Mycelium-enhanced bacterial degradation of organic pollutants under bioavailability restrictions

This work examines the role of mycelia in enhancing the degradation by attached bacteria of organic pollutants that have poor bioavailability. Two oomycetes, Pythium oligandrum and Pythium aphanidermatum, were selected as producers of mycelial networks, while Mycobacterium gilvum VM552 served as a model polycyclic aromatic hydrocarbon (PAH)-degrading bacterium. The experiments consisted of bacterial cultures exposed to a non-disturbed non-aqueous phase liquid (NAPL) layer containing a heavy fuel spiked with 14C-labeled phenanthrene that were incubated in the presence or absence of the mycelia of the oomycetes in both shaking and static conditions. At the end of the incubation, the changes in the total alkane and PAH contents in the NAPL residue were quantified. The results revealed that with shaking and the absence of mycelia, the strain VM552 grew by utilizing the bulk of alkanes and PAHs in the fuel; however, biofilm formation was incipient and phenanthrene was mineralized following zero-order kinetics, due to bioavailability limitation. The addition of mycelia favored biofilm formation and dramatically enhanced the mineralization of phenanthrene, up to 30 times greater than the rate without mycelia, possibly by providing a physical support to bacterial colonization and by supplying nutrients at the NAPL/water interface. The results in the static condition were very different because the bacterial strain alone degraded phenanthrene with sigmoidal kinetics but could not degrade alkanes or the bulk of PAHs. We suggest that bacteria/oomycete interactions should be considered not only in the design of new inoculants in bioremediation, but also in biodegradation assessments of chemicals present in natural environments

Role of natural surfactants in bioremediation and bioavailability of PAH

Motivation: Polycyclic aromatic hydrocarbons (PAHs) are organic compounds found in most polluted areas mainly due to anthropogenicactivity. Such compounds entail several damages to human health and the environment in general because of their toxicityand carcinogenecity. Moreover, due to their recalcitrance and ubiquity, they supose a problem where research groups focustheir attention(1). In our case, efforts to find solutions to PAH pollution are aimed at bioremediation, looking for chemicalstrategies for improving the bioavailability in the biorremediation of contaminated areas, always without increasing the risk tothe environment where they are adsorbed.The main objectives of this project are the tuning of the fluorimetry method to detect hydrocarbons in aqueous samples and totest the effectiveness of a novel commercial rhamnolipid versus another one previously used, obtained from a cell culture atthe laboratory.Methods: We used a strain of Mycobacterium gilvum as biodegrader organism, and we have tested its ability to use these compoundsas carbon source (1, 2) in biodegradation experiments against different concentrations of pyrene (4-rings PAH as arepresentative compound of this group) supplied dissolved and crystalline in aqueous solutions. The variation in theconcentration of pyrene is measured using fluorimetry techniques in an equipment able to submit a sample to ultravioletradiation and collect the radiation emitted by the sample in a graph, where we will be able to detect a peak representing thepyrene in a specific and known length wave. We also studied the effect of a commercial rhamnolipid recently bought by thelaboratory, which is expected to increase the bioavailability of such compounds due to its surfactant effect, thus overcomingone of the main barriers to remediation and being a friendly alternative with the environment because of its naturally origin (2).Results: The bacteria is able to assimilate the supplied pyrene. When rhamnolipids are added, the final concentration of pyreneremaining in the saturated samples is less than in the cases we are not providing the rhamnolipid. When the pyrene issupplied as crystals, passive dosing occurs so that it dissolves until equilibrium is reached. When M. gilvum is added in thatpoint, pyrene is removed from the aqueous phase by breaking the balance and allowing a greater amount of crystals to bedissolved and removed from the medium.Conclusions: It has been found that using this commercial rhamnolipid is more effective, because it allows a greater solubility and theadvantage of having it available simply and quickly

Mobilization of Pollutant-Degrading Bacteria by Eukaryotic Zoospores

This study was supported by the Spanish Ministry of Science and Innovation (CGL2010-22068-C02-01 and CGL2013- 44554-R), the Andalusian Government (RNM 2337), and the CSIC JAE Program (RS). PvW has funding support from the BBSRC and NERC. Thanks are also given to Sara Hosseini of the Uppsala BioCenter, SLU, Uppsala, Sweden for a useful discussion on oomycete zoospores.Peer reviewedPostprin

Rhizosphere-enhanced biosurfactant action on slowly desorbing PAHs incontaminated soil

We studied how sunflower plants affect rhamnolipid biosurfactant mobilization of slowly desorbing fractions of polycyclic aromatic hydrocarbons (PAHs) in soil froma creosote-contaminated site. Desorption kinetics of 13 individual PAHs revealed that the soil contained initially up to 50% slowly desorbing fractions. A rhamnolipid biosurfactantwas applied to the soil at the completion of the sunflower cycle (75 days in greenhouse conditions). After this period, the PAHs that remained in the soil were mainly present in a slowly desorbing form as a result of the efficient biodegradation of fast-desorbing PAHs by native microbial populations. The rhamnolipid enhanced the bioavailable fraction of the remaining PAHs by up to 30%, as evidenced by a standardized desorption extraction with Tenax, but the enhancement occurredwith only planted soils. The enhanced bioavailability did not decrease residual PAH concentrations under greenhouse conditions, possibly due to ecophysiological limitations in the biodegradation process thatwere independent of the bioavailability. However, biodegradationwas enhanced during slurry treatment of greenhouse planted soils that received the biosurfactant. The addition of rhamnolipids caused a dramatic shift in the soil bacterial community structure, which was magnified in the presence of sunflower plants. The stimulated groups were identified as fast-growing and catabolically versatile bacteria. This new rhizosphere microbial biomass possibly interacted with the biosurfactant to facilitate intra-aggregate diffusion of PAHs, thus enhancing the kinetics of slow desorption. Our results show that the usually limited biosurfactant efficiency with contaminated field soils can be significantly enhanced by integrating the sunflower ontogenetic cycle into the bioremediation design

Scientific concepts and methods for moving persistence assessments into the 21st century

The evaluation of a chemical substance's persistence is key to understanding its environmental fate, exposure concentration, and, ultimately, environmental risk. Traditional biodegradation test methods were developed many years ago for soluble, nonvolatile, single-constituent test substances, which do not represent the wide range of manufactured chemical substances. In addition, the Organisation for Economic Co-operation and Development (OECD) screening and simulation test methods do not fully reflect the environmental conditions into which substances are released and, therefore, estimates of chemical degradation half-lives can be very uncertain and may misrepresent real environmental processes. In this paper, we address the challenges and limitations facing current test methods and the scientific advances that are helping to both understand and provide solutions to them. Some of these advancements include the following: (1) robust methods that provide a deeper understanding of microbial composition, diversity, and abundance to ensure consistency and/or interpret variability between tests; (2) benchmarking tools and reference substances that aid in persistence evaluations through comparison against substances with well-quantified degradation profiles; (3) analytical methods that allow quantification for parent and metabolites at environmentally relevant concentrations, and inform on test substance bioavailability, biochemical pathways, rates of primary versus overall degradation, and rates of metabolite formation and decay; (4) modeling tools that predict the likelihood of microbial biotransformation, as well as biochemical pathways; and (5) modeling approaches that allow for derivation of more generally applicable biotransformation rate constants, by accounting for physical and/or chemical processes and test system design when evaluating test data. We also identify that, while such advancements could improve the certainty and accuracy of persistence assessments, the mechanisms and processes by which they are translated into regulatory practice and development of new OECD test guidelines need improving and accelerating. Where uncertainty remains, holistic weight of evidence approaches may be required to accurately assess the persistence of chemicals. Integr Environ Assess Manag 2022;18:1454-1487. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Keywords: Bioavailability; Biodegradability; Biodegradation; Degradation half-lives; Persistence assessment

Healthcare workers hospitalized due to COVID-19 have no higher risk of death than general population. Data from the Spanish SEMI-COVID-19 Registry

Aim To determine whether healthcare workers (HCW) hospitalized in Spain due to COVID-19 have a worse prognosis than non-healthcare workers (NHCW). Methods Observational cohort study based on the SEMI-COVID-19 Registry, a nationwide registry that collects sociodemographic, clinical, laboratory, and treatment data on patients hospitalised with COVID-19 in Spain. Patients aged 20-65 years were selected. A multivariate logistic regression model was performed to identify factors associated with mortality. Results As of 22 May 2020, 4393 patients were included, of whom 419 (9.5%) were HCW. Median (interquartile range) age of HCW was 52 (15) years and 62.4% were women. Prevalence of comorbidities and severe radiological findings upon admission were less frequent in HCW. There were no difference in need of respiratory support and admission to intensive care unit, but occurrence of sepsis and in-hospital mortality was lower in HCW (1.7% vs. 3.9%; p = 0.024 and 0.7% vs. 4.8%; p<0.001 respectively). Age, male sex and comorbidity, were independently associated with higher in-hospital mortality and healthcare working with lower mortality (OR 0.211, 95%CI 0.067-0.667, p = 0.008). 30-days survival was higher in HCW (0.968 vs. 0.851 p<0.001). Conclusions Hospitalized COVID-19 HCW had fewer comorbidities and a better prognosis than NHCW. Our results suggest that professional exposure to COVID-19 in HCW does not carry more clinical severity nor mortality

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries