Peptostreptococcus

A Gram-positive, obligate anaerobic genus that has emerged as one of the most consistently enriched taxa in colorectal cancer. The key pathogenic species P. anaerobius promotes colorectal carcinogenesis through multiple mechanisms including cholesterol biosynthesis induction, reactive oxygen species (ROS) generation, and nf kappa b activation. The genus also plays a role in periodontal disease, connecting oral and gut pathology.

Role in Gut Ecosystem

  • Low-abundance member of the normal gut microbiota that expands dramatically under dysbiotic conditions, particularly in the CRC tumor microenvironment [1].
  • Iron-dependent organism; its expansion in CRC may be facilitated by the iron-rich environment of bleeding tumors and the disrupted nutritional immunity landscape of the tumor microenvironment [2].
  • Part of the oral-gut translocation pathway — normally abundant in the oral cavity, Peptostreptococcus can colonize the colon when oral barrier function is compromised or gastric acid is suppressed [3].

Mechanisms of CRC Promotion

  • Cholesterol biosynthesis: P. anaerobius activates cholesterol biosynthesis pathways in colonic epithelial cells, promoting cell proliferation [4]. This connects to the broader observation that altered lipid metabolism characterizes CRC progression.
  • ROS generation: Induces reactive oxygen species in host cells, contributing to DNA damage, genomic instability, and mutagenesis — hallmarks of carcinogenesis [4] [2].
  • NF-kB activation: Triggers nf kappa b signaling in colonic epithelial and immune cells, driving chronic inflammation that supports tumor initiation and progression [4].
  • Immune modulation: Promotes a pro-tumor immune microenvironment by recruiting myeloid-derived suppressor cells (MDSCs) and polarizing tumor-associated macrophages [5].

Disease Associations

Colorectal Cancer

  • Among the top 3 most consistently enriched genera in CRC across the Islam 2022 meta-analysis of 27 CRC studies, alongside fusobacterium and porphyromonas [1].
  • Enriched in both old-onset and young-onset CRC, demonstrating a consistent CRC-microbiome signature [6].
  • Listed in the Hanus 2021 comprehensive catalog of bacteria involved in colorectal carcinogenesis alongside F. nucleatum, enterotoxigenic B. fragilis, and pks+ escherichia coli [4].

Periodontal Disease

  • Core member of the subgingival pathogenic consortium in periodontitis.
  • Oral Peptostreptococcus may translocate to the gut, contributing to the oral-gut-axis in CRC development.

Multiple Sclerosis -- Oral Microbiome

  • In the oral cavity, Peptostreptococcus was higher in healthy controls than in MS patients, with potential protective effects via indoleacrylic acid production that increases IL-10 secretion [3].

Key Metabolites

  • Indoleacrylic acid — tryptophan derivative; increases IL-10 (anti-inflammatory) in oral context
  • ROS-inducing factors — promote oxidative DNA damage in colonic epithelium
  • Cholesterol pathway activators — drive epithelial proliferation in CRC

Key Sources

Connections

  • colorectal cancer — one of the most consistently CRC-enriched genera; multi-mechanism carcinogenesis
  • fusobacterium — co-enriched CRC pathogen; complementary pro-tumor mechanisms
  • porphyromonas — co-enriched in CRC; shared oral-gut translocation pathway
  • iron — iron-dependent growth; benefits from iron-rich tumor microenvironment
  • nf kappa b — activates NF-kB pro-inflammatory signaling in CRC
  • oxidative stress — ROS generation contributes to genomic instability
  • inflammation — chronic inflammation driver via NF-kB and immune cell recruitment
  • escherichia coli — pks+ E. coli is a fellow CRC-promoting pathobiont
  • dysbiosis — expansion reflects cancer-associated dysbiotic state

References (6)

  1. Md Zohorul Islam, Melissa Tran, Tao Xu et al. (2022). Reproducible and opposing gut microbiome signatures distinguish autoimmune diseases and cancers: a systematic review and meta-analysis. Microbiome. doi:10.1186/s40168-022-01373-1
  2. Norouzi-Beirami MH, Marashi SA, Banaei-Moghaddam AM et al. (2020). Beyond Taxonomic Analysis of Microbiomes: A Functional Approach for Revisiting Microbiome Changes in Colorectal Cancer. Frontiers in Microbiology. doi:10.3389/fmicb.2019.03117
  3. Zangeneh Z, Abdi-Ali A, Khamooshian K et al. (2021). Bacterial Variation in the Oral Microbiota in Multiple Sclerosis Patients. PLoS ONE. doi:10.1371/journal.pone.0260384
  4. Hanus M, Parada-Venegas D, Landskron G et al. (2021). Immune System, Microbiota, and Microbial Metabolites: The Unresolved Triad in Colorectal Cancer Microenvironment. Frontiers in Immunology. doi:10.3389/fimmu.2021.612826
  5. Yu L, Zhao G, Wang L et al. (2022). A Systematic Review of Microbial Markers for Risk Prediction of Colorectal Neoplasia. British Journal of Cancer. doi:10.1038/s41416-022-01740-7
  6. Youwen Qin, Xin Tong, Wei-Jian Mei et al. (2024). Consistent signatures in the human gut microbiome of old- and young-onset colorectal cancer. Nature Communications. doi:10.1038/s41467-024-47523-x

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