Integrons, which are genetic components commonly found in bacteria, possess the remarkable capacity to capture gene cassettes, incorporate them into their structure, and thereby contribute to an increase in genomic complexity and phenotypic diversity. This adaptive mechanism allows integrons to play a significant role in acquiring, expressing, and spreading antibiotic resistance genes in the modern age. To assess the current challenges posed by integrons, it is necessary to have a thorough understanding of their characteristics. This review aims to elucidate the structure and evolutionary history of integrons, highlighting how the use of antibiotics has led to the preferential selection of integrons in various environments. Additionally, it explores their current involvement in antibiotic resistance and their dissemination across diverse settings, while considering potential transmission factors and routes. This review delves into the arrangement of gene cassettes within integrons, their ability to rearrange, the mechanisms governing their expression, and the process of excision. Furthermore, this study examines the presence of clinically relevant integrons in a wide range of environmental sources, shedding light on how anthropogenic influences contribute to their propagation into the environment.

Intercropping of soybean and sugarcane is an important strategy to promote sustainable development of the sugarcane industry. In fact, our understanding of the interaction between the rhizosphere and bacterial communities in the intercropping system is still evolving; particularly, the influence of different sugarcane varieties on rhizosphere bacterial communities in the intercropping process with soybean, still needs further research. Here, we evaluated the response of sugarcane varieties ZZ1 and ZZ9 to the root bacterial community during intercropping with soybean. We found that when ZZ9 was intercropped with soybean, the bacterial diversity increased significantly as compared to that when ZZ1 was used. ZZ9 played a major role in changing the bacterial environment of the root system by affecting the diversity of rhizosphere bacteria, forming a rhizosphere environment more conducive to the growth of sugarcane. In addition, our study found that ZZ1 and ZZ9 had differed significantly in their utilization of nutrients. For example, nutrients were affected by different functional genes in processes such as denitrification, P-uptake and transport, inorganic P-solubilization, and organic P-mineralization. These results are significant in terms of providing guidance to the sugarcane industry, particularly for the intercropping of sugarcane and soybean in Guangxi, China.

Background: Biochar is mainly used to enhance soil fertility, microbial activity, improve plant performance and reduce disease incidence. Methods: A greenhouse experiment was designed to investigate the response of biochar on rhizosphere soil chemical properties, enzyme activity, microbial communities, and sugarcane Pokkah boeng disease (PB). Two sugarcane varieties Zhongzhe 9 (Z9) and ROC22, susceptible/resistant to PB, were cultivated and treated with: no biochar, 15 t ha⁻¹ biochar, and 30 t ha⁻¹ biochar. Results: The amendment of 30 t ha⁻¹ of biochar (B2) significantly improve soil pH by 1.50% and 9.61% compared with that of B1 and B0, followed by 0.51% increase by 15 t ha⁻¹ of biochar (B1) compared with that of control (B0). The application of 15 t ha⁻¹ biochar significantly increased available phosphorus (AP) and ammonium nitrogen (NH₄⁺–N) by 209.93 mg kg⁻¹ and 12.1 mg kg⁻¹, while the application of 30 t ha⁻¹ of biochar significantly increased 241.04 mg kg⁻¹ of available potassium (AK) (P < 0.05). Furthermore, biochar application increased the activities of soil acid phosphatase (S-ACP), urease (S-UE), and sucrase (S-SC). Alpha diversity analysis showed that the addition of biochar significantly altered the variety and abundance of rhizosphere microorganisms (P < 0.01) and increased the relative abundance of beneficial microorganisms Rhodanobacteraceae, Stachybotryaceae, Agaricacea, Talaromyces, Nectriaceae, Sistotrema, and Bacillus (P < 0.01). There was a significant decrease in the relative abundance of the soil pathogen Fusarium (P < 0.01). Conclusion: These findings suggested that the application of 15 t ha⁻¹ biochar could bring desirable variations in soil functionalities, modulate soil microbial community by increasing soil health and reduce the disease index of PB. Graphical

Individual applications of biochar (B) or organic manure (M) have been reported to improve soil fertility and plant performance. Their synergistic effects on paddy soil physicochemical properties, microbial communities, and rice productivity remain under explored. This study investigated the effects of B (20 t ha− 1), M (15 t ha− 1), and their combined application (BM, 10 + 7.5 t ha− 1) on soil physicochemical properties, microbial communities, rice plant growth and yield. Our findings revealed that B, M, and BM significantly improved soil physicochemical properties compared to control (CK). BM enhanced total nitrogen and available phosphorus by 34% and 26%, respectively, compared to CK. Soil pH, soil organic carbon, available nitrogen, and available potassium showed higher values in all treatments compared to the CK, with no significant differences among B, M, or their combined applications. Chlorophyll a, b, plant growth, dry matter and yield attributes showed the trend of BM > M > B > CK. These changes were attributed to the enhancement of beneficial soil bacteria, including Proteobacteria, Firmicutes, Actinobacteria and Bacteroidota in the BM treatment. Individual biochar treatment reduced Chloroflexi and Firmicutes but increased Proteobacteria and Actinobacteria. In contrast, individual manure application enhanced Firmicutes and Nitrospirota. Among fungal communities, Chaetomium and Pinnularia showed higher relative abundances in the combined treatment, playing roles in organic matter decomposition and plant growth, respectively. We conclude that the integrated use of biochar and manure enhances rice performance primarily by fostering a soil microbiome conducive to nutrient cycling and plant growth. Combined B + M application is therefore recommended as a sustainable strategy for improving paddy soil quality and crop yield.

Integrons are hot spots for acquiring gene cassettes from the environment and play a major role in the bacterial evolution and dissemination of antimicrobial resistance (AMR), thus posing a serious threat. There are currently studies on integrons and antibiotic resistance genes; however, the presence and association of integrons in different agricultural crops and their subsequent dissemination and role in AMR have not been reported previously. This study examines the abundance of integrons, their gene cassette diversity in various crop soils, and their role in the dissemination of AMR in the southern region of China. Samples from different agri-crop soil, such as rice (R.S), sugarcane (S.S), citrus (C.S), banana (B.S), agricultural runoff (the point where the runoff of all sites meet (R.O)), and wild (non-agricultural) soil (W.S), were collected. Quantitative PCR was used to determine the abundance of integrons, and clone libraries were constructed to examine the gene cassette arrays. All the tested samples were found positive for Class-I (CL1) integrons and revealed a higher concentration and higher relative abundance of R.S than the others, with the least found at the W.S site. The W.S CL1 cassette arrays were found empty, and no putative conserved domains were found. The R.O was found to contain a high number of gene cassettes with various functions, while the smallest number of gene cassettes was found in the S.S among the crop soils. Most of the gene cassettes presented by the R.O were primarily shared with other sites, and the antibiotic-resistant genes were consistently observed to be dominant. The constructed clone libraries represented a diverse gene cassette array with 16% novel gene cassettes that play a vital role in pathogenesis, transportation, biosynthesis, and AMR. Most resistance-related gene cassettes were associated with the genes encoding resistance to quaternary ammonium compound (QAC) and aminoglycosides. This study highlights the significant differences in the abundance of integrons among various agricultural soils and offers deep insight into the pools of gene cassettes that play a key role in the dissemination of integrons and AMR.