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R2A agar (Reasoner's 2A agar) is a culture medium developed to study bacteria which normally inhabit potable water. These bacteria tend to be slow-growing species and would quickly be suppressed by faster-growing species on a richer culture medium.

Since its development in 1985, it has been found to allow the culturing of many other bacteria that will not readily grow on fuller, complex organic media.

Typical composition (% w/v)

• Proteose peptone, 0.05%
• Casamino acids, 0.05%
• Yeast extract, 0.05%
• Dextrose, 0.05%
• Soluble starch, 0.05%
• Dipotassium phosphate, 0.03%
• Magnesium sulfate, 0.005%
• Sodium pyruvate, 0.03%
• Agar, 1.5%

Final pH 7.2 ± 0.2 @ 25 °C

References

1. van der Linde K, Lim BT, Rondeel JM, Antonissen LP, de Jong GM (October 1999). "Improved bacteriological surveillance of haemodialysis fluids: a comparison between Tryptic soy agar and Reasoner's 2A media". Nephrol. Dial. Transplant. 14 (10): 2433–7. doi:10.1093/ndt/14.10.2433. PMID 10528669.
2. Sandle, T. (July 2004). "An approach for the reporting of microbiological results from water systems". PDA J Pharm Sci Technol. 58 (4): 231–7. PMID 15368993.
3. ^ Reasoner DJ, EE Geldreich EE (Jan 1985). "A new medium for the enumeration and subculture of bacteria from potable water". Appl. Environ. Microbiol. 49 (1): 1–7. Bibcode:1985ApEnM..49....1R. doi:10.1128/aem.49.1.1-7.1985. PMC 238333. PMID 3883894.

• Microbiological media
• Cell culture media