Influence of tissue and geographic locality on culturable endophytic bacteria of Atractylodes macrocephala

The endophytic bacterial community and their diversity are closely related to the host’s growth and development. This paper explores the culturable endophytic bacteria in the stems, leaves, roots and rhizomes of Atractylodes macrocephala (AM) of four localities (Yuqian, Wenxian, Pan’an and Pingjiang) and the potential correlation between the bacteria and plant bioactive compounds. A total of 118 endophytic bacteria belonging to 3 phyla, 5 classes, 11 orders, 26 families and 48 genera were isolated and identified from the four AM tissues. Among them, Bacillus was the dominant genus. In AM, the tissue type and locality influenced the endophytic bacterial community. Approximately 29.7 and 28.8% of the endophytic bacteria exhibited tissue specificity and geographic specificity, respectively. Furthermore, high-performance liquid chromatography revealed that the sesquiterpenoid (atractylenolide I, atractylenolide Ⅱ and atractylon) content was more in the rhizomes of Wenxian than in those of Pingjiang, Yuqian and Pan’an. The multiple linear regression was used to screen the bacterial strains related to the bioactive compounds of AM. The relative frequency of Microbacterium positively correlated with atractylenolide I and atractylon content in AM but negatively correlated with atractylenolide Ⅱ content. The study also provides a theoretical framework for future research on endophytic bacteria as alternative sources of secondary plant metabolites.

Composition and Diversity Of Endophytic Bacterial Community in Seeds of Upland Rice Resources from Different Origin Habitats in China

Upland rice has the characteristics of strong drought tolerance and wide adaptability. Cultivating upland rice with high yield and high quality can solve the contradiction between food shortage, water shortage, and population increase in countries all over the world, and is of great significance to the sustainable development of agriculture. In this study, high-throughput sequencing technology based on the Illumina Miseq platform was used to investigate the structure and diversity of endophytic bacterial communities using 12 upland rice variety seeds from different areas in Yunnan Province of China as materials. This study aims to reveal the "core microbiota" of the endophytic bacteria in upland rice seeds in the Yunnan Province of China by examining their diversity and community structures. The results showed that 39 endophytic OTUs were found to coexist in all samples. At the phylum level, the first dominant phyla in the 12 seed samples were Proteobacteria (66.92-99.98%). At the genus level, Pantoea (9.75-99.24%), Pseudomonas (0.11-37.24%), Curtobacterium (0.01-19.90%), Microbacterium (0.01-14.95%), Methylobacterium (0.40-5.86%), Agrobacterium (0.01-4.53%), Sphingomonas (0.04-1.56%), Aurantimonas (0.01-1.45%) and Rhodococcus (0.11-1.09%) served as the dominant genera that coexisted in all the upland rice seeds tested and represent the core microbiota in upland rice seeds. Through the correlation analysis with upland rice habitat environmental factors, the effects of climate and altitude on the structure and diversity of endophytic bacterial community in upland rice seeds were further revealed. The results showed that environmental factors such as temperature, precipitation and altitude have great influences on the structure of endophytic bacterial community in upland rice seeds. This study is of great significance to explore the relationship between upland rice and its endophytic bacteria and to tap the resources of drought-tolerant bacteria to improve the yield of local upland rice.

Flavonoids Modulate Bacterial Endophyte Communities of Ginkgo Biloba Leaves

Plant-specialized secondary metabolites have ecological functions in mediating interactions between plants and their entophytes. Here, we aimed to reveal the interaction between flavonoid synthesis and endophytic bacterial communities in wild Ginkgo trees spanning 100-800 years. We found that flavonoids including quercetin, kaempferol and isorhamnetin decreased while the microbial diversity in leaves increased with the age of sampled trees. Older trees had more unique genera and shifted their endophytic bacterial community structure. Also, Mantel tests and correlation analysis indicated a generally significant (p < 0.05) negative correlation between endophytic bacterial communities and flavonoids. Additionally, both deterministic and stochastic processes could play roles in the assembly of endophytic bacterial communities in Ginkgo trees with a progressive increase in stochastic processes as flavonoid concentrations decreased. This study provides a mechanistic understanding of how flavonoids modulate the endophytic microbial community assembly.

Insights into the endophytic bacterial community comparison and their potential role in the dimorphic seeds of halophyte Suaeda glauca

Background Seed dimorphism has been thought to be a bet-hedging strategy that helps plants survive in the disturbed environment and has been widely studied for its ecological adaptation mechanism. Many studies showed that seed-associated microorganisms play an important role in enhancing plant fitness, but information regarding endophytic bacteria associated with dimorphic seeds is limited. This study explores the influence of seed coat structure and seed phytochemical properties on the community composition and diversity of endophytic bacteria of dimorphic seeds of Suaeda glauca. In this study, we used 16S rRNA high-throughput gene sequencing method to compare the community composition and bacterial diversity between brown and black seeds of Suaeda glauca. Results A significant difference was observed in seed coat structure and phytochemical properties between brown and black seeds of S. glauca. Total 9 phyla, 13 classes, 31 orders, 53 families, 102 genera were identified in the dimorphic seeds. The dominant phyla were Proteobacteria, Firmicutes, and Actinobacteria. The results showed that seed dimorphism had little impact on the diversity and richness of endophytic bacterial communities but significantly differs in the relative abundance of the bacterial community between brown and black seeds. At the phylum level, Actinobacteria tend to be enriched significantly in brown seeds. At the genus level, Rhodococcus, Ralstonia, Pelomonas and Bradyrhizobium tend to be enriched significantly in brown seeds, while Marinilactibacillus was mainly found in black seeds. Besides, brown seeds harbored a large number of bacteria with plant-growth-promoting traits, whereas black seeds presented bacteria with enzyme activities (i.e., pectinase, cellulolytic and xylanolytic activities). Conclusion The endophytic bacterial community compositions were significantly different between dimorphic seeds of Suaeda glauca, and play an important role in the ecological adaptation of dimorphic seeds by performing different biological function roles. The endophytic bacterial communities of the dimorphic seeds may be influenced mainly by the seed coat structureand partly by the seed phytochemical characteristics. These findings provide valuable information for better understanding of the ecological adaptation strategy of dimorphic seeds in the disturbed environment.

Composition and Diversity of Endophytic Bacterial Community in Seeds of Upland Rice Resources from Different Origin Habitats in Yunnan Province of China

Upland rice has the characteristics of strong drought tolerance and wide adaptability. Cultivating upland rice with high yield and high quality can solve the contradiction between food shortage, water shortage, and population increase in countries all over the world, and is of great significance to the sustainable development of agriculture. This study aims to reveal the "core microbiota" of the endophytic bacteria in upland rice seeds in the Yunnan Province of China by examining their diversity and community structures. Through the correlation analysis with upland rice habitat environmental factors, the effects of climate and altitude on the structure and diversity of endophytic bacterial community in upland rice seeds were further revealed. In this study, high-throughput sequencing technology based on the Illumina Miseq platform was used to investigate the structure and diversity of endophytic bacterial communities using 12 upland rice variety seeds from different areas in Yunnan Province of China as materials. Here, 39 endophytic OTUs (0.68%) were found to coexist in all samples. At the phylum level, the first dominant phyla in the 12 seed samples were Proteobacteria (66.92–99.98%). At the genus level, Pantoea (9.75–99.24%), Pseudomonas (0.11–37.24%), Curtobacterium (0.01–19.90%), Microbacterium (0.01–14.95%), Methylobacterium (0.40–5.86%), Agrobacterium (0.01–4.53%), Sphingomonas (0.04–1.56%), Aurantimonas (0.01–1.45%) and Rhodococcus (0.11–1.09%), which represent the core microbiota in upland rice seeds, served as the dominant genera that coexisted in all the upland rice seeds tested. Environmental factors such as temperature, precipitation and altitude have great influences on the structure of endophytic bacterial community in upland rice seeds. This study is of great significance to explore the relationship between upland rice and its endophytic bacteria and to tap the resources of drought-tolerant bacteria to improve the yield of local upland rice.