The transcriptional regulation of the glyoxylate cycle in SAR11 in response to iron fertilization in the Southern Ocean

• Published in: Environmental Microbiology Reports
• Main Authors: Beier, Sara, Gálvez, María J., Molina, Veronica, Sarthou, Géraldine, Quéroué, Fabien, Blain, Stephane, Obernosterer, Ingrid
• Other Authors: Agence Nationale de la Recherche, CONICYT-PCHA, Ecos-sud
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2015
• Subjects: Southern Ocean
• Online Access: http://dx.doi.org/10.1111/1758-2229.12267; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2F1758-2229.12267; http://onlinelibrary.wiley.com/wol1/doi/10.1111/1758-2229.12267/fullpdf

Summary 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 SAR 11 clade in response to natural iron fertilization in the S outhern O cean. 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). SAR 11 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 SAR 11 that is highly sensitive to the degree of iron and carbon limitation in the marine environment.