Unveiling the physiological and metabolic interactions of bacterial diversity in the root and rhizosphere of Nauclea officinalis using an in-vitro and in-silico hybrid bioinformatics approach

This paper analyzed the bacterial diversity in the root and rhizospheric soil of wild Nauclea officinalis in Yinggeling Nature Reserve, Hainan Province, China, and explored the relationship between the nitrogen-fixing and nitrogen-promoting bacteria in root and the strictosamide content in the stem and leaf of this plant. High-throughput sequencing techniques combined with related in-silico bioinformatics were employed to study the microbial community structure of bacterial flora. HPLC analysis revealed the tissue-dependent strictosamide content in the stem and leaf of the plant. The results recorded a total of 1360175 effective sequences from the root and rhizospheric soil samples, which were divided into 4279 OUTs. Endophytic bacterial species were classified into 36 phyla, 102 classes, 202 orders, 316 families and 558 genera, indicating an extremely rich bacterial community and highly complex ecological interactions. According to the community structural analysis, the dominant species of the root endophytic bacteria were Paraburkholderia (11.33%), Chloroplast_ unclassified (7.34%), Bacillus (6.86%), Azorhizobium (5.57%) and Stenotrophomonas (5.29%); the dominant rhizospheric bacteria species were Subgroup (19.79%), Acidobacteriales (7.17%) and Gemmataceae (5.96%). The content of strictosamide in the stem and leaf samples was different, which was positively correlated with the composition and abundance of some nitrogen-fixing and nitrogen-promoting bacteria in the plant root. The results will improve understanding of bacterial ecological diversity and their physiological impacts on plant metabolism and provide theoretical basis for the green planting of N. officinalis.