Metagenomic insights into the impact of litter from poultry Concentrated Animal Feeding Operations (CAFOs) to adjacent soil and water microbial communities

Microplastics affect the nitrogen nutrition status of soybean by altering the nitrogen cycle in the rhizosphere soil

Microplastics (MPs) are widely distributed in agricultural systems. However, studies on the comprehensive effects of MPs on nitrogen cycling in crop rhizosphere soil, and the changes this effect causes to crop growth is still limited. In this study, we investigated how three types of 5 % MPs (polystyrene, PS; polyethylene, PE; polyvinyl chloride, PVC) affect soybean growth by altering rhizosphere soil nitrogen cycling. These MPs have no direct toxic effects on soybean under hydroponic conditions. However, under soil cultivation conditions, PE and PS promoted soybean growth and increased soybean roots nitrogen content and nitrogen assimilation enzyme activity, while PVC does the opposite. Further study found that PE and PS increased the inorganic nitrogen content, and the activity of nitrogen cycle-related enzymes and the abundance of genes and microorganism in rhizosphere soil. Meanwhile, PVC significantly reduced the inorganic nitrogen contents, inhibited the activity of nitrogen cycling related enzymes, and destroyed the microbial community structure in rhizosphere soil. More importantly, PVC significantly reduced the abundance of nitrogen cycle-related genes and microorganisms, and increased the abundance of viruses. These results indicated that PE and PS promote soybean growth by activating the nitrogen cycle in the rhizosphere soil and increasing the soil nitrogen content, whereas PVC inhibits soybean growth by disrupting the nitrogen cycle in the rhizosphere soil and reducing its nitrogen content.

Spatial Heterogeneity in Soil Microbial Communities Impacts Their Suitability as Bioindicators for Evaluating Productivity in Agricultural Practices

Soil microorganisms are increasingly recognized as critical regulators of farmland soil fertility and crop productivity. However, the impacts of spatial heterogeneity in soil microbial communities on bioindicators for evaluating agricultural practices remain poorly understood and warrant further validation. Through field experiments, this study investigated the differential effects of agricultural practice treatments on soil properties and bacterial communities between two main farmland soil compartments: intra-row and inter-row. Additionally, we explored the potential correlations between key taxa and soil properties, as well as maize biomass. Results revealed marked disparities in soil properties, bacterial community compositions, and co-occurrence network patterns between intra-row and inter-row soils. Agricultural practice treatments exerted significant impacts on bacterial community structures and network topological features in both intra-row and inter-row soils. Subsequent correlation analysis demonstrated strong relationships between soil properties and most keystone species. In addition, 42 and 41 indicator species were identified in intra-row and inter-row soils, respectively, including shared genera such as Solirubrobacter, Blastococcus, Iamia, Conexibacter, and Lysobacter. Notably, 22 key indicator species in intra-row soils displayed significant positive/negative correlations with maize biomass, whereas only 4 key indicator species showed negative correlations in inter-row soils. These findings highlight differential responses of bacterial communities to agricultural practices in distinct soil compartments. The intra-row soils harbored more bacterial taxa significantly associated with maize biomass, while the inter-row soils better reflected the effects of agricultural interventions. This study confirms the spatial variability of microbial communities as effective bioindicators for evaluating agricultural practice strategies. Identification of compartment-specific indicators provides novel microbiological insights into supporting precision agriculture practices.

Whole genome sequencing revealed high occurrence of antimicrobial resistance genes in bacteria isolated from poultry manure

BACKGROUND

Global demand for food has driven expansion and intensification of livestock production, particularly in developing nations where antibiotic use is often routine. Waste from poultry production, including manure, is commonly utilized as fertilizers in agroecosystems, risking environmental contamination with potentially zoonotic bacteria and antimicrobial resistance genes (ARGs).

METHODS

Here, 33 bacterial isolates were recovered from broiler (n = 17) and layer (n = 16) chicken manure by aerobic culture using Luria Bertani agar. Antimicrobial susceptibility testing (AST) was performed using disc diffusion method. MALDI-ToF and 16S rRNA sequencing were used to identify and compare a subset of antibiotic-resistant isolates (n = 13). Comparison of whole genome sequence assemblies and phenotypic assays were used to assess capacity for biofilm formation, heavy metal tolerance and virulence.

RESULTS

AST by disc diffusion revealed all isolates were resistant to a minimum of three antibiotics, with resistance to ampicillin, co-trimoxazole, fluoroquinolones, tetracyclines, streptomycin, rifampicin and/or chloramphenicol detected. Stutzerimonas sp. and Acinetobacter sp. were the common genera observed in this study. Genome sequencing of each selected isolate revealed carriage of multiple ARGs capable of conferring resistance to many antimicrobials commonly employed in poultry production and human medicine, including tetracyclines, quinolones, macrolides, sulfonamide and cephalosporins.

CONCLUSIONS

The high occurrence of ARGs in studied bacterial isolates confirms that poultry manure could act as a source of genetic material that could be transferred to commensal microbiota and opportunistic pathogens of humans. Understanding the complex resistome interplay between humans, animals, and the environment requires a One Health approach, with implications for agricultural settings and public health.

A comprehensive review of antibiotic resistance gene contamination in agriculture: Challenges and AI-driven solutions

Since their discovery, the prolonged and widespread use of antibiotics in veterinary and agricultural production has led to numerous problems, particularly the emergence and spread of antibiotic-resistant bacteria (ARB). In addition, other anthropogenic factors accelerate the horizontal transfer of antibiotic resistance genes (ARGs) and amplify their impact. In agricultural environments, animals, manure, and wastewater are the vectors of ARGs that facilitate their spread to the environment and humans via animal products, water, and other environmental pathways. Therefore, this review comprehensively analyzed the current status, removal methods, and future directions of ARGs on farms. This article 1) investigates the origins of ARGs on farms, the pathways and mechanisms of their spread to surrounding environments, and various strategies to mitigate their spread; 2) determines the multiple factors influencing the abundance of ARGs on farms, the pathways through which ARGs spread from farms to the environment, and the effects and mechanisms of non-antibiotic factors on the spread of ARGs; 3) explores methods for controlling ARGs in farm wastes; and 4) provides a comprehensive summary and integration of research across various fields, proposing that in modern smart farms, emerging technologies can be integrated through artificial intelligence to control or even eliminate ARGs. Moreover, challenges and future research directions for controlling ARGs on farms are suggested.