花生根际微生物的分离及高效功能菌株筛选

【背景】花生根际分布着丰富的微生物类群，分离筛选多种功能的高效微生物是研发高效复合菌肥的基础。【目的】从花生根际土壤及根表分离微生物，分析可培养微生物的多样性，筛选高效解有机磷和无机磷、产吲哚乙酸(indole-3-acetic acid, IAA)和铁载体功能的菌株，为研发花生微生物菌肥打下基础。【方法】利用稀释涂布法，从采自山东省栖霞市、平度市、烟台市莱山区 3个样点的花生根际土、根表样品中分离微生物，基于16S rRNA基因序列对其进行系统发育分析，并通过初筛和复筛筛选高效解磷、产IAA和铁载体的菌株。【结果】共分离、纯化、保藏147株菌，其中75株分离自根际土壤，72株分离自根表样品。系统发育分析表明所有的菌分布于放线菌门(Actinomycetota)、芽孢杆菌门(Bacillota)、拟杆菌门(Bacteroidota)和假单胞菌门(Pseudomonadota)这4个门的40个属，优势属为链霉菌属(Streptomyces, 21.77%)、芽孢杆菌属(Bacillus, 16.33%)；根表样品微生物的多样性高于根际样品；共筛选到解有机磷菌株62株，短波单胞菌(Brevundimonas) YTU21021解有机磷能力最强为1.12 mg/L；解无机磷菌株31株，不动杆菌(Acinetobacter) YTU21009解无机磷能力最强为7.04 mg/L；产IAA的菌株63株，肠杆菌(Enterobacter) YTU21054产IAA量最高，达184.19 mg/L；产铁载体细菌7株，伯克氏菌(Burkholderia) YTU21051产铁载体能力最强，A_s/A_r为0.90。【结论】花生根际和根表样品中可培养微生物多样性较为丰富，本研究筛选到的高效功能菌丰富了花生根际功能微生物资源，为后续与高效根瘤菌联合研发花生复合微生物菌肥奠定了基础。

Isolation and efficient strain screening of microorganisms from peanut rhizosphere

Background] The rhizosphere soil harbors diverse microorganisms. The isolation and screening of efficient strains with different functions is the premise for the development of efficient composite microbial fertilizers. Objective] To isolate microorganisms from the rhizosphere soil and root surface of peanut and screen out efficient strains with organic and inorganic phosphorus-solubilizing, indole-3-acetic acid (IAA)-producing, and siderophore-producing functions, so as to lay a foundation for the research and development of microbial fertilizers for peanut. Methods] The dilution-plate coating method was employed to isolate the microorganisms from the peanut rhizosphere soil and root surface samples collected from Qixia City, Pingdu City, and Laishan district of Yantai City in Shandong Province. The microorganisms were identified by the phylogenetic analysis based on the 16S rRNA gene sequences. The strains with efficient organic and inorganic phosphorus-solubilizing, IAA-producing, and siderophore-producing functions were obtained through primary and secondary screening. Results] A total of 147 strains were isolated, purified, and preserved in this study, including 75 strains isolated from the rhizosphere soil samples and 72 strains from the root surface samples. The isolates belonged to 40 genera of 4 phyla including Actinomycetota, Bacillota, Bacteroidota, and Pseudomonadota. Streptomyces (21.77%) and Bacillus (16.33%) were the dominant genera. The root surface samples had higher alpha diversity of microbial community than the rhizosphere samples. Among the 62 strains with organic phosphorus-solubilizing ability, Brevundimonas sp. YTU21021 showed the highest activity of 1.12 mg/L. Among the 31 strains with inorganic phosphorus-solubilizing ability, Acinetobacter sp. YTU21009 showed the highest activity of 7.04 mg/L. Among the 63 strains that could produce IAA, Enterobacter sp. YTU21054 showed the highest yield of 184.19 mg/L. Among the 7 strains capable of producing siderophores, Burkholderia sp. YTU21051 presented the highest efficiency with the A_s/A_r ratio of 0.9. Conclusion] There are diverse culturable microorganisms in the rhizosphere and root surface samples of peanut. The efficient functional strains obtained in this study enrich the functional microbial resources in peanut rhizosphere and lay a foundation for the development of composite microbial fertilizers with efficient rhizobia for peanut.