Publications

Nutrient enrichment induces a shift in dissolved organic carbon (DOC) metabolism in oligotrophic freshwater sediments

Dissolved organic carbon (DOC) turnover in aquatic environments is modulated by the presence of other key macronutrients, including nitrogen (N) and phosphorus (P). The ratio of these nutrients directly affects the rates of microbial growth and nutrient processing in the natural environment. The aim of this study was to investigate how labile DOC metabolism responds to changes in nutrient stoichiometry using 14C tracers in conjunction with untargeted analysis of the primary metabolome in upland peat river sediments. N addition led to an increase in 14C-glucose uptake, indicating that the sediments were likely to be primarily N limited. The mineralisation of glucose to 14CO2 reduced following N addition, indicating that nutrient addition induced shifts in internal carbon (C) partitioning and microbial C use efficiency (CUE). This is directly supported by the metabolomic profile data which identified significant differences in 22 known metabolites (34% of the total) and 30 unknown metabolites (16% of the total) upon the addition of either N or P. 14C-glucose addition increased the production of organic acids known to be involved in mineral P dissolution (e.g. gluconic acid, malic acid). Conversely, when N was not added, the addition of glucose led to the production of the sugar alcohols, mannitol and sorbitol, which are well known microbial C storage compounds. P addition resulted in increased levels of several amino acids (e.g. alanine, glycine) which may reflect greater rates of microbial growth or the P requirement for coenzymes required for amino acid synthesis. We conclude that inorganic nutrient enrichment in addition to labile C inputs has the potential to substantially alter in-stream biogeochemical cycling in oligotrophic freshwaters.

Is soluble protein mineralisation and protease activity in soil regulated by supply or demand?

Protein represents a major input of organic matter to soil and is an important source of carbon (C) and nitrogen (N) for microorganisms. Therefore, determining which soil properties influence protein mineralisation in soil is key to understanding and modelling soil C and N cycling. However, the effect of different soil properties on protein mineralisation, and especially the interactions between soil properties, are poorly understood. We investigated how topsoil and subsoil properties affect protein mineralisation along a grassland altitudinal (catena) sequence that contained a gradient in soil type and primary productivity. We devised a schematic diagram to test the key edaphic factors that may influence protein mineralisation in soil (e.g. pH, microbial biomass, inorganic and organic N availability, enzyme activity and sorption). We then measured the mineralisation rate of 14C-labelled soluble plant-derived protein and amino acids in soil over a two-month period. Correlation analysis was used to determine the associations between rates of protein mineralisation and soil properties. Contrary to expectation, we found that protein mineralisation rate was nearly as fast as for amino acid turnover. We ascribe this rapid protein turnover to the low levels of protein used here, its soluble nature, a high degree of functional redundancy in the microbial community and microbial enzyme adaptation to their ecological niche. Unlike other key soil N processes (e.g. nitrification, denitrification), protease activity was not regulated by a small range of factors, but rather appeared to be affected by a wide range of interacting factors whose importance was dependent on altitude and soil depth [e.g. above-ground net primary productivity (NPP), soil pH, nitrate, cation exchange capacity (CEC), C:N ratio]. Based on our results, we hypothesise that differences in soil N cycling and the generation of ammonium are more related to the rate of protein supply rather than limitations in protease activity and protein turnover per se.

Ultrastructure of the stipe and apothecium of Sclerotinia sclerotiorum

No abstract is provided for this article.

A real-time test of food hazard awareness

Purpose – Food poisoning attributable to the home generates a large disease burden, yet is an unregulated and largely unobserved domain. Investigating food safety awareness and routine practices is fraught with difficulties. The purpose of this paper is to develop and apply a new survey tool to elicit awareness of food hazards. Data generated by the approach are analysed to investigate the impact of oberservable heterogeneity on food safety awareness. Design/methodology/approach – The authors develop a novel Watch-and-Click survey tool to assess the level of awareness of a set of hazardous food safety behaviours in the domestic kitchen. Participants respond to video footage stimulus, in which food hazards occur, via mouse clicks/screen taps. This real-time response data is analysed via estimation of count and logit models to investigate how hazard identification patterns vary over observable characteristics. Findings – User feedback regarding the Watch-and-Click tool approach is extremely positive. Substantive results include significantly higher hazard awareness among the under 60s. People who thought they knew more than the average person did indeed score higher but people with food safety training/experience did not. Vegetarians were less likely to identify four of the five cross-contamination hazards they observed. Originality/value – A new and engaging survey tool to elicit hazard awareness with real-time scores and feedback is developed, with high levels of user engagement and stakeholder interest. The approach may be applied to elicit hazard awareness in a wide range of contexts including education, training and research.

Seasonal and diurnal surveillance of treated and untreated wastewater for human enteric viruses

Understanding the abundance and fate of human viral pathogens in wastewater is essential when assessing the public health risks associated with wastewater discharge to the environment. Typically, however, the microbiological monitoring of wastewater is undertaken on an infrequent basis and peak discharge events may be missed leading to the misrepresentation of risk levels. To evaluate diurnal patterns in wastewater viral loading, we undertook 3-day sampling campaigns with bi-hourly sample collection over three seasons at three wastewater treatment plants. Untreated influent was collected at Ganol and secondary-treated effluent was sampled at Llanrwst and Betws-y-Coed (North Wales, UK). Our results confirmed the presence of human adenovirus (AdV), norovirus genotypes I and II (NoVGI and NoVGII) in both influent and effluent samples while sapovirus GI (SaVGI) was only detected in influent water. The AdV titre was high and relatively constant in all samples, whereas the NoVGI, NoVGII and SaVGI showed high concentrations during autumn and winter and low counts during the summer. Diurnal patterns were detected in pH and turbidity for some sampling periods; however, no such changes in viral titres were observed apart from slight fluctuations in the influent samples. Our findings suggest that viral particle number in wastewater is not affected by daily chemical fluctuations. Hence, a grab sample taken at any point during the day may be sufficient to enumerate the viral load of wastewater effluent within an order of magnitude while four samples a day are recommended for testing wastewater influent samples.

Migration of heavy metals in soil as influenced by compost amendments

Soils contaminated with heavy metals can pose a major risk to freshwaters and food chains. In this study, the success of organic and inorganic intervention strategies to alleviate toxicity in a highly acidic soil heavily contaminated with As, Cu, Pb, and Zn was evaluated over 112 d in a mesocosm trial. Amelioration of metal toxicity was assessed by measuring changes in soil solution chemistry, metal leaching, plant growth, and foliar metal accumulation. Either green waste- or MSW-derived composts increased plant yield and rooting depth, reduced plant metal uptake, and raised the pH and nutrient status of the soil. We conclude that composts are well suited for promoting the re-vegetation of contaminated sites; however, care must be taken to ensure that very short-term leaching pulses of heavy metals induced by compost amendment are not of sufficient magnitude to cause contamination of the wider environment.

An in vitro effect of ‘Dazomet’ on phenolase activity in exudates of Sclerotinia sclerotiorum

No abstract is provided for this article.

Cover crops affect the partial nitrogen balance in a maize-forage cropping system

Part of the nitrogen (N) fertilizer applied to crops is lost to the environment, contributing to global warming, eutrophication, and groundwater contamination. However, low N supply stimulates soil organic N turnover and carbon (C) loss, since the soil N/C ratio in soil is quasi-constant, ultimately resulting in land degradation. Grasses such as ruzigrass (Urochloa ruziziensis) grown as winter pasture or a cover crop in rotation with maize (Zea mays) can reduce N leaching, however, this may induce N deficiency and depress yields in the subsequent maize crop. Despite the potential to decrease N loss, this rotation may negatively affect the overall N balance of the cropping system. However, this remains poorly quantified. To test this hypothesis, maize, fertilized with zero to 210 kg N ha−1, was grown after ruzigrass, palisade grass (Urochloa brizanta) and Guinea grass (Pannicum maximum), and the N inputs, outputs and partial N balance determined. Despite the intrinsically poor soil quality associated with the tropical Ultisol, maize grown after the grasses was efficient in acquiring N, resulting in a negative N balance even when 210 kg ha−1 of N was applied after Guinea grass. Losses by leaching, N2O emission and NH3 volatilization did not exceed 13.8 kg ha−1 irrespective of the grass type. Despite a similar N loss among grasses, Guinea grass resulted in a higher N export in the maize grain due to a higher yield, resulting in a more negative N balance. Soil N depletion can lead to C loss, which can result in land degradation.

Rye cover crop incorporation and high watertable mitigate greenhouse gas emissions in cultivated peatland

Drainage and cultivation of peat soils almost always result in rapid soil degradation and a loss of soil organic matter (SOM). Winter cover crop cultivation and subsequent incorporation and watertable elevation have been considered as potential strategies to improve soil quality and decrease nutrient loss in drained and cultivated peatlands. However, the combined effect of residue incorporation and watertable management on greenhouse gas (GHG) emissions in these highly productive fen peat soils remains unknown. In the present study, two winter cover crops with contrasting carbon/nitrogen ratios (vetch [ Vicia sativa ], 45–60; rye [ Secale cereale ], 13–14) were incorporated into peat soils as green manure (without extra synthetic/organic N addition) at two watertable depths (−50 and −30 cm). Our results showed that fast mineralization of incorporated residues can cause a large pulse of GHG release under favourable environmental conditions. Both vetch and rye incorporation increased CO 2 emissions compared with the bare soil treatments due to labile C addition and removal of N constraints. However, the two cover crops had strongly contrasting effects on N 2 O emissions. Incorporation of low C/N ratio vetch stimulated N 2 O emissions (average 21.8 ± 7.3 mg N m −2 hr −1 ) compared with the bare soil treatments, whereas high C/N ratio rye decreased N 2 O emissions (average 0.09 ± 0.03 mg N m −2 hr −1 ). Raising the watertable slightly reduced CO 2 emissions from an average of 1.3 ± 0.4 (the bare soils) to 0.9 ± 0.3 g C m −2 hr −1 by inhibiting SOM mineralization but significantly increased N 2 O emissions in the vetch treatments by stimulating denitrification. CH 4 fluxes were not affected by watertable depth, and their contribution to total global warming potential was negligible. Therefore, we conclude that high C/N ratio cover crops (e.g., rye) in combination with a raised watertable may represent a viable management option to mitigate GHG fluxes in fen peat soils.

Carbon and Nitrogen Dynamics in an Oxisol as Affected by Liming and Crop Residues under No-Till

The short-term effects of surface lime application and black oat (Avena strigosa Schreb.) residues, with or without N fertilization, were evaluated in a long-term no-till (NT) system on a sandy clay loam, a kaolinitic, thermic Typic Hapludox from the state of Paraná, Brazil. The main plot treatments were: control and dolomitic lime applied on soil surface at 8 Mg ha−1. Three treatments with crop residues were evaluated on the subplots: (i) fallow, (ii) black oat residues, and (iii) black oat residues after N fertilization at 180 kg ha−1. Black oat dry biomass was not affected by the treatments during 3 yr. Surface liming increased soil pH, microbial biomass, microbial activity, and bacterial/fungal ratio at the soil surface (0–5 cm), resulting in increased amino acid turnover, water-soluble humic substances formation, and N mineralization and nitrification. While the application of black oat did increase the soil pH, overall it had much less effect on soil biological processes and C and N pools than did lime. We concluded that black oat cannot replace the need for lime to optimize crop production in these tropical NT systems. In the long term, however, black oat should aid in the amelioration of acidity and replenishment of soil organic C pools and should help reduce erosion. Overall, this study suggests that overapplication of inorganic fertilizer N may occur in some tropical NT systems. Further experiments are required in NT systems to investigate the use of slow-release N fertilizers in combination with lime and black oat as a mechanism to reduce acidification and promote sustainability.

Diurnal changes in pathogenic and indicator virus concentrations in wastewater

Wastewater-based epidemiology (WBE) has been commonly used for monitoring SARS-CoV-2 outbreaks. As sampling times and methods (i.e. grab vs composite) may vary, diurnal changes of viral concentrations in sewage should be better understood. In this study, we collected untreated wastewater samples hourly for 4 days at two wastewater treatment plants in Wales to establish diurnal patterns in virus concentrations and the physico-chemical properties of the water. Simultaneously, we also trialled three absorbent materials as passive samples as a simple and cost-efficient alternative for the collection of composite samples. Ninety-six percent of all liquid samples (n = 74) and 88% of the passive samplers (n = 59) were positive for SARS-CoV-2, whereas 87% and 97% of the liquid and passive samples were positive for the faecal indicator virus crAssphage, respectively. We found no significant daily variations in the concentration of the target viruses, ammonium and orthophosphate, and the pH and electrical conductivity levels were also stable. Weak positive correlations were found between some physico-chemical properties and viral concentrations. More variation was observed in samples taken from the influent stream as opposed to those taken from the influent tank. Of the absorbent materials trialled as passive samples, we found that tampons provided higher viral recoveries than electronegative filter paper and cotton gauze swabs. For all materials tested, viral recovery was dependent on the virus type. Our results indicate that grab samples may provide representative alternatives to 24-h composite samples if taken from the influent tank, hence reducing the costs of sampling for WBE programmes. Tampons are also viable alternatives for cost-efficient sampling; however, viral recovery should be optimised prior to use.

Microbes as Engines of Ecosystem Function: When Does Community Structure Enhance Predictions of Ecosystem Processes?

Microorganisms are vital in mediating the earth's biogeochemical cycles; yet, despite our rapidly increasing ability to explore complex environmental microbial communities, the relationship between microbial community structure and ecosystem processes remains poorly understood. Here, we address a fundamental and unanswered question in microbial ecology: 'When do we need to understand microbial community structure to accurately predict function?' We present a statistical analysis investigating the value of environmental data and microbial community structure independently and in combination for explaining rates of carbon and nitrogen cycling processes within 82 global datasets. Environmental variables were the strongest predictors of process rates but left 44% of variation unexplained on average, suggesting the potential for microbial data to increase model accuracy. Although only 29% of our datasets were significantly improved by adding information on microbial community structure, we observed improvement in models of processes mediated by narrow phylogenetic guilds via functional gene data, and conversely, improvement in models of facultative microbial processes via community diversity metrics. Our results also suggest that microbial diversity can strengthen predictions of respiration rates beyond microbial biomass parameters, as 53% of models were improved by incorporating both sets of predictors compared to 35% by microbial biomass alone. Our analysis represents the first comprehensive analysis of research examining links between microbial community structure and ecosystem function. Taken together, our results indicate that a greater understanding of microbial communities informed by ecological principles may enhance our ability to predict ecosystem process rates relative to assessments based on environmental variables and microbial physiology.

VSOP observations of bright compact southern Hemisphere AGN

Plant species-specific rhizobiome assembly in the hyper-arid Atacama Desert

The hyper-arid core of the Atacama Desert represents one of the oldest and driest regions of the world and is characterized by high aridity (precipitation <2 mm y^-1), hypersaline soil conditions, extremes in temperature (-5 °C to 50 °C), intense UV irradiation and low organic matter content. Despite this, the Yungay area within the hyper-arid core is capable of supporting vegetation adapted to these extreme environmental conditions, including <i>Distichlis spicata</i> and <i>Suaeda foliosa</i>, which access deep groundwater resources. Little is known, however, about the below-ground microbial community that these plants support. To understand plant-microbe interactions in this environment, we investigated the physicochemical properties in the rhizosphere soils of <i>D. spicata</i> and <i>S. foliosa</i>. In addition, DNA was extracted from the rhizosphere soil and 16S rRNA gene amplicon sequencing performed to describe the taxonomic composition of the bacterial community. Our results revealed significant differences in the physicochemical properties between the rhizosphere soils of the two native plants. <i>D. spicata</i> showed higher Electrical Conductivity (EC), while <i>S. foliosa</i> had elevated ammonium concentrations. The microbial composition also varied between the plant species: Firmicutes (Bacillota), Proteobacteria (Pseudomonadota), Halobacteria, and Actinobacteriota (Actinomycetota) were dominant in both plant rhizosphere samples, but their relative abundance differed. In this context, Halobacteria were highly represented in the soils of <i>D. spicata</i> and Firmicutes (Bacillota) in those from <i>S. foliosa</i>. Furthermore, bacterial genera such as <i>Enterococcus</i> were only present in the <i>S. foliosa</i> rhizosphere, while <i>Natrinema</i> was highly represented in soil from under <i>D. spicata</i> (33.4%) in comparison to <i>S. foliosa</i> (1.5%). The microbial community of <i>D. spicata</i> was strongly influenced by EC, whereas that of <i>S. foliosa</i> correlated more with ammonium levels. These findings advance our understanding of microbial community adaptation in one of Earth's most extreme environments and provide new insights into plant-microbe interaction in hyper-arid soils.

Earthworms mediate the influence of polyethylene (PE) and polylactic acid (PLA) microplastics on soil bacterial communities

There is a growing body of evidence that suggests that both biodegradable and conventional (non-degradable) microplastics (MP) are hazardous to soil health by affecting the delivery of key ecological functions such as litter decomposition, nutrient cycling and water retention. Specifically, soil fauna may be harmed by the presence of MPs while also being involved in their disintegration, degradation, migration and transfer in soil. Therefore, a comprehensive understanding of the interactions between MPs and soil fauna is essential. Here, we conducted a 120-day soil microcosm experiment applying polyethylene (PE) and polylactic acid (PLA), in the absence/presence of the earthworm Eisenia nordenskioldi to estimate the relative singular and combined impact of MPs and earthworms on the soil bacterial community. Our findings revealed contrasting effects of PE and PLA on the composition and diversity of soil bacteria. All treatments affected the community and network structure of the soil bacterial community. Compared to the control (no MPs or earthworms), PE decreased bacterial alpha diversity, while PLA increased it. Patescibacteria were found to be significantly abundant in the PE group whereas Actinobacteria and Gemmatimonadetes were more abundant in PE, and PLA and earthworms groups. The presence of earthworms appeared to mediate the impact of PE/PLA on soil bacteria, potentially through bacterial consumption or by altering soil properties (e.g., pH, aeration, C availability). Earthworm presence also appeared to promote the chemical aging of PLA. Collectively, our results provide novel insights into the soil-fauna-driven impact of degradable/nondegradable MPs exposure on the long-term environmental risks associated with soil microorganisms.

Plastic pollution and human pathogens: Towards a conceptual shift in risk management at bathing water and beach environments

Emerging evidence indicates that micro- and macro-plastics present in water can support a diverse microbial community, including potential human pathogens (e.g., bacteria, viruses). This interaction raises important concerns surrounding the role and suitability of current bathing water regulations and associated pathogen exposure risk within beach environments. In response to this, we critically evaluated the available evidence on plastic-pathogen interactions and identified major gaps in knowledge. This review highlighted the need for a conceptual shift in risk management at public beaches recognising: (i) interconnected environmental risks, e.g., associations between microbial compliance parameters, potential pathogens and both contemporary and legacy plastic pollution; and (ii) an appreciation of risk of exposure to plastic co-pollutants for both water and waterside users. We present a decision-making framework to identify options to manage plastic-associated pathogen risks alongside short- and longer-term research priorities. This advance will help deliver improvements in managing plastic-associated pathogen risk, acknowledging that human exposure potential is not limited to only those who engage in water-based activity. We argue that adopting these recommendations will help create an integrated approach to managing and reducing human exposure to pathogens at bathing, recreational water and beach environments.

Electron probe microanalysis of cell walls of Cunninghamella echinulata

Hyphal and spore walls of Cunninghamella echinulata (Thaxt.) Thaxt., were examined by electron probe microanalysis. Phosphorus, sulphur, calcium, chlorine and magnesium were positively identified and their presence confirmed by chemical and spectrochemical analysis. Results indicate that polyphosphate in walls of Mucorales is associated with chitosan through an ionic linkage.

Toileting behaviours of the UK public: insights for reducing gender bias wastewater-based epidemiology sampling strategies

Cross-sectional survey results from a toileting behaviour survey conducted between the 27th to the 28th of June 2022. Participants (<em>n</em> = 2109) were aged 18 years or older and were living in the UK. The survey consisted of 17 closed-ended questions, with 7 of the questions addressing specific demographic topics and 10 questions addressed toileting behaviour. The questionnaire was designed by a team consisting of environmental microbiologists, public health specialists, wastewater-based epidemiologists, and social scientists, based on the study objectives and incorporating information from previous studies on the same topic. First, self-report questions were asked on typical frequency of urination and defecation, followed by self-reports of frequency of urination and defecation at a variety of locations including at home, at work, educational buildings, transport hubs, and in public toilets. The comfort in urination/defecation at these locations for defecation and urination was also measured. Other questions about toileting behaviour and health monitoring were measured by statements with a 5-point Likert scale (e.g., strongly disagree to strongly agree).