Specialization in a Nitrogen-Fixing Symbiosis: Proteome Differences Between Sinorhizobium medicae Bacteria and Bacteroids

• DOI: 10.1094/mpmi-07-21-0180-r
• Publication Date: 2021-08-17T15:45:30Z
• Authors: Svetlana N. Yurgel; Yi Qu; Jennifer T. Rice; Nivethika Ajeethan; Erika M. Zink; Joseph M. Brown; Sam Purvine; Mary S. Lipton; Michael L. Kahn
• Keywords: Sinorhizobium meliloti; Proteome; Medicago truncatula; Metabolic pathway; Sinorhizobium

Using tandem mass spectrometry (MS/MS), we analyzed the proteome of Sinorhizobium medicae WSM419 growing as free-living cells and in symbiosis with Medicago truncatula. In all, 3,215 proteins were identified, over half open reading frames predicted from genomic sequence. The abundance 1,361 displayed strong lifestyle bias. total, 1,131 had similar levels bacteroids cells, low 723 prevented statistically significant assignments. Nitrogenase subunits comprised approximately 12% quantified bacteroid proteins. Other major included symbiosis-specific cytochromes FixABCX, which transfer electrons to nitrogenase. Bacteroids normal involved amino acid biosynthesis, glycolysis or gluconeogenesis, pentose phosphate pathway; however, several degradation pathways repressed. This suggests that maintain a relatively independent anabolic metabolism. Tricarboxylic cycle highly expressed no other catabolic pathway emerged an obvious candidate supply energy reductant nitrogen fixation. Bacterial stress response induced bacteroids. Many are not encoded S. meliloti Rm1021 detected, understanding functions these might clarify why forms more effective M. truncatula than Rm1021.[Formula: see text] Copyright © 2021 Author(s). is access article distributed under CC BY-NC-ND 4.0 International license.