Rhizosphere is a dynamic interface where soil, plant roots and microorganisms exchange substances. Rhizospheric actinomycetes are an important component of root actinomycetes and one of the main sources of bioactive substances. In this study, five different rhizospheric soil samples of a mangrove plant, Acanthus ilicifolius, were collected from the Dongzhaigang Mangrove Nature Reserve of Hainan province. A combination of high-throughput sequencing and traditional pure culture strategies were used to explore the diversity of the rhizospheric actinomycetes of A. ilicifolius and the potential to produce bioactive substances in the samples. The V3 to V4 regions of 16S rRNA gene in the rhizospheric samples of A. ilicifolius were sequenced and analyzed by Illumina Novaseq 6000 sequencing platform. A total of 32 phyla (including 25 effectively identified phyla) were annotated, of which Proteobacteria is the dominant phyla. α-diversity analysis showed that the rhizospheric bacterial community of A. ilicifolius was very abundant. The microbial communities of actinomycetes were analyzed, and 33 validated genera, four tentative genera and 28 uncultured new genera were noted. KEGG functional prediction analysis in different levels showed that rhizospheric actinomycetes were mainly involved in the biosynthesis of secondary metabolites including various antibiotics. Meanwhile, actinomycetes were isolated by the traditional pure culture method. After isolation, purification, morphological characteristics grouping and rearrangement, the diversity of actinomycetes of mangrove A. ilicifolius was analyzed by PCR amplification, sequencing and comparison of 16S rRNA gene sequences. The antimicrobial activity was screened by the agar diffusion method. PCR-based gene screening technology was used to detect the possible antibiotic biosynthesis genes of the representative strains of PKS-I, PKS-II and NRPS. A total of 33 representative strains of rhizospheric actinomycetes were obtained from four genera, of which Streptomyces was the dominant genus, and 2 genera could not be detected by high-throughput sequencing method. The positive rates of NRPS and PKS-II genes of the representative strains were very high (more than 90%). 24.24% of rhizospheric actinomycetes had the activity against at least one or more indicator microorgnisms. In this study, high-throughput sequencing and traditional pure culture methods were used to show that rhizospheric actinomycetes of a mangrove plant A. ilicifolius from Dongzhaigang had a very rich actinomycetic diversity. The rhizospheric actinomyces of A. ilicifolius has good potential to synthesize secondary metabolites, which could provide rich microbial resources for the screening of bioactive compounds, and also provide an important basis for the development of subsequent new drugs.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |