Bacterial Community Composition and its Functional Potential in Ulcerative Colitis Patients:A Case Study

Ulcerative Colitis (UC) is a chronic inflammatory bowel disease characterized by recurring inflammation in the colon. This study aimed to showcase the challenges related to the characterization of the enteric microbial community structure using 16S rRNA gene amplicon sequencing and its functional potentialusing metagenomic sequencing in five patients with UC during active disease and remission. The results revealed inter-individual and intra-individual differences in the microbial community composition. Differential abundance analysis identified specific genera associated with disease state, such asFaecalibacterium and Anaerostipes, which showed positive- and negative correlations, respectively. Prevotella was observed only during active disease. The high level of inter-individual taxonomicdifferences makes it difficult to link the changes to the disease. Functional analysis identified genes related to virulence and inflammatory bowel disease specifically during active disease. Although the approach showed great potential, it was limited by the vast amount of sequencing effort used on host DNA. Further research with a larger cohort and optimized DNA extraction protocols is needed in order validate the results and explore the functional roles of relevant epithelial-associated bacteria which is essential for unravelling the intricate host-microbiota interactions underlying disease pathogenesis

Application of ecosystem-specific reference databases for increased taxonomic resolution in soil microbial profiling

Intensive agriculture systems have paved the way for a growing human population. However, the abundant use of mineral fertilizers and pesticides may negatively impact nutrient cycles and biodiversity. One potential alternative is to harness beneficial relationships between plants and plant-associated rhizobacteria to increase nutrient-use efficiency and provide pathogen resistance. Plant-associated microbiota profiling can be achieved using high-throughput 16S rRNA gene amplicon sequencing. However, interrogation of these data is limited by confident taxonomic classifications at high taxonomic resolution (genus- or species level) with the commonly applied universal reference databases. High-throughput full-length 16S rRNA gene sequencing combined with automated taxonomy assignment (AutoTax) can be used to create amplicon sequence variant resolved ecosystems-specific reference databases that are superior to the traditional universal reference databases. This approach was used here to create a custom reference database for bacteria and archaea based on 987,353 full-length 16S rRNA genes from Askov and Cologne soils. We evaluated the performance of the database using short-read amplicon data and found that it resulted in the increased genus- and species-level classification compared to commonly use universal reference databases. The custom database was utilized to evaluate the ecosystem-specific primer bias and taxonomic resolution of amplicon primers targeting the V5–V7 region of the 16S rRNA gene commonly used within the plant microbiome field. Finally, we demonstrate the benefits of custom ecosystem-specific databases through the analysis of V5–V7 amplicon data to identify new plant-associated microbes for two legumes and two cereal species