Metabolomic Data Structure Formatting

metabolomic-data-structure-formatting

Summary

Convert raw mass-spectrometry metabolomic data into standardized QIIME 2 artifact formats (FeatureTable[Frequency] and MassSpectrometryFeatures) to enable downstream chemical tree construction and phylogenetic diversity analysis. This skill bridges peak-detection pipelines (MZmine2) and chemically-informed feature comparison.

When to use

Apply this skill after peak detection in MZmine2 has produced an MGF file (containing MS1 and MS2 spectra) and a feature abundance table (CSV or BIOM), but before running q2-qemistree tree construction or any QIIME 2-based metabolomic analysis. Use it when you have LC-MS/MS untargeted metabolomic profiles that need to be harmonized into a standard artifact format for reproducible, tool-agnostic downstream processing.

When NOT to use

• Data is already in QIIME 2 artifact format (.qza files) — skip import and proceed directly to tree construction.
• MGF file lacks MS2 spectra or has unmatched MS1 entries — troubleshoot peak detection in MZmine2 first.
• Feature table contains pre-aggregated or taxonomically classified rows — formatting assumes unaggregated MS1 features only.

Inputs

• MGF file with MS1 and MS2 spectra (from MZmine2 peak detection)
• Feature abundance table in CSV or BIOM format (peak areas per sample, from MZmine2)

Outputs

• QIIME 2 artifact of type MassSpectrometryFeatures (.qza)
• QIIME 2 artifact of type FeatureTable[Frequency] (.qza)

How to apply

First, export the peak-detection results from MZmine2 as two files: (1) an MGF file containing both MS1 and MS2 spectral information, and (2) a feature abundance table in CSV or BIOM format. Validate the MGF file for completeness—ensure every MS1 entry has a corresponding MS2 entry and that no formatting errors are present. Then, import both files into QIIME 2 artifact format using qiime tools import, specifying the MGF as type MassSpectrometryFeatures and the abundance table as type FeatureTable[Frequency]. QIIME 2 will validate schema compliance and report errors if MS1/MS2 pairing is incomplete or if the feature table has malformed entries, halting the import if needed. This produces standardized, versioned artifacts suitable for meta-analyses and reproducible comparative metabolomic workflows.

Related tools

• MZmine2 (Upstream peak detection and MS feature extraction; produces MGF and feature abundance tables consumed by this formatting skill) — http://mzmine.github.io
• QIIME 2 (Artifact framework and validation engine; qiime tools import performs the format conversion and schema validation) — https://docs.qiime2.org

Examples

qiime tools import --input-path feature-table.biom --output-path feature-table.qza --type FeatureTable[Frequency] && qiime tools import --input-path sirius.mgf --output-path sirius.mgf.qza --type MassSpectrometryFeatures

Evaluation signals

• QIIME 2 import command completes without schema validation errors and produces .qza artifacts with correct type annotations.
• MGF file validation passes: all MS1 entries have corresponding MS2 entries (error message reports unmatched pairs if present).
• Feature table dimensions match between input CSV/BIOM and output artifact (sample count, feature count, abundance range preserved).
• Artifact can be successfully read and queried using qiime qemistree subcommands in downstream tree-building steps.
• Metadata (m/z, retention time, spectral similarity) embedded in MGF headers survive import and are accessible in artifact.
• No features are silently dropped or renamed during import (output feature count equals input feature count).

Limitations

• MGF formatting errors (missing MS1/MS2 pairings, malformed headers) will halt import with an error message; troubleshooting must occur upstream in MZmine2.
• QIIME 2 import does not validate chemical plausibility of m/z or retention time values; garbage-in garbage-out holds.
• Feature table must have samples as columns and features (MS1 m/z × RT combinations) as rows; transpose-then-import if reversed.
• Only ~70–90% of MS1 features typically receive downstream fingerprint predictions in q2-qemistree due to MS2 spectral quality and user-defined tolerances (e.g., ppm-max, zodiac-threshold); features without fingerprints are filtered out post-hierarchy construction.
• SIRIUS version compatibility: q2-qemistree was initially developed for SIRIUS 4.0.1 and has been adapted for versions ≥4.4.29; older or newer versions may fail.

Evidence

• [readme] To generate a tree that relates the MS1 features in your experiment, we need to pre-process mass-spectrometry data (.mzXML, .mzML or .mzDATA files) using MZmine2 and produce the following inputs: 1. An MGF file with both MS1 and MS2 information.: "To generate a tree that relates the MS1 features in your experiment, we need to pre-process mass-spectrometry data (.mzXML, .mzML or .mzDATA files) using MZmine2 and produce the following inputs: 1."
• [readme] If the MGF file has formatting errors (eg. no MS1 are included in the MGF, or if an MS1 entry does not have a corresponding MS2 entry), then an appropriate error message will help users troubleshoot this step before proceeding forward.: "If the MGF file has formatting errors (eg. no MS1 are included in the MGF, or if an MS1 entry does not have a corresponding MS2 entry), then an appropriate error message will help users troubleshoot"
• [readme] We import these files into the appropriate QIIME 2 artifact formats as follows: qiime tools import --input-path feature-table.biom --output-path feature-table.qza --type FeatureTable[Frequency]: "We import these files into the appropriate QIIME 2 artifact formats as follows: qiime tools import --input-path feature-table.biom --output-path feature-table.qza --type FeatureTable[Frequency]"
• [other] Load the feature table (abundance matrix) and feature metadata (m/z, retention time, and/or spectral similarity annotations) into QIIME 2 artifact format.: "Load the feature table (abundance matrix) and feature metadata (m/z, retention time, and/or spectral similarity annotations) into QIIME 2 artifact format."
• [readme] MS1 features without fingerprints are filtered out of this feature table. This is done because SIRIUS predicts molecular substructures for a subset of features (typically for 70-90% of all MS1 features) in an experiment: "MS1 features without fingerprints are filtered out of this feature table. This is done because SIRIUS predicts molecular substructures for a subset of features (typically for 70-90% of all MS1"