Bacteriophages

Phage Biology#

Host Specificity#

Phages are typically highly specific, targeting individual bacterial species or even strains. This specificity makes them precision tools—capable of removing specific taxa without disrupting the broader microbial community, unlike broad-spectrum antibiotics.

Phage-Driven Dysbiosis#

Parkinson's Disease#

The most extensively documented phage-dysbiosis connection involves the gut phageome in Parkinson's Disease. Lytic phages targeting lactic acid bacteria—particularly Lactococcus—are more than 10-fold enriched in PD gut microbiomes, with corresponding depletion of the targeted bacteria (,^{[1]Tetz 2018 -- Bacteriophage and Gut Dysbiosis in Parkinson's DiseaseGeorge Tetz, Stuart M Brown, Yuhan Hao et al. · 2018Open reference 1 ↓} cross-sectional).

This phage-bacterial predator-prey dynamic offers a mechanistic explanation for the selective bacterial depletion observed in PD that cannot be explained by diet or medication alone.

The depleted lactic acid bacteria are key producers of Short-Chain Fatty Acids (SCFAs) and contribute to gut barrier integrity; their loss removes metal-buffering capacity and increases free Iron, Zinc, and Manganese availability for metal-tolerant pathogens.

Autism Spectrum Disorder#

The ASD gut phageome shows wider diversity and higher abundance than typically developing controls, with significant expansion of Caudoviricetes bacteriophages (,^{[2]Shahin 2023 — Metagenomics Revealed a Correlation of Gut Phageome with Autism Spectrum DisorderKhashayar Shahin, Abbas Soleimani-Delfan, Zihan He et al. · 2023Open reference 2 ↓} computational-prediction).

Phages infecting Bacteroidaceae and prophages within Faecalibacterium are enriched in ASD, potentially contributing to the depletion of this protective commensal observed across ASD microbiome studies.

Colorectal Cancer and Metabolic Disease#

Gut virome alterations are documented in colorectal adenomas (^{[3]Characteristics of the gut virome in patients with premalignant colorectal adenomaPan Zhang, Xiaofeng Tuo, Jiong Jiang et al. · 2025Open reference 3 ↓}), post-surgical CRC recurrence (^{[4]Alterations in colorectal cancer virome and its persistence after surgerySi Xian Ho, Jia-Hao Law, Chin-Wen Png et al. · 2024Open reference 4 ↓}), and metabolic syndrome (^{[5]Gut Virome Profiling Identifies a Widespread Bacteriophage Family Associated with Metabolic SyndromePatrick A. de Jonge, Koen Wortelboer, Torsten P. M. Scheithauer et al. · 2022Open reference 5 ↓}).

In healthy individuals, prophages (integrated, quiescent) predominate; in disease states, extracellular lytic phage virions increase, suggesting activation of prophages under disease-associated stress.

Phage Therapy#

Cardiometabolic Applications#

Targeted phage therapy against specific gut bacteria has shown promise in animal models: phages against cytolysin-positive Enterococcus faecalis reduced liver disease in humanized mice, and Klebsiella pneumoniae-targeting phages reduced steatohepatitis Metal-Driven Inflammation without altering the broader microbiota (,^{[7]Opportunities and challenges in phage therapy for cardiometabolic diseasesKoen Wortelboer, Hilde Herrema · 2024Open reference 7 ↓} animal-model).

Fecal virome transplantation (FVT)—transferring the phage-containing filtrate of fecal matter—can alter gut microbiota composition similarly to full FMT, offering a bacteria-free alternative.

Temperate Phage Engineering#

An emerging approach uses temperate phages not to kill bacteria but to alter their function through lysogenic conversion—shifting metabolite production from harmful to beneficial (e.g., increased SCFA production). CRISPR-Cas systems could engineer phages for enhanced specificity.

Cross-References#

• Parkinson's Disease—Primary disease model for phage-driven gut dysbiosis
• Autism Spectrum Disorder—Phageome expansion and diversification documented
• Colorectal Cancer—Virome alterations in adenomas and post-surgical persistence
• dysbiosis—Phage predation as an underexplored driver of microbial imbalance
• Gut Microbiome—Phageome as the "dark matter" of the gut ecosystem
• Short-Chain Fatty Acids (SCFAs)—Lost when phage predation depletes SCFA-producing commensals
• Iron—Freed when metal-buffering commensals are phage-depleted
• Antimicrobial Resistance—Phage therapy as an alternative to antibiotics for MDR infections