Genome-Resolved Characterization of Stage-Associated Microbial Composition and Functional Potential During Spontaneous Ugba Fermentation

Ugba, a traditional African condiment made from oil bean seeds, has been poorly characterized at the genome level. A study sought to analyze a single spontaneous ugba fermentation using a method called genome-resolved shotgun metagenomics, which was conducted at three stages: Early (0-24 hours), Mid (48-96 hours), and Late (120-144 hours).

Thirty metagenome-assembled genomes (MAGs) were identified and grouped based on their abundance over time. The Early-stage population was mainly made up of Bacteroidota-associated MAGs, which had the highest density of enzymes that break down carbohydrates. These MAGs also had a wide range of glycoside hydrolase genes, suggesting their potential to break down the plant-derived components of the seed.

As the fermentation progressed to the Mid stage, the MAG composition changed significantly. Both Core and Late-associated MAGs increased as the fermentation matured. Further analysis revealed functional differences among Corynebacterium MAGs: C. nuruki encoded a complete urease system, while C. phoceense_A encoded genes for glutamate dehydrogenase and nitrate reduction.

The fermentation also led to a gradual increase in pH from 7.15 to 8.01. Overall, the study demonstrated that the microbial population changed over time and acquired new functional capabilities. This research provides a detailed, genome-resolved understanding of microbial composition and functional potential during spontaneous ugba fermentation, shedding light on the microbial organization of this traditional African fermented food.