Overview
ISO/TS 29843-2:2021 - "Soil quality - Determination of soil microbial diversity - Part 2" defines a simple PLFA extraction method for assessing soil microbial diversity by measuring phospholipid fatty acids (PLFA). The technical specification describes a streamlined laboratory workflow - from lipid extraction to chromatographic analysis - that yields quantitative and qualitative fingerprints of the viable microbial biomass in soils.
Key topics and technical requirements
- Scope: extraction of only phospholipid fatty acids (PLFA) from soils using the simple method (as distinct from the extended PLFA procedure in ISO/TS 29843-1).
- Principle: lipid extraction (Bligh–Dyer type), fractionation on silica (SI) columns, conversion of PL to fatty acid methyl esters (FAME/PL‑FAME) by mild alkaline transmethylation, and analysis by gas chromatography (GC) or GC–MS.
- Sample & reagents: guidance on soil sampling/preparation (referenced ISO 18400-206), use of chloroform/methanol (CM) and citrate buffer (Bligh and Dyer solvent), antioxidants (BHT), internal/quantification standards (e.g., C19:0 FAME, BAME or commercial FAME mixes).
- Apparatus & operating parameters: silica SPE or home-made columns, ultrasonic bath, centrifuge, oven, vortex, and a GC with fused‑silica capillary column (≥30 m length, 0.25 mm i.d., 0.25 μm film). Helium carrier gas; GC‑FID or GC‑MS recommended.
- Procedural steps: example initial sample mass (2 g fresh soil) and solvent volumes are specified; extraction, SI column separation (neutral lipids/glycolipids/phospholipids), derivatization (methanolic KOH), clean‑up, and FAME analysis.
- Quality considerations: use analytical/HPLC‑grade solvents; include internal and external standards; options to use commercial SPE cartridges.
Applications and users
- Who uses it: environmental and soil testing laboratories, soil ecologists, agronomists, remediation consultants, research groups studying microbial ecology, and regulators assessing soil quality.
- Practical uses:
- Quantifying viable microbial biomass across bacteria, archaea and microeukaryotes.
- Comparing microbial community structure between soil samples (rapid detection of community shifts).
- Complementing molecular/genotypic data with phenotypic lipid-based profiles.
- Routine monitoring in agriculture, land‑use change studies, pollution/bioremediation assessments, and ecological research.
- Advantages: accessible to most analytical labs, simpler and faster than extended PLFA methods while providing robust biomass estimates and community-level differentiation.
Related standards
- ISO/TS 29843-1 (extended PLFA extraction method) - offers higher resolution and broader fatty acid coverage.
- ISO 18400-206 - soil sampling and handling for microbiological assessments (referenced).
Keywords: ISO/TS 29843-2:2021, soil quality, PLFA, phospholipid fatty acid analysis, simple PLFA extraction method, soil microbial diversity, Bligh–Dyer extraction, FAME, GC‑MS, environmental monitoring.