While previous studies on AcH 505 provided valuable information on its interactions with the host plant and ectomycorrhizal

fungi, they were all based on in vitro experiments; to date, no studies on its effects in soil have been conducted. The discovery of bacteria that promote the establishment and maintenance PLX3397 of mycorrhizas triggered a search for their mechanisms of actions, and a number of publications have described in vitro experiments on MHB-fungus interactions, e.g. [5, 20, 22]. However, much remains to be learned about how MHB-fungus interactions work under natural conditions and how they are affected by the host plant [4]. We therefore investigated the growth responses of AcH 505 and the mycorrhizal fungus Piloderma croceum using a soil-based culture system that was established for studying multitrophic interactions in oaks as part of the TrophinOak collaborative project [23], see also http://​www.​trophinoak.​de. The pedunculate oak Quercus robur belongs to the Fagaceae family and is obligately ectomycorrhizal under natural conditions. It is host to several symbiotic fungi, including both basidio- and ascomycete species [24]. One of its notable symbiont is Piloderma croceum, which has become a model fungus for studying the formation of oak mycorrhizas [25]. In a preliminary investigation,

we observed that AcH 505 promotes the formation of mycorrhizas in oak microcosms. The number of mycorrhizas per microcosm was counted CFTRinh-172 prior to harvesting and was found to be slightly increased by inoculation with AcH 505 according to the test of equal proportions (p = 0.05). The study conducted herein was conducted to assess i) whether the effects of Streptomyces sp. AcH 505 and the ectomycorrhizal fungus Piloderma croceum on one-another depend on the presence of a host plant, ii) the possible influence of the microbial community on both Isotretinoin micro-organisms and iii) how the two micro-organisms influence each other. For this purpose, AcH 505 and P. croceum were cultivated alone and together under four different culture conditions: in the presence of both the host plant (Q. robur) and soil microbes (represented by a

microbial filtrate), in the presence of the host but not soil microbes, in the presence of soil microbes but no host plant, and in the presence of neither soil microbes nor the host. In microcosms including the plant rhizosphere as well as bulk soil samples were taken for quantification analysis. The experimental setup is summarised in Additional file 1. The abundances of AcH 505 and P. croceum mycelia were estimated by quantitative real-time PCR [26]. Primers were CYT387 clinical trial designed to target an intergenic region of the AcH 505 genome, between the gyrA and gyrB genes. The abundance of eukaryotes in environmental samples can be determined using qPCR experiments targeting the highly variable internal transcribed spacer (ITS) regions of rDNA operons [27, 28].