cChinese strong-flavored liquor (CSFL) accounts for more than 70% of all Chinese liquor production. Microbes in pit mud play key roles in the fermentation cellar for the CSFL production. However, microbial diversity, community structure, and cellar-agerelated changes in pit mud are poorly understood. Here, we investigated the prokaryotic community structure and diversity in pit-mud samples with different cellar ages (1, 10, 25, and 50 years) using the pyrosequencing technique. Results indicated that prokaryotic diversity increased with cellar age until the age reached 25 years and that prokaryotic community structure changed significantly between three cellar ages (1, 10, and 25 years). Significant correlations between prokaryotic communities and environmental variables (pH, NH 4 ؉ , lactic acid, butyric acid, and caproic acid) were observed. Overall, our study results suggested that the long-term brewing operation shapes unique prokaryotic community structure and diversity as well as pit-mud chemistry. We have proposed a three-phase model to characterize the changes of pit-mud prokaryotic communities. C hinese strong-flavored liquor (CSFL), also called "Luzhou flavor liquor," accounts for more than 70% of Chinese liquor production (1). It is produced by the unique and traditional Chinese solid-state fermentation technique, which has a history of several thousand years. In brief, a cellar is constructed by digging a rectangular soil pit in which the entire inner wall is covered with precultured pit mud. The precultured pit mud is usually prepared by mixing aged pit mud (as an inoculum), fresh common soil, and water and incubating the mixture for about a year in an anaerobic cellar before use. The raw materials for the fermentation, including wheat, sorghum, and corn, are mixed, crushed, and distilled by steaming. The steamed raw material is supplied with 2% to 3% (wt/wt) Daqu-starter, which mainly includes mold and yeast, and placed into the cellar. The cellar is sealed with common mud, and fermentation is allowed to proceed for 60 days. Fermented material is then taken out of the cellar and distilled to make Chinese liquor. The process described above is periodically repeated after new fermentation materials are supplied.Microbes in the pit mud produce various flavor components such as butyric acid, caproic acid, and ethyl caproate. In particular, ethyl caproate is recognized as a key component affecting the CSFL flavor and quality. In general, CSFL quality improves with increasing cellar age. High-quality liquor is produced only in old cellars, which are maintained at least for 20 years by continuous use (2, 3). In particular, some long-aged cellars have been used for several hundred years without interruption, and well-known CSFLs such as Wuliangye, Jiannanchun, and Luzhoulaojiao are brewed in such long-aged cellars (1, 4). High CSFL quality is attributed to the maturing process of pit mud, which results in a well-balanced microbial community structure and diversity in the pit mud to produce distinctive flavo...

Incorporation of plant residues strongly enhances the methane production and emission from flooded rice fields. Temperature and residue type are important factors that regulate residue decomposition and CH 4 production. However, the response of the methanogenic archaeal community to these factors in rice field soil is not well understood. In the present experiment, the structure of the archaeal community was determined during the decomposition of rice root and straw residues in anoxic rice field soil incubated at three temperatures (15°C, 30°C, and 45°C). More CH 4 was produced in the straw treatment than root treatment. Increasing the temperature from 15°C to 45°C enhanced CH 4 production. Terminal restriction fragment length polymorphism analyses in combination with cloning and sequencing of 16S rRNA genes showed that Methanosarcinaceae developed early in the incubations, whereas Methanosaetaceae became more abundant in the later stages. Methanosarcinaceae and Methanosaetaceae seemed to be better adapted at 15°C and 30°C, respectively, while the thermophilic Methanobacteriales and rice cluster I methanogens were significantly enhanced at 45°C. Straw residues promoted the growth of Methanosarcinaceae, whereas the root residues favored Methanosaetaceae. In conclusion, our study revealed a highly dynamic structure of the methanogenic archaeal community during plant residue decomposition. The in situ concentration of acetate (and possibly of H 2 ) seems to be the key factor that regulates the shift of methanogenic community.Plant residues are a by-product of rice production. The incorporation of plant residues into rice field soil is a common practice in Asian agriculture that could help to maintain the soil fertility. However, the incorporation of plant residues strongly enhances the methane emissions from rice fields (8,13,38,39). It has been shown that the decomposition of straw residues in rice field soil is performed by a spatially wellorganized consortium: the hydrolysis and primary fermentation reactions are mainly localized on the straw residue while the syntrophic and methanogenic reactions occur in the adjacent soil (14). There was an astonishing richness of archaeal diversity present on rice roots and in the surrounding paddy soil (4,16,17,29). Although it was shown that the structure of methanogenic archaea in the rice field soil remained relatively constant over the growing season of rice plants (24), the incorporation of rice straw selectively enhanced the growth of Methanosarcinaceae and Methanobacteriales and suppressed rice cluster I (RC-I) methanogens and Methanomicrobiales (7). Apparently, the members of the methanogenic community respond differently to the incorporation of organic residues. Rice straw and root residues are the major forms of organic residues incorporated into rice field soils. It was shown that the decomposition of root residues was slower than straw residues (26). However, it is unknown whether such a difference in the rates of decomposition is also reflected in the structure ...

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