Jackson Evelyn F, Echlin Haley L, Jackson Colin R
Department of Biological Sciences, Southeastern Louisiana University, Hammond, LA 70402, USA.
FEMS Microbiol Ecol. 2006 Nov;58(2):236-46. doi: 10.1111/j.1574-6941.2006.00152.x.
A combination of analyses were used to characterize the changes that occur in a bacterial community present in the phyllosphere of the epiphytic resurrection fern, Polypodium polypodioides, as the fern rehydrates from a desiccation-resistant, physiologically inactive state. Enrichment assays showed an increase in the viable count of bacteria using labile organic substrates following rainfall. Isolates obtained from enrichments were predominantly Gram-positive bacteria affiliated with various groups of the Actinobacteria and Firmicutes. In contrast, sequencing of 16S rRNA genes clones obtained from whole community DNA revealed that much of the community was dominated by other taxa, particularly the Alphaproteobacteria. Similar isolates were obtained from both dry and hydrated P. polypodioides fronds, whereas 16S rRNA gene sequencing of community DNA revealed different ribotypes on the dry and wet fern, and an overall reduction in richness following wetting. Wetting also produced changes in phyllosphere extracellular enzyme activity, with an initial burst of activity following rainfall and a subsequent burst approximately 48 h later. These findings suggest that the resurrection fern harbors a complex phyllosphere community, and that rehydration of the fern following rainfall may act as an enrichment culture stimulating certain bacterial populations and changing the overall community structure and activity.
运用多种分析方法来描述附生复活蕨（Polypodium polypodioides）叶际中存在的细菌群落的变化，该蕨类植物从抗干燥的生理非活性状态重新水化。富集试验表明，降雨后利用不稳定有机底物的细菌活菌数增加。从富集中获得的分离物主要是隶属于放线菌和厚壁菌门不同类群的革兰氏阳性菌。相比之下，从整个群落DNA中获得的16S rRNA基因克隆的测序结果显示，群落的大部分由其他分类群主导，特别是α-变形菌纲。从干燥和水化的多足蕨叶片中都获得了类似的分离物，而群落DNA的16S rRNA基因测序显示，干燥和湿润蕨类植物上的核糖体类型不同，湿润后丰富度总体降低。湿润还导致叶际胞外酶活性发生变化，降雨后活性最初激增，随后约48小时后再次激增。这些发现表明，复活蕨拥有一个复杂的叶际群落，降雨后蕨类植物的重新水化可能起到富集培养的作用，刺激某些细菌种群并改变整个群落的结构和活性。
