Background: Outdated scientific literature claimed that bacteria was a cancerogenic agent. These studies were technically disfavored and the hypothesis of the role of bacteria in cancer was almost completely abandoned for many years. The aim of the present study was to investigate the role of microbiome in carcinogenesis and the potential role of engineered bacteria for the treatment of cancer.

Materials and Methods: The literature review was performed on Pubmed/Medline, EMBASE, Google Scholar database in accordance to the PRISMA Guidelines. The screening, and eligibility session was performed to conduct the data synthesis of the included studies.

Results: The screening process included a total of 415 papers, while 389 articles were considered for the eligibility session. A total of 334 scientific products were excluded and 55 articles were considered for the descriptive synthesis. Recent reports, however, have produced new results on the role of various microorganisms in tumors. Here, we reviewed the scientific literature on this issue in order to provide an updated organic framework on the topic.

Conclusions: Although basic research studies investigated and confirmed the role of bacteria in cancer induction, maintenance and resistance to therapy, the more recent literature is oriented to modern diagnostic approaches from the basic scientific knowledge to the clinical practice. The approaches to biological and immunological onco-therapy, by natural or bioengineered bacteria, were also addressed.

Background: Known for its myriad health benefits, konjac glucomannan (KGM), a fermentable fiber, has alleviated constipation and enhanced the population of beneficial gut bacteria. The purpose of this study was to investigate the effects of different concentrations of KGM on the intestinal microorganisms of mice.

Methods: We utilized the Illumina HiSeq high-throughput sequencing platform to scrutinize mouse gut bacteria's 16S ribosomal RNA (rRNA) V3+V4 region, investigating the effects of feeding low, medium and high KGM doses on the intestinal flora. The multi-faceted analysis included species composition, alpha, and beta diversity analysis, Linear discriminant analysis effect size (LEfSe) flora differential analysis, correlation of flora correlation, and predictive functional analysis, offering comprehensive insights into the varying impacts of KGM dosages.

Results: The investigation revealed intriguing distinctions in gut microbiota between KGM and control groups. A phylum-level breakdown showed that Firmicutes and Bacteroidetes as the primary microflora across all samples. Notably, the high-dose KGM group exhibited an increased abundance of Firmicutes compared to the control group, coupled with a contrasting decrease in Bacteroidetes. Furthermore, Actinobacteria proliferation was markedly enhanced within the high-dose KGM group. Compared with the control group, all KGM dose groups (low, medium and high) displayed a decline in Deferribacteres, Verrucomicrobia and Proteobacteria. Moreover, mice treated with high-dose KGM showed significantly increased gut populations of Coriobacteriales, Eggerthellaceae, Enterorhabdus, Lactobacillales, Lactobacillaceae, Lactobacillus, Lachnospiraceae_NK4A136_group and others. Interestingly, at the genus level, a positive correlation was observed among Staphylococcus, Corynebacterium and Jeotgalicoccus. In the medium-dose KGM group, amino acid metabolism surged noticeably compared to the control group.

Conclusions: Our study demonstrates that KGM significantly influences gut microbiota composition in mice. Key shifts include the enhancement of Firmicutes and Actinobacteria, decreasing Deferribacteres, Verrucomicrobia and Proteobacteria, and augmented amino acid metabolism. These findings underline KGM's potential as a prebiotic agent.