RT Journal Article SR Electronic T1 Extended hopanoid lipids promote bacterial motility, surface attachment, and root nodule development in the Bradyrhizobium diazoefficiens-Aeschynomene afraspera symbiosis JF bioRxiv FD Cold Spring Harbor Laboratory SP 423301 DO 10.1101/423301 A1 B.J. Belin A1 E.T. Tookmanian A1 J. de Anda A1 G. C. L Wong A1 D.K. Newman YR 2018 UL http://biorxiv.org/content/early/2018/09/20/423301.abstract AB Hopanoids are steroid-like bacterial lipids that enhance membrane rigidity and promote bacterial growth under diverse stresses. Roughly 10% of bacteria contain genes involved in hopanoid biosynthesis, and these genes are particularly conserved in plant-associated organisms. We previously found that the extended class of hopanoids (C35) in the nitrogen-fixing soil bacterium Bradyrhizobium diazoefficiens promotes its root nodule symbiosis with the tropical legume Aeschynomene afraspera. By quantitatively modeling root nodule development, we identify independent roles for hopanoids in the initiation of root nodule formation and in determining the rate of root nodule maturation. In vitro studies demonstrate that extended hopanoids support B. diazoefficiens motility and surface attachment, which may correlate with stable root colonization in planta. Confocal microscopy of maturing root nodules reveals that root nodules infected with extended hopanoid-deficient B. diazoefficiens contain unusually low densities of bacterial symbionts, indicating that extended hopanoids are necessary for persistent, high levels of host infection. This work identifies extended hopanoids as regulators of the efficiency of Bradyrhizobia nitrogen-fixing symbioses, agriculturally and economically significant associations with growing importance in a changing climate.