Decrypting phytomicrobiome of the neurotoxic actinorhizal species, Coriaria myrtifolia, and dispersal boundary of Frankia cluster 2 in soil outward compatible host rhizosphere

Tracking the trajectory of frankia research through bibliometrics: trends and future directions

Frankia represent a unique group of filamentous, sporangia-forming bacteria, renowned for their exceptional capacity to establish symbiotic partnerships with actinorhizal plants. The objective of this paper is to offer quantitative insights into the current state of frankia research and its future potential. A comprehensive bibliometric analysis covering the years 2000-2022 was conducted using Scopus and SciVal. A steady increase in both annual publication and international collaboration has been observed, particularly since 2013. Research performance metrics for the last 5 years (2018-2022) indicate China and India as leaders with high Field-Weighted Citation Impact scores. This analysis highlighted prominent authors, research groups, and the evolving research landscape, suggesting an increasing focus on molecular and genomic aspects. The genomic era has transformed our understanding of frankia biology, highlighting their significance in diverse ecological and agricultural contexts. This study comprehensively maps the evolving landscape of frankia research, emphasizing key milestones that have catalysed international interest in frankia-actinorhizal research, expanding our perception of frankia's capabilities beyond its traditional symbiotic role. As research in this field progresses, a deeper comprehension of frankia-plant interactions, symbiotic signalling, and the intricacies of metabolic pathways holds the promise of revealing innovative techniques for optimizing nitrogen fixation and broadening the spectrum of host plants.

High Frankia abundance and low diversity of microbial community are associated with nodulation specificity and stability of sea buckthorn root nodule

Introduction

Actinorhizal symbioses are gaining attention due to the importance of symbiotic nitrogen fixation in sustainable agriculture. Sea buckthorn (Hippophae L.) is an important actinorhizal plant, yet research on the microbial community and nitrogen cycling in its nodules is limited. In addition, the influence of environmental differences on the microbial community of sea buckthorn nodules and whether there is a single nitrogen-fixing actinomycete species in the nodules are still unknown.

Methods

We investigated the diversity, community composition, network associations and nitrogen cycling pathways of the microbial communities in the root nodule (RN), nodule surface soil (NS), and bulk soil (BS) of Mongolian sea buckthorn distributed under three distinct ecological conditions in northern China using 16S rRNA gene and metagenomic sequencing. Combined with the data of environmental factors, the effects of environmental differences on different sample types were analyzed.

Results

The results showed that plants exerted a clear selective filtering effect on microbiota, resulting in a significant reduction in microbial community diversity and network complexity from BS to NS to RN. Proteobacteria was the most abundant phylum in the microbiomes of BS and NS. While RN was primarily dominated by Actinobacteria, with Frankia sp. EAN1pec serving as the most dominant species. Correlation analysis indicated that the host determined the microbial community composition in RN, independent of the ecological and geographical environmental changes of the sea buckthorn plantations. Nitrogen cycle pathway analyses showed that RN microbial community primarily functions in nitrogen fixation, and Frankia sp. EAN1pec was a major contributor to nitrogen fixation genes in RN.

Discussion

This study provides valuable insights into the effects of eco-geographical environment on the microbial communities of sea buckthorn RN. These findings further prove that the nodulation specificity and stability of sea buckthorn root and Frankia sp. EAN1pec may be the result of their long-term co-evolution.