Division of Plant Ecology and Systematics, Biology Department, KU Leuven, Heverlee, Belgium.
PLoS One. 2013;8(3):e56917. doi: 10.1371/journal.pone.0056917. Epub 2013 Mar 11.
Microbial communities in floral nectar have been shown to be characterized by low levels of species diversity, yet little is known about among-plant population variation in microbial community composition.
METHODOLOGY/PRINCIPAL FINDINGS: We investigated the microbial community structure (yeasts and bacteria) in floral nectar of ten fragmented populations of the bee-pollinated forest herb Pulmonaria officinalis. We also explored possible relationships between plant population size and microbial diversity in nectar, and related microbial community composition to the distance separating plant populations. Culturable bacteria and yeasts occurring in the floral nectar of a total of 100 plant individuals were isolated and identified by partially sequencing the 16S rRNA gene and D1/D2 domains of the 26S rRNA gene, respectively. A total of 9 and 11 yeast and 28 and 39 bacterial OTUs was found, taking into account a 3% (OTU0.03) and 1% sequence dissimilarity cut-off (OTU0.01). OTU richness at the plant population level (i.e. the number of OTUs per population) was low for yeasts (mean: 1.7, range: 0-4 OTUs0.01/0.03 per population), whereas on average 6.9 (range: 2-13) OTUs0.03 and 7.9 (range 2-16) OTUs0.01 per population were found for bacteria. Both for yeasts and bacteria, OTU richness was not significantly related to plant population size. Similarity in community composition among populations was low (average Jaccard index: 0.14), and did not decline with increasing distance between populations.
CONCLUSIONS/SIGNIFICANCE: We found low similarity in microbial community structure among populations, suggesting that the assembly of nectar microbiota is to a large extent context-dependent. Although the precise factors that affect variation in microbial community structure in floral nectar require further study, our results indicate that both local and regional processes may contribute to among-population variation in microbial community structure in nectar.
已证实，花内微生物群落的物种多样性水平较低，但对于植物种群间微生物群落组成的变化知之甚少。
方法/主要发现：我们调查了 10 个分散的蜂授粉森林草本植物肺草（Pulmonaria officinalis）种群的花内微生物群落结构（酵母和细菌）。我们还探索了植物种群大小与花蜜中微生物多样性之间的可能关系，并将微生物群落组成与植物种群之间的距离相关联。通过部分测序 16S rRNA 基因和 26S rRNA 基因的 D1/D2 结构域，分别对总共 100 株植物个体的花内可培养细菌和酵母进行了分离和鉴定。考虑到 3%（OTU0.03）和 1%（OTU0.01）序列差异截断值，共发现 9 个和 11 个酵母和 28 个和 39 个细菌 OTU。在植物种群水平上的 OTU 丰富度（即每个种群的 OTU 数量）较低，酵母的平均值为 1.7（范围：0-4 个 OTU0.01/0.03/种群），而细菌的平均值分别为 6.9（范围：2-13）个 OTU0.03 和 7.9（范围：2-16）个 OTU0.01/种群。对于酵母和细菌，OTU 丰富度与植物种群大小均无显著相关性。种群间群落组成的相似性较低（平均 Jaccard 指数：0.14），且随着种群间距离的增加而没有下降。
结论/意义：我们发现种群间微生物群落结构的相似性较低，表明花蜜微生物组的组装在很大程度上取决于环境。尽管影响花内微生物群落结构变化的确切因素需要进一步研究，但我们的研究结果表明，局部和区域过程都可能导致花蜜中微生物群落结构的种群间变化。
