Effect of reduced pH on inorganic polyphosphate accumulation by Burkholderia cepacia complex isolates

Burkholderia cepacia complex (Bcc) isolates causing pulmonary infection in cystic fibrosis (CF) patients grow within an acidic environment in the lung. As exposure to acid pH has been shown to increase intracellular inorganic polyphosphate (polyP) formation in some bacteria, we investigated the inter-relationship between acidic pH and polyP accumulation in Bcc isolates.

The formation of polyP by one Burkholderia cenocepacia clinical isolate was initially examined at a range of pH values by measuring total intracellular polyP accumulation and phosphate uptake. The pattern of polyP accumulation corresponded with the pattern of phosphate uptake with the maximum for both occurring at pH 5.5. Phosphate uptake and formation of polyP by this isolate was further determined over 48 h at pH 5.5, 6.5 and 7.5; formation of polyP was maximal at pH 5.5 at all time points studied. Sixteen of 17 additional clinical and environmental Bcc isolates examined also exhibited maximum phosphate uptake at pH 5.5.

Both clinical and environmental Bcc isolates, of five genomovars, show enhanced formation of polyP in an acidic environment. Given both the speculated role of polyP in pathogenesis, cell signalling and biofilm formation and the acidic nature of the CF lung, this may be of considerable clinical importance.

Growth of Bcc in an acidic environment, such as that found in the lungs of CF patients may be influenced in part by polyP accumulation.