Sargassum seaweed has inundated Caribbean coastlines, disrupting ecosystems while presenting opportunities for sustainable products like liquid biofertilizers. This study evaluated the microbiological and biosecurity profiles of two liquid biofertilizers produced in the Dominican Republic: Sargassum-based (SBLB-INTEC) and conventional (LB-BANELINO). Both exhibited essential minerals (K, Ca, Mg) and low heavy metal concentrations, meeting agricultural safety standards. Metagenomic analysis (16S rRNA) identified diverse bacterial and archaeal communities, mainly consisting of beneficial taxa such as Firmicutes, Proteobacteria, and Methanobacteria, with no detectable pathogens. Ecotoxicological assays with Lactuca sativa showed phytotoxicity at high concentrations, mitigated by dilution (≤6.25%) and pH adjustment (7.0), achieving germination indexes above 80%. These results suggest that Sargassum-based biofertilizers could be a viable alternative for enhancing soil fertility and promoting sustainable crop production, particularly in coastal agricultural systems where conventional fertilizers may be limited or environmentally harmful. Moreover, this study highlights the critical role of ecotoxicological testing in ensuring biofertilizer safety and underscores Sargassum’s potential as a renewable resource for sustainable farming.

Viruses are the most abundant biological entities in all ecosystems of the world. Their ubiquity makes them suitable candidates for indicating fecal contamination in rivers. Recently, a group of Bacteroidetes bacteriophages named CrAssphages, which are highly abundant, sensitive, and specific to human feces, were studied as potential viral biomarkers for human fecal pollution in water bodies. In this study, we evaluated the presence, diversity, and abundance of viruses with a focus on crAssphages via metagenomic analysis in an Amazonian river and conducted correlation analyses on the basis of physicochemical and georeferencing data. Several significant differences in viral alpha diversity indexes were observed among the sample points, suggesting an accumulation of viral organisms in the river mouth, whereas beta diversity analysis revealed a significant divergence between replicates of the most downstream point (IT4) when compared to the rest of the samples, possibly due to increased human impact at this point. In terms of the presence of crAssphage, the analysis identified 61 crAssphage contigs distributed along the Itacaiúnas River. Moreover, our analysis revealed significant correlations between 19 crAssphage contigs and human population density, substantiating the use of these viruses as possible markers for human fecal pollution in the Itacaiúnas River. This study is the first to assess the presence of crAssphages in an Amazonian river, with results suggesting the potential use of these viruses as markers for human fecal pollution in the Amazon. IMPORTANCE: The Amazon biome is one of the most diverse ecosystems in the world and contains the most vast river network; however, the continuous advance of urban centers toward aquatic bodies exacerbates the discharge of pollutants into these water bodies. Fecal contamination contributes significantly to water pollution, and the application of an improved fecal indicator is essential for evaluating water quality. In this study, we evaluated the presence, diversity, and abundance of crAssphages in an Amazonian river and performed correlation analysis on the basis of physicochemical and georeferencing data to test whether crAssphages are viable fecal pollution markers. Our analysis revealed both the presence of crAssphages and their correlation with physicochemical data and showed significant correlations between the relative abundance of crAssphages and human density. These results suggest the potential use of these viruses as markers for water quality assessment in Amazonian rivers.

Sargassum seaweed is increasingly abundant in the Caribbean, creating ecological disruption but also providing biomass for agricultural inputs. This study compares the microbial diversity and safety of a Sargassum ‐based liquid biofertilizer (SBLB‐INTEC) with those of a conventional product (LB‐BANELINO) using 16S rRNA amplicon sequencing, rather than culture‐dependent methods. Both formulations contained key nutrients (K, Ca, and Mg) and low levels of heavy metals. They harbored dense but relatively simple bacterial communities dominated by Firmicutes, particularly Bacilli, with Proteobacteria and other phyla at lower abundances. Staphylococcus (Staphylococcaceae) was highly abundant in both products, while SBLB‐INTEC showed a somewhat more balanced community, including Delftia and other Comamonadaceae. Shannon diversity tended to be higher in SBLB‐INTEC, but differences in alpha‐ and beta‐diversity between formulations were not statistically significant. Because 16S data cannot distinguish viable from nonviable cells or resolve strain‐level pathogenicity, these results do not prove the absence of pathogens; instead, they provide a genus‐level baseline to guide targeted culture, qPCR, and functional assays. Overall, the combination of a favorable chemical profile and microbial groups commonly associated with nutrient cycling and plant‐associated functions suggests that SBLB‐INTEC could become a valuable component of integrated nutrient management in tropical agriculture, offering hope for a more sustainable future pending confirmatory plant‐response and biosafety studies. We recommend integrating these microbial data into a national biofertilizer monitoring framework, combining metagenomic surveys with targeted qPCR and resistance gene screening.

The Amazon rainforest represents nearly 40% of the world’s tropical forests and has undergone extensive conversion to pasture, profoundly altering soil microbial communities. Given that bacteriophage-driven selective pressure shapes bacterial defense systems (the defensome) as well as mobile genetic elements (MGEs), we examined the diversity and distribution of these genetic components in native forest soils and in pasture soils under two management regimes (with and without fertilization) in the Brazilian Amazon. Metagenomic sequencing revealed pronounced differences in bacterial community structure between forest and pasture sites ( R = 0.942), whereas phages communities exhibited no significant variation. Pasture soils—particularly those under fertilization—showed higher abundances of functional genes and mobile genetic elements, including conjugative plasmid-associated genes and insertion sequences. Defensome analyses indicated an increased prevalence of retrons and Pycsar systems in managed soils, while a greater diversity of defense genes was observed in non-fertilized pastures. A strong positive correlation was observed between defensome diversity and MGE diversity, suggesting coordinated dynamics between viral selective pressure and horizontal gene transfer. These findings indicate that forest-to-pasture conversion reshapes microbial functional potential and amplifies genetic mechanisms linked to phage defense and gene mobility, with potential consequences for ecosystem functioning and the dissemination of antimicrobial resistance.

This short communication presents novel molecular tools designed for the endangered species Brycon orbignyanus. In conservation studies, the development of population-specific markers tailored to particular geographic regions is essential. In this study, the prevalence of imperfect microsatellites highlights a evolution of this type of microsatellite in a population of Pelotas, Rio Grande do Sul. Therefore, the methodology used can serve as a guideline for genetic variability analysis even before conducting in vitro or in situ tests. These findings contribute significantly to technological prospecting and hold promise for applications in conservation programs. Additionally, they provide a basis for in vitro assays, such as PCR, to support species monitoring efforts.