AEM cover article: Professor Xu Zhenghong’s team reported the evolution mode and driving factors of the pit mud flora under the influence of long-term wine production

The mud pit creates a unique micro-environment for the fermentation of Luzhou-flavor liquor.
Recent research and long-term practical experience have shown that the microorganisms living in the pit mud play a vital role in the formation of the unique flavor of Luzhou-flavor liquor.
Role
.

Liquor circles often say that “the wine is good when the cellar is old”, “the millennium-old cellar is tens of thousands of years old, and the wine is good depends on the age of the cellar”.
Then, under the influence of hundreds of years of human wine production, what happens to the microbial community in the pit mud? The change? What are the driving factors for this change? How does it affect the quality of liquor? In order to answer the above questions, the team studied the differences in pit mud microbial communities and main microbial metabolites of different ages, inferred the main functional populations of the pit mud microbial community, and discussed the selection pressure of the evolution of the pit mud microbial community
.

The study found that the content of four major acids in pit mud, including lactic acid, caproic acid, acetic acid and butyric acid, increased with the increase of pit age, and esters accounted for 50.
3%-64.
5% of volatile compounds
.

The pit mud flora is dominated by bacteria and archaea.
Clostridia accounts for 39.
7%-81.
2% of the total bacterial abundance, and Methanomicrobia accounts for 32.
8%-92.
9% of the total archaea
.

At the genus level, the bacteria and archaeal groups with the highest abundance are Caproiciproducens and Methanosarcina, respectively.
With the increase of pit age, the relative and absolute abundance of the two Both are on the rise.
Correlation analysis shows that the two genera have a significant positive correlation with most metabolites
.

On this basis, we further explored the influence of acetic acid and lactic acid as carbon sources on the evolution of new mud bacteria under anaerobic culture conditions.
The results showed that both carbon sources are conducive to the enrichment of Clostridia, and the effect of lactic acid is better.
We further analyzed the effect of continuous feeding of lactic acid.
After 15 days of culture, the relative abundance of caproic acid bacteria increased from 0.
22% to 40.
9%, which significantly improved the microbial structure of the new mud
.

The research results explained that under the influence of decades or even hundreds of years of continuous wine-making activities, the pit mud microbial community showed regular and directional changes, and initially revealed the influencing factors of the directional evolution of the pit mud microbial community.
The enrichment of functional microorganisms provides a new way
.

 The cover image is provided by Luzhou Laojiao Co.
, Ltd.
, showing the 1573 National Treasure Pits
.

(Cover link: https://journals.
asm.
org/toc/aem/87/17) Research results "Mining the Factors Driving the Evolution of the Pit Mud Microbiome under the Impact of Long-Term Production of Strong-Flavor Baijiu" It was officially published in Applied and Environmental Microbiology (IF=4.
792) (original link: https://doi.
org/10.
1128/AEM.
00885-21) and was selected as the cover paper of the current issue
.

Professor Xu Zhenghong is the corresponding author of the paper, and associate researcher Chai Lijuan is the first author
.

The above-mentioned research work was funded by the National Key Research and Development Program (2018YFC1603800), the National Natural Science Foundation of China (31901658), the Chinese Postdoctoral Science Foundation (2020M671407), and the National First-level Disciplinary Project of Light Industry Technology and Engineering (LITE2018-11)
.

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