Project description:The spread of antibiotic resistance genes (ARG) into agricultural soils, products, and foods severely limits the use of organic fertilizers in agriculture. In this study, experimental land plots were fertilized, sown, and harvested for two consecutive agricultural cycles using either mineral or three types of organic fertilizers: sewage sludge, pig slurry, or composted organic fraction of municipal solid waste. The analysis of the relative abundances of more than 200,000 ASV (Amplicon Sequence Variants) allowed the identification of a small, but significant (<10%) overlap between soil and fertilizer microbiomes, particularly in soils sampled the same day of the harvest (post-harvest soils). Loads of clinically relevant ARG were significantly higher (up to 100 fold) in fertilized soils relative to the initial soil. The highest increases corresponded to post-harvest soils treated with organic fertilizers, and they correlated with the extend of the contribution of fertilizers to the soil microbiome. Edible products (lettuce and radish) showed low, but measurable loads of ARG (sul1 for lettuces and radish, tetM for lettuces). These loads were minimal in mineral fertilized soils, and strongly dependent on the type of fertilizer. We concluded that at least part of the observed increase on ARG loads in soils and foodstuffs were actual contributions from the fertilizer microbiomes. Thus, we propose that adequate waste management and good pharmacological and veterinarian practices may significantly reduce the potential health risk posed by the presence of ARG in agricultural soils and plant products.
Project description:Abstract: Proteins contribute to a major part of the organic nitrogen in forest soils. This nitrogen is mobilized and becomes available to trees as a result of the depolymerizing activities of symbiotic ectomycorrhizal fungi. The mechanisms by which these fungi depolymerize proteins and assimilate the released nitrogen are poorly characterized. Biochemical analysis and transcriptome profiling were performed to examine the proteolytic machinery and the uptake system of the ectomycorrhizal basidiomycete Paxillus involutus during the assimilation of organic nitrogen from various protein sources and extracts of organic matter. All substrates induced secretion of peptidase activity with an acidic pH optimum, mostly contributed by aspartic peptidases. The peptidase activity was transiently repressed by ammonium. Transcriptional analysis revealed a large number of extracellular endo- and exopeptidases. The expression levels of these peptidases were regulated in parallel with transporters and enzymes involved in the assimilation and metabolism of the released peptides and amino acids. For the first time the molecular components of the protein degradation pathways of an ectomycorrhizal fungus are described. The data suggest that the transcripts encoding these components are regulated in response to the chemical properties and the availability of the protein substrates. Firoz Shah, Francois Rineau, Björn Canbäck, Tomas Johansson and Anders Tunlid (2013) The molecular components of the extracellular protein-degradation pathways of the ectomycorrhizal fungus Paxillus involutus (submitted) A one-chip study (data from 9 subarrays collected from a 12-plex Nimblegen microarray (ID: 461228)) using total RNA recovered from glass-bead cultures of Paxillus involutus (ATCC200175) after amendments of 3 different substrates (3 replicates of each).
Project description:Effects of organic amendments on microbiota associated with the Culex nigripalpus mosquito vector of the Saint Louis and West Nile viruses
Project description:Abstract: Proteins contribute to a major part of the organic nitrogen in forest soils. This nitrogen is mobilized and becomes available to trees as a result of the depolymerizing activities of symbiotic ectomycorrhizal fungi. The mechanisms by which these fungi depolymerize proteins and assimilate the released nitrogen are poorly characterized. Biochemical analysis and transcriptome profiling were performed to examine the proteolytic machinery and the uptake system of the ectomycorrhizal basidiomycete Paxillus involutus during the assimilation of organic nitrogen from various protein sources and extracts of organic matter. All substrates induced secretion of peptidase activity with an acidic pH optimum, mostly contributed by aspartic peptidases. The peptidase activity was transiently repressed by ammonium. Transcriptional analysis revealed a large number of extracellular endo- and exopeptidases. The expression levels of these peptidases were regulated in parallel with transporters and enzymes involved in the assimilation and metabolism of the released peptides and amino acids. For the first time the molecular components of the protein degradation pathways of an ectomycorrhizal fungus are described. The data suggest that the transcripts encoding these components are regulated in response to the chemical properties and the availability of the protein substrates. Firoz Shah, Francois Rineau, Björn Canbäck, Tomas Johansson and Anders Tunlid (2013) The molecular components of the extracellular protein-degradation pathways of the ectomycorrhizal fungus Paxillus involutus (submitted) A one-chip study (data from 12 subarrays collected from 12-plex Nimblegen microarray (IDs: 527896) using total RNA recovered from glass-bead cultures of Paxillus involutus (ATCC200175) after amendments of nitrogen (+/-NH4) to substrate followed by incubation for different periods of time (3 replicates of each).
Project description:BackgroundAddition of organic amendments has been commonly adopted as a means to restore degraded soils globally. More recently, the use of woody organic amendments has been recognized as a viable method of capturing and retaining water and restoring degraded and desertified soil, especially in semi-arid regions. However, the impacts of woody amendments on soil microbial community structure, versus other traditional organic supplements is less understood.MethodsThree locally available natural organic materials of different qualities, i.e., cow manure (CM), corn straw (CS), and chipped poplar branches (PB) were selected as treatments in Ningxia, Northern China and compared with control soils. Four microcosms served as replicates for each treatment. All treatments contained desertified soil; treatments with amendments were mixed with 3% (w/w) of one of the above organic materials. After 7 and 15 months from the start of the experiment, soil samples were analyzed for chemical and physical properties, along with biological properties, which included microbial α-diversity, community structure, and relative abundance of microbial phyla.ResultsBoth bacterial and fungal α-diversity indices were weakly affected by amendments throughout the experimental period. All amendments yielded different microbial community compositions than the Control soils. The microbial community composition in the CS and PB treatments also were different from the CM treatment. After 15 months of the experiment, CS and PB exhibited similar microbial community composition, which was consistent with their similar soil physical and chemical properties. Moreover, CS and PB also appeared to exert similar effects on the abundance of some microbial taxa, and both of these treatments yield different abundances of microbial taxa than the CM treatment.ConclusionNew local organic amendment with PB tended to affect the microbial community in a similar way to the traditional local organic amendment with CS, but different from the most traditional local organic amendment with CM in Ningxia, Northern China. Moreover, the high C/N-sensitive, and lignin and cellulose decompose-related microbial phyla increased in CS and PB have benefits in decomposing those incorporated organic materials and improving soil properties. Therefore, we recommend that PB should also be considered as a viable soil organic amendment for future not in Ningxia, but also in other places.
Project description:Organic fertilizers have been shown to stimulate CH4 uptake from agricultural soils. Managing fertilizer application to maximize this effect and to minimize emission of other greenhouse gasses offers possibilities to increase sustainability of agriculture. To tackle this challenge, we incubated an agricultural soil with different organic amendments (compost, sewage sludge, digestate, cover crop residues mixture), either as single application or in a mixture and subjected it to different soil moisture concentrations using different amounts of organic amendments. GHG fluxes and in vitro CH4 oxidation rates were measured repeatedly, while changes in organic matter and abundance of GHG relevant microbial groups (nitrifiers, denitrifiers, methanotrophs, methanogens) were measured at the end of the incubation. Overall the dynamics of the analyzed GHGs differed significantly. While CO2 and N2O differed considerably between the treatments, CH4 fluxes remained stable. In contrast, in vitro CH4 oxidation showed a clear increase for all amendments over time. CO2 fluxes were mostly dependent on the amount of organic residue that was used, while N2O fluxes were affected more by soil moisture. Several combinations of amendments led to reductions of CO2, CH4, and/or N2O emissions compared to un-amended soil. Most optimal GHG balance was obtained by compost amendments, which resulted in a similar overall GHG balance as compared to the un-amended soil. However, compost is not very nutrient rich potentially leading to lower crop yield when applied as single fertilizer. Hence, the combination of compost with one of the more nutrient rich organic amendments (sewage sludge, digestate) provides a trade-off between maintaining crop yield and minimizing GHG emissions. Additionally, we could observe a strong increase in microbial communities involved in GHG consumption in all amendments, with the strongest increase associated with cover crop residue mixtures. Future research should focus on the interrelation of plants, soil, and microbes and their impact on the global warming potential in relation to applied organic amendments.