Phosphate buffer depletion under biological conditions

[C_Sagan_Returns]

Whether plants, animals or bacteria, life requires Phosphorous (P) in order to carry out cellular work and provide the hook or glue which links the nucleosides of DNA and RNA. Hypothetically speaking, if one were to prepare media will phosphate buffer, it’s not improbable that Phosphate ions might inadvertently be used as a nutrient. Such processes would eventually destroy the buffer's capacity to stabilize pH. Even under conditions of lower pH (acidic), small amounts of PO4 will be present and their absorption/disappearance should be compensated for according to Le Chat's principle.

 

How is this avoided? Are other P sources used? Or are P buffers used in combination with others for when P is entirely depleted?

 

Thanks,

CSR

Edited January 2, 2009 by C_Sagan_Returns

[CharonY]

Usually it is not much of a problem. Generally speaking, if the phosphate concentration is in the range of roughly 10-100 µM it is not growth limiting anymore. For many cells very high P-concentrations can in fact be growth inhibiting. If phospate buffers are used in media, they tend to be in the in the lower mmol range to avoid this.

So, even if phosphate is the sole buffer, usually the utilization by cells does not alter the its buffer capacity too much.