Occurrence and diversity of bacterial communities in Tuber magnatum during truffle maturation
Occurrence and diversity of bacterial communities in Tuber magnatum during truffle maturation
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DOI：
10.1111/j.1462-2920.2007.01338.x
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发表时间：
2007-09-01
影响因子：
5.1
通讯作者：
Stocchi, Vilberto
中科院分区：
文献类型：
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作者：
Barbieri, Elena;Guidi, Chiara;Stocchi, Vilberto
块茎是一种子囊菌和专性外生菌根共生体，形成伪劣的子实体，通常被称为意大利白松露。采用独立于培养物和依赖于16S rRNA基因的方法研究了与大块菌相关的细菌群落的多样性。根据含有成熟孢子的ASCI的百分比，18块松露被分成三组，代表不同程度的子囊成熟。未成熟子囊、中间子囊和成熟子囊的可培养细菌分数分别为(4.17+/-1.61)×10(7)、(2.60+/-1.22)×10(7)和(1.86+/-1.32)×10(6)cfu g(-1)。细菌总数比cfu g(-1)高两个数量级。克隆文库的测序结果表明，在筛选的771个克隆中，存在明显的α-变形杆菌(634个克隆，约占82%)，隶属于中华根瘤菌、根瘤菌和慢生根瘤菌。细菌可培养部分以伽马变形杆菌为代表(384株细菌中有210株，约占55%)，以荧光假单胞菌为主。荧光原位杂交证实α-变形杆菌(85.8%)是块菌群落的主要成分，β-变形杆菌(1.5%)、伽马变形杆菌(1.9%)、拟杆菌(2.1%)、菲米库特(2.4%)和放线菌(3%)仅占少数。分子方法使鉴定α-变形杆菌成为与巨大毛滴虫肉瘤相关的细菌成分的主要成分成为可能，而与成熟程度无关。
Tuber magnatum, an ascomycetous fungus and obligate ectomycorrhizal symbiont, forms hypogeous fruit bodies, commonly called Italian white truffles. The diversity of bacterial communities associated with T. magnatum truffles was investigated using culture-independent and -dependent 16S rRNA gene-based approaches. Eighteen truffles were classified in three groups, representing different degrees of ascocarp maturation, based on the percentage of asci containing mature spores. The culturable bacterial fraction was (4.17 +/- 1.61) x 10(7), (2.60 +/- 1.22) x 10(7) and (1.86 +/- 1.32) x 10(6) cfu g(-1) for immature, intermediate and mature ascocarps respectively. The total of bacteria count was two orders of magnitude higher than the cfu g(-1) count. Sequencing results from the clone library showed a significant presence of alpha-Proteobacteria (634 of the 771 total clones screened, c. 82%) affiliated with Sinorhizobium, Rhizobium and Bradyrhizobium spp. The bacterial culturable fraction was generally represented by gamma-Proteobacteria (210 of the 384 total strains isolated, c. 55%), which were mostly fluorescent pseudomonads. Fluorescent in situ hybridization confirmed that alpha-Proteobacteria (85.8%) were the predominant components of truffle bacterial communities with beta-Proteobacteria (1.5%), gamma-Proteobacteria (1.9%), Bacteroidetes (2.1%), Firmicutes (2.4%) and Actinobacteria (3%) only poorly represented. Molecular approaches made it possible to identify alpha-Proteobacteria as major constituents of a bacterial component associated with T. magnatum ascoma, independently from the degree of maturation.