title: The transcriptional regulation of the glyoxylate cycle in SAR11 in response to iron fertilization in the Southern Ocean.
abstract: The tricarboxylic acid (TCA) cycle is a central metabolic pathway that is present in all aerobic organisms and initiates the respiration of organic material. The glyoxylate cycle is a variation of the TCA cycle, where organic material is recycled for subsequent assimilation into cell material instead of being released as carbon dioxide. Despite the importance for the fate of organic matter, the environmental factors that induce the glyoxylate cycle in microbial communities remain poorly understood. In this study, we assessed the expression of isocitrate lyase, the enzyme that induces the switch to the glyoxylate cycle, of the ubiquitous SAR11 clade in response to natural iron fertilization in the Southern Ocean. The cell-specific transcriptional regulation of the glyoxylate cycle, as determined by the ratio between copy numbers of isocitrate lyase gene transcripts and isocitrate genes, was consistently lower in iron fertilized than in high-nutrient, low chlorophyll waters (by 2.4- to 16.5-fold). SAR11 cell-specific isocitrate lyase gene transcription was negatively correlated to chlorophyll a, and bulk bacterial heterotrophic metabolism. We conclude that the glyoxylate cycle is a metabolic strategy for SAR11 that is highly sensitive to the degree of iron and carbon limitation in the marine environment.
authors.affiliation: CNRS, Sorbonne Universités, UPMC Univ Paris 06, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, F-66650, Banyuls/mer, France.
authors.forename: Sara
authors.initials: S
authors.lastname: Beier
authors.affiliation: CNRS, Sorbonne Universités, UPMC Univ Paris 06, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, F-66650, Banyuls/mer, France.|Graduate program in Oceanography, Department of Oceanography, University of Concepción, Chile.
authors.forename: María J
authors.initials: MJ
authors.lastname: Gálvez
authors.affiliation: Departamento de Biología, Facultad de Ciencias Naturales y Exactas, Universidad de Playa Ancha, Avda. Leopoldo Carvallo 270, Playa Ancha, Valparaíso, Chile.
authors.forename: Veronica
authors.initials: V
authors.lastname: Molina
authors.affiliation: LEMAR-UMR CNRS UBO IRD 6539, Technopole Brest Iroise, Place Nicolas Copernic, Plouzané, F29280, France.
authors.forename: Géraldine
authors.initials: G
authors.lastname: Sarthou
authors.affiliation: LEMAR-UMR CNRS UBO IRD 6539, Technopole Brest Iroise, Place Nicolas Copernic, Plouzané, F29280, France.|Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas 7001, Australia.|Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tas 7001, Australia.
authors.forename: Fabien
authors.initials: F
authors.lastname: Quéroué
authors.affiliation: CNRS, Sorbonne Universités, UPMC Univ Paris 06, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, F-66650, Banyuls/mer, France.
authors.forename: Stephane
authors.initials: S
authors.lastname: Blain
authors.affiliation: CNRS, Sorbonne Universités, UPMC Univ Paris 06, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, F-66650, Banyuls/mer, France.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Obernosterer
mesh_terms: D001419:Bacteria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D006038:Glyoxylates / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D007522:Isocitrate Lyase / Q000032:analysis / Q000235:genetics; D053858:Metabolic Networks and Pathways; D009792:Oceans and Seas; D012623:Seawater / Q000737:chemistry* / Q000382:microbiology*; D014158:Transcription, Genetic
chemical_list: D006038:Glyoxylates; D007501:Iron; D007522:Isocitrate Lyase; C031150:glyoxylic acid