Mortierellaceae species are among the most frequent and globally distributed soil fungi. However, the factors shaping their diversity and distribution remain obscure. Several species have been reported to be associated to bacteria, but the kind and frequency of such associations were not addressed up to now. We hypothesized that such associations could be important for Mortierellaceae ecology. Therefore, our aim was to understand the driving factors responsible for the Mortierellaceae diversity, community composition and bacterial associations in alpine and subalpine habitats. For answering our question, we collected both snow-free and snow-covered soil at sampling sites from different habitats: bare alpine soil in a glacier forefield, alpine dwarf-willow habitats, and high-altitude Pinus cembra forests. The isolations were carried out by direct cultivation without any antibiotics to the isolation media. Altogether, we obtained 389 Mortierellaceae isolates representing 29 operational taxonomic units (OTUs). Many OTUs could be placed to the genera Mortierella sensu stricto, Dissophora, Entomortierella, Gamsiella, Linnemannia, and Podila, but others could not unambiguously be assigned to a genus. Our results demonstrate that both, the distribution as well as the diversity of the Mortierellaceae species, were significantly influenced by habitat, soil pH, and snow-cover. We noticed that >30% of our isolates were associated to a non-contaminant bacterium. The bacteria associated to our Mortierellaceae isolates belonged to seven different genera. Pseudomonas was the most frequently detected genus associated to the isolated Mortierellaceae species and found to be species-specific. Mortierellaceae-bacteria pairs, including those with Pseudomonas, were influenced by location, habitat, and snow-cover. The majority of the bacteria-fungus associations were epihyphal, but we also detected potential endohyphal bacterial species belonging to Mycoavidus, Burkholderiaceae, and Paraburkholderia. Taken together, the non-random associations we detected suggest that bacteria-fungus associations are ecologically meaningful – an interesting path that needs to be investigated further.

中文翻译：

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栖息地、积雪和土壤 pH 值影响被孢霉属物种的分布和多样性及其与细菌的关联

Mortierellaceae 物种是最常见和全球分布的土壤真菌之一。然而，影响其多样性和分布的因素仍然模糊不清。据报道，有几种物种与细菌有关，但到目前为止还没有解决这种关联的种类和频率。我们假设这种关联对被孢霉科生态学可能很重要。因此，我们的目标是了解导致高山和亚高山栖息地被孢霉科多样性、群落组成和细菌关联的驱动因素。为了回答我们的问题，我们在来自不同栖息地的采样点收集了无雪和雪覆盖的土壤：冰川前场的裸露高山土壤、高山矮柳栖息地和高海拔松树林。分离是通过直接培养进行的，分离培养基中没有任何抗生素。我们总共获得了代表 29 个操作分类单位 (OTU) 的 389 株被孢霉菌株。许多 OTU 可以归入狭义被孢霉属、Dissophora、内被孢霉属、Gamsiella、Linnemannia 和 Podila 属，但其他的不能明确地归入一个属。我们的结果表明，被孢霉科物种的分布和多样性都受到栖息地、土壤 pH 值和积雪的显着影响。我们注意到 > 30% 的分离株与非污染细菌有关。与我们的被孢霉分离株相关的细菌属于七个不同的属。假单胞菌是与分离的被孢霉科物种相关的最常检测到的属，并且发现具有物种特异性。Mortierellaceae-细菌对，包括那些假单胞菌，受位置、栖息地和积雪的影响。大多数细菌-真菌关联是表生菌丝，但我们也检测到属于支链丝菌属、伯克霍尔德菌科和帕拉伯克霍尔德菌属的潜在内菌丝菌种。综上所述，我们检测到的非随机关联表明细菌-真菌关联具有生态意义——这是一条需要进一步研究的有趣路径。但我们也检测到属于支链杆菌、伯克霍尔德菌科和帕拉伯克霍尔德菌属的潜在内菌丝菌种。综上所述，我们检测到的非随机关联表明细菌-真菌关联具有生态意义——这是一条需要进一步研究的有趣路径。但我们也检测到属于支链杆菌、伯克霍尔德菌科和帕拉伯克霍尔德菌属的潜在内菌丝菌种。综上所述，我们检测到的非随机关联表明细菌-真菌关联具有生态意义——这是一条需要进一步研究的有趣路径。