Microorganisms

Probiotics hold great potential in aquaculture, as they can effectively modulate gut microbiota and improve fish health, thereby enhancing farming efficiency. Translating this potential into practical application critically relies on screening high-efficacy probiotic strains. This study evaluated the growth-promoting and health-enhancing effects of probiotic candidates Lactobacillus rhamnosus GG (LGG), Lactobacillus plantarum FZU310 (LP-FZU310) and Bacillus subtilis FZU103 (BS-FZU103) in largemouth bass (Micropterus salmoides). After feeding different probiotics for 30 days, the growth, antioxidant, and intestinal enzyme indicators of M. salmoides were detected. BS-FZU103 demonstrated superior efficacy among the tested strains, showing significant differences in both specific growth rate (SGR) (p < 0.05) and condition factor (CF) (p < 0.05). It also markedly enhanced hepatic antioxidant status, elevating superoxide dismutase and glutathione peroxidase activities while reducing malondialdehyde levels by 80%. Improved liver integrity was indicated by significant decreases in serum alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase. Digestively, BS-FZU103 specifically increased intestinal amylase activity by 14.7%, without affecting protease or lipase, suggesting enhanced carbohydrate digestion. 16S rRNA sequencing revealed BS-FZU103 remodeled gut microbiota, increasing Proteobacteria abundance at the phylum level and enriching Bacillus while reducing Clostridium sensu stricto 1 at the genus level. Functional prediction based on PICRUSt2 indicated an enhanced metabolic potential of the gut microbiota, with inferred upregulation of pathways related to carbohydrate transport and metabolism (e.g., ABC transporters) and intestinal enzymatic activities. Collectively, BS-FZU103 is associated with metabolic modulation, promoting M. salmoides growth through gut microbiota remodeling, hepatic antioxidant fortification, and targeted augmentation of carbohydrate utilization efficiency.

Continuous cropping of Brassica napus impairs sustainable production via soil nutrient imbalance and microecological degradation. We evaluated rhizosphere soil properties and microbial communities under rotations crops (Triticum aestivum [TaBn], Beta vulgaris [BvBn], Glycine max [GmBn], Sorghum bicolor [SbBn], Hordeum vulgare [HvBn], and Brassica napus [BnBn]). BvBn had the highest total nitrogen, total potassium, available potassium, and organic matter contents. TaBn exhibited the highest soil enzyme activities, and its bacterial/fungal Chao1/Simpson indices and unique operational taxonomic units (OTUs; bacteria: 333, fungi: 37) exceeded other patterns. Principal coordinate analysis showed distinct microbial community separation in BvBn/TaBn versus BnBn. TaBn enriched dominant bacterial phyla Pseudomonadota and Actinomycetota; all preceding crops increased fungal phylum Ascomycota while reducing Mucoromycota. Comprehensive assessment confirmed all preceding crops, except oilseed rape altered rhizosphere microbial structure, with TaBn as the optimal preceding crops.

The antimicrobial resistance crisis necessitates novel therapeutics. Selenium nanoparticles (SeNPs) offer promise, but their precise bactericidal mechanism remains poorly defined. This study aimed to define the antibacterial action of SeNPs synthesized via a green method with ascorbic acid and sodium citrate. The resulting SeNPs were monodisperse (17.8 ± 0.66 nm), crystalline, and highly stable (zeta potential: −69.9 ± 4.3 mV), exhibiting potent bactericidal activity against multidrug-resistant E. coli. To generate a mechanistic hypothesis, we integrated phenotypic analyses with a preliminary, single-replicate proteomic profiling. Recognizing this as an exploratory step, we focused our analysis on proteins with the most substantial changes. This revealed a coherent pattern of a targeted dual assault on core cellular processes. The data indicate that SeNPs simultaneously induce oxidative stress while severely depleting key components of the primary antioxidant glutathione system; key detoxification enzymes—glutathione S-transferase and glutaredoxin 2—were depleted 18- to 19-fold, while the stress protein HchA was reduced by over 63-fold. Concurrently, the patterns point toward a crippling of central energy metabolism; iron–sulfur enzymes in the TCA cycle, including aconitate hydratase (8.1-fold decrease) and succinate dehydrogenase (13.9-fold decrease), were severely suppressed, and oxidative phosphorylation was impaired (e.g., 4.7-fold decrease in NADH dehydrogenase subunit B). We propose that this coordinated disruption creates a lethal feedback loop leading to metabolic paralysis. Consequently, this work provides a detailed and testable mechanistic hypothesis for SeNPs action, positioning them as a candidate for a potent, multi-targeted antimicrobial strategy against drug-resistant pathogens.