Abstract
Cyanobacteria, the only prokaryotes capable of oxygenic photosynthesis, are present in diverse ecological niches and play crucial roles in global carbon and nitrogen cycles. To proliferate in nature, cyanobacteria utilize a host of stress responses to accommodate periodic changes in environmental conditions. A detailed knowledge of the composition of, as well as the dynamic changes in, the proteome is necessary to gain fundamental insights into such stress responses. Toward this goal, we have performed a large-scale proteomic analysis of the widely studied model cyanobacterium Synechocystis sp. PCC 6803 under 33 different environmental conditions. The resulting high-quality dataset consists of 22,318 unique peptides corresponding to 1955 proteins, a coverage of 53% of the predicted proteome. Quantitative determination of protein abundances has led to the identification of 1198 differentially regulated proteins. Notably, our analysis revealed that a common stress response under various environmental perturbations, irrespective of amplitude and duration, is the activation of atypical pathways for the acquisition of carbon and nitrogen from urea and arginine. In particular, arginine is catabolized via putrescine to produce succinate and glutamate, sources of carbon and nitrogen, respectively. This study provides the most comprehensive functional and quantitative analysis of the Synechocystis proteome to date, and shows that a significant stress response of cyanobacteria involves an uncommon mode of acquisition of carbon and nitrogen.
Highlights
Cyanobacteria, the only prokaryotes capable of oxygenic photosynthesis, are present in diverse ecological niches and play crucial roles in global carbon and nitrogen cycles
Determination of the Composition of Synechocystis Proteome—To obtain a comprehensive proteomics description of Synechocystis, we collected samples from cells grown under 33 different environmental conditions
The kinetics of pigment loss, a typical observable phenotype associated with nutrient starvation in cyanobacteria, were quite variable between nutritional conditions (Fig. 1), possibly because of the ability of cyanobacteria to store some, but not all, nutrients in the form of inclusion bodies that can be utilized during starvation
Summary
Culture Conditions—Synechocystis cultures were grown to a density of 2 ϫ 108 cells/ml as described [39]. The washed cells were inoculated into complete BG11 medium and sampled following 0, 4, 6, 8, and 16 days. For growth under nutrient deplete conditions, washed cells were grown in BG11 depleted of either nitrate (nitrogen depletion), sulfate (sulfur depletion), or phosphate (phosphorus depletion), and sampled following 6 days. Cells were incubated twice in 20 mM 4-morpholineethanesulfonic acid (MES), 10 mM EDTA, pH 5.0 for 10 min, inoculated in BG11 depleted of iron, and sampled following 6 days. Membrane and soluble fractions from total cell extracts were prepared as described [35] with minor modifications. The pellet comprising membrane fractions was washed with 100 mM ammonium bicarbonate buffer (pH 8.0) and centrifuged again at 150,000 ϫ g at 4 °C for 20 min. Transmembrane hidden Markov models predicted helices shorter than 15 amino acids and those overlapping with signal peptides were discarded. Length, and mass histograms were generated for the subset of observed fully tryptic peptides of Ն5 amino acids in length and Ն500 Da and compared with ideal tryptic digests of the observed proteins, using the same constraints
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
