No. Bacteriostatic water should not be used to prepare cell culture media, supplements, buffers or washes, or for anything that will contact living cells in culture. The reason is the preservative, and it is not a marginal effect.
Benzyl alcohol and cultured cells
Bacteriostatic water contains 0.9% (9 mg/mL) benzyl alcohol. The same membrane-disrupting action that makes benzyl alcohol effective against bacteria acts on mammalian and other eukaryotic cell membranes. At preservative concentrations it is cytotoxic to cultured cells, causing membrane damage, loss of viability and, in sub-lethal exposures, altered growth and gene expression that will confound any experiment. Diluting bacteriostatic water into a large volume of medium reduces the concentration but does not remove the compound, and the residual level is still an uncontrolled variable that no reviewer will accept.
Other reasons it does not belong in culture work
- Tonicity. Bacteriostatic water is hypotonic, essentially solute-free. That is expected of a water grade, but it means the product brings nothing to a culture system except the preservative.
- Not certified for culture. Cell-culture-grade water is specified for endotoxin, nuclease and mycoplasma-relevant purity in ways that a general bacteriostatic product is not labeled for, even though bacteriostatic water is itself endotoxin-tested.
- Antimicrobial interference. Culture systems that intentionally include bacteria, such as co-culture or microbiome models, would be directly disrupted by a bacteriostatic agent.
What to use instead
| Need | Use |
|---|---|
| Media and supplement preparation | Cell-culture-grade water, endotoxin-tested, preservative-free |
| Sterile diluent for reagents that contact cells | Preservative-free sterile water or sterile PBS, single-use |
| Isotonic washes | Sterile PBS or sterile saline, preservative-free |
| Molecular biology reagents | Nuclease-free water |
The comparison with preservative-free sterile water is in bacteriostatic water vs. sterile water.
Where bacteriostatic water does fit
Bacteriostatic water is designed for repeated small withdrawals of sterile, endotoxin-controlled water from a single sealed vial over several weeks, in work where the preservative is harmless: dissolving or diluting lyophilized research materials that will not be applied to living cells, preparing dilution series for non-cellular assays, and similar bench roles. Its other exclusion, UV-detected analytical methods where benzyl alcohol produces a peak, is covered in benzyl alcohol as a preservative.
A practical rule
If the liquid will ever touch a living cell, use preservative-free water. If it will not, and the workflow benefits from a multi-use vial, bacteriostatic water is the right tool. Keeping the two physically separate on the bench, with distinct labeling, prevents the mix-up that most often causes trouble.
More on the product itself: what is bacteriostatic water.
All BAC Water Supply products are supplied for laboratory research use only and are not for human or veterinary use.