Overview
SIST ISO 21338:2011 - "Water quality - Kinetic determination of the inhibitory effects of sediment, other solids and coloured samples on the light emission of Vibrio fischeri (kinetic luminescent bacteria test)" - specifies a kinetic direct‑contact method to measure toxic effects of sediments, turbid or coloured waters, and aqueous extracts on the bioluminescence of the marine bacterium Vibrio fischeri (NRRL B‑11177). Unlike endpoint-only tests, this kinetic approach records light emission from the moment bacteria are dispensed into the sample, avoiding the need for sedimentation or colour correction and enabling robust results for problematic samples.
Key technical topics and requirements
- Principle: Dispense bacterial suspension into the sample in the luminometer and record luminescence continuously from injection through defined contact times (examples: peak within 0–5 s, and readings at 5, 15 and 30 min).
- Test organism: Vibrio fischeri (NRRL B‑11177); can use fresh, liquid‑ or freeze‑dried preparations.
- Instrumentation: Luminometer with automatic dispenser (minimum injection volume 0.2 ml) capable of continuous recording (e.g., 0.2 s intervals) and simultaneous injection/recording.
- Temperature control: Samples and bacteria kept at (15 ± 1) °C during contact (thermo‑block recommended).
- Reagents: Sodium chloride diluent (20 g NaCl per litre) and other standard reagents; reference substances and concentrations are specified for quality control.
- Endpoints and metrics:
- LID (Lowest Ineffective Dilution) - most concentrated test batch with <20% inhibition.
- EC20 / EC50 - effective concentrations producing 20% and 50% light reduction, interpolated from dilution series.
- Interferences: Consider effects of high oxygen demand, volatile/reactive substances, pH outside 6.0–8.5, and high salt/osmolarity (avoid >35 g/L NaCl equivalent in test mixtures).
Practical applications and users
SIST ISO 21338:2011 is used for:
- Environmental laboratories assessing sediment toxicity and contaminated solids.
- Wastewater and effluent testing where turbidity or colour impairs standard tests.
- Regulatory monitoring of leachates, eluates and soil/waste extracts.
- Consultants and researchers needing kinetic toxicological profiles (inhibition vs. concentration vs. time).
Benefits include reliable testing of turbid/coloured samples without pre‑clarification, faster kinetic data for toxicants, and better comparability when selecting bacterial preparations and instruments.
Related standards
- ISO 11348-1, -2, -3 (Luminescent bacteria test using fresh, liquid‑dried, and freeze‑dried bacteria)
- ISO 5667-16 (Sampling - guidance on biotesting)
- ISO 5814 (Dissolved oxygen measurement)
Keywords: SIST ISO 21338:2011, water quality, Vibrio fischeri, kinetic luminescent bacteria test, sediment testing, turbid samples, EC50, LID, luminometer.