北部湾红树土壤真菌-细菌共生体多样性及与野生线虫生态关系研究

Diversity of fungal-bacterial symbionts in the Beibu Gulf mangrove soil and their ecological relationships with wild nematodes

关键词:  红树林, 红树土壤, 真菌-细菌共生体, 共生体多样性, 真菌内生细菌, 土壤线虫

Key words:  mangroves, mangrove soils, fungal-bacterial symbionts, symbiont diversity, fungal endophytic bacteria, soil nematodes

摘要:

为研究北部湾海域红树土壤生境真菌-细菌共生体的多样性,并探究红树土壤生境中的真菌-细菌共生体和野生线虫的生态关系,该研究采用纯培养方法对红树土壤样品进行真菌分离纯化,用细菌16S rRNA引物筛选真菌-细菌共生体并分析内共生细菌多样性,采用真菌ITS引物测序进行真菌宿主多样性分析,从红树土壤中分离野生线虫并进行鉴定分类,利用20%的发酵液探究共生体与野生线虫的生态关系。结果表明:(1)从14个红树土壤样品中分离得到50株真菌,筛选得到29对真菌-细菌共生体,内共生细菌包括伯克霍尔德菌属(Burkholderia)、泛菌属(Pantoea)、鞘氨醇单胞菌属(Sphingomonas)和普罗威登斯菌属(Providencia),其中20株属于伯克霍尔德菌属,广泛与真菌宿主形成共生,经ITS鉴定29对共生体宿主真菌隶属于2门4纲7目11科12属22种。(2)从钦州黄槿土壤来源的共生体GXIMD14377中经菌丝破碎法分离得到其内共生细菌,经16S鉴定为分散泛菌(Pantoea dispersa)。(3)从钦州黄槿土壤中分离培养得到以分散泛菌为食物的野生线虫,经分子鉴定其为秀丽隐杆线虫。(4)部分共生体发酵液对野生线虫具有拮抗作用,其中共生体GXIMD14385(Fusarium solani-Burkholderia territorii)对野生线虫的拮抗作用最强,校正死亡率为(84.25±3.61)%。此外,共生体GXIMD14377(Fusarium oxysporum-Pantoea dispersa)对野生线虫表现拮抗作用,而该野生线虫对共生细菌存在捕食关系。综上认为,北部湾海域红树具有多样性丰富的真菌-细菌共生体,红树土壤生境中的共生体、内共生细菌和野生线虫之间存在三方关系。该研究是首次针对红树林生境中的真菌-细菌共生体及其所处生境下野生线虫之间生态关系展开的研究,其结果为探究红树土壤中真菌-细菌共生相互关系与野生线虫生态关系奠定了基础。

Abstract:

To study the diversity of fungal-bacterial symbionts in the Beibu Gulf mangrove soil habitats and their ecological relationships with wild nematodes, the microbial interactions within mangrove soil habitats through a multi-methodological approach were systematically investigated. In view of this, mangrove soil samples were collected from the Beibu Gulf region, and pure culture methods were employed to isolate and purify fungal strains. The 16S rRNA primer was used to screen fungal-bacterial symbionts and analyze the diversity of endosymbiotic bacteria. The ITS primer was used to analyze fungal host diversity. The wild nematodes were isolated and identified from mangrove soil. And 20% fermentation broth was used to explore the relationship between symbionts and wild nematodes. The results were as follows:(1)A total of 50 strains of fungi were isolated from 14 mangrove soil samples, and 29 pairs fungal-bacterial symbionts were obtained. The endosymbiotic bacteria included the genera Burkholderia, Pantoea, Sphingomonas and Providencia, among which 20 strains belonged to the genus Burkholderia, which widely formed symbiosis with fungal hosts. According to the identification of ITS, 29 pairs of symbiont host fungi belonged to 2 phyla, 4 classes, 7 orders, 11 families, 12 genera and 22 species.(2)The endosymbiont bacteria were isolated from the symbiont GXIMD14377 derived from the soil of Hibiscus tiliaceus in Qinzhou via the hyphal fragmentation method and identified as Pantoea dispersa through 16S rRNA gene sequencing.(3)The wild nematodes fed on P. dispersa were isolated and cultured from the soil of Hibiscus tiliaceus in Qinzhou, and were identified as Caenorhabditis elegans.(4)It was found that fermentation broths of some symbionts exhibited antagonistic effects on wild nematodes. Among them, the symbiont GXIMD14385(Fusarium solani-Burkholderia territorii)showed the strongest antagonistic effect on wild nematodes, with an corrected mortality of(84.25±3.61)%. Furthermore, the symbiont GXIMD14377(Fusarium oxysporum-Pantoea dispersa)showed antagonistic effects on wild nematodes, which had predation relationships with symbiotic bacteria. In conclusion, the results indicate that the mangroves in the Beibu Gulf have a rich diversity of fungal-bacterial symbionts. There is a tripartite relationship exists between symbionts, endosymbiotic bacteria, and wild nematodes in the soil habitat of mangroves. This study is the first to explore the ecological relationship between fungal-bacterial symbionts and wild nematodes in mangrove habitats. This study lays the foundation for investigating the fungal-bacterial symbiotic interactions and their ecological relationships with wild nematodes in mangrove soils.