Aminobacter sp MSH1 invades sand filter community biofilms while retaining 2,6-dichlorobenzamide degradation functionality under C- and N-limiting conditions

Aminobacter sp. MSH1 is of interest for bioaugmentation of biofiltration units in drinking water treatment plants (DWTPs) due to its ability to degrade the groundwater micropollutant 2,6-dichlorobenzamide (BAM). Using a continuous flow chamber biofilm model, MSH1 was previously shown to colonize surfaces and degrade BAM at trace concentrations as low as 1 mu g/L under the oligotrophic conditions found in DWTPs. In DWTP filtration units, MSH1 has to compete with the resident biofilm microbiota for space and nutrients. Using the same model, we examined how a sand filter community (SFC) affects MSH1's BAM-degrading activity and biofilm formation under C-and N-limiting conditions when fed with trace concentrations of BAM. MSH1 was inoculated simultaneously with the SFC (co-colonization mode) or after the SFC formed a biofilm (invasion mode). MSH1 successfully established in the SFC biofilm showing growth and activity. In co-colonization mode, MSH1 decreased in number in the presence of the SFC and formed isolated colonies, while specific BAM-degradation activity increased. In the invasion mode, MSH1 also decreased in numbers in the presence of the SFC but formed mixed colonies, while specific BAM degradation was unaffected. Our results show that MSH1 invades and performs successfully in an SFC biofilm under the oligotrophic conditions of DWTPs

Optimizing the bioenergy water footprint by selecting SRC willow canopy phenotypes: regional scenario simulations

© The Author(s) 2019. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Background and Aims: Bioenergy is central for the future energy mix to mitigate climate change impacts; however, its intricate link with the water cycle calls for an evaluation of the carbon–water nexus in biomass production. The great challenge is to optimize trade-offs between carbon harvest and water use by choosing cultivars that combine low water use with high productivity. Methods: Regional scenarios were simulated over a range of willow genotype × environment interactions for the major UK soil × climate variations with the process-based model LUCASS. Soil available water capacity (SAWC) ranged from 51 to 251 mm and weather represented the north-west (wet, cool), north-east (dry, cool), south-west (wet, warm) and south-east (dry, warm) of the UK. Scenario simulations were evaluated for small/open narrow-leaf (NL) versus large/closed broad-leaf (BL) willow canopy phenotypes using baseline (1965–89) and warmer recent (1990–2014) weather data. Key Results: The low productivity under baseline climate in the north could be compensated by choosing BL cultivars (e.g. ‘Endurance’). Recent warmer climate increased average productivity by 0.5–2.5 t ha−1, especially in the north. The modern NL cultivar ‘Resolution’ had the smallest and most efficient water use. On marginal soils (SAWC <100 mm), yields remained below an economic threshold of 9 t ha−1 more frequently under baseline than recent climate. In the drought-prone south-east, ‘Endurance’ yielded less than ‘Resolution’, which consumed on average 17 mm year−1 less water. Assuming a planting area of 10 000 ha, in droughty years between 1.3 and 4.5 × 106 m3 of water could be saved, with a small yield penalty, for ‘Resolution’. Conclusions: With an increase in air temperature and occasional water scarcities expected with climate change, high-yielding NL cultivars should be the preferred choice for sustainable use of marginal lands and reduced competition with agricultural food crops.Peer reviewedFinal Published versio

Measurements of air pollution emission factors for marine transportation in SECA

The chemical composition of the plumes of seagoing ships was investigated during a two weeks long measurement campaign in the port of Rotterdam, Hoek van Holland, The Netherlands, in September 2009. Altogether, 497 ships were monitored and a statistical evaluation of emission factors (g kg-1 fuel) was provided. The concerned main atmospheric components were SO2, NO2, NOX and the aerosol particle number. In addition, the elemental and water-soluble ionic composition of the emitted particulate matter was measured. Emission factors were expressed as a function of ship type, power and crankshaft rotational speed. The average SO2 emission factor was found to be roughly half of what is allowed in sulphur emission control areas (16 34 vs. 30 g kg-1 fuel), and exceedances of this limit were rarely registered. A significant linear relationship was observed between the SO2 and particle number emission factor. The slope of the regression line, 2x1018 (kg fuel)-1, provides the average number of sulphate particles from 1 kg sulphur burnt with the fuel, while the intercept, 0.5x1016 (kg fuel)-1, gives the average number of primary particles (mainly soot and ash) formed during the burning of 1 kg fuel. Water-soluble ionic composition analysis of the aerosol samples from the plumes showed that approx. 144 g of sulphate particles were emitted from 1 kg sulphur burnt with the fuel. The mass median diameter of sulphate particles estimated from the measurements was 42 nm.JRC.H.2-Air and Climat

Effect of Operating and Sampling Conditions on the Exhaust Gas Composition of Small-Scale Power Generators

Small stationary diesel engines, like in generator sets, have limited emission control measures and are therefore responsible for 44% of the particulate matter (PM) emissions in the United States. The diesel exhaust composition depends on operating conditions of the combustion engine. Furthermore, the measurements are influenced by the used sampling method. This study examines the effect of engine loading and exhaust gas dilution on the composition of small-scale power generators. These generators are used in different operating conditions than road-transport vehicles, resulting in different emission characteristics. Experimental data were obtained for gaseous volatile organic compounds (VOC) and PM mass concentration, elemental composition and nitrate content. The exhaust composition depends on load condition because of its effect on fuel consumption, engine wear and combustion temperature. Higher load conditions result in lower PM concentration and sharper edged particles with larger aerodynamic diameters. A positive correlation with load condition was found for K, Ca, Sr, Mn, Cu, Zn and Pb adsorbed on PM, elements that originate from lubricating oil or engine corrosion. The nitrate concentration decreases at higher load conditions, due to enhanced nitrate dissociation to gaseous NO at higher engine temperatures. Dilution on the other hand decreases PM and nitrate concentration and increases gaseous VOC and adsorbed metal content. In conclusion, these data show that operating and sampling conditions have a major effect on the exhaust gas composition of small-scale diesel generators. Therefore, care must be taken when designing new experiments or comparing literature results

The effect of dissolved organic matter on the stability and activity of a pesticide-degrading bacterial consortium

The uncontrolled use of pesticides to secure food production has resulted into the contamination of surface water and groundwater bodies. Microbial biodegradation is considered as a major process that contributes to the removal of pesticides from the environment. Bacteria have been isolated which display specialized catabolic pathways that enable them to use pesticides as sole source of energy and carbon. In natural ecosystems, pesticides are considered micropollutants which are pollutants present in water at trace concentrations in the pg L-1 to µg L-1 range and are often only temporarily available. It has been questioned whether such concentrations can sustain pesticide degrading populations and whether degradation of pesticides at micropollutant concentrations still occurs. Natural environments contain dissolved organic matter (DOM) at concentrations of 1-20 mg L-1 and is considered as the major source of carbon and energy for heterotrophic communities. The DOM is a supplementary source of nutrients and energy for residing pesticide degrading populations. However, DOM can also have negative effects on pollutant biodegradation, for instance by exerting catabolic repression. Up till now, the net effects of natural DOM on pesticide biodegradation are scarcely explored especially in case of the biodegradation of pesticides occurring at relevant micropollutant concentrations of pesticides The overall aim of this research was to explore the effects of the quantity and quality of DOM on pesticide degradation at macro- and micropollutant concentrations. The DOM quantity in European surface waters is measured at a median concentration of 5 mg L-1 dissolved organic carbon (DOC). DOM quality is determined by the molecular properties of the occurring organic compounds (e.g. spectroscopic properties) and is related to its biodegradability. As an experimental system, the degradation of the phenylurea herbicide linuron was examined by members of the genus Variovorax and/or by a triple-species bacterial consortium. This consortium consists of three strains which synergistically mineralize linuron. Variovorax sp. strain WDL1 initiates linuron mineralization by transforming linuron to 3,4-dichloroaniline (3,4-DCA) and N,O-dimethylhydroxylamine (N,O-DMHA). Comamonas testosteroni WDL7 lives on excreted 3,4-DCA while Hyphomicrobium sulfonivorans WDL6 feeds on N,O-DMHA.In a first part of the research, the metabolic capabilities of the linuron degrading bacteria were explored. By determining C-source utilization profiles in Biolog GN2 microtiter plate assays, it was found that the consortium displays an extended metabolic capability compared to individual linuron degrading strains and its members. This was due to the respiration of C-sources by the consortium for which respiration was unobtainable by the individual members. The data suggest that the consortium members cooperate in the utilization of C-sources other than linuron. This feature can contribute in consolidating community composition in the presence of micropollutant concentrations of linuron or in its absence. By examining the biodegradable DOC in environmental DOM (eDOM) by the consortium and its members and concomitant growth, we observed that this cooperation extends towards the utilization of eDOM as carbon source. The data suggest that for both DOM of low and high recalcitrance, cooperation existed within the consortium. All consortium members benefited from the cooperation, however the balance of benefits for each strain shifted according to DOM recalcitrance. All together, the results show that compared to individual heterotrophic pesticide degrading bacteria, consortia can benefit to a greater extent of dissolved carbon resources available in an environment due to metabolic cooperation and that consortia have to be included to evaluate the effect of DOM on pesticide degradation.In a second part of the research, the activity of bacterial cultures towards the degradation of linuron at concentrations ranging from 10 mg L-1 to 1 µg L-1 was explored in batch experiments. Several linuron degrading pure Variovorax strains and the consortium were tested. All cultures tested were able to degrade linuron at initial concentrations as low as 1 µg L-1 and that degradation proceeded beyond the detection limit of 1 ng L-1. Degradation rates however varied up to a factor 70 between the different strains and were concentration dependent. Inclusion of strain WDL1 in the consortium did not dramatically improve the degradation of linuron at concentrations lower than 100 µg L-1. In addition, the effect of supplementary C-substrates including eDOM of varying quality and quantity on linuron degradation was assessed. Effects of supplementary C-sources on linuron degradation were especially noted at a concentration of 10 mg L-1 linuron. In case of pure cultures, citrate as a supplementary C-source repressed linuron degradation and increased accumulation of 3,4-DCA. eDOM, even when only 20% biodegradable, increased the linuron degradation rate 2-fold. At micropollutant concentrations a 2-fold increase in linuron degradation rates was observed with strain WDL1 for eDOM, suggesting that eDOM can stimulate linuron degradation by pure cultures at micropollutant concentrations. However, with the consortium, the magnitude of both negative and positive effects of eDOM obtained with pure cultures diminished greatly.Bacteria grow in the environment as a community on surfaces and form so-called biofilms. That is why in the last part of the research we explored the effects of eDOM on linuron degradation in continuously irrigated biofilm setups with focus on the consortium. It was first shown that the consortium was able to form biofilms in flow chambers irrigated with eDOM of both low and high quality at environmentally relevant concentrations of 5 mg L-1 DOC. The structure and composition of the biofilms clearly depended on the DOM formulation applied. The biofilms were afterwards irrigated with linuron at a concentration of either 10 mg L-1 or 100 µg L-1. Clearly, the linuron degrading activity of the biofilm depended on the DOM used for growing the biofilm and the linuron concentration. In case of a linuron feed of 10 mg L-1, for some DOM complete failure of linuron degradation was observed. The ability of these biofilms to degrade linuron correlated with the relative abundance and co-localization of WDL1 and WDL7, while the linuron degrading activity correlated with biomass. Moreover, degradation of 100 µg L-1 linuron was maximally 30% for all biofilms. Second, the effect of eDOM on linuron degradation at concentrations of 10 mg L-1 was explored. Easily degradable DOM like citrate inhibited linuron degradation and was accompanied with the accumulation of 3,4-DCA. More recalcitrant DOM stimulated linuron degradation as the effluent concentrations of linuron decreased. After changing the feed to only linuron, both positive and negative effects of the DOMs were rapidly lost and degradation occurred with an efficiency similar to this recorded for control biofilms which had never been in contact with DOM. In a final experimental setup, the effect of DOM on linuron degradation of concentrations as low as 10 µg L-1 in biofilms was explored. While the consortium was shown to form biofilms on linuron concentrations of 1000 µg L-1, 100 µg L-1 and 10 µg L-1 with removal efficiencies going from 80% to 30%, no significant effect of DOM of both low and high quality was recorded, despite changes in biofilm structure and composition. It can be concluded that at high linuron concentrations, the presence of DOM as supplementary C-source affects linuron degradation by pure bacterial cultures positively at high linuron concentrations. In microbial communities, smaller effects of DOM on linuron degradation were found than with isolates, likely related to the robustness of communities. Microbial communities are the rule rather than the exception in natural ecosystems. All previously isolated linuron degrading cultures showed the ability to degrade linuron at micropollutant concentrations. The effect of DOM did however no longer apply at these concentrations. On the other hand, biofilm experiments suggest that growth on DOM in periods of absence of linuron can significantly affect subsequent linuron degradation.nrpages: 223status: publishe

Effect of the quality and quantity of dissolved organic carbon on degradation of the phenylurea herbicide linuron by a microbial biofilm

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Variovorax sp. mediated biodegradation of the phenyl urea herbicide linuron at micropollutant concentrations and effects of natural dissolved organic matter as supplementary carbon source

In nature, pesticides are often present as micropollutants with concentrations too low for efficient biodegradation and growth of heterotrophic pollutant degrading bacteria. Instead, organic carbon present in environmental dissolved organic matter (eDOM) constitutes the main carbon source in nature. Information on how natural organic carbon affects degradation of pollutants and micropollutants in particular, is however poor. Linuron degrading Variovorax sp. strains SRS16, WDL1 and PBLH6 and a triple-species bacterial consortium from which WDL1 originated, were examined for their ability to degrade linuron at micropollutant concentrations and the effect hereon of different eDOM formulations of varying biodegradability as supplementary C-source was explored. Individual strains and the consortium degraded linuron at initial concentrations as low as 1 µg L-1 till concentrations below 4 ng L-1. Degradation kinetics differed among strains with rates that differed up to 70-fold at the lowest linuron concentrations and with lag phases ranging from 0 to 7 days. Linuron biodegradation by the individual strains was inhibited by an easily biodegradable compound such as citrate but stimulated by eDOM at a linuron concentration of 10 mg L-1. Effects were strongly reduced or became non-existent at micropollutant linuron concentrations. Effects of eDOM on degradation at 10 mg L-1 linuron by WDL1 were reduced when WDL1 was incubated together with its original consortium members. This is the first report on eDOM effects on degradation of pesticides at micropollutant concentrations and indicates these effects are limited and depend on linuron and eDOM concentrations, eDOM quality and the bacterial culture.status: publishe

Soil-Bacterium Compatibility Model as a Decision-Making Tool for Soil Bioremediation

Bioremediation of organic pollutant contaminated soil involving bioaugmentation with dedicated bacteria specialized in degrading the pollutant is suggested as a green and economically sound alternative to physico-chemical treatment. However, intrinsic soil characteristics impact the success of bioaugmentation. The feasibility of using partial least-squares regression (PLSR) to predict the success of bioaugmentation in contaminated soil based on the intrinsic physico-chemical soil characteristics and, hence, to improve the success of bioaugmentation, was examined. As a proof of principle, PLSR was used to build soil-bacterium compatibility models to predict the bioaugmentation success of the phenanthrene-degrading Novosphingobium sp. LH128. The survival and biodegradation activity of strain LH128 were measured in 20 soils and correlated with the soil characteristics. PLSR was able to predict the strain's survival using 12 variables or less while the PAH-degrading activity of strain LH128 in soils that show survival was predicted using 9 variables. A three-step approach using the developed soil-bacterium compatibility models is proposed as a decision making tool and first estimation to select compatible soils and organisms and increase the chance of success of bioaugmentation.status: publishe