R2A agar

R2A agar (Reasoner's 2A agar) is a culture medium^[1] developed to study bacteria which normally inhabit potable water.^[2] These bacteria tend to be slow-growing species and would quickly be suppressed by faster-growing species on a richer culture medium.^[3]

Since its development in 1985,^[3] it has been found to allow the culturing of many other bacteria that will not readily grow on fuller, complex organic media.^{[citation needed]}

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.