Iron is an essential nutrient for all organisms and in particular for photoautotrophic organisms. The development of large diatom blooms upon nutrient resupply demonstrates the metabolic plasticity inherent to their ability to recover rapidly from nutrient limitation. Although diatoms often dominate phytoplankton communities in nutrient-rich ecosystems, members of this diverse group are also adapted to survive and persist in nutrient-limited conditions. A high genomic plasticity, as seen from the fraction of genes acquired through horizontal gene transfer, provides the platform for these complex adaptations to a low-iron world.ĭiatoms are important primary producers in the ocean, contributing approximately 40% to global marine productivity. Further, our data identify candidate components of a high-affinity iron-uptake system, with several of the involved genes and domains originating from duplication events. A novel contribution enhancing iron economy of phototrophic growth is observed with the iron-regulated substitution of three metal-containing fructose-bisphosphate aldolases involved in metabolic conversion of carbohydrates for enzymes that do not contain metals. Conclusionsīeneficial adaptations to low-iron environments include strategies to lower the cellular iron requirements and to enhance iron uptake. As a consequence of iron deprivation, the photosynthetic machinery undergoes a remodeling to adjust the light energy utilization with the overall decrease in photosynthetic electron transfer complexes. The complex response comprises cellular retrenchment as well as remodeling of bioenergetic pathways, where the abundance of iron-rich photosynthetic proteins is lowered, whereas iron-rich mitochondrial proteins are preserved. The combined efforts in genomics, transcriptomics and proteomics reveal an unexpected metabolic flexibility in response to iron availability for T. The oceanic diatom Thalassiosira oceanica shows a remarkable tolerance to low-iron conditions and was chosen as a model for deciphering the cellular response upon shortage of this essential micronutrient. Phytoplankton growth is widely limited by the availability of iron, an essential component of the photosynthetic apparatus. Biogeochemical elemental cycling is driven by primary production of biomass via phototrophic phytoplankton growth, with 40% of marine productivity being assigned to diatoms.
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