Bacteroidetes are abundant pathogen-suppressing members of the plant microbiome that contribute prominently to rhizosphere phosphorus mobilisation, a frequent growth-limiting nutrient in this niche. However, the genetic traits underpinning their success in this niche remain largely unknown, particularly regarding their phosphorus acquisition strategies. By combining cultivation, multi-layered omics and biochemical analyses we first discovered that all plant-associated Bacteroidetes express constitutive phosphatase activity, linked to the ubiquitous possession of a unique phosphatase, PafA. For the first time, we also reveal a subset of Bacteroidetes outer membrane SusCD-like complexes, typically associated with carbon acquisition, and several TonB-dependent transporters, are induced during Pi-depletion. Furthermore, in response to phosphate depletion, the plant-associated Flavobacterium used in this study expressed many previously characterised and novel proteins targeting organic phosphorus. Collectively, these enzymes exhibited superior phosphatase activity compared to plant-associated Pseudomonas spp. Importantly, several of the novel low-Pi-inducible phosphatases and transporters, belong to the Bacteroidetes auxiliary genome and are an adaptive genomic signature of plant-associated strains. In conclusion, niche adaptation to the plant microbiome thus appears to have resulted in the acquisition of unique phosphorus scavenging loci in Bacteroidetes, enhancing their phosphorus acquisition capabilities. These traits may enable their success in the rhizosphere and also present exciting avenues to develop sustainable agriculture.

拟杆菌是植物微生物组中丰富的病原体抑制成员，对根际磷的动员有显着贡献，这是该生态位中常见的限制生长的营养素。然而，支撑它们在这一领域取得成功的遗传特征在很大程度上仍然未知，特别是关于它们的磷获取策略。通过结合培养、多层组学和生化分析，我们首先发现所有与植物相关的拟杆菌都表达组成型磷酸酶活性，这与普遍存在的独特磷酸酶 PafA 相关。我们还首次揭示了拟杆菌的一个子集在 Pi 耗尽期间诱导通常与碳获取相关的外膜 SusCD 样复合物和几种 TonB 依赖性转运蛋白。此外，为了响应磷酸盐耗尽，本研究中使用的植物相关黄杆菌表达了许多以前表征过的新型蛋白质靶向有机磷。总的来说，与植物相关的假单胞菌属相比，这些酶表现出更高的磷酸酶活性 。重要的是，几种新型低 Pi 诱导型磷酸酶和转运蛋白属于拟杆菌辅助基因组，是植物相关菌株的适应性基因组特征。总之，生态位对植物微生物组的适应似乎导致了拟杆菌中独特的磷清除位点的获得，从而增强了它们的磷获取能力。这些特性可能使它们在根际获得成功，也为发展可持续农业提供了令人兴奋的途径。