Microbial Metabolomics Service — LC-MS & GC-MS Profiling for Bacteria, Fungi & Microbiome

How We Analyze Microbial Metabolomes

A single bacterial culture contains volatile SCFAs at mM, polar central carbon intermediates at uM, non-polar lipids, and trace signaling molecules at nM — no single instrument covers this range. We layer four complementary approaches from the same sample, from broad discovery to targeted validation to multi-omics integration.

Metabolic Quenching & Sample Collection — Why It Matters for Microbial Metabolomics

Unlike mammalian tissue where metabolism stops upon excision, a microbial sample remains metabolically active throughout collection and processing. A bacterial pellet centrifuged at room temperature for 10 minutes has a completely different metabolome than the same culture at the moment of harvest — ATP/ADP ratios collapse, central carbon intermediates shift, and volatile metabolites escape. These are the protocols we use to capture the true in vivo metabolome:

Analytical Platforms for Microbial Metabolomics

SCIEX QTRAP 6500+ (Figure from SCIEX)

Thermo Q Exactive Orbitrap (Figure from Thermo)

Agilent 7890B-5977A GC-MS (Figure from Agilent)

Waters ACQUITY UPLC (Figure from Waters)

Microbial Metabolomics Workflow — From Quenching to Biological Insight

1

Metabolic Quenching & Sample Collection

• Bacterial/yeast: cold methanol (-40 degree C, 1:3-5 ratio, under 1 sec). Filamentous fungi/biofilm: rapid filtration + liquid N2. Fecal: flash-frozen within 5 min. Full protocols in the Quenching section above.
• Intracellular (pellet) and extracellular (supernatant) fractions collected and analyzed separately for every sample.

2

Metabolite Extraction

• Intracellular — cold methanol:water:chloroform biphasic + stable isotope IS cocktail
• Extracellular — lyophilization + methanol:water
• Fecal — MTBE:methanol:water for polar + lipid in one extraction
• GC-MS samples — derivatization (MSTFA/MBTFA)

3

Dual-Platform LC-MS/MS + GC-MS Acquisition

• LC-MS/MS — HILIC + RP C18, MRM (targeted) or SWATH DIA (untargeted)
• GC-MS — SIM (targeted) or full scan (untargeted)
• HS-SPME-GC-MS — microbial headspace VOC profiling
• Sequence: blank → calibrators → QC → randomized samples (QC every 8-10 injections)

4

Data Processing & Statistical Analysis

• Peak detection, alignment, imputation; normalization by IS, quantile, or dry weight
• Univariate (FDR-corrected) + multivariate (PCA, PLS-DA/OPLS-DA, permutation testing)
• Metabolite annotation: MS/MS matching against HMDB, METLIN, MassBank, GNPS, MiMeDB

5

Biological Interpretation & Multi-Omics Integration

• KEGG/Reactome/MetaCyc pathway enrichment (ORA + MSEA, FDR-corrected) with integrated pathway maps
• Multi-omics: metabolomics + 16S rRNA or metagenomics for microbe-metabolite association networks
• Final package: QC report, processed data, metabolite ID table (MSI Level 1-4), statistical analysis, publication-ready figures

Sample Types & Requirements for Microbial Metabolomics

Applications of Microbial Metabolomics

Specialized Microbial Research Services

The core workflow above — quenching, dual-platform LC-MS/MS + GC-MS, intra/extracellular separation — applies to any culturable microorganism: E. coli, Bacillus, Pseudomonas, Streptomyces, Saccharomyces, Aspergillus, and beyond. The services below add organism-specific quenching, targeted panels, and domain-specific data interpretation for projects requiring deeper expertise. Additional pathogen and species protocols available on request.

Microbial Metabolomics Deliverables

• Quantitative Data Tables — Absolute concentrations (uM, nmol/g dry weight, or nmol/10^6 cells) or normalized peak areas (untargeted) for all detected metabolites. Intra- and extracellular fractions reported separately. Excel and CSV.
• QC Report — Pooled QC RSD per metabolite class, IS recovery per sample, calibration curves (targeted), blank carryover, batch-effect documentation. Quenching efficiency indicators included.
• Metabolite Identification Table — MSI Level 1-4 confidence, m/z, RT, MS/MS matches, database IDs (HMDB, KEGG, METLIN, GNPS), and identification confidence per metabolite. Microbial-specific databases (MetaCyc, MiMeDB) searched in addition to standard libraries.
• Statistical Analysis & Figures — PCA/PLS-DA/OPLS-DA, volcano plots, hierarchical clustering heatmaps, KEGG/MetaCyc pathway enrichment, microbe-metabolite correlation networks (when paired with sequencing data). Publication-ready figures (300 DPI TIFF + vector PDF).

Microbial Metabolomics Data — Chromatograms, Multivariate Analysis & Pathway Maps

HILIC LC-MS chromatogram of polar metabolites extracted from cold methanol-quenched E. coli culture, showing amino acids, nucleotides, and central carbon intermediates with sharp peak resolution.

PCA scores plot demonstrating clear separation between intracellular (cell pellet) and extracellular (spent medium) metabolite pools from the same bacterial culture, validating the quenching and fractionation protocol.

Hierarchical clustering heatmap of intracellular metabolites across bacterial growth phases (lag, log, stationary, death), showing coordinated metabolic reprogramming during the growth cycle.

Microbe-metabolite correlation network integrating metabolomics with 16S rRNA sequencing data, linking specific bacterial taxa to their metabolic products in a gut microbiome study.

Case Study — How Metabolic Quenching Revealed the True Intracellular Metabolome of E. coli During Antibiotic Stress

Global metabolic profiling of Escherichia coli cultures: an evaluation of metabolite extraction methods for both extracellular and intracellular metabolites

Winder, C.L., Dunn, W.B., Schuler, S., Broadhurst, D., Jarvis, R., Stephens, G.M., & Goodacre, R. | Analytical Chemistry, 2008, 80, 2937-2945 | IF: 6.7

DOI: 10.1021/ac7023409

The Challenge

Bacterial metabolomics was plagued by a fundamental question no one wanted to address: how much of what you measure is actually inside the cell, and how much leaked out during sample processing? Cold methanol quenching — the standard method for stopping bacterial metabolism — causes membrane damage and metabolite leakage in many species. If 40% of your intracellular ATP leaks into the quenching solvent before you measure it, your "intracellular ATP concentration" is wrong. Winder et al. set out to quantify this leakage systematically — comparing six extraction methods across intracellular and extracellular fractions of E. coli with rigorous spike-recovery validation.

The Results

Using GC-MS untargeted metabolomics with cold methanol quenching followed by chloroform:methanol:water extraction (the same protocol we use for bacterial cultures), the study found:

• Cold methanol quenching at -48 degree C preserved the intracellular metabolome with minimal leakage (below 5% of total pool for most metabolites) — but only when quenching was completed within 1 second of harvest. Delayed quenching (even 30 seconds at room temperature) caused up to 40% loss of high-energy phosphates and a 3-fold increase in extracellular amino acids from cell lysis.
• Intracellular and extracellular fractions carried distinct metabolic signatures — 142 metabolites were detected in the intracellular fraction vs. 89 in the extracellular fraction, with only 38 shared. The two pools are metabolically distinct and must be analyzed separately.
• The method detected 200+ metabolite features per sample with intra-batch CV below 15% — demonstrating that rigorous quenching does not compromise data quality when executed correctly.

Why It Matters

This study confirmed what microbiologists suspected but couldn't quantify: metabolic quenching is not a technical detail — it is the difference between measuring the real metabolome and measuring an artifact. A bacterial culture processed without proper quenching reports "intracellular" metabolite concentrations that are contaminated with extracellular leakage, distorted by ongoing metabolism during centrifugation, and useless for modeling metabolic flux. Our quenching protocols are designed around this paper's findings: cold methanol at -40 degree C, 1:5 ratio, complete within 1 second, intra and extracellular fractions analyzed separately.

What This Means for You

If your experiment compares wild-type vs. mutant bacterial strains, antibiotic-treated vs. untreated cultures, or different growth phases — the quenching method determines whether you detect real metabolic differences or processing artifacts. Our protocol is validated to preserve the in vivo metabolome. Each sample's quenching parameters (temperature, ratio, time-to-quench) are documented in the QC report so you can confirm pre-analytical integrity.

How We Deliver the Same

• Cold methanol quenching at -40 degree C, 1:3-5 ratio, under 1 second — the validated protocol from Winder et al.
• Intracellular and extracellular fractions extracted and analyzed separately — not pooled into one ambiguous "cell pellet" value
• Stable isotope IS spiked at homogenization for absolute quantification with documented spike recovery
• Same GC-MS platform (Agilent 7890B-5977A) for metabolite detection across the same chemical diversity range

Reference

1. Winder, C.L., Dunn, W.B., Schuler, S., Broadhurst, D., Jarvis, R., Stephens, G.M., & Goodacre, R. Global metabolic profiling of Escherichia coli cultures: an evaluation of metabolite extraction methods for both extracellular and intracellular metabolites. Analytical Chemistry 80, 2937-2945 (2008).

Frequently Asked Questions About Microbial Metabolomics

Selected Publications in Microbial Metabolomics