Metagenomics
One-Sentence Definition
Metagenomics sequences DNA (or RNA) from an entire microbial community without isolating individual organisms in pure culture.
Simple Explanation
Instead of growing one colony, you sequence everything in the sample — stool, water, CSF cell-free DNA — then computationally sort who is there.
Detailed Scientific Explanation
- Shotgun metagenomics: all DNA; species + genes (AMR/virulence) possible
- Amplicon: see 16S Amplicon Analysis (cheaper taxonomy, less function)
- Clinical mNGS: sterile-site diagnostics for unknown meningitis/sepsis (specialized)
- Challenges: host DNA, contamination, relative abundance ≠ pathogenicity, incomplete databases
Mechanism
Extract → library → sequence → remove host → taxonomic classifiers / assembly → gene catalogs → interpretation vs controls.
Clinical Importance
- Culture-negative infections; polymicrobial contexts; microbiome medicine
- Interpretation must respect Pathogen vs Normal Microbiota
Research Importance
- Microbiome–AMR resistome reservoirs; ecology of HGT
Diagnostic Relevance
- Emerging under MOC - Diagnostic & Lab Methods; costly; needs expert stewardship of results
AMR Relevance
- Community resistome surveys; not always linked to treatable infection in that host
Related Methods
- Whole-Genome Sequencing (isolate) vs metagenome
- PCR panels as targeted alternative
Related MOCs
- MOC - Bioinformatics in Microbiology · MOC - Antimicrobial Resistance (AMR) · MOC - Fundamentals of Microbiology
Active Recall Questions
- Shotgun vs 16S amplicon?
- Why can metagenomic DNA+ mislead clinicians?
- Name one sterile-site use case for mNGS.
Connections
- Normal Microbiota · Infectious Disease · AI in Microbiology (classifiers)