Growth of Cyanobacteria Is Constrained by the Abundance of Light and Carbon Assimilation Proteins

• Published in: Cell reports (Cambridge) 2018-10, Vol.25 (2), p.478-486.e8
• Main Authors: Jahn, Michael, Vialas, Vital, Karlsen, Jan, Maddalo, Gianluca, Edfors, Fredrik, Forsström, Björn, Uhlén, Mathias, Käll, Lukas, Hudson, Elton P.
• Format: Article
• Language: English
• Subjects: Bacterial Proteins - metabolism; bet-hedging; Carbon Dioxide - pharmacology; carbon limitation; cellular economy; coarse-grained model; cyanobacteria; Cyanobacteria - drug effects; Cyanobacteria - growth & development; Cyanobacteria - radiation effects; Gene Expression Regulation, Bacterial; Light; light limitation; Proteome - analysis; Proteome - drug effects; Proteome - radiation effects; resource allocation; shotgun proteomics
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2018.09.040

Cyanobacteria must balance separate demands for energy generation, carbon assimilation, and biomass synthesis. We used shotgun proteomics to investigate proteome allocation strategies in the model cyanobacterium Synechocystis sp. PCC 6803 as it adapted to light and inorganic carbon (Ci) limitation. When partitioning the proteome into seven functional sectors, we find that sector sizes change linearly with growth rate. The sector encompassing ribosomes is significantly smaller than in E. coli, which may explain the lower maximum growth rate in Synechocystis. Limitation of light dramatically affects multiple proteome sectors, whereas the effect of Ci limitation is weak. Carbon assimilation proteins respond more strongly to changes in light intensity than to Ci. A coarse-grained cell economy model generally explains proteome trends. However, deviations from model predictions suggest that the large proteome sectors for carbon and light assimilation are not optimally utilized under some growth conditions and may constrain the proteome space available to ribosomes. [Display omitted] •The proteome of a photosynthetic bacterium was probed under light and CO2 limitation•Protein abundance changed linearly with growth rate according to growth law•The response to light limitation exceeds the response to CO2•A resource allocation model suggests that proteins are not always utilized optimally Jahn et al. used shotgun proteomics to investigate resource allocation strategies in the model cyanobacterium Synechocystis as it adapted to light and carbon limitation. They found that cells reorganize their proteome following a growth optimization strategy but deviate from this strategy to keep protein reserves even under nutrient-replete conditions.