title: Trade-Off between Growth and Carbohydrate Accumulation in Nutrient-Limited Arthrospira sp. PCC 8005 Studied by Integrating Transcriptomic and Proteomic Approaches.
abstract: Cyanobacteria have a strong potential for biofuel production due to their ability to accumulate large amounts of carbohydrates. Nitrogen (N) stress can be used to increase the content of carbohydrates in the biomass, but it is expected to reduce biomass productivity. To study this trade-off between carbohydrate accumulation and biomass productivity, we characterized the biomass productivity, biomass composition as well as the transcriptome and proteome of the cyanobacterium Arthrospira sp. PCC 8005 cultured under N-limiting and N-replete conditions. N limitation resulted in a large increase in the carbohydrate content of the biomass (from 14 to 74%) and a decrease in the protein content (from 37 to 10%). Analyses of fatty acids indicated that no lipids were accumulated under N-limited conditions. Nevertheless, it did not affect the biomass productivity of the culture up to five days after N was depleted from the culture medium. Transcriptomic and proteomic analysis indicated that de novo protein synthesis was down-regulated in the N-limited culture. Proteins were degraded and partly converted into carbohydrates through gluconeogenesis. Cellular N derived from protein degradation was recycled through the TCA and GS-GOGAT cycles. In addition, photosynthetic energy production and carbon fixation were both down-regulated, while glycogen synthesis was up-regulated. Our results suggested that N limitation resulted in a redirection of photosynthetic energy from protein synthesis to glycogen synthesis. The fact that glycogen synthesis has a lower energy demand than protein synthesis might explain why Arthrospira is able to achieve a similar biomass productivity under N-limited as under N-replete conditions despite the fact that photosynthetic energy production was impaired by N limitation.
authors.affiliation: KU Leuven campus Kortrijk, Laboratory Aquatic Biology, E. Sabbelaan 53, 8500, Kortrijk, Belgium.
authors.forename: Orily
authors.initials: O
authors.lastname: Depraetere
authors.affiliation: Department of Proteomic and Microbiology, Research Institute for Biosciences, University of Mons, Place du Parc 20, 7000, Mons, Belgium.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Deschoenmaeker
authors.affiliation: Expert Group for Molecular and Cellular Biology MCB, Belgian Nuclear Research Center SCK.CEN, 2400, Mol, Belgium.
authors.forename: Hanène
authors.initials: H
authors.lastname: Badri
authors.affiliation: Expert Group for Molecular and Cellular Biology MCB, Belgian Nuclear Research Center SCK.CEN, 2400, Mol, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Monsieurs
authors.affiliation: KU Leuven campus Kortrijk, Research Unit Food & Lipids, Department of Molecular and Microbial Systems Kulak, Etienne Sabbelaan 53, 8500, Kortrijk, Belgium.
authors.forename: Imogen
authors.initials: I
authors.lastname: Foubert
authors.affiliation: Expert Group for Molecular and Cellular Biology MCB, Belgian Nuclear Research Center SCK.CEN, 2400, Mol, Belgium.
authors.forename: Natalie
authors.initials: N
authors.lastname: Leys
authors.affiliation: Department of Proteomic and Microbiology, Research Institute for Biosciences, University of Mons, Place du Parc 20, 7000, Mons, Belgium.
authors.forename: Ruddy
authors.initials: R
authors.lastname: Wattiez
authors.affiliation: KU Leuven campus Kortrijk, Laboratory Aquatic Biology, E. Sabbelaan 53, 8500, Kortrijk, Belgium.
authors.forename: Koenraad
authors.initials: K
authors.lastname: Muylaert
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018533:Biomass; D050260:Carbohydrate Metabolism; D015964:Gene Expression Regulation, Bacterial; D005943:Gluconeogenesis; D050356:Lipid Metabolism; D009584:Nitrogen / Q000378:metabolism; D059748:Proteolysis; D040901:Proteomics; D053545:Spirulina / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D059467:Transcriptome
chemical_list: D001426:Bacterial Proteins; D009584:Nitrogen