Overview
ISO 10712:1995 - Water quality - Pseudomonas putida growth inhibition test (Pseudomonas cell multiplication inhibition test) - specifies a standardized biological method to determine the inhibitory effect of surface, ground and waste waters (and water-soluble substances) on the growth of Pseudomonas putida. The method measures cell multiplication by turbidity after a test period of 16 h ± 1 h, and derives concentration-response metrics (EC10, EC50) to quantify toxicity.
Key topics and technical requirements
- Test organism: Pseudomonas putida (e.g., MIGULA Berlin 33/Z DSM 50026 or NCIB 9494 strains, or equivalent sensitivity).
- Principle: Compare bacterial growth in varying dilutions of the sample against a control; determine inhibition of cell multiplication from turbidity measurements.
- Measurement: Optical density / turbidity measured (formazine nephelometric units, FNU) per ISO 7027 (example wavelength 436 nm).
- Incubation conditions:
- Test temperature: 23 °C ± 1 °C (dark).
- Preculture incubation: ~5 h ± 0.5 h to exponential phase.
- Inoculum initial turbidity in test culture: 5 FNU.
- Result metrics: EC10 and EC50 derived from the concentration-effect relationship (inhibition (%) vs sample concentration).
- Validity criteria: Control inoculum must multiply by a factor of at least 60 during the test. Reference substance 3,5‑dichlorophenol EC50 should fall between 10–30 mg/L.
- Limitations: Not suitable for highly coloured samples, or samples containing undissolved, volatile, precipitating or reactive substances that alter nutrient solution or undergo biochemical/photochemical degradation. Best for water-soluble substances.
Applications and users
Practical uses of ISO 10712:1995:
- Routine environmental monitoring of surface, groundwater and wastewater for microbial inhibition.
- Wastewater treatment plant testing and effluent toxicity screening.
- Regulatory and compliance testing where biological water quality indicators are required.
- Ecotoxicology and research labs studying acute inhibitory effects on heterotrophic freshwater bacteria.
Typical users:
- Accredited water testing laboratories
- Environmental regulators and consultants
- Industrial wastewater compliance teams
- Academic researchers in aquatic toxicology
Related standards
- ISO 7027:1990 - referenced for turbidity measurement (formazine nephelometric units, FNU).
- Prepared by ISO/TC 147/SC 5 (Water quality - Biological methods).
Keywords: ISO 10712:1995, Pseudomonas putida growth inhibition test, water quality, cell multiplication inhibition, EC50, EC10, turbidity, FNU, aquatic toxicity, biological water quality testing.
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