Section for Microbial Ecology and Biotechnology, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
State Key Laboratory of Agricultural Microbiology, Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan, China.
Appl Environ Microbiol. 2020 May 5;86(10). doi: 10.1128/AEM.02969-19.
This study investigated the effects of long-term soil fertilization on the composition and potential for phosphorus (P) and nitrogen (N) cycling of bacterial communities associated with hyphae of the P-solubilizing fungus Using a baiting approach, hyphosphere bacterial communities were recovered from three soils that had received long-term amendment in the field with mineral or mineral plus organic fertilizers. hyphae recruited bacterial communities with a decreased diversity and an increased abundance of relative to what was observed in soil communities. As core bacterial taxa, and spp. were present in all hyphosphere samples irrespective of soil fertilization. However, the type of fertilization showed significant impacts on the diversity, composition, and distinctive taxa/operational taxonomic units (OTUs) of hyphosphere communities. The soil factors P (Olsen method), exchangeable Mg, exchangeable K, and pH were important for shaping soil and hyphosphere bacterial community compositions. An increased relative abundance of organic P metabolism genes was found in hyphosphere communities from soil that had not received P fertilizers, which could indicate P limitation near the fungal hyphae. Additionally, hyphae recruited bacterial communities with a higher abundance of N fixation genes than found in soil communities, which might imply a role of hyphosphere communities for fungal N nutrition. Furthermore, the relative abundances of denitrification genes were greater in several hyphosphere communities, indicating an at least partly anoxic microenvironment with a high carbon-to-N ratio around the hyphae. In conclusion, soil fertilization legacy shapes hyphosphere microbiomes and their functional potential related to P and N cycling. P-solubilizing strains are introduced as biofertilizers to agricultural soils to improve plant P nutrition. Currently, little is known about the ecology of these biofertilizers, including their interactions with other soil microorganisms. This study shows that communities dominated by and colonize hyphae in soil and that the compositions of these communities depend on the soil conditions. The potential of these communities for N and organic P cycling is generally higher than that of soil communities. The high potential for organic P metabolism might complement the ability of the fungus to solubilize inorganic P, and it points to the hyphosphere as a hot spot for P metabolism. Furthermore, the high potential for N fixation could indicate that recruits bacteria that are able to improve its N nutrition. Hence, this community study identifies functional groups relevant for the future optimization of next-generation biofertilizer consortia for applications in soil.
本研究调查了长期土壤施肥对与溶磷真菌菌丝相关的细菌群落组成和磷（P）和氮（N）循环潜力的影响。采用诱饵法，从长期用矿物或矿物加有机肥田间改良的三种土壤中回收了菌丝体细菌群落。与土壤群落相比，菌丝体招募的细菌群落多样性降低，相对丰度增加。作为核心细菌类群，属和种存在于所有菌丝体样本中，无论土壤施肥类型如何。然而，施肥类型对菌丝体群落的多样性、组成和特有分类群/操作分类单元（OTUs）有显著影响。土壤因素 P（Olsen 法）、可交换 Mg、可交换 K 和 pH 对土壤和菌丝体细菌群落组成具有重要影响。在未施 P 肥的土壤中，发现有机 P 代谢基因的相对丰度增加，这可能表明真菌菌丝附近存在 P 限制。此外，与土壤群落相比，菌丝体招募的细菌群落具有更高的固氮基因丰度，这可能意味着菌丝体群落对真菌 N 营养具有作用。此外，在几个菌丝体群落中，反硝化基因的相对丰度更高，表明菌丝周围存在至少部分缺氧的微环境和高碳氮比。总之，土壤施肥遗留物塑造了菌丝体微生物组及其与 P 和 N 循环相关的功能潜力。溶磷菌被引入农业土壤作为生物肥料，以改善植物的 P 营养。目前，人们对这些生物肥料的生态学知之甚少，包括它们与其他土壤微生物的相互作用。本研究表明，以属和种为主的群落定殖于土壤中的菌丝体，这些群落的组成取决于土壤条件。这些群落的 N 和有机 P 循环潜力一般高于土壤群落。有机 P 代谢的高潜力可能补充真菌溶解无机 P 的能力，并指出菌丝体是 P 代谢的热点。此外，固氮潜力高可能表明真菌招募了能够改善其 N 营养的细菌。因此，这项群落研究确定了与未来优化用于土壤的下一代生物肥料联合体应用相关的功能群。
