Green tea is a popular non-alcoholic beverage consumed worldwide and has been shown to be beneficial for human health. However, further exploration is needed to fully understand its function in reducing obesity and regulating gut microbes. Here, we investigated the modulatory effects of green tea and its functional components on high-fat diet (HF)-induced metabolic alterations and gut microbiota in obese mice. Our results showed that 1%, 2%, and 4% of green tea promotes weight loss, with the 2% and 4% groups exhibiting distinct gut microflora clusters compared to the HF group. These results were comparable to those observed in the tea polyphenols (TPP)-treated group, suggesting the TPP in green tea plays a crucial role in body weight control and gut microbiota regulation. Additionally, 32 bacteria were identified as potential obesity markers via 16S rRNA gene sequencing. The 16SrDNA gene is a chromosomal gene present in all bacterial species, highly conserved in structure and function, that can reflect the differences between different taxa. The 16S rRNA-based analysis revealed that Akkermansia, a gut-beneficial bacteria, significantly increased in the TPP group.

Continuous fertilization may modify soil nutrient pools and microbial communities in tea plantations, but their joint relationships with nitrogen-cycling genes and tea-leaf composition remain incompletely characterized. Soil properties, tea quality, and shotgun metagenomic profiles were examined after 16 years of four field management regimes: no fertilization (CK), chemical fertilization (CF), organic manure (OM), and combined organic–mineral fertilization (OMN). Relative to CK, OMN had higher soil organic matter (73.30%), total nitrogen (76.12%), total phosphorus (140.45%), alkali-hydrolyzable nitrogen (128.20%), available phosphorus (182.35%), available potassium (93.89%), and nitrate nitrogen (313.86%). OMN also increased tea-shoot free amino acids (29.60%) and catechins (21.96%) relative to CK, whereas caffeine (13.45%) and water-extract content (6.73%) were lower. Microbial richness indices (ACE, Chao1, and observed species) were higher under OMN than CK by 22.46%, 18.24%, and 22.90%, respectively. Community composition differed among treatments (ANOSIM: R = 1, p = 0.001). Of 32,733 annotated nitrogen-cycling genes, 21,874 were shared among treatments, while OMN had the largest treatment-specific gene set (1912). Soil nutrient properties covaried with nitrogen-cycling gene profiles. These endpoint observations indicate distinct soil, microbial, and tea-chemical characteristics under sustained fertilizer regimes; metagenomic gene profiles describe functional potential rather than measured nitrogen-transformation rates.