Dipartimento di Scienze Chimiche, Complesso Universitario Monte Sant'Angelo, Università di Napoli Federico II, Via Cintia 4, Napoli I-80126, Italy.
IRD, Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), UMR IRD/SupAgro/INRA/UM2/CIRAD, TA-A82/J, Campus de Baillarguet, 34398 Montpellier cedex 5, France.
Nat Commun. 2014 Oct 30;5:5106. doi: 10.1038/ncomms6106.
Lipopolysaccharides (LPSs) are major components of the outer membrane of Gram-negative bacteria and are essential for their growth and survival. They act as a structural barrier and play an important role in the interaction with eukaryotic hosts. Here we demonstrate that a photosynthetic Bradyrhizobium strain, symbiont of Aeschynomene legumes, synthesizes a unique LPS bearing a hopanoid covalently attached to lipid A. Biophysical analyses of reconstituted liposomes indicate that this hopanoid-lipid A structure reinforces the stability and rigidity of the outer membrane. In addition, the bacterium produces other hopanoid molecules not linked to LPS. A hopanoid-deficient strain, lacking a squalene hopene cyclase, displays increased sensitivity to stressful conditions and reduced ability to survive intracellularly in the host plant. This unusual combination of hopanoid and LPS molecules may represent an adaptation to optimize bacterial survival in both free-living and symbiotic states.
脂多糖（LPSs）是革兰氏阴性细菌外膜的主要成分，对其生长和存活至关重要。它们充当结构屏障，并在与真核宿主的相互作用中发挥重要作用。在这里，我们证明了一种光合作用的慢生根瘤菌菌株，是含羞草属豆类的共生体，合成了一种独特的脂多糖，其带有通过共价键连接到脂 A 上的藿烷。重建脂质体的生物物理分析表明，这种藿烷-脂 A 结构增强了外膜的稳定性和刚性。此外，该细菌还产生其他未与 LPS 连接的藿烷分子。缺乏鲨烯霍烯环化酶的藿烷缺陷型菌株对胁迫条件更加敏感，并且在宿主植物内的体内生存能力降低。这种藿烷和 LPS 分子的不寻常组合可能代表了一种适应，以优化细菌在自由生活和共生状态下的生存。
