Simultaneous nitrogen and dissolved methane removal from an upflow anaerobic sludge blanket reactor effluent using an integrated fixed-film activated sludge system.

One of the main drawbacks of upflow anaerobic sludge blanket (UASB) reactors that treat low-strength sewage at room temperature is related to the low quality of their effluents in terms of dissolved methane, organic matter, and nitrogen content. The present study aims to evaluate the feasibility of using an integrated fixed-film activated sludge (IFAS) system as an alternative post-treatment technology to mitigate the environmental impact of such effluents. For this purpose, a pilot plant composed of a UASB (120 L) followed by an IFAS (66 L) system was operated for 407 days. Special attention was paid to the suspended biomass retention capacity and the dissolved methane and nitrogen removal potential of the IFAS post-treatment system. Furthermore, the role of carriers on denitrification and nitrification processes and the microbial communities present in the biofilm were also analyzed. Average total chemical oxygen demand (CODT) and ammonium removal efficiencies of 92 ± 3% and around 57 ± 16% were attained throughout the entire operation, respectively. During a first period in which biomass was maintained in both biofilms and suspension, and nitrite was the main electron acceptor, maximum nitrogen removal and methane removal efficiencies of 32.5 mg TN L-1 and 93% were observed in the IFAS system, respectively. However, throughout the second period, in which suspended biomass was completely washed out from the IFAS system, and nitrate became the main electron acceptor, these values decreased to 18 ± 4 mg TN Lfeed-1 and 77 ± 12%, respectively. Surprisingly, throughout the entire operation, it was observed that around 50 and 41% of the total nitrogen and methane removals observed in the IFAS system, respectively, were carried out in the aerobic compartment. Aerobic methane oxidizers and anammox were detected with significant relative abundances in the biofilm carriers used in the anoxic and aerobic compartments using 16S rRNA gene amplicon sequencing analysis. Therefore, the use of an IFAS system could be suited to diminish greenhouse gas emissions and nutrients concentration for those sewage treatment plants that used UASB systems, especially in countries with temperate and warm climates.

Enhancement of struvite pellets crystallization in a full-scale plant using an industrial grade magnesium product.

A full-scale struvite crystallization system was operated for the treatment of the centrate obtained from the sludge anaerobic digester in a municipal wastewater treatment plant. Additionally, the feasibility of an industrial grade Mg(OH)2 as a cheap magnesium and alkali source was also investigated. The struvite crystallization plant was operated for two different periods: period I, in which an influent with low phosphate concentration (34.0 mg P·L-1) was fed to the crystallization plant; and period II, in which an influent with higher phosphate concentration (68.0 mg P·L-1) was used. A high efficiency of phosphorus recovery by struvite crystallization was obtained, even when the effluent treated had a high level of alkalinity. Phosphorus recovery percentage was around 77%, with a phosphate concentration in the effluent between 10.0 and 30.0 mg P·L-1. The experiments gained struvite pellets of 0.5-5.0 mm size. Moreover, the consumption of Mg(OH)2 was estimated at 1.5 mol Mg added·mol P recovered-1. Thus, industrial grade Mg(OH)2 can be an economical alternative as magnesium and alkali sources for struvite crystallization at industrial scale.

On interfacial properties of tetrahydrofuran: Atomistic and coarse-grained models from molecular dynamics simulation.

We have determined the interfacial properties of tetrahydrofuran (THF) from direct simulation of the vapor-liquid interface. The molecules are modeled using six different molecular models, three of them based on the united-atom approach and the other three based on a coarse-grained (CG) approach. In the first case, THF is modeled using the transferable parameters potential functions approach proposed by Chandrasekhar and Jorgensen [J. Chem. Phys. 77, 5073 (1982)] and a new parametrization of the TraPPE force fields for cyclic alkanes and ethers [S. J. Keasler et al., J. Phys. Chem. B 115, 11234 (2012)]. In both cases, dispersive and coulombic intermolecular interactions are explicitly taken into account. In the second case, THF is modeled as a single sphere, a diatomic molecule, and a ring formed from three Mie monomers according to the SAFT-γ Mie top-down approach [V. Papaioannou et al., J. Chem. Phys. 140, 054107 (2014)]. Simulations were performed in the molecular dynamics canonical ensemble and the vapor-liquid surface tension is evaluated from the normal and tangential components of the pressure tensor along the simulation box. In addition to the surface tension, we have also obtained density profiles, coexistence densities, critical temperature, density, and pressure, and interfacial thickness as functions of temperature, paying special attention to the comparison between the estimations obtained from different models and literature experimental data. The simulation results obtained from the three CG models as described by the SAFT-γ Mie approach are able to predict accurately the vapor-liquid phase envelope of THF, in excellent agreement with estimations obtained from TraPPE model and experimental data in the whole range of coexistence. However, Chandrasekhar and Jorgensen model presents significant deviations from experimental results. We also compare the predictions for surface tension as obtained from simulation results for all the models with experimental data. The three CG models predict reasonably well (but only qualitatively) the surface tension of THF, as a function of temperature, from the triple point to the critical temperature. On the other hand, only the TraPPE united-atoms models are able to predict accurately the experimental surface tension of the system in the whole temperature range.

Occurrence and fate of CECs (OMPs, ARGs and pathogens) during decentralised treatment of black water and grey water.

Decentralised wastewater treatment is becoming a suitable strategy to reduce cost and environmental impact. In this research, the performance of two technologies treating black water (BW) and grey water (GW) fractions of urban sewage is carried out in a decentralised treatment of the wastewater produced in three office buildings. An Anaerobic Membrane Bioreactor (AnMBR) treating BW and a Hybrid preanoxic Membrane Bioreactor (H-MBR) containing small plastic carrier elements, treating GW were operated at pilot scale. Their potential on reducing the release of contaminants of emerging concern (CECs) such as Organic Micropollutants (OMPs), Antibiotic Resistance Genes (ARGs) and pathogens was studied. After 226 d of operation, a stable operation was achieved in both systems: the AnMBR removed 92.4 ± 2.5 % of influent COD, and H-MBR removed 89.7 ± 3.5 %. Regarding OMPs, the profile of compounds differed between BW and GW, being BW the matrix with more compounds detected at higher concentrations (up to µg L-1). For example, in the case of ibuprofen the concentrations in BW were 23.63 ± 3.97 µg L-1, 3 orders of magnitude higher than those detected in GW. The most abundant ARGs were sulfonamide resistant genes (sul1) and integron class 1 (intl1) in both BW and GW. Pathogenic bacteria counts were reduced between 1 and 3 log units in the AnMBR. Bacterial loads in GW were much lower than in BW, being no bacterial re-growth observed for the GW effluents after treatment in the H-MBR. None of the selected enteric viruses was detected in GW treatment line.

Coexistence of granulomatous enteric inflammation and neoplasia in an adult sheep.

A 7-year-old dairy sheep suffering from chronic loss of weight without diarrhea or anorexia was euthanized after failing to respond to any treatment (antibiotic and antiparasitic). The main findings at the necropsy of this animal were multifocal miliary nodules in several organs, mainly in the Peyer's patches of the small intestine, and a segmental thickening of the jejunal wall. Histologic examination of the samples taken at the necropsy showed a multifocal chronic granulomatous inflammation, with mineralization and caseous necrosis at the core of the larger granulomas and scarce intrahistiocytic acid-fast bacilli consistent with a disseminated digestive tuberculosis. Polymerase chain reaction and bacteriological culture from these samples confirmed Mycobacterium avium subsp avium to be the etiologic agent of this infection. Histologically, the cause of the segmental thickening of the jejunal wall was found to be a small intestine adenocarcinoma, which in some areas coexisted with the granulomatous lesion.

Working with energy and mass balances: a conceptual framework to understand the limits of municipal wastewater treatment.

At present all municipal waste water treatment plants (WWTPs) are energy consumers. Electrical energy requirements for oxygen transfer are large in secondary biological systems. Nevertheless, from a thermodynamic point of view chemical oxygen demand (COD) is an energy source. Combustion of every kilogram of COD releases 3.86 kWh of energy. In this manuscript some measures are presented, from a conceptual point of view, in order to convert the actual concept of wastewater treatment as an 'energy sink' to an 'energy source' concept. In this sense, electrical self-sufficiency in carbon removal WWTPs could be obtained by increasing the sludge load to the anaerobic sludge digester. Nitrogen removal increases the energy requirements of WWTPs. The use of a combined two-stage biological treatment, using a high loaded first stage for carbon removal and a second stage combined nitrification-anammox process for nitrogen removal in the water line, offers a way to recover self-sufficiency. This is not a proven technology at ambient temperature, but its development offers an opportunity to reduce the energy demand of WWTPs.

Immunization of adult dairy cattle with a new heat-killed vaccine is associated with longer productive life prior to cows being sent to slaughter with suspected paratuberculosis.

The objective of this study was to evaluate the efficacy of a new heat-killed Mycobacterium avium ssp. paratuberculosis (MAP) vaccine for control of premature culling in tuberculosis-free dairy cattle. Feces and gastrointestinal tissues were collected from 50 vaccinated cows and 38 nonvaccinated cows at slaughter and analyzed by bacteriological culture and histopathology. Vaccination was associated with a significant reduction of the frequency of vaccinated animals with MAP in feces and gut tissues compared with the nonvaccinated animals. In addition, the frequency of vaccinated animals with heavy bacterial load in gut tissues was 40% lower than the frequency of the nonvaccinated animals with the same MAP load. The peak age of paratuberculosis-associated culling was from 4.5 to 5 yr old (21%) in the vaccinated animals and from 3 to 4.5 yr old (60%) in the nonvaccinated animals. The vaccinated and nonvaccinated animals with suspected paratuberculosis were culled at an average age of 4.7 and 3.7 yr old, respectively. Therefore, a significant increase in the productive life of the vaccinated animals sent to slaughter with suspected paratuberculosis was observed. In addition, our analysis revealed a positive effect of the vaccine on the carcass weights of the animals with severe histopathological lesions at slaughter compared with the nonvaccinated animals. In summary, our findings suggest a therapeutic effect of the vaccine and a significant attenuation of pre-existing infection in cows naturally infected with paratuberculosis that were adults at the time of vaccination.

Mathematical model optimized for prediction and health care planning for COVID-19.

OBJECTIVE: The COVID-19 pandemic has threatened to collapse hospital and ICU services, and it has affected the care programs for non-COVID patients. The objective was to develop a mathematical model designed to optimize predictions related to the need for hospitalization and ICU admission by COVID-19 patients. DESIGN: Prospective study. SETTING: Province of Granada (Spain). POPULATION: COVID-19 patients hospitalized, admitted to ICU, recovered and died from March 15 to September 22, 2020. STUDY VARIABLES: The number of patients infected with SARS-CoV-2 and hospitalized or admitted to ICU for COVID-19. RESULTS: The data reported by hospitals was used to develop a mathematical model that reflects the flow of the population among the different interest groups in relation to COVID-19. This tool allows to analyse different scenarios based on socio-health restriction measures, and to forecast the number of people infected, hospitalized and admitted to the ICU. CONCLUSIONS: The mathematical model is capable of providing predictions on the evolution of the COVID-19 sufficiently in advance as to anticipate the peaks of prevalence and hospital and ICU care demands, and also the appearance of periods in which the care for non-COVID patients could be intensified.

Genetic variation of toll-like receptor genes and infection by Mycobacterium avium ssp. paratuberculosis in Holstein-Friesian cattle.

Toll-like receptors (TLR) are membrane proteins that play a key role in innate immunity, by recognizing pathogens and subsequently activating appropriate responses. Mutations in TLR genes are associated with susceptibility to inflammatory and infectious diseases in humans. In cattle, 3 members of the TLR family, TLR1, TLR2, and TLR4, are associated with Mycobacterium avium ssp. paratuberculosis infection, although the extent of this association for the TLR1 and TLR4 receptors has not yet been determined. Moreover, the causal variant in the TLR2 gene has not yet been unequivocally established. In this study, 24 single nucleotide polymorphisms (SNP) in the bovine TLR1, TLR2, and TLR4 genes were selected from the literature, databases, and in silico searches, for a population-based genetic association study of a Spanish Holstein-Friesian sample. Whereas previous results regarding the TLR1 gene were not corroborated, a risk haplotype was detected in TLR2; however, its low frequency indicates that this detected association should be interpreted with caution. In the case of the TLR4 gene, 3 tightly linked SNP were found to be associated with susceptibility to M. avium ssp. paratuberculosis infection. Moreover, one of these SNP, the SNP c.-226G>C, which is localized in the 5'UTR region of the TLR4 gene, has been reported to be able to alter TLR4 expression, raising the possibility that this mutation may contribute to the response of the individual to infection.

Struvite crystallization versus amorphous magnesium and calcium phosphate precipitation during the treatment of a saline industrial wastewater.

Struvite crystallization (MgNH(4)PO(4)·6H(2)O, MAP) could be an alternative for the sustainable and economical recovery of phosphorus from concentrated wastewater streams. Struvite precipitation is recommended for those wastewaters which have high orthophosphate concentration. However the presence of a cheap magnesium source is required in order to make the process feasible. For those wastewater treatment plants (WWTP) located near the seashore magnesium could be economically obtained using seawater. However seawater contains calcium ions that could interfere in the process, by promoting the precipitation of amorphous magnesium and calcium phosphates. Precipitates composition was affected by the NH(4)(+)/PO(4)(3-) molar ratio used. Struvite or magnesium and calcium phosphates were obtained when NH(4)(+)/PO(4)(3-) was fixed at 4.7 or 1.0, respectively. This study demonstrates that by manipulating the NH(4)(+)/PO(4)(3-) it is possible to obtain pure struvite crystals, instead of precipitates of amorphous magnesium and calcium phosphates. This was easily performed by using either raw or secondary treated wastewater with different ammonium concentrations.

Three stages MBR (methanogenic, aerobic biofilm and membrane filtration) for the treatment of low-strength wastewaters.

The use of a new three stages MBR process with a first methanogenic UASB stage, a second stage with aerobic biofilm growing on small carrier elements maintained in suspension and third stage with membrane filtration module is presented. The objective of the first methanogenic chamber is to diminish COD of the raw wastewater, producing a biogas rich in methane, and decrease the sludge production. In the second stage, the remaining soluble biodegradable COD is oxidized by heterotrophs. In the third stage, the membrane modules could be operated at higher fluxes than those reported for AnMBR systems, and similar to those obtained in aerobic MBRs. In this sense, the concept of these three stages MBR is to join the advantages of the methanogenic and aerobic membrane bioreactor processes, by reducing energy requirements for aeration, producing biogas with high methane percentage and a permeate with very low COD content. A synthetic wastewater was fed to the three stages MBR. COD in the influent was between 200 and 1,200 mg/L, ammonium ranged from 10 to 35 mg/L and phosphorous concentration was 8 mg/L. OLR in-between 1 and 3 kg COD/(m3 d) and a HRT of 13-21 h were applied. Temperature was between 17.5 and 23.2 degrees C. During the whole operating period the COD removal efficiencies were in the range of 90 and 96% of which in between 40 and 80% was removed in the first methanogenic chamber. Biogas production with methane content between 75 and 80% was observed. With regard to membrane operation, average permeabilities around 150 L/(m2 h bar) were achieved, operating with fluxes of 11-15 L/(m2 h).

A knowledge-based control system for air-scour optimisation in membrane bioreactors.

Although membrane bioreactors (MBRs) technology is still a growing sector, its progressive implementation all over the world, together with great technical achievements, has allowed it to reach a mature degree, just comparable to other more conventional wastewater treatment technologies. With current energy requirements around 0.6-1.1 kWh/m3 of treated wastewater and investment costs similar to conventional treatment plants, main market niche for MBRs can be areas with very high restrictive discharge limits, where treatment plants have to be compact or where water reuse is necessary. Operational costs are higher than for conventional treatments; consequently there is still a need and possibilities for energy saving and optimisation. This paper presents the development of a knowledge-based decision support system (DSS) for the integrated operation and remote control of the biological and physical (filtration and backwashing or relaxation) processes in MBRs. The core of the DSS is a knowledge-based control module for air-scour consumption automation and energy consumption minimisation.

Lack of evidence of paratuberculosis in wild canids from Southwestern Europe.

Wild carnivores are at the top of the trophic chain. They are predators and carrion consumers, and thus, prone to come in contact with disease agents contaminating the environment or infecting live or dead animals. We hypothesized that wild canids could be used as sentinels for the detection of regions with higher Mycobacterium avium paratuberculosis (MAP) prevalence in wild and domestic animals. To test this hypothesis, we set up an ELISA to test 262 wolf (Canis lupus) and fox (Vulpes vulpes) sera for MAP-specific antibodies and processed a subset of samples for culture (n = 61), MAP-specific PCR (15) and histopathology (14). In wolves, the optical density (OD) values in the ELISA were continuously distributed. Ten fox sera (4%) had OD readings of over twice the mean, suggesting contact with mycobacteria. However, all samples tested by PCR were negative for both IS900 and ISMAP02 sequences, and samples cultured for MAP yielded no growth. No visible paratuberculosis or tuberculosis-compatible lesions were recorded. On histopathological examination, no lesions compatible with mycobacterial diseases were observed. These results suggest that wild canids show little or no evidence of paratuberculosis and are unlikely to be useful sentinels for the detection of MAP in Southwestern Europe.

Paratuberculosis vaccination specific and non-specific effects on cattle lifespan.

Records of cattle vaccination against paratuberculosis (PTB) have been analyzed to determine whether or not non-specific effect (NSE) on overall mortality similar to that observed in BCG vaccinated humans occurs in animals. The results of a previously reported slaughterhouse study on PTB prevalence were used as a reference on the age incidence of advanced patent (clinical) epidemio-pathogenic forms. In the proper vaccine study, cows in 30 cattle farms in the Basque Country, Spain were followed-up for between 1 and 13 years. Vaccinated groups were composed by 1008 (592 right-censored) animals younger than 3 months treated as calves and by 3761 (3160 right-censored) vaccinated at any older age. Controls were 339 (157 right-censored) and 4592 (2213 right-censored) age matched animals, respectively. Individual last year presence in the annual testing was considered age at culling or death. A survival analysis was carried out according age at vaccination of vaccinated versus non-vaccinated animals. PTB age incidence in the slaughterhouse study was subtracted from the difference between vaccinated and non-vaccinated animals at the same age in order to estimate PTB-specific and non-specific effects. The maximum difference was observed at the 2-3 years interval with a 33.9% mortality reduction in the calf vaccinated group. This corresponded also with the maximum NSE that was 24.5% for a PTB incidence of 9.5%. Overall, vaccination afforded to calves a 26.5% yearly mortality protection, split between 11.1% PTB-specific and 15.4% NSE. These results support a NSE on total mortality associated with PTB vaccination that appeared to persist for up to 6-7 years. This confirms for the first time in an animal field study the innate immune system memory predicted by the recently proposed trained immunity theory. Contrasting the literature, no deleterious effects of killed vaccines on females were observed. Mortality reduction would offset vaccination costs and could improve livestock systems efficiency and potentially reduce antibiotic use. Clinical trial registered with Spanish Agency for Drugs and Sanitary products (AEMPS) as 11/012/ECV.

Mathematical model optimized for prediction and health care planning for COVID-19. / Modelo matemático optimizado para la predicción y planificación de la asistencia sanitaria por la COVID-19.

OBJECTIVE: The COVID-19 pandemic has threatened to collapse hospital and ICU services, and it has affected the care programs for non-COVID patients. The objective was to develop a mathematical model designed to optimize predictions related to the need for hospitalization and ICU admission by COVID-19 patients. DESIGN: Prospective study. SETTING: Province of Granada (Spain). POPULATION: COVID-19 patients hospitalized, admitted to ICU, recovered and died from March 15 to September 22, 2020. STUDY VARIABLES: The number of patients infected with SARS-CoV-2 and hospitalized or admitted to ICU for COVID-19. RESULTS: The data reported by hospitals was used to develop a mathematical model that reflects the flow of the population among the different interest groups in relation to COVID-19. This tool allows to analyse different scenarios based on socio-health restriction measures, and to forecast the number of people infected, hospitalized and admitted to the ICU. CONCLUSIONS: The mathematical model is capable of providing predictions on the evolution of the COVID-19 sufficiently in advance as to anticipate the peaks of prevalence and hospital and ICU care demands, and also the appearance of periods in which the care for non-COVID patients could be intensified.

Genetic association between bovine NOD2 polymorphisms and infection by Mycobacterium avium subsp. paratuberculosis in Holstein-Friesian cattle.

Nucleotide-Binding Oligomerization Domain 2 (NOD2) has been reported to be a candidate gene for Mycobacterium avium subsp. paratuberculosis (MAP) infection in a Bos taurus × Bos indicus mixed breed based on a genetic association with the c.2197T>C single nucleotide polymorphism (SNP). Nevertheless, this SNP has also been reported to be monomorphic in the B. taurus species. In the present work, 18 SNPs spanning the bovine NOD2 gene have been analysed in a genetic association study of two independent populations of Holstein-Friesian cattle. We found that the C allele of SNP c.*1908C>T, located in the 3'-UTR region of the gene, is significantly more frequent in infected animals than in healthy ones, which supports the idea that the bovine NOD2 gene plays a role in susceptibility to MAP infection. However, in silico analyses of the NOD2 nucleotide sequence did not yield definitive data about a possible direct effect of SNP c.*1908C>T on susceptibility to infection and led us to consider its linkage disequilibrium with the causative variant. A more exhaustive genetic association study including all putative, functional SNPs from this gene and subsequent functional analyses needs to be conducted to achieve a more complete understanding of how different variants of NOD2 may affect susceptibility to MAP infection in cattle.

SP110 as a novel susceptibility gene for Mycobacterium avium subspecies paratuberculosis infection in cattle.

The intracellular pathogen resistance 1 (Ipr1) gene has been reported to play a role in mediating innate immunity in a mouse model of Mycobacterium tuberculosis infection, and polymorphisms of its human ortholog, SP110 nuclear body protein, have been suggested to be associated with tuberculosis. Thus, the bovine SP110 gene was considered to be a promising candidate for a genetic association study of bovine paratuberculosis, or Johne's disease, a chronic granulomatous enteritis caused by Mycobacterium avium ssp. paratuberculosis (MAP). Initially, single nucleotide polymorphisms (SNP) within the bovine SP110 gene were identified, and subsequently a population-based genetic association study was carried out. Seventeen new SNP along the SP110 gene were identified in Holstein-Friesian cattle, and 6 more were compiled from public databases. A total of 14 SNP were included in the association study of 2 independent populations. The SNP c.587A>G was found to be significantly associated with MAP infection, with the major allele A appearing to confer greater disease susceptibility in one of the analyzed populations. In addition, 2 haplotypes containing this SNP were also found to be associated with infection in the same population. The SNP c.587A>G is a nonsynonymous mutation that causes an amino acid change in codon 196 from asparagine to serine. In silico analyses point to SNP c.587A>G as a putative causal variant for susceptibility to MAP infection. The elucidation of the precise mechanism by which this SNP can exert its effect in the protein and, as a result, in the risk of infection, requires future functional analyses. Likewise, the absence of genetic association in one of the analyzed populations renders it necessary to carry out this study in other independent populations, with the aim of substantiating the repeatability of the present results. Nevertheless, the present results deepen our understanding of the genetic basis of susceptibility and resistance mechanisms related to MAP infection in cattle and, in turn, constitute a step forward toward the implementation of marker-assisted selection in breeding programs aimed at controlling paratuberculosis.

Identification of single nucleotide polymorphisms in the bovine solute carrier family 11 member 1 (SLC11A1) gene and their association with infection by Mycobacterium avium subspecies paratuberculosis.

Johne's disease is a chronic enteritis caused by Mycobacterium avium ssp. paratuberculosis (MAP) that causes substantial financial losses for the cattle industry. Susceptibility to MAP infection is reported to be determined in part by genetic factors, so marker-assisted selection could help to obtain bovine populations that are increasingly resistant to MAP infection. Solute carrier family 11 member 1 (SLC11A1) was adjudged to be a potential candidate gene because of its role in innate immunity, its involvement in susceptibility to numerous intracellular infections, and its previous association with bovine MAP infection. The objectives of this study were to carry out an exhaustive process of discovery and compilation of polymorphisms in SLC11A1 gene, and to perform a population-based genetic association study to test its implication in susceptibility to MAP infection in cattle. In all, 57 single nucleotide polymorphisms (SNP) were detected, 25 of which are newly described in Bos taurus. Twenty-four SNP and two 3'-untranslated region polymorphisms, previously analyzed, were selected for a subsequent association study in 558 European Holstein-Friesian animals. The SNP c.1067C>G and c.1157-91A>T and a haplotype formed by these 2 SNP yielded significant association with susceptibility to MAP infection. The c.1067C>G is a nonsynonymous SNP that causes an amino acid change in codon 356 from proline to alanine (P356A) that could alter SLC11A1 protein function. This association study supports the involvement of SLC11A1 gene in susceptibility to MAP infection in cattle. Our results suggest that SNP c.1067C>G may be a potential causal variant, although functional studies are needed to assure this point.

Strigolactones, signals for parasitic plants and arbuscular mycorrhizal fungi.

Although strigolactones play a critical role as rhizospheric signaling molecules for the establishment of arbuscular mycorrhizal (AM) symbiosis and for seed germination of parasitic weeds, scarce data are available about interactions between AM fungi and strigolactones. In the present work, we present background data on strigolactones from studies on their seed germination activity on the parasitic weeds Orobanche and Striga, the importance of nitrogen and phosphorus for this seed germination activity, and what this could mean for AM fungi. We also present results on the susceptibility of plants to AM fungi and the possible involvement of strigolactones in this AM susceptibility and discuss the role of strigolactones for the formation and the regulation of the AM symbiosis as well as the possible implication of these compounds as plant signals in other soil-borne plant-microbe interactions.