Identification and functional characterization of Pseudomonas fluorescens as a novel intratumoral bacterium in colorectal cancer.

Colorectal cancer (CRC) remains a major global health burden as one of the leading causes of cancer-related mortality. Recent research has highlighted the crucial role of gut microbiota in CRC development. Through high-throughput full-length 16 S rDNA sequencing of tumor and adjacent non-tumor tissues from 14 CRC patients, significant microbial differences were identified. At the phylum level, Firmicutes (52.59%), Bacteroidetes (18.51%), and Proteobacteria (14.89%) dominated both tissue types, while at the genus level, Bacteroides (8.02%) and Escherichia (4.50%) showed the highest abundance. Notably, 17 bacterial species exhibited differential abundance between tumor and normal tissues, with Anaerotignum faecicola and Pseudomonas fluorescens being significantly enriched in tumor tissues. Functional prediction analysis revealed the microbiota’s predominant involvement in carbohydrate metabolism, amino acid metabolism, and energy metabolism pathways. Subsequent validation in 20 additional patient samples confirmed P. fluorescens enrichment in tumor tissues, and in vitro experiments demonstrated its ability to promote CRC cell viability and proliferation. These findings provide valuable insights into CRC-associated microbial signatures and suggest P. fluorescens as a potential contributor to tumor progression, offering new directions for developing diagnostic markers and therapeutic interventions in CRC management.