Availability of different nitrogen forms changes the microbial communities and enzyme activities in the rhizosphere of maize lines with different nitrogen use efficiency

We studied how the Lo5 and T250 maize lines, characterized by high and low nitrogen use efficiency (NUE), respectively, modified the microbial biomass, enzymatic activities and microbial community structure in the rhizosphere after exposure to different N forms. The two maize lines were grown for 4 weeks in rhizoboxes allowing precise sampling of rhizosphere and bulk soil with no nutrient additions, and then exposed to with nitric-, ammonium- and urea-N. After N exposure, the plants were inserted back into their original rhizoboxes to allow the root exudates diffusion into the rhizosphere. After 24 h rhizosphere soil were sampled and analyzed. Microbial biomass and soil enzymatic activities were increased after the exposure to different N forms of both maize lines. The plant exposure to different N forms also induced changes in the rhizosphere bacterial and fungal communities composition. Plant responses to the availability of different N forms was a dominant factor regulating activity and composition of the rhizosphere microbial communities, likely due to changes in the rhizodepositions. Therefore different N forms used for fertilization of agriculturally relevant plants such as maize can result in different plant mediated effects on the microbial activity and community structure in the rhizosphere

Soil volatile analysis by proton transfer reaction-time of flight mass spectrometry (PTR-TOF-MS)

We analyzed the volatile organic compounds (VOCs) emitted from different soils by using the PTR-MS-TOF technique under laboratory conditions and compared them with soil chemical biochemical activities. The emitted VOCs were related to soil microbial biomass, soil respiration and some soil enzyme activities so as to evaluate if size and activity of soil microbial communities influenced the soil VOCs profiles. Our results showed that the emitted VOCs discriminated between soils with different properties and management, and differences in the VOCs emission profiles were likely related to the active metabolic pathways in the microbial communities of the three studied soil. Our results also showed that some soil enzyme activities such as \u3b2-glucosidase and arylsulfatase were possibly involved in the release of compounds fueling microbial metabolic pathways leading to the production of specific VOCs. It was concluded that the PTR-MS-TOF technique is suitable for analyze VOCs emission from soil and that studies comparing soil enzyme activities and soil volatile profiles can reveal the origin of VOCs and give further insights on microbial activity and soil functionality

Utilisation of chemically stabilized arsenic-contaminated soil in a landfill cover

The aim of the study was to determine if an As-contaminated soil, stabilized using zerovalent iron (Fe0) and its combination with gypsum waste, coal fly ash, peat, or sewage sludge, could be used as a construction material at the top layer of the landfill cover. A reproduction of 2 m thick protection/vegetation layer of a landfill cover using a column setup was used to determine the ability of the amendments to reduce As solubility and stimulate soil functionality along the soil profile. Soil amendment with Fe0 was highly efficient in reducing As in soil porewater reaching 99 % reduction, but only at the soil surface. In the deeper soil layers (below 0.5 m), the Fe treatment had a reverse effect, As solubility increased dramatically exceeding that of the untreated soil or any other treatment by one to two orders of magnitude. A slight bioluminescence inhibition of Vibrio fischeri was detected in the Fe0 treatment. Soil amendment with iron and peat showed no toxicity to bacteria and was the most efficient in reducing dissolved As in soil porewater throughout the 2 m soil profile followed by iron and gypsum treatment, most likely resulting from a low soil density and a good air diffusion to the soil. The least suitable combination of soil amendments for As immobilization was a mixture of iron with coal fly ash. An increase in all measured enzyme activities was observed in all treatments, particularly those receiving organic matter. For As to be stable in soil, a combination of amendments that can keep the soil porous and ensure the air diffusion through the entire soil layer of the landfill cover is required

Enzyme activity and microbial community structure in the rhizosphere of two maize lines differing in N use efficiency

Results: High NUE Lo5 maize induced faster inorganic N depletion in the rhizosphere and larger changes in microbial biomass and enzyme activities than the low NUE T250 maize line. The two maize lines induced differences in the studied microbial groups in the rhizosphere, with the larger modifications induced by the high NUE Lo5 maize line. Aims: Study of the changes in soil microbial biomass, enzyme activity and the microbial community structure in the rhizosphere of two contrasting maize lines differing in the nitrogen use efficiency (NUE). Methods: The Lo5 and T250 inbred maize characterized by high and low NUE, respectively, were grown in rhizoboxes allowing precise sampling of rhizosphere and bulk soil and solution. We also determined microbial biomass, enzyme activities involved in the C, N, P and S cycles, and the microbial community structure using a phylogenetic group specific PCR-DGGE approach in the rhizosphere and bulk soil of both Lo5 and T250 maize lines. Conclusions: The Lo5 maize line with higher NUE induced larger changes in soil chemical properties and in the enzyme activity, soil microbial biomass and community structure than the low NUE T250 maize line, probably due to differences in the root exudates of the two maize lines

Maize lines with different nitrogen use efficiency select bacterial communities with different \u3b2-glucosidase-encoding genes and glucosidase activity in the rhizosphere

We studied the molecular diversity of \u3b2-glucosidase-encoding genes, microbial biomass, cellulase, N-acetyl-glucosaminidase, \u3b2-glucosidase, and \u3b2-galactosidase activities in the rhizosphere and bulk soil of two maize lines differing in nitrogen use efficiency (NUE). The maize lines had significant differences in diversity of \u3b2-glucosidase-encoding genes in their rhizosphere, and Actinobacteria and Proteobacteria were the dominating phyla in all samples, but representatives of Bacteroidetes, Chloroflexi, Deinococcus-Thermus, Firmicutes, and Cyanobacteria were also detected. Among the Proteobacteria, \u3b2-glucosidase genes from \u3b1-, \u3b2-, and \u3b3-Proteobacteria were dominant in the rhizosphere of the high NUE maize line, whereas \u3b4-Proteobacteria \u3b2-glucosidase genes were dominant in the rhizosphere of the low NUE maize line. The high NUE maize line also showed higher glucosidase activities in the rhizosphere than the low NUE maize line. We concluded that plants with high NUE select bacterial communities in the rhizosphere differing in the diversity of \u3b2-glucosidase-encoding genes which likely result in higher C-hydrolyzing enzyme activities. These effects on the diversity of \u3b2-glucosidase-encoding genes may influence the C dynamics in the agro-ecosystems

Nitrate induction and physiological responses of two maize lines differing in nitrogen use efficiency: effects on N availability, microbial diversity and enzyme activity in the rhizosphere

Aim: The rate of nitrate (NO3 12) uptake and changes in rhizosphere properties were studied growing seedlings of two maize inbred lines differing in nitrogen use efficiency (NUE) in rhizoboxes. Results: Changes in NO3 12 uptake rates occurred in response to anion addition (induction) in seedlings grown both in hydroponic culture and in soil in rhizoboxes. The characterization of root exudate composition showed a line-specific metabolite profile, which was also affected by NO3 12 availability. The induction affected respiration, nitrification, ammonification and enzyme activities of the rhizosphere. Furthermore, the composition of rhizosphere bacterial communities of the two maize lines differed suggesting the selective capacity of plants. Conclusions: Overall, results showed a strong and fast modification of rhizospheric soil properties in response to physiological changes in plants caused by fluctuating NO3 12 availability

Electronic Nose: A First Sensors Array Optimization for Pesticides Detection Based on Wilks' A-Statistic

This paper describes an E-Nose aimed to Pesticide Detection which uses an array of different commercial gas sensors. In order to optimize the array reducing the redundancies due to similar sensors answers, Wilks’ A-statistic has been used

A Simple Takagi-Sugeno Fuzzy Modelling Case Study for an Underwater Glider Control System

this paper is a section of several preliminaryvstudies versus the realization of Underwater Drones of the Università degli Studi “Roma Tre” Science Department: we describe an application of Takagi-Sugeno fuzzy logic modelling to the longitudinal control for the underwater glider in order to simplify the calculation effort