neither the common genotypic ratio nor ratios based on chemical structure demonstrated clear and consistent trends with environmental conditions. Targeted phenotypic biomarker ratios and microbial biomass also detected significant differences with soil health management practices of decreased tillage, cover crops, organic nutrients, residue retention, and rotation diversity. Therefore, with standardized microbial biomass and biomarker calculations that significantly vary with environmental conditions and management practices, these results support a wider understanding and adoption of the PLFA method in soil health management.

Phosphorus limitation induced by nitrogen addition changed soil microbial community structure in a subtropical Pinus taiwanensis forest.

Soil microorganisms play an important role in the biogeochemical cycles of terrestrial ecosystems. How-ever, it is still unclear how the amount and duration of nitrogen (N) addition affect soil microbial community structure and whether there is a correlation between the changes in microbial community structure and their nutrient limi-tation status. In this study, we conducted an N addition experiment in a subtropical Pinus taiwanensis forest to simulate N deposition with three treatments: control (CK, 0 kg N·hm-2·a-1), low N (LN, 40 kg N·hm-2·a-1), and high N (HN, 80 kg N·hm-2·a-1). Basic soil physicochemical properties, phospholipid fatty acids content, and carbon (C), N and phosphorus (P) acquisition enzyme activities were measured after one and three years of N addition. The relative nutrient limitation status of soil microorganisms was analyzed using ecological enzyme stoichiometry. The results showed that one-year N addition did not affect soil microbial community structure. Three-year LN treatment significantly increased the contents of Gram-positive bacteria (G+), Gram-negative bacteria (G-), actinomycetes (ACT), and total phospholipid fatty acids (TPLFA), whereas three-year HN treatment did not significantly affect soil microbial community, indicating that bacteria and ACT might be more sensitive to N addition. Nitrogen addition exacerbated soil C and P limitation. Phosphorus limitation was the optimal explanatory factor for the changes in soil microbial community structure. It suggested that P limitation induced by N addition might be more beneficial for the growth of certain oligotrophic bacteria (e.g. G+) and the microorganisms participating in the P cycling (e.g. ACT), with consequences on soil microbial community structure of subtropical Pinus taiwanensis forest.

Forest management causes soil carbon loss by reducing particulate organic carbon in Guangxi, Southern China

BackgroundThe loss of soil organic carbon (SOC) following conversion of natural forests to managed plantations has been widely reported. However, how different SOC fractions and microbial necromass C (MNC) respond to forest management practices remains unclear. MethodsWe sampled 0–10 ​cm mineral soil from three different management plantations and one protected forest in Guangxi, Southern China, to explore how forest management practices affect SOC through changing mineral-associated C (MAOC) and particulate organic C (POC), as well as fungal and bacterial necromass C. ResultsCompared with the protected forest, SOC and POC in the abandoned, mixed and Eucalyptus plantations significantly decreased, but MAOC showed no significant change, indicating that the loss of SOC was mainly from decreased POC under forest management. Forest management also significantly reduced root biomass, soil extractable organic C, MNC, and total microbial biomass (measured by phospholipid fatty acid), but increased fungi-to-bacteria ratio (F:B) and soil peroxidase activity. Moreover, POC was positively correlated with root biomass, total microbial biomass and MNC, and negatively with F:B and peroxidase activity. These results suggested that root input and microbial properties together regulated soil POC dynamics during forest management. ConclusionOverall, this study indicates that forest management intervention significantly decreases SOC by reducing POC in Guangxi, Southern China, and suggests that forest protection can help to sequester more soil C in forest ecosystems.

Effects of Different Chinese Hickory Husk Returning Modes on Soil Nutrition and Microbial Community in Acid Forest Soil

Chinese hickory (Carya cathayensis Sarg.) is an important economic forest in Southeastern China. A large amount of hickory husk waste is generated every year but with a low proportion of returning. Meanwhile, intensive management has resulted in soil degradation of Chinese hickory plantations. This study aims to investigate the effects of three Chinese hickory husk returning modes on soil amendment, including soil acidity, soil nutrition, and microbial community. The field experiment carried out four treatments: control (CK), hickory husk mulching (HM), hickory husk biochar (BC), and hickory husk organic fertilizer (OF). The phospholipid fatty acid (PLFA) biomarker method was employed to determine the soil microbial community. After one year of treatment, the results showed that: (i) HM and BC significantly increased soil pH by 0.33 and 1.71 units, respectively; (ii) HM, BC and OF treatments significantly increased the soil organic carbon, alkaline nitrogen, available phosphorous, and available potassium. The OF treatment demonstrated the most significant improvement in the soil nutrient; (iii) The soil microbial biomass significantly increased in the HM, BC and OF treatments, and all microbial groups showed an increasing trend. HM treatment increased the fungal/bacterial ratio (F/B). The OF treatment significantly decreased the Shannon-Wiener diversity (H’) and evenness index (J) of the microbial community (P < 0.05). Considering the treatments effects, costs, and ease of operation, our recommended returning modes of Chinese hickory husk are mulching and organic fertilizer produced by composting with manure.

How Soil Microbial Communities from Industrial and Natural Ecosystems Respond to Contamination by Polycyclic Aromatic Hydrocarbons

Soil microbial community plays a major role in removal of polycyclic aromatic hydrocarbons (PAHs) from soil, and bioremediation potentially offers an attractive and economic approach to the clean-up of polluted areas. To evaluate the contribution of different microbial groups in soil PAH degradation, enzymatic activity and phospholipid fatty acids (PLFAs) were analysed in a mesocosm trial in three different soils (two natural and one industrial) artificially contaminated with 3- and 5-rings PAHs. The Metabolic Activity Index (MAI) was applied to investigate the microbial community stability, in terms of resistance and resilience. Gram+ and Gram- bacteria were the predominant microbial groups in all soil types. In the first stage of incubation, fungi were predominant in the industrial soil, followed by mycorrhizae and actinomycetes, indicating their stimulation after PAH addition. In the two natural soils, several groups were predominant: actinomycetes in one, fungi and mycorrhizae in the other, indicating a different response of the two natural soils to PAH contamination. Regarding MAI calculated on the enzymatic activities, one natural soil showed a microbial community neither resistant nor resilient in respect to the other and to the industrial soil. Our results highlight that the microbial community changes its composition and then physiological functions according to the land use as a result of PAH addition.

Elevated plasma phospholipid n-3 docosapentaenoic acid concentrations during hibernation.

Factors for initiating hibernation are unknown, but the condition shares some metabolic similarities with consciousness/sleep, which has been associated with n-3 fatty acids in humans. We investigated plasma phospholipid fatty acid profiles during hibernation and summer in free-ranging brown bears (Ursus arctos) and in captive garden dormice (Eliomys quercinus) contrasting in their hibernation patterns. The dormice received three different dietary fatty acid concentrations of linoleic acid (LA) (19%, 36% and 53%), with correspondingly decreased alpha-linolenic acid (ALA) (32%, 17% and 1.4%). Saturated and monounsaturated fatty acids showed small differences between summer and hibernation in both species. The dormice diet influenced n-6 fatty acids and eicosapentaenoic acid (EPA) concentrations in plasma phospholipids. Consistent differences between summer and hibernation in bears and dormice were decreased ALA and EPA and marked increase of n-3 docosapentaenoic acid and a minor increase of docosahexaenoic acid in parallel with several hundred percent increase of the activity index of elongase ELOVL2 transforming C20-22 fatty acids. The highest LA supply was unexpectantly associated with the highest transformation of the n-3 fatty acids. Similar fatty acid patterns in two contrasting hibernating species indicates a link to the hibernation phenotype and requires further studies in relation to consciousness and metabolism.

Levels of Metals and Microbial Biomass in Cobalt Coleman Mine Tailings (Canada) Three Decades after Land Reclamation

Investigations of restored metal contaminated tailings in Canada with regard to their long-term ability to sustain plant and associated microbiological populations are limited. The specific objectives of the present study were to assess (1) The current levels of total and bioavailable metals and (2) Microbial biomass in Cobalt Coleman mine tailings reclaimed in 1990. The level of microbial biomass was determined using Phospholipid Fatty Acid analysis (PLFA). Metal analysis revealed that the concentration of total Arsenic (As) was >100 and 20 ´ higher in the Nipissing tailing compared to the non-tailing site and the Cart Lake tailing. The same trend was observed to a lesser degree for total Cobalt (Co) and Copper (Cu) concentrations. Overall, the total metal levels remain high >30 years after phytoremediation, but the bioavailable metal amount was low. This suggests that soil metal impacts on biota are minimal. The reclaimed tailing exhibited significantly lower levels (p≤0.05) of organic matter compared to non-tailing reference areas. More importantly, the analyses revealed significantly high (p≤0.05) total microbial biomass in non-tailing soil samples (with higher organic matter content) compared to tailing soils. A strong positive correlation (r = 0.87) was observed between organic matter and total microbial biomass. In contrast to other studies, the pH of the two tailing sites was neutral (7.1 and 7.5) and negatively correlated (r = -95) with bacterial and fungal abundance. Bacteria dominated the microbial communities in all the sites including the non-tailing area, indicating that the targeted region is still under severe environmental stress. Overall, the metal levels in the targeted tailings remain high and the phytoremediation did not improve significantly the soil quality (organic matter, microbial biomass) over the last three decades.

Plasma phospholipid fatty acid profile, estimated desaturase activities and prevalence of the metabolic syndrome in a general population cohort: A cross-sectional study

BACKGROUND: An altered plasma fatty acid (FA) profile and desaturase activities have been associated with several metabolic diseases, including the MetS, but studies in the general populations are lacking, and only few studies have investigated a broad spectrum of FA in plasma phospholipids (PL). OBJECTIVE: We investigated, cross-sectionally, the relationship of the FA profile and desaturase activities in plasma PL with the prevalence of MetS in a general population in The Netherlands. METHODS: Baseline characteristic data from 850 participants (male: 50.2%) aged 38-68 years recruited in the Lifelines cohort study were obtained. The FA profile was determined in fasting plasma PL, and desaturase activities were estimated from product/precursor ratios. The MetS was defined according to International Diabetes Federation. Logistic regressions were used to examine the relation of the FA profile with the prevalence of MetS, and Bonferroni correction was applied to account for multiple testing. RESULTS: 151 participants (17.7%) had the MetS. After adjustment for several confounders and Bonferroni correction, higher tertiles of C18 : 0 (the early precursor of de novo lipogenesis pathway), C18 : 3n6 and C20 : 3n6 (both consistent with a high Δ6 desaturase (D6D) activity), and D6D activity itself were associated with a higher prevalence of MetS, while higher tertiles of C18 : 1n7, C24 : 0, and C24 : 1n9 (very long chain FA) as well as stearoyl-CoA desaturase (SCD)-18 were inversely associated with the MetS. CONCLUSIONS: This study shows that a wide-ranging plasma PL FA profile and estimated desaturase activities were different between adults with and without the MetS in a general representative population and implicates the importance of monitoring individual FAs and desaturase activities as novel modifiable biomarkers for the MetS.

Exploring the potential effect of phospholipase A2 antibody to extend beef shelf-life in a beef liposome model system

The objective of this study was to elucidate the effect of phospholipase A2 (PLA2) and a PLA2 antibody (aPLA2) on phospholipid (PL) hydrolysis in beef and to understand how the altered PL composition may affect lipid oxidation and antioxidant capacity of beef in an in vitro system. Various combinations of PLA2 and aPLA2 were introduced to a beef liposome model system and exposed to a retail display. The PL and free fatty acid (FFA) profiles, antioxidant capacity and lipid oxidation were measured for the liposome system. Key PL classes were reduced and the release of polyunsaturated FFAs was increased with the inclusion of PLA2 in the treatments (P < 0.05). There was no inhibition of PL hydrolysis with the addition of aPLA2. PLA2 showed strong antioxidant capacity in the liposome system (P < 0.01), but lipid oxidation still increased in samples treated with PLA2 throughout the retail display (P < 0.01). Finally, aPLA2 treatments demonstrated potential to decrease lipid oxidation (P < 0.01).

Metabolomic profiles of metformin in breast cancer survivors: a pooled analysis of plasmas from two randomized placebo-controlled trials

BackgroundObesity is a major health concern for breast cancer survivors, being associated with high recurrence and reduced efficacy during cancer treatment. Metformin treatment is associated with reduced breast cancer incidence, recurrence and mortality. To better understand the underlying mechanisms through which metformin may reduce recurrence, we aimed to conduct metabolic profiling of overweight/obese breast cancer survivors before and after metformin treatment.MethodsFasting plasma samples from 373 overweight or obese breast cancer survivors randomly assigned to metformin (n = 194) or placebo (n = 179) administration were collected at baseline, after 6 months (Reach For Health trial), and after 12 months (MetBreCS trial). Archival samples were concurrently analyzed using three complementary methods: untargeted LC–QTOF-MS metabolomics, targeted LC–MS metabolomics (AbsoluteIDQ p180, Biocrates), and gas chromatography phospholipid fatty acid assay. Multivariable linear regression models and family-wise error correction were used to identify metabolites that significantly changed after metformin treatment.ResultsParticipants (n = 352) with both baseline and study end point samples available were included in the analysis. After adjusting for confounders such as study center, age, body mass index and false discovery rate, we found that metformin treatment was significantly associated with decreased levels of citrulline, arginine, tyrosine, caffeine, paraxanthine, and theophylline, and increased levels of leucine, isoleucine, proline, 3-methyl-2-oxovalerate, 4-methyl-2-oxovalerate, alanine and indoxyl-sulphate. Long-chain unsaturated phosphatidylcholines (PC ae C36:4, PC ae C38:5, PC ae C36:5 and PC ae C38:6) were significantly decreased with the metformin treatment, as were phospholipid-derived long-chain n-6 fatty acids. The metabolomic profiles of metformin treatment suggest change in specific biochemical pathways known to impair cancer cell growth including activation of CYP1A2, alterations in fatty acid desaturase activity, and altered metabolism of specific amino acids, including impaired branched chain amino acid catabolism.ConclusionsOur results in overweight breast cancer survivors identify new metabolic effects of metformin treatment that may mechanistically contribute to reduced risk of recurrence in this population and reduced obesity-related cancer risk reported in observational studies.Trial registrationClinicalTrials.gov identifier: NCT01302379 and EudraCT Protocol #: 2015-001001-14.

Assessment of the ecotoxicological impact of captan@ZnO35–45nm and captan@SiO2 20–30nm nanopesticide on non-target soil microorganisms – A 100-day case study

Nanopesticide application should enable efficient pest management with smaller doses of an active ingredient. Nevertheless, the environmental risk assessment of nanopesticides is currently in its initial stages due to limited access to nanopesticides. Therefore, we synthesised nanofungicides with captan as an organic active ingredient and ZnO35–45nm or SiO2 20–30nm as nanocarriers (captan@ ZnO35–45nm and captan@ SiO2 20–30nm) and evaluated their environmental risk by testing different microbial parameters as its potential biomarkers. First, physicochemical analysis (SEM-EDS, XPS, and FTIR) confirmed the presence of captan in nanofungicides, and they maintained 43–61 % antifungal efficiency against pathogen fungi compared to captan. Second, a laboratory toxicity assay (spot test) showed that nanofungicides generally revealed 10–100-fold lower growth inhibition of non-target microbial strains compared to captan. Next, the effect of nanofungicides on the abundance, structure and function of non-target soil microorganisms was evaluated during the 100-day microcosm using orchard soil and compared to control, captan, and nanocarriers. The changes in the total number of bacteria, ammonia-oxidising bacteria (AOB) and fungi were enumerated using the copy number of the qPCR approach based on the copy number of 16S rRNA, amoA and ITS genes. The functional potential and microbial structure were estimated based on Community Level Physiological Profiles (CLPPs) and Phospholipid Fatty Acids (PLFAs) profiles. Generally, results indicated that nanofungicides affected soil microorganisms by changing, in different scale, various microbial parameters, but their negative effect was generally lower than pesticide. Although qPCR results revealed the harmful effect of all tested compounds on total bacteria number (16S rRNA) on day 42, and captan@ZnO35–45nm and nanocarrier SiO2 20–30nm still affected amoA gene copy number on day 100, but the total fungal abundance in orchard soil was not affected. Furthermore, the analyses of functional and structural microbial diversity indicated the recovery process that was the fastest for captan@SiO2 20–30nm nanofungicide. On the contrary, ZnO35–45nm increased and prolonged the negative effect of captan in synthesised nanofungicide and generally exerted a more profound and/or longer effect than SiO2 20–30nm nanocarrier. Therefore we conclude that SiO2 20–30nm has better potential to be used as a nanocarrier compared to ZnO35–45nm. More studies are needed but soil microorganisms as sensitive biomarkers should be used for environmental risk assessment of nanopesticides.