Laboratory of Plant Systematics, Katholieke Universiteit Leuven, Leuven, Belgium.
PLoS One. 2011 Apr 26;6(4):e19265. doi: 10.1371/journal.pone.0019265.
South African plant species of the genera Fadogia, Pavetta and Vangueria (all belonging to Rubiaceae) are known to cause gousiekte (literally 'quick disease'), a fatal cardiotoxicosis of ruminants characterised by acute heart failure four to eight weeks after ingestion. Noteworthy is that all these plants harbour endophytes in their leaves: nodulating bacteria in specialized nodules in Pavetta and non-nodulating bacteria in the intercellular spaces between mesophyll cells in Fadogia and Vangueria.
Isolation and analyses of these endophytes reveal the presence of Burkholderia bacteria in all the plant species implicated in gousiekte. Although the nodulating and non-nodulating bacteria belong to the same genus, they are phylogenetically not closely related and even fall in different bacterial clades. Pavetta harborii and Pavetta schumanniana have their own specific endophyte--Candidatus Burkholderia harborii and Candidatus Burkholderia schumanniana--while the non-nodulating bacteria found in the other gousiekte-inducing plants show high similarity to Burkholderia caledonica. In this group, the bacteria are host specific at population level. Investigation of gousiekte-inducing plants from other African countries resulted in the discovery of the same endophytes. Several other plants of the genera Afrocanthium, Canthium, Keetia, Psydrax, Pygmaeothamnus and Pyrostria were tested and were found to lack bacterial endophytes.
The discovery and identification of Burkholderia bacteria in gousiekte-inducing plants open new perspectives and opportunities for research not only into the cause of this economically important disease, but also into the evolution and functional significance of bacterial endosymbiosis in Rubiaceae. Other South African Rubiaceae that grow in the same area as the gousiekte-inducing plants were found to lack bacterial endophytes which suggests a link between bacteria and gousiekte. The same bacteria are consistently found in gousiekte-inducing plants from different regions indicating that these plants will also be toxic to ruminants in other African countries.
南非 Fadogia、Pavetta 和 Vangueria 属植物（均属于茜草科）被认为会引起“gousiekte”（字面意思是“快速疾病”），这是一种致命的反刍动物心脏中毒，在摄入后四到八周会出现急性心力衰竭。值得注意的是，所有这些植物的叶子中都含有内生菌：Pavetta 中具有特殊结节的固氮细菌和 Fadogia 和 Vangueria 中在叶肉细胞之间的细胞间隙中的非固氮细菌。
对这些内生菌的分离和分析表明，在所有与“gousiekte”有关的植物物种中都存在 Burkholderia 细菌。尽管固氮和非固氮细菌属于同一属，但它们在系统发育上没有密切关系，甚至属于不同的细菌进化枝。Pavetta harborii 和 Pavetta schumanniana 有其自身特定的内生菌——候选 Burkholderia harborii 和候选 Burkholderia schumanniana——而在其他引起“gousiekte”的植物中发现的非固氮细菌与 Burkholderia caledonica 高度相似。在这个群体中，细菌在种群水平上具有宿主特异性。对来自其他非洲国家的引起“gousiekte”的植物的调查导致发现了相同的内生菌。还测试了 Afrocanthium、Canthium、Keetia、Psydrax、Pygmaeothamnus 和 Pyrostria 属的其他几种植物，发现它们缺乏细菌内生菌。
在引起“gousiekte”的植物中发现和鉴定 Burkholderia 细菌不仅为研究这种具有重要经济意义的疾病的原因开辟了新的视角和机会，而且为茜草科内生细菌的进化和功能意义开辟了新的视角和机会。在与引起“gousiekte”的植物生长在同一地区的其他南非茜草科植物中发现它们缺乏细菌内生菌，这表明细菌与“gousiekte”之间存在联系。在来自不同地区的引起“gousiekte”的植物中始终发现相同的细菌，这表明这些植物也会对其他非洲国家的反刍动物有毒。
