RESUMEN
Plant-associated microorganisms that affect plant development, their composition, and their functionality are determined by the host, soil conditions, and agricultural practices. How agricultural practices affect the rhizosphere microbiome has been well studied, but less is known about how they might affect plant endophytes. In this study, the metagenomic DNA from the rhizosphere and endophyte communities of root and stem of maize plants was extracted and sequenced with the "diversity arrays technology sequencing," while the bacterial community and functionality (organized by subsystems from general to specific functions) were investigated in crops cultivated with or without tillage and with or without N fertilizer application. Tillage had a small significant effect on the bacterial community in the rhizosphere, but N fertilizer had a highly significant effect on the roots, but not on the rhizosphere or stem. The relative abundance of many bacterial species was significantly different in the roots and stem of fertilized maize plants, but not in the unfertilized ones. The abundance of N cycle genes was affected by N fertilization application, most accentuated in the roots. How these changes in bacterial composition and N genes composition might affect plant development or crop yields has still to be unraveled. IMPORTANCE We investigated the bacterial community structure in the rhizosphere, root, and stem of maize plants cultivated under different agricultural techniques, i.e., with or without N fertilization, and with or without tillage. We found that the bacterial community was defined mostly by the plant compartment and less by agricultural techniques. In the roots, N fertilizer application affected the bacterial community structure, the microbiome functionality, and the abundance of genes involved in the N cycle, but the effect in the rhizosphere and stem was much smaller. Contrary, tillage did not affect the maize microbiome. This study enriches our knowledge about the plant-microbiome system and how N fertilization application affected it.
Asunto(s)
Microbiota , Suelo , Suelo/química , Endófitos , Nitrógeno , Zea mays/microbiología , Fertilizantes , Rizosfera , Bacterias/genética , Productos Agrícolas , Microbiología del SueloRESUMEN
Composting and vermicomposting are an environmentally friendly way to reduce pathogens in organic wastes and generate a valuable product that provides nutrients for crops. However, how the bacterial community structure changes during these different processes and if the bacteria applied with the (vermi)composted products survive in an arable cultivated soil is still largely unknown. In this study, we monitored how the bacterial community structure changed during conditioning, composting with and without Eisenia fetida, and when the end-product was applied to arable soil cultivated with wheat Triticum sp. L. The organic wastes used were biosolid, cow manure, and a mixture of both. Large changes occurred in the relative abundance of some of the most abundant bacterial genera during conditioning, but the changes were much smaller during composting or vermicomposting. The bacterial community structure was significantly different in the organic wastes during conditioning and (vermi)composting but adding E. fetida had no significant effect on it. Changes in the relative abundance of the bacterial groups in the (vermi)composted waste applied to the arable soil cultivated with wheat were small, suggesting that most survived even after 140 days. As such, applying (vermi)composted organic wastes not only adds nutrients to a crop but also contributes to the survival of plant growth-promoting bacteria found in the (vermi)compost. However, putative human pathogens found in the biosolid also survived in the arable soil, and their relative abundance remained high but mixing the biosolid with cow manure reduced that risk. It was found that applying (vermi)composted organic wastes to an arable soil not only provides plant nutrients and adds bacteria with plant growth-promoting capacities, but some putative pathogens also survived.
Asunto(s)
Compostaje , Animales , Bacterias , Biosólidos , Bovinos , Monitoreo del Ambiente , Femenino , Estiércol/microbiología , Suelo/química , TriticumRESUMEN
Biosolids are a by-product of wastewater treatment, and their nutritional composition makes them ideal for fertilizing crops. However, pre-treatments, such as conditioning and/or (vermi)composting, are often required to stabilize the product and remove pathogens. Biosolids, cow manure, and a 50-50% mixture were conditioned for 21 days, composted or vermicomposted with Eisenia fetida (Savigny 1826) for 28 days, and applied to soil cultivated with wheat (Triticum sp. L.), while emissions of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) were monitored. Emissions of CH4 were large from the biosolid and N2O from the cow manure during conditioning. Emissions of CH4 remained high during (vermi)composting of the biosolids, while the emissions of N2O from the cow manure dropped. The addition of E. fetida did not affect the emissions of greenhouse gases during (vermi)composting. The emission of N2O was higher when (vermi)composted biosolid was applied to soil cultivated with wheat than when (vermi)composted cow manure was applied. The global warming potential (GWP) of the sum of the emitted greenhouse gases (GHG) during conditioning, (vermi)composting, and when the final product was applied to soil was 3 times larger from the cow manure than from the biosolid, but mixing biosolid with cow manure eliminated that difference. It was concluded that mixing biosolid with cow manure might be a simple way to reduce the GWP of the emitted GHG during storage, (vermi)composting, and when applied to soil.
Asunto(s)
Compostaje , Gases de Efecto Invernadero , Animales , Biosólidos , Dióxido de Carbono/análisis , Bovinos , Femenino , Gases de Efecto Invernadero/análisis , Estiércol , Metano/análisis , Nitrógeno/análisis , Óxido Nitroso/análisis , Suelo , TriticumRESUMEN
Mine tailings and wastewater generate man-made environments with several selective pressures, including the presence of heavy metals, arsenic and high cyanide concentrations, but severe nutritional limitations. Some oligotrophic and pioneer bacteria can colonise and grow in mine wastes containing a low concentration of organic matter and combined nitrogen sources. In this study, Pseudomonas mendocina P6115 was isolated from mine tailings in Durango, Mexico, and identified through a phylogenetic approach of 16S rRNA, gyrB, rpoB, and rpoD genes. Cell growth, cyanide consumption, and ammonia production kinetics in a medium with cyanide as sole nitrogen source showed that at the beginning, the strain grew assimilating cyanide, when cyanide was removed, ammonium was produced and accumulated in the culture medium. However, no clear stoichiometric relationship between both nitrogen sources was observed. Also, cyanide complexes were assimilated as nitrogen sources. Other phenotypic tasks that contribute to the strain's adaptation to a mine tailing environment included siderophores production in media with moderate amounts of heavy metals, arsenite and arsenate tolerance, and the capacity of oxidizing arsenite. P. mendocina P6115 harbours cioA/cioB and aoxB genes encoding for a cyanide-insensitive oxidase and an arsenite oxidase, respectively. This is the first report where P. mendocina is described as a cyanotrophic and arsenic oxidizing species. Genotypic and phenotypic tasks of P. mendocina P6115 autochthonous from mine wastes are potentially relevant for biological treatment of residues contaminated with cyanide and arsenic.