Pesticide toxicity on soil microorganisms is an emerging issue in pesticide risk assessment, dictated by the pivotal role of soil microorganisms in ecosystem services. However, the focus has traditionally been on parent compounds, while transformation products (TPs) are largely overlooked. We tested the hypothesis that TPs can be major contributors to the soil microbial toxicity of pesticides using iprodione and its main TP, 3,5-dichloroaniline, as model compounds. We demonstrated, by measuring functional and structural endpoints, that 3,5-dichloroaniline and not iprodione was associated with adverse effects on soil microorganisms, with nitrification being mostly affected. Pioneering in vitro assays with relevant ammonia-oxidizing bacteria and archaea verified the greater toxicity of 3,5-dichloroaniline. Our findings are expected to advance environmental risk assessment, highlighting the potential of ammonia-oxidizing microorganisms as indicators of the soil microbial toxicity of pesticides and stressing the need to consider the contribution of TPs to pesticide soil microbial toxicity.

Pesticides are intentionally applied to agricultural fields for crop protection. They can harm non-target organisms such as soil microorganisms involved in important ecosystem functions with impacts at the global scale. Within the frame of the pesticide registration process, the ecotoxicological impact of pesticides on soil microorganisms is still based on carbon and nitrogen mineralization tests, despite the availability of more extensive approaches analyzing the abundance, activity or diversity of soil microorganisms. In this study, we used a high-density DNA microarray (PhyloChip) and 16S rDNA amplicon next-generation sequencing (NGS) to analyze the impact of the organophosphate insecticide chlorpyrifos (CHL), the phenyl-urea herbicide isoproturon (IPU), or the triazole fungicide tebuconazole (TCZ) on the diversity and composition of the soil bacterial community. To our knowledge, it is the first time that the combination of these approaches are applied to assess the impact of these three pesticides in a lab-to-field experimental design. The PhyloChip analysis revealed that although no significant changes in the composition of the bacterial community were observed in soil microcosms exposed to the pesticides, significant differences in detected operational taxonomic units (OTUs) were observed in the field experiment between pesticide treatments and control for all three tested pesticides after 70 days of exposure. NGS revealed that the bacterial diversity and composition varied over time. This trend was more marked in the microcosm than in the field study. Only slight but significant transient effects of CHL or TCZ were observed in the microcosm and the field study, respectively. IPU was not found to significantly modify the soil bacterial diversity or composition. Our results are in accordance with conclusions of the Environmental Food Safety Authority (EFSA), which concluded that these three pesticides may have a low risk toward soil microorganisms.

Films of carrot cellulose nanofibrils (CCNFs) with the addition of low-viscosity chitosan (CHIT) were prepared by the vacuum filtration. The chitosan content in the films varied from 9 to 33% (dry wt. basis). The surface morphology of the films was investigated by scanning electron microscopy, and it was found that chitosan was dispersed in the CCNF matrix. The interaction between CCNFs and CHIT was evaluated in terms of Fourier transform infrared spectroscopy (FTIR). The obtained results suggested physical interactions rather than hydrogen bonding between CCNFs and CHIT. This finding also supports the results of the water wettability experiment. The addition of chitosan to the nanocellulose matrix causes an increase in the water contact angle, i.e., the surface of the composites becomes more hydrophobic. This increase is probably connected to an interaction between nanocellulose and chitosan forming a denser structure. Analyses of thermal properties showed that the composites are stable under high temperature, and the degradation occurred above 300 °C. It was found that the addition of CHIT to CCNF matrices caused a decrease in the Young’s modulus—the higher that the concentration of chitosan in the composite was, the lower the Young’s modulus (decreased from 14.71 GPa for CCNFs to 8.76 GPa for CCNF/CHIT_5). Additionally, the tensile strength of composites, i.e., the maximum force that causes a fracture decreased after the addition of chitosan (decreased from 145.83 MPa for CCNFs to 129.43 MPa for CCNF/CHIT_5). The results indicated the highest inhibitory effect of the investigated composites against E. coli and S. epidermidis. Whereas M. luteus was inhibited only by the higher concentration of chitosan in the tested composites, inhibition was not found against C. krissii and all tested filamentous fungi. Graphic

In this research, it was proposed to use carrot cellulose nanofibrils (CCNF) isolated from carrot pomace modified with silver nanoparticles (AgNPs) as a filler of polylactic acid (PLA) composites matrix. The new procedure was based on two steps: first, the preparation of nanocellulose modified with metal nanoparticles, and then the combination with PLA. Two concentrations—0.25 mM and 2 mM—of AgNO₃ were used to modify CCNF. Then, PLA was mixed with the filler (CCNF/AgNPs) in two proportions 99:1 and 96:4. The influence of CCNF/AgNPs on mechanical, hydrophilic, thermal, and antibacterial properties of obtained nanocomposites was evaluated. The greatest improvement of mechanical properties was observed for composite containing CCNF with 2 mM of AgNPs, which obtained the lowest Young modulus and highest strain at break. The degradation temperature was lower for PLA with CCNF/AgNPs, but crystallization temperature wasn’t influenced. The addition of CCNF/AgNPs also increased hydrophilicity. The transmission rates of oxygen, nitrogen, and carbon dioxide also increased after the addition of CCNF/AgNPs to PLA. The antibacterial function against Escherichia coli and Bacillus cereus was obtained after the addition of AgNPs but only at the contact surface with the material made, suggesting the lack of migration of nanoparticles from the composite.

Waste exogenous organic matter, including spent mushroom substrate (SMS) and chicken manure (CM), can be used as the basis of a soil-improving cropping system in sustainable agriculture. However, there is—as yet—a lack of information about important quality indicators such as the fungal community relative abundance, structure and biodiversity in soils treated with these additives. In this study, the responses of the soil fungal community composition and mycobiome diversity to SMS and CM application compared to the control soil were evaluated using a combination of the following molecular approaches: quantitative polymerase chain reactions, denaturing gradient gel electrophoresis, terminal restriction fragment length polymorphism, and next-generation sequencing. The most abundant phylum for both treatments was Ascomycota, followed by Basidiomycota. The application of SMS and CM increased the abundance of fungi, including Tremellomycetes and Pezizomycetes for the SMS additive, while the Mortierellomycetes, Pezizomycetes, and Leotiomycetes levels increased after CM addition. SMS and CM beneficially reduced the relative abundance of several operational taxonomic units (OTUs) which are potential crop pathogens. The results provide a novel insight into the fungal community associated with organic additives, which should be beneficial in the task of managing the soil mycobiome as well as crop protection and productivity.