Forms of phosphorus in bacteria and fungi isolated from two Australian soils

Abstract

To understand the origin of organic and condensed forms of phosphorus (P) in soils, detailed information about P forms in microorganisms is required. We isolated 7 bacteria and 8 fungi from two Australian soils and analyzed the P forms in their pure cultures by extraction with NaOH-EDTA followed by 31P solution nuclear magnetic (NMR) spectroscopy. The bacteria belonged to the actinobacteria and the fungi to the ascomycota, as determined by rDNA sequencing. The proportions of broad forms of P were significantly different between the bacterial and fungal isolates (analysis of similarities, p = 0.001). Ortho-, pyro- and polyphosphate were present in higher proportions in fungi, while monoester and diester P were present in higher proportions in bacteria. Spectral deconvolution of the monoester region revealed 15 distinct resonances. The three major ones, which were identified by spiking experiments as glycerol 1-phosphate, glycerol 2-phosphate and adenosine-5'-monophosphate (AMP), comprised 56-74% of P in the monoester region. Ordination by principal component analysis and testing for treatment effects using analysis of similarities showed significant separation of P distribution in the monoester region between bacterial and fungal isolates (p = 0.007). However, neither group of microorganisms had a specific single P form which might be considered characteristic. As such, it may be difficult to distinguish soil P from bacterial or fungal origins, with the possible exception of a predominantly fungal origin of pyro- and polyphosphate. The identification of three major resonances in the monoester region of microorganisms is important, since the same resonances are found in 31P NMR spectra of soil extracts.