Defining an additivity framework for mixture research in inducible whole-cell biosensors

A novel additivity framework for mixture effect modelling in the context of whole cell inducible biosensors has been mathematically developed and implemented in R. The proposed method is a multivariate extension of the effective dose (EDp) concept. Specifically, the extension accounts for differential maximal effects among analytes and response inhibition beyond the máximum permissive concentrations. This allows a multivariate extension of Loewe additivity, enabling direct application in a biphasic dose-response framework. The proposed additivity definition was validated, and its applicability illustrated by studying the response of the cyanobacterial biosensor Synechococcus elongatus PCC 7942 pBG2120 to binary mixtures of Zn, Cu, Cd, Ag, Co and Hg. The novel method allowed by the first time to model complete dose-response profiles of an inducible whole cell biosensor to mixtures. In addition, the approach also allowed identification and quantification of departures from additivity (interactions) among analytes. The biosensor was found to respond in a near additive way to heavy metal mixtures except when Hg, Co and Ag were present, in which case strong interactions occurred. The method is a useful contribution for the whole cell biosensors discipline and related areas allowing to perform appropriate assessment of mixture effects in non-monotonic dose-response frameworksThis research was supported by MINECO grants CGL2010-15675 and CTM2013-45775-C2-2-R

A portable geometry-independent tomographic system for gamma-ray, a next generation of nuclear waste characterization

One of the main activities of the nuclear industry is the characterisation of radioactive waste based on the detection of gamma radiation. Large volumes of radioactive waste are classified according to their average activity, but often the radioactivity exceeds the maximum allowed by regulators in specific parts of the bulk. In addition, the detection of the radiation is currently based on static detection systems where the geometry of the bulk is fixed and well known. Furthermore, these systems are not portable and depend on the transport of waste to the places where the detection systems are located. However, there are situations where the geometry varies and where moving waste is complex. This is especially true in compromised situations.We present a new model for nuclear waste management based on a portable and geometry-independent tomographic system for three-dimensional image reconstruction for gamma radiation detection. The system relies on a combination of a gamma radiation camera and a visible camera that allows to visualise radioactivity using augmented reality and artificial computer vision techniques. This novel tomographic system has the potential to be a disruptive innovation in the nuclear industry for nuclear waste management

Early and differential bacterial colonization on microplastics deployed into the effluents of wastewater treatment plants

Título del Post Print: Early and differential bacterial colonization on microplasticsMicrobial colonization of microplastics (MPs) in aquatic ecosystems is a well-known phenomenon; however, there is insufficient knowledge of the early colonization phase. Wastewater treatment plant (WWTP) effluents have been proposed as important pathways for MPs entry and transport in aquatic environments and are hotspots of bacterial pathogens and antibiotic resistance genes (ARGs). This study aimed at characterizing bacterial communities in the early stage of biofilm formation on seven different types of MPs deployed in two different WWTPs effluents as well as measuring the relative abundance of two ARGs (sulI and tetM) on the tested MPs. Illumina Miseq sequencing of the 16S rRNA showed significant higher diversity of bacteria on MPs in comparison with free-living bacteria in the WWTP effluents. β-diversity analysis showed that the in situ environment (sampling site) and hydrophobicity, to a lesser extent, had a role in the early bacterial colonization phase. An early colonization phase MPs-core microbiome could be identified. Furthermore, specific core microbiomes for each type of polymer suggested that each type might select early attachment of bacteria. Although the tested WWTP effluent waters contained antibiotic resistant bacteria (ARBs) harboring the sulI and tetM ARGs, MPs concentrated ARBs harboring the sulI gene but not tetM. These results highlight the relevance of the early attachment phase in the development of bacterial biofilms on different types of MP polymers and the role that different types of polymers might have facilitating the attachment of specific bacteria, some of which might carry ARGsFinancial support was provided by the Spanish Ministry of Economy and Competitiveness (CTM2016-74927-C2-1/2-R

Combined toxicity of graphite-diamond nanoparticles and thiabendazole to Daphnia magna

Carbon-based nanomaterials exhibit unique properties that make them suitable for a wide variety of industrial and biomedical applications. In this work, we studied the acute toxicity of graphite-diamond nanoparticles (GDN) combined with the fungicide thiabendazole (TBZ) to the immobilization of the cladoceran Daphnia magna in the presence and absence of the micro green algae Raphidocelis subcapitata, supplied as food source. The toxicity of GDN to D. magna decreased in the presence of R. subcapitata, while that of TBZ increased, the latter suggesting a carrier effect to TBZ. GDN-TBZ mixtures were fitted to the most common conceptual models applied to mixture toxicity: Concentration Addition (CA), Independent Action (IA) and Combination Index (CI). For GDN-TBZ mixtures in the absence of food the best fit was obtained with dose ratio deviation from CA model, while in the presence of food, dose level deviation from CA gave a better fit. The binary mixtures of GDN and TBZ showed synergistic toxic interactions at low concentrations, which could be attributed to the increased bioavailability of TBZ adsorbed on GDN. For higher concentrations of GDN, the binary mixtures turned antagonistic due to particle agglomeration. Our study provides evidence that deviations from additivity are dose dependent and relevant for the risk assessment of mixtures of nanoparticles with other chemical pollutants.publishe

The small Ca 2+ -binding protein CSE links Ca 2+ signalling with nitrogen metabolism and filament integrity in Anabaena sp. PCC 7120

Funder: FP7 People: Marie-Curie Actions; doi: http://dx.doi.org/10.13039/100011264; Grant(s): 2013–607607Abstract: Background: Filamentous cyanobacteria represent model organisms for investigating multicellularity. For many species, nitrogen-fixing heterocysts are formed from photosynthetic vegetative cells under nitrogen limitation. Intracellular Ca2+ has been implicated in the highly regulated process of heterocyst differentiation but its role remains unclear. Ca2+ is known to operate more broadly in metabolic signalling in cyanobacteria, although the signalling mechanisms are virtually unknown. A Ca2+-binding protein called the Ca2+ Sensor EF-hand (CSE) is found almost exclusively in filamentous cyanobacteria. Expression of asr1131 encoding the CSE protein in Anabaena sp. PCC 7120 was strongly induced by low CO2 conditions, and rapidly downregulated during nitrogen step-down. A previous study suggests a role for CSE and Ca2+ in regulation of photosynthetic activity in response to changes in carbon and nitrogen availability. Results: In the current study, a mutant Anabaena sp. PCC 7120 strain lacking asr1131 (Δcse) was highly prone to filament fragmentation, leading to a striking phenotype of very short filaments and poor growth under nitrogen-depleted conditions. Transcriptomics analysis under nitrogen-replete conditions revealed that genes involved in heterocyst differentiation and function were downregulated in Δcse, while heterocyst inhibitors were upregulated, compared to the wild-type. Conclusions: These results indicate that CSE is required for filament integrity and for proper differentiation and function of heterocysts upon changes in the cellular carbon/nitrogen balance. A role for CSE in transmitting Ca2+ signals during the first response to changes in metabolic homeostasis is discussed

Construction of a self-luminescent cyanobacterial bioreporter that detects a broad range of bioavailable heavy metals in aquatic environments

Frontiers in Microbiology 6 (2015): 186 This Document is Protected by copyright and was first published by Frontiers. All rights reserved. It is reproduced with permissionA self-luminescent bioreporter strain of the unicellular cyanobacterium Synechococcus sp. PCC 7942 was constructed by fusing the promoter region of the smt locus (encoding the transcriptional repressor SmtB and the metallothionein SmtA) to luxCDABE from Photorhabdus luminescens; the sensor smtB gene controlling the expression of smtA was cloned in the same vector. The bioreporter performance was tested with a range of heavy metals and was shown to respond linearly to divalent Zn, Cd, Cu, Co, Hg, and monovalent Ag. Chemical modeling was used to link bioreporter response with metal speciation and bioavailability. Limits of Detection (LODs), Maximum Permissive Concentrations (MPCs) and dynamic ranges for each metal were calculated in terms of free ion concentrations. The ranges of detection varied from 11 to 72 pM for Hg2+ (the ion to which the bioreporter was most sensitive) to 1.54-5.35 μM for Cd2+ with an order of decreasing sensitivity as follows: Hg2+ >> Cu2+ >> Ag+ > Co2+ = Zn2+ > Cd2+. However, the maximum induction factor reached 75-fold in the case of Zn2+ and 56-fold in the case of Cd2+, implying that Zn2+ is the preferred metal in vivo for the SmtB sensor, followed by Cd2+, Ag+ and Cu2+ (around 45-50-fold induction), Hg2+ (30-fold) and finally Co2+ (20-fold). The bioreporter performance was tested in real environmental samples with different water matrix complexity artificially contaminated with increasing concentrations of Zn, Cd, Ag, and Cu, confirming its validity as a sensor of free heavy metal cations bioavailability in aquatic environmentsThis study was funded by MINECO grants CGL2010-15675 and CTM2013-45775-C2-2-

Microplastics as vectors of the antibiotics azithromycin and clarithromycin: effects towards freshwater microalgae

Water pollution due to microplastics (MPs) is recognized as a major anthropogenic impact. Once MPs reach the ecosystems, they are exposed to a variety of other pollutants, which can be sorbed on them, transported and eventually desorbed. In this work, we tested the hypothesis that MPs can behave as conveyors for delivering chemicals toxic to aquatic microorganisms by investigating the vector role of MPs of polyethylene terephthalate (PET), polylactic acid (PLA), polyoxymethylene (POM) and polystyrene (PS) to the macrolide antibiotics azithromycin (AZI) and clarithromycin (CLA). AZI and CLA were chosen, as they are included in the Watch List for EU monitoring concerning water policy by Decision (EU) 2018/840. MPs were loaded in contact with 500 μg/L of AZI or 1000 μg/L of CLA. Results showed that both antibiotics were sorbed on all tested MPs. The more hydrophobic AZI was sorbed in higher proportion than CLA. Both antibiotics were desorbed from MPs upon contact with water with percentages between 14.6 ± 2.6% for AZI and 1.9 ± 1.4% for CLA of the concentrations to which the MPs were initially exposed. Virgin MPs were not toxic to the cyanobacterium Anabaena sp. PCC7120. However, antibiotic-loaded MPs significantly inhibited the growth and chlorophyll content of the cyanobacterium. Most of the sorbed antibiotics became released upon contact with cyanobacterial cultures, which was the cause for the observed toxicity. Therefore, MPs can play a role as vectors of antibiotics in freshwaters systems affecting the basic trophic level of photosynthetic microorganismsFinancial support was provided by the Spanish Ministry of Economy and Competitiveness (CTM2016-74927C2-1-R/2-R). We also thank the EnviroPlaNet Network Thematic Network of Micro and Nanoplastics in the Environment (RED2018-102345-T; Ministerio de Ciencia, Innovacion y Universidades

Physicochemical and biological interactions between cerium oxide nanoparticles and a 1,8-naphthalimide derivative

This Accepted Manuscript is available for reuse under a CC BY-NC-ND licence after the 24 month embargo period provided that all the terms of the licence are adhered toCerium (Ce) oxide nanoparticles (CNPs) have attracted attention due to their high bioactivity and unique redox-chemistry. The oxygen vacancies at the surface of the nanoparticle explain the autocatalytic properties of CNPs in which the Ce3+ atoms occupy the center of the oxygen vacancies surrounded by Ce4+ atoms. Until now, CNPs have been associated with organic molecules at the synthesis stage to extend their applications or improve their stability. However, there is a lack of information regarding the post-synthesis interaction of CNPs and organic molecules that could enhance or induce new properties. Due to their unique optical properties and their many uses in different areas such as supramolecular chemistry or biomedicine, we have chosen a derivative from the family of naphthalimides (the 4-amino-1,8-naphthalimide-N-substituted; ANN) to study the interaction with different CNPs (CNP1-4) and their joint bioactivity compared to that of the same compounds alone. ANN-CNP complexes were formed as revealed by spectroscopic studies, but, the interaction was markedly different depending on the physicochemical properties of CNPs and their surface content of Ce3+ sites. The ANN adsorption on all CNPs involved the amino group in the naphthalene moiety as shown by NMR spectroscopy, while the pyrrolidine ring was mainly involved in the specific interaction between ANN and CNP1. The biological effect of each CNP and ANN individually and forming complexes was assessed using a bioluminescent model bacterium. The results showed that ANN and CNP with the higher content of surface Ce3+ (CNP1) when combined acted additively towards the used model organism. In the opposite, ANN-CNP2, ANN-CNP3 and ANN-CNP4 complexes were antagonistic when the nanoparticles dominated the mixture. The results of this study contribute to expand the knowledge of the interaction between nanoparticles and organic molecules which may be useful for understanding the behavior of nanoparticles in complex matricesThis research was supported by CTM2013-45775-C2-1-R and CTM2013-45775-C2-2-R grants from MINECO. Cerium oxide nanoparticles were kindly provided by S. Seal and S. Das (University of Central Florida, U.S.A). Gerardo Pulido-Reyes thanks the Spanish Ministry of Education for the award of an FPU grant (FPU12/01796

The small Ca 2+ -binding protein CSE links Ca 2+ signalling with nitrogen metabolism and filament integrity in Anabaena sp. PCC 7120

Funder: FP7 People: Marie-Curie Actions; doi: http://dx.doi.org/10.13039/100011264; Grant(s): 2013–607607Abstract: Background: Filamentous cyanobacteria represent model organisms for investigating multicellularity. For many species, nitrogen-fixing heterocysts are formed from photosynthetic vegetative cells under nitrogen limitation. Intracellular Ca2+ has been implicated in the highly regulated process of heterocyst differentiation but its role remains unclear. Ca2+ is known to operate more broadly in metabolic signalling in cyanobacteria, although the signalling mechanisms are virtually unknown. A Ca2+-binding protein called the Ca2+ Sensor EF-hand (CSE) is found almost exclusively in filamentous cyanobacteria. Expression of asr1131 encoding the CSE protein in Anabaena sp. PCC 7120 was strongly induced by low CO2 conditions, and rapidly downregulated during nitrogen step-down. A previous study suggests a role for CSE and Ca2+ in regulation of photosynthetic activity in response to changes in carbon and nitrogen availability. Results: In the current study, a mutant Anabaena sp. PCC 7120 strain lacking asr1131 (Δcse) was highly prone to filament fragmentation, leading to a striking phenotype of very short filaments and poor growth under nitrogen-depleted conditions. Transcriptomics analysis under nitrogen-replete conditions revealed that genes involved in heterocyst differentiation and function were downregulated in Δcse, while heterocyst inhibitors were upregulated, compared to the wild-type. Conclusions: These results indicate that CSE is required for filament integrity and for proper differentiation and function of heterocysts upon changes in the cellular carbon/nitrogen balance. A role for CSE in transmitting Ca2+ signals during the first response to changes in metabolic homeostasis is discussed

Co, Zn and Ag-MOFs evaluation as biocidal materials towards photosynthetic organisms

In the present study, the biocidal activity of three different metal organic frameworks (MOFs) based on Co (Co-SIM1), Zn (Zn-SIM1) and Ag (Ag-TAZ) has been evaluated towards one green alga and two cyanobacteria. These organisms are present in fresh- and seawater and take part in the early stages of the biofouling process. The biocidal activity of these materials was evaluated by measuring chlorophyll a concentration and by inhibition zone testing. After 24 h of exposure the three different MOFs caused > 50% of chlorophyll a concentration inhibition towards both cyanobacteria, however, although the green alga presented a great sensitivity for Ag-TAZ (reaching 90% of chlorophyll a concentration inhibition), it was much more resistant to the rest of MOFs. Bioavailability of these metals was studied using ICP-MS, the chemical speciation program Visual MINTEQ, and a heavy metal bioreporter bioanalytical tool. We have elucidated that the biocidal activity presented by these MOFs was due to the dissolved metals released from them and more exactly, it depended on the bioavailability presented by these metal ions, which was closely related with the free ion concentration. This article highlights the potential use of different MOFs as biocidal material towards photosynthetic organisms and reveals important differences in the sensitivity between these organisms that should be taken into account in order to increase the biocidal spectrum of these materialsThis research was supported by the Spanish Ministry of Economy, CTM2013-45775-C2-1-R and CTM2013-45775-C2-2-