Identification of silage bacterial clusters and analysis of their microecological characteristics

Enterotypes refer to the different bacterial clusters in the gut microecosystem, which are closely related to host physiology, digestion, disease, and other phenotypes. However, whether there are clear clusters in the silage microecosystem, and the fermentation quality and characteristics of unique cluster silage remain unknown. To determine whether distinct bacterial clusters exist in the silage microecosystem and to characterize their fermentation properties, we analyzed the bacterial community composition and fermentation quality of 156 silage samples, and further explored their underlying microbial ecological features.

We confirmed three distinct clusters in the silage microbiome, which were named according to their dominant bacterial taxa: the E-cluster (characterized by a higher abundance of unclassified Enterobacteriaceae (UG)), the P-cluster (enriched with Pseudomonas and Janthinobacterium), and the L-cluster (dominated by Lactobacillus). These microbial clusters were closely associated with fermentation quality: the L-cluster exhibited superior silage quality compared to the E- and P-clusters. Meanwhile, the microbial functional profiles differed significantly among the three clusters of silage. Numerous pathways were significantly enriched in the P-cluster, such as the Biosynthesis of other secondary metabolites, etc. Moreover, bacterial co-occurrence networks of three clusters silage displayed cooperative interactions mainly, P-cluster silage network was more complex and tighter, E-cluster silage has more functional microbial units and more stable. Furthermore, the assembly of microbial communities in the three silage clusters was dominated by stochastic processes. Specifically, the E-cluster and L-cluster were governed by ecological drift, while dispersal limitation was more influential in the P-cluster.

Overall, we found in our study that the silage microbiome can be divided into three clusters, and different clusters have significant differences in fermentation quality, microbial diversity and compositions, functional profiles, microbial network characteristics and community assembly mechanisms. These results could broaden our comprehension of the silage microbial ecology processes and also provide a scientific basis on which to develop a method to precisely regulate silage quality.