High-throughput screenings have linked several microorganisms in the human gut microbiome to colorectal cancer (CRC). Molecular processes that drive carcinogenesis have been discovered in some situations, such as bacterial membrane proteins or secreted compounds that interact with human cancer cells. However, it is unknown whether most gut microorganisms promote or prevent cancer cell proliferation. Over 150 cultivated bacterial strains were evaluated for their impact on cell development using bacteria-free supernatants (secretomes) and inactivated cells. The researchers observed the impacts at the family and strain levels that varied a lot between bacterial cells and secretomes, implying that various molecular pathways are at work. Bacteroidaceae, Enterobacteriaceae, and Erysipelotrichaceae bacteria secretomes boosted cell proliferation, however, most Fusobacteriaceae cells and secretomes slowed it down, contradicting previous findings. The presence of specific functional genes was linked to cell growth rates in various bacteria, including the virulence genes TcdA and TcdB in Clostridiales and FadA in Fusobacteriaceae, both of which impeded growth. Genes of the cobalamin synthesis route were concentrated in Bacteroidaceae cells that improved growth, while genes of the ethanolamine consumption pathway were enriched in Fusobacteriaceae cells that inhibited growth. The study shows how different gut bacteria have a wide range of effects on cell growth, contribute to a better understanding of the gut microbiome’s effects on host cells, as well as provide a vital tool for identifying candidate target genes for microbiome-based diagnostics and therapeutic interventions strategies.