## 4 Discussion  
### Microorganisms as Integral Components of Wine Terroir  
The present findings align with the growing body of literature highlighting the distinct biogeographical patterns of soil and must microbiota, which underpin the integration of microbiological components into _terroir_ conceptualization [11,18,19]. Our results reveal significant inter-regional variations in both vineyard soil and grape must microbiota, particularly in the relative abundance of key microbial taxa. _Proteobacteria_, _Firmicutes_, _Actinobacteria_, and _Bacteroidetes_ dominated the bacterial communities in soils across all sampled regions, while _Ascomycota_ and _Basidiomycota_ were the major fungal phyla. These observations are consistent with previous metagenomic studies that demonstrate the prevalence of these microbial groups in viticultural ecosystems [19, 20, 21]. Notably, inter-vineyard variability in microbial abundance was particularly pronounced for fermentative yeasts  
Figure 6: Direct and indirect effects of weather, soil properties, and microbial diversity (Shannon index) on wine regionality. Note: PLS-PM was employed to analyze the influence of the main predictive factors on wine metabolite profiles (**a**) and to derive the standardized total effects (direct and indirect effects) from the model (**b**). Climate and soil properties represent composite variables encompassing multiple observed parameters (see the Section 2). The red line with an arrow indicates a positive effect and the blue line with an arrow indicates a negative effect. Numbers adjacent to arrows are path coefficients that indicate the effect size of the relationship. The correlations between the specific parameters of the variables are indicated in parentheses. R\({}^{2}\) denotes the proportion of the variance explained. Significance levels: *, \(p\) < 0.05; **, \(p\) < 0.01; **, \(p\) < 0.001. (_Saccharomyces, Candida_, and _Hansenispora_) and lactic acid bacteria (_Fructobacillus_) in grape musts, reflecting dynamic interactions between indigenous microbiota and environmental factors during grape ripening. Furthermore, previous studies have shown that distinct vineyard soil microbiomes can influence grape and wine composition, thereby shaping the wine _terrori_[4; 22]. Soil serves as a critical reservoir for yeast inoculants in grape must, which may influence fermentation kinetics and metabolite production [20], thereby acting as a key determinant of the chemical profiles of wine. Our results further highlight the importance of fungal diversity in mediating these effects, particularly in yeast-dominated fermentations that drive sensory attributes. Environmental factors (e.g., vineyard weather) and geographical characteristics of vineyards influence the microbial diversity and spatial distribution patterns of microbiota in soil ecosystems [23]. [PERSON] et al. (2020) investigated microbial diversity in vineyard soils and grape must in South Australia, revealing significant differences in microbial community structures between these two environments attributable to seasonal or interannual variations [24]. This study also indirectly demonstrated that microbial biogeographical communities in soils and must from different vineyards are distinct. These findings are consistent with prior research on the microbial biogeography of wine and further support the notion that microorganisms are integral to _terrori_[6; 18; 23]. Soil bacteria and fungi can differentiate wine regions, with their distribution being influenced by soil properties and weather conditions, as confirmed by previous work [21; 25]. Both fungal and bacterial diversity are strongly influenced by soil properties and weather conditions, particularly pH and PRE Avg. Soil pH affects the membrane potential and proton motive force of bacteria and fungi, thereby influencing their uptake of nutrients.