Defense compounds generally inhibit microbial colonization of plants. In this study, we examined the presence of endophytes in Passiflora edulis seeds that accumulate resveratrol and piceatannol at extremely high levels as defense compounds. Interestingly, although no microbial colonies appeared on an agar growth medium from the cut or homogenized seeds, colonies were generated from cut seedlings derived from the seeds. A total of 19 bacterial strains were isolated, of which 15 were classified as Gram-positive. As we hypothesized that extremely high levels of piceatannol in the seeds would inhibit the growth of endophytes cultured directly from the seeds, we examined the antimicrobial activity of this compound against the isolated bacteria. Piceatannol exerted bacteriostatic rather than bactericidal effects on most of the bacteria tested. These results suggest that the bacteria remain static in the seeds due to the presence of piceatannol and are transmitted to the seedlings during the germination process, enabling colonies to be established from the seedlings on the agar medium. We also investigated the biocatalytic activity of the isolated bacteria toward resveratrol and piceatannol. One bacterium, Brevibacterium sp. PE28-2, converted resveratrol and piceatannol to their respective derivatives. This strain is the first endophyte shown to exhibit such activity.

中文翻译：

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西番莲种子可培养内生细菌的多样性及特征

防御化合物通常抑制植物的微生物定植。在这项研究中，我们检查了Passiflora edulis中内生菌的存在以极高水平积累白藜芦醇和 piceatannol 作为防御化合物的种子。有趣的是，虽然切下或均质化的种子在琼脂生长培养基上没有出现微生物菌落，但从种子中切下的幼苗中产生了菌落。共分离出19株细菌，其中15株为革兰氏阳性。由于我们假设种子中极高水平的 piceatannol 会抑制直接从种子培养的内生菌的生长，因此我们检查了该化合物对分离细菌的抗菌活性。Piceatannol 对大多数测试的细菌发挥抑菌作用而不是杀菌作用。这些结果表明，由于云杉醇的存在，细菌在种子中保持静止，并在发芽过程中传播到幼苗，从而能够在琼脂培养基上从幼苗建立菌落。我们还研究了分离的细菌对白藜芦醇和 piceatannol 的生物催化活性。一种细菌，短杆菌属 PE28-2，将白藜芦醇和piceatannol 转化为它们各自的衍生物。该菌株是第一个表现出这种活性的内生菌。