The microbial community in pit mud, particularly the archaeal community, plays a pivotal role in the solid-state multi-microorganism fermentation process of strong-flavor Baijiu. This study systematically analyzed physicochemical properties, archaeal succession, and volatile metabolites across pit ages (3, 45, 100 years) and spatial layers (upper/middle/lower) in pit mud. It revealed the mechanisms by which environmental factors drive archaeal community composition and metabolic function. Results revealed marked spatiotemporal variations in pit mud's archaea and metabolites, with 45-year-old samples (especially mid-layer) showing peak archaeal diversity and highest volatile compound richness (predominantly esters). The phyla Methanobacteriota and Halobacteriota were identified as the dominant archaeal groups, with the genus Methanothrix being exclusively detected in 100-year pit mud. The genus Methanoculleus reached its highest abundance in 45-year pit mud and exhibited a progressive increase along the pit depth gradient. The Pearson correlation analysis revealed significant associations between the archaeal community structure and key environmental factors, including pH, humus, ammonium nitrogen, available phosphorus, and multiple metal elements, suggesting that these factors collectively influence archaeal community assembly. The functional prediction (PICRUSt2) further elucidated the synergistic relationship between archaeal key enzymes involved in methanogenesis and critical flavor compound synthesis. This study offers a new perspective on the notion that "older pit mud is always better." Our findings show that, in this evaluation, 45-year-old pit mud exhibited superior overall quality compared to 100-year-old pit mud. This indicates that pit mud quality is closely related to archaeal succession and influenced by multiple factors.IMPORTANCEThe assembly of microbial communities is a long-term process, and temporal patterns in environmental communities cannot be studied in isolation-spatial patterns must also be considered. The functional roles of rare archaeal communities in the pit mud ecosystem are equally important, yet they remain understudied. To elucidate the temporal and spatial dynamics of archaeal succession in this ecosystem, the archaeal communities in pit mud from different temporal and spatial contexts were investigated. This study offers a new perspective on the notion that "older pit mud is always better." Our findings show that, in this evaluation, 45-year-old pit mud exhibited superior overall quality compared to 100-year-old pit mud, suggesting that pit mud quality is likely influenced by multiple complex factors.
Huang et al. (Mon,) studied this question.