Identification of extracellular glycerophosphodiesterases in Pseudomonas and their role in soil organic phosphorus remineralisation

Abstract

In soils, phosphorus (P) exists in numerous organic and inorganic forms. However, plants can only acquire inorganic orthophosphate (Pi), meaning global crop production is frequently limited by P availability. To overcome this problem, rock phosphate fertilisers are heavily applied, often with negative environmental and socio-economic consequences. The organic P fraction of soil contains phospholipids that are rapidly degraded resulting in the release of bioavailable Pi. However, the mechanisms behind this process remain unknown. We identified and experimentally confirmed the function of two secreted glycerolphosphodiesterases, GlpQI and GlpQII, found in Pseudomonas stutzeri DSM4166 and Pseudomonas fluorescens SBW25, respectively. A series of co-cultivation experiments revealed that in these Pseudomonas strains, cleavage of glycerolphosphorylcholine and its breakdown product G3P occurs extracellularly allowing other bacteria to benefit from this metabolism. Analyses of metagenomic and metatranscriptomic datasets revealed that this trait is widespread among soil bacteria with Actinobacteria and Proteobacteria, specifically Betaproteobacteria and Gammaproteobacteria, the likely major players.

Nutrient Acquisition, Rather Than Stress Response Over Diel Cycles, Drives Microbial Transcription in a Hyper-Arid Namib Desert Soil

“…The ugp genes were principally transcribed by members of the Order Rhizobiales (Class alpha-Proteobacteria), potentially replacing Pi transport as a phosphorus acquisition mechanism (Figure 2B). Plant exudates or membrane phospholipids are possible sources of G3P in soils (Ding et al, 2012; Collins et al, 2014; Lidbury et al, 2017). The glpQ gene product can cleave these compounds, releasing G3P and triggering activation of the ugp transporter genes (Brzoska and Boos, 1988).…”

Maintenance and assessment of cell viability in formulation of non‐sporulating bacterial inoculants

“…An enhanced secretion of certain enzymes related to phosphate uptake was shown to be triggered by low phosphate conditions. A subsequent study proved that even co‐cultured bacteria could benefit from this extracellularly occurring metabolism (Lidbury et al ., ). Although this example is related to the nutrient provision of co‐formulated partners, it might be transferred to the provision of desiccation protectants.…”

Contrasting P acquisition strategies of the bacterial communities associated with legume and grass in subtropical orchard soil

“…This difference suggests that bacteria associated with stylo prefer Po mineralization as an important strategy for P acquisition. glpQ encodes phosphodiesterase catalyzing the hydrolysis of the phosphorus diester (Lidbury et al, 2017). Canellas et al (2004) indicated that legumes increased soil phosphorus diester content more effectively than grass.…”