Background Colorectal cancer (CRC) is a malignant tumor of the digestive system with an increasing incidence and has been troubling human beings persistently. Recently, with the development of high-throughput sequencing technology, numerous studies show that intestinal microorganisms are involved in the occurrence and development of CRC, showing great potential in early diagnosis and early treatment of CRC, but the mechanism of action and diagnostic value of key strains remain more studies. This study combined 16S rDNA high-throughput sequencing technology with the classical microbial strain isolation and culture method, detected specific strains related to the occurrence and development of CRC, and explored its correlation with the occurrence and development of CRC through some experiments in vitro.

Methods 1. Through 16S rDNA high-throughput sequencing technologies, differences in intestinal flora structure between CRC patients and healthy people were analyzed, and a lot of CRC-related specific species and OTU sequences were appraised. 2. According to the result of sequencing above, the selective medium was designed; the strain in conformity with the previous sequencing results was achieved using the classic crossed way of cultivation of microorganisms as the target strain. 3. The effects of the target strain on proliferation, migration and invasion of SW480 cells were detected by CCK8, EDU and Transwell experiments respectively.

Results 1. Through 16S rDNA sequencing analysis of fecal samples from CRC patients and healthy people, significant differences were found in intestinal microbial composition between CRC patients and healthy people, and some bacteria genera with significant differences were found. 2. Multiple strains associated with CRC were purified, isolated and identified, and a potential target strain (Veillonella sp. CP-25) that may be related to the occurrence and development of CRC was selected. 3. It was further verified that Veillonella sp.CP-25 could significantly promote the proliferation and invasion ability of SW480 cells.

Conclusions The changes in intestinal flora are closely related to the development of CRC, and the specific bacteria may play a significant role. A CRC-related strain Veillonella sp.CP-25 was isolated and purified from the feces of CRC patients. Veillonella sp.CP-25 promotes the occurrence and development of CRC.