Abstract: Fusobacterium is a genus of gram-negative, filamentous, anaerobic bacteria found as normal flora in the mouth and large bowel, and often in necrotic tissue. A comparison of microbial ribonucleic acids (RNA) between colorectal carcinoma (CRC) tissue and adjacent normal control tissue found the over-representation of F. nucleatum in CRC tissue. RNA abundance was measured by polymerase chain reaction (PCR)-amplifying RNA from the tissue, constructing libraries, sequencing the RNA in the libraries, pairing sequences from CRC and normal tissue, and quantifying RNA abundance. Detection of Fusobacterium in a gastrointestinal sample is indicative of gastrointestinal cancer.