@article{fdi:010065459,
  title = {{S}pecific hopanoid classes differentially affect free-living and symbiotic states of {B}radyrhizobium diazoefficiens},
  author = {{K}ulkarni, {G}. and {B}usset, {N}. and {M}olinaro, {A}. and {G}argani, {D}. and {C}haintreuil, {C}l{\'e}mence and {S}ilipo, {A}. and {G}iraud, {E}ric and {N}ewman, {D}. {K}.},
  editor = {},
  language = {{ENG}},
  abstract = {{A} better understanding of how bacteria resist stresses encountered during the progression of plant-microbe symbioses will advance our ability to stimulate plant growth. {H}ere, we show that the symbiotic system comprising the nitrogen-fixing bacterium {B}radyrhizobium diazoefficiens and the legume {A}eschynomene afraspera requires hopanoid production for optimal fitness. {W}hile methylated (2{M}e) hopanoids contribute to growth under plant-cell-like microaerobic and acidic conditions in the free-living state, they are dispensable during symbiosis. {I}n contrast, synthesis of extended ({C}-35) hopanoids is required for growth microaerobically and under various stress conditions (high temperature, low p{H}, high osmolarity, bile salts, oxidative stress, and antimicrobial peptides) in the free-living state and also during symbiosis. {T}hese defects might be due to a less rigid membrane resulting from the absence of free or lipid{A}-bound {C}-35 hopanoids or the accumulation of the {C}-35 hopanoid diploptene. {O}ur results also show that {C}-35 hopanoids are necessary for symbiosis only with the host {A}eschynomene afraspera but not with soybean. {T}his difference is likely related to the presence of cysteine-rich antimicrobial peptides in {A}eschynomene nodules that induce drastic modification in bacterial morphology and physiology. {T}he study of hopanoid mutants in plant symbionts thus provides an opportunity to gain insight into host-microbe interactions during later stages of symbiotic progression, as well as the microenvironmental conditions for which hopanoids provide a fitness advantage. {IMPORTANCE} {B}ecause bradyrhizobia provide fixed nitrogen to plants, this work has potential agronomical implications. {A}n understanding of how hopanoids facilitate bacterial survival in soils and plant hosts may aid the engineering of more robust agronomic strains, especially relevant in regions that are becoming warmer and saline due to climate change. {M}oreover, this work has geobiological relevance: hopanes, molecular fossils of hopanoids, are enriched in ancient sedimentary rocks at discrete intervals in {E}arth history. {T}his is the first study to uncover roles for 2{M}e- and {C}-35 hopanoids in the context of an ecological niche that captures many of the stressful environmental conditions thought to be important during (2{M}e)-hopane deposition. {T}hough much remains to be done to determine whether the conditions present within the plant host are shared with niches of relevance to the rock record, our findings represent an important step toward identifying conserved mechanisms whereby hopanoids contribute to fitness.},
  keywords = {},
  booktitle = {},
  journal = {{M}bio},
  volume = {6},
  numero = {5},
  pages = {e01251--15 [9 p.]},
  ISSN = {2150-7511},
  year = {2015},
  DOI = {10.1128/m{B}io.01251-15},
  URL = {https://www.documentation.ird.fr/hor/fdi:010065459},
}