The quantitative proteomic response of Synechocystis sp. PCC6803 to phosphate acclimation

Matthew A Fuszard,Nigel G Ternan,Catherine A Biggs,Saw Yen Ow,Kenneth F Reardon,Josseilin Noirel,Phillip C Wright,Chee Sian Gan,Geoff Mcmullan

doi:10.1186/2046-9063-9-5

Abstract

BackgroundInorganic phosphate (Pi) is a critical nutrient for all life and is periodically limiting in marine and freshwater provinces, yet little is understood how organisms acclimate to fluctuations in Pi within their environment. To investigate whole cell adaptation, we grew Synechocystis sp. PCC6803, a model freshwater cyanobacterium, in 3%, and 0.3% inorganic phosphate (Pi) media. The cells were allowed to acclimate over 60 days, and cells were harvested for quantitative high throughput mass spectrometry-based proteomics using the iTRAQ™ labelling technology.ResultsIn total, 120 proteins were identified, and 52 proteins were considered differentially abundant compared to the control. Alkaline phosphatase (APase) activities correlated significantly (p < 0.05) with observed relative PhoA abundances. PstS1 and PstS2 were both observed, yet PstS1 was not differentially more abundant than the control. Phycobilisome protein abundances appeared to be coordinated, and are significantly less abundant in 0.3% Pi than 3% Pi cultures. Also, the central metabolic cell function appears to have shifted towards the production of (NADPH) reducing energy and nucleotide sugars.ConclusionsThis acclimation response bears strong similarity to the previously reported response to nitrogen deprivation within Synechocystis sp. PCC 6803. However, it also demonstrates some characteristics of desiccation stress, such as the regulation of fatty acids and increased abundance of rehydrin in the 3% Pi culture.

Highlights

Inorganic phosphate (Pi) is a critical nutrient for all life and is periodically limiting in marine and freshwater provinces, yet little is understood how organisms acclimate to fluctuations in Pi within their environment
The control culture reached an OD730 of 7 at the end of the 60-day cultivation, whereas the phosphate-limited cultures only reached a maximum OD730 of 0.9 and 0.5. Their specific growth rates were calculated as 0.20 day-1 for the control culture, 0.012 day-1 for 3% Pi culture and 0.002 day-1 for 0.3% Pi culture
13 detected proteins were more abundant in the 3% Pi culture, whereas the abundances of 12 proteins were observed to have increased within the 0.3% Pi culture (Table 1)

Summary

Introduction

Inorganic phosphate (Pi) is a critical nutrient for all life and is periodically limiting in marine and freshwater provinces, yet little is understood how organisms acclimate to fluctuations in Pi within their environment. There have been relatively few investigations into the cell-wide response of microorganisms to this form of nutrient stress, over longer periods that reflect adaptation rather than short-term response. An understanding of these processes will be of use in the basic understanding of microbes and the niches they occupy, but could be applied to develop biomarkers to follow stages in the phosphorus biogeochemical cycle within aquatic environments. The identification of novel proteins associated with Pi uptake could be exploited in the removal of Pi for water quality improvement, whilst enzymes involved in the catabolism of organophosphorus molecules are of interest in the pharmaceutical and agribiotech industrial sectors

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