Diversity of bacterial endophyte in Eucalyptus clones and their implications in water stress tolerance

The mango bacterial black spot altered the endophyte community structure and diversity

Mango bacterial black spot is a major disease limiting mango production, which is now causing increasingly severe economic losses. In this study, we analyzed the differences in the composition and structure of bacterial and fungal communities in the pulp and leaves between the healthy mangoes of variety Kate and those affected by bacterial black spot, and attempted to explore potential biocontrol microorganisms for mangoes. The results showed there existed significant differences in microbial communities, the bacterial Stenotrophomonas, Curtobacterium, Massilia and fungous Penicillium, Alternaria, Aureobasidiu showed great abundance both in pulps and leaves. Some potential pathogenic bacteria, such as Pseudomonas, Xanthomonas, and Burkholderia, were also significantly enriched in the infected groups. In both the infected and healthy groups, the overall community structure of endophytic bacteria and fungi within the same organs was more similar, indicating that the composition of endophytes is organ-specific. After infection, the abundance of the potential probiotic bacterium class Paenibacillus was significantly increased both in leaves and pulp, suggesting that the pathogen invasion stimulated the defense systems of endophytes. Presumably, these Paenibacillus might be developed as defense bacteria for black spot as well as other plant diseases.

Biological functions of endophytic bacteria in Robinia pseudoacacia 'Hongsen'

Introduction

Endophytes and their host plants have co-evolved for a very long time. This relationship has led to the general recognition of endophytes as a particular class of microbial resources. R. pseudoacacia 'Hongsen' is drought- and barren-resistant species that can be grown in both the north and south of China, efficiently addresses the ecological issues caused by China's 'southern eucalyptus and northern poplar. Up to date, cultured-dependent studies are available for the R. pseudoacacia nitrogen-fixing and other endophytes. Therefore, the present research studied the R. pseudoacacia 'Hongsen,' microbiome in detail by high-throughput sequencing and culture dependant.

Methods

This study examined microbial species and functional diversity in Robinia pseudoacacia 'Hongsen' using culture-dependent (isolation) and culture-independent techniques.

Results

A total of 210 isolates were isolated from R. pseudoacacia 'Hongsen.' These isolates were clustered into 16 groups by the In Situ PCR (IS-PCR) fingerprinting patterns. 16S rRNA gene sequence analysis of the representative strain of each group revealed that these groups belonged to 16 species of 8 genera, demonstrating the diversity of endophytes in R. pseudoacacia 'Hongsen'. 'Bacillus is the most prevalent genus among all the endophytic bacteria. High-throughput sequencing of endophytic bacteria from R. pseudoacacia 'Hongsen' of the plant and the rhizosphere soil bacteria showed that the bacterial populations of soil near the root, leaf, and rhizosphere differed significantly. The microbial abundance decreased in the endophytes as compared to the rhizosphere. We observed a similar community structure of roots and leaves. With and without root nodules, Mesorhizobium sp. was significantly different in R. pseudoacacia 'Hongsen' plant.

Discussion

It was predicted that R. pseudoacacia 'Hongsen' plant endophytic bacteria would play a significant role in the metabolic process, such as carbohydrate metabolism, amino acid metabolism, membrane transport, and energy metabolism.

Deciphering the role of non-Frankia nodular endophytes in alder through in vitro and genomic characterization

Endophytic bacterial populations are well-positioned to provide benefits to their host plants such as nutrient acquisition and plant hormone level manipulation. Actinorhizal plants such as alders are well known for their microbial symbioses that allow them to colonize harsh environments whether natural or anthropized. Although the nitrogen-fixing actinobacterium Frankia sp. is the main endophyte found in alder root nodules, other bacterial genera, whose roles remain poorly defined, inhabit this niche. In this study, we isolated a diverse panel of non-Frankia nodular endophytes (NFNE). Some NFNE were isolated from alders grown from surface-sterilized seeds and maintained in sterile conditions, suggesting these may have been seed-borne. In vitro testing of 24 NFNE revealed some possessed putative plant growth promotion traits. Their genomes were also sequenced to identify genes related to plant growth promotion traits. This study highlights the complexity of the alder nodular microbial community. It paves the way for further understanding of the biology of nodules and could help improve land reclamation practices that involve alders.

Microbial Community, Metabolic Potential and Seasonality of Endosphere Microbiota Associated with Leaves of the Bioenergy Tree Paulownia elongata × fortunei

The microbial structure and metabolic function of plant-associated endophytes play a key role in the ecology of various environments, including trees. Here, the structure and functional profiles of the endophytic bacterial community, associated with Paulownia elongata × fortunei, in correlation with seasonality, were evaluated using Biolog EcoPlates. Biolog EcoPlates was used to analyse the functional diversity of the microbiome. The total communities of leaf endophyte communities were investigated using 16S rRNA V5–V7 region amplicon deep sequencing via Illumina MiSeq. Community level physiological profiling (CLPP) analysis by the Biolog EcoPlate™ assay revealed that the carboxylic acids (19.67–36.18%) and amino acids (23.95–35.66%) were preferred by all by all communities, whereas amines and amides (0.38–9.46%) were least used. Seasonal differences in substrate use were also found. Based on the sequencing data, mainly phyla Proteobacteria (18.4–97.1%) and Actinobacteria (2.29–78.7%) were identified. A core microbiome could be found in leaf-associated endophytic communities in trees growing in different locations. This work demonstrates the application of Biolog EcoPlates in studies of the functional diversity of microbial communities in a niche other than soil and shows how it can be applied to the functional analyses of endomicrobiomes. This research can contribute to the popularisation of Biolog EcoPlates for the functional analysis of the endomicrobiome. This study confirms that the analysis of the structure and function of the plant endophytic microbiome plays a key role in the health control and the development of management strategies on bioenergy tree plantations.

Niche specificity and functional diversity of the bacterial communities associated with Ginkgo biloba and Panax quinquefolius

Plant-associated bacteria can establish mutualistic relationships with plants to support plant health. Plant tissues represent heterogeneous niches with distinct characteristics and may thus host distinct microbial populations. The objectives of this study are to investigate the bacterial communities associated with two medicinally and commercially important plant species; Ginkgo biloba and Panax quinquefolius using high Throughput Sequencing (HTS) of 16S rRNA gene, and to evaluate the extent of heterogeneity in bacterial communities associated with different plant niches. Alpha diversity showed that number of operational taxonomic units (OTUs) varied significantly by tissue type. Beta diversity revealed that the composition of bacterial communities varied between tissue types. In Ginkgo biloba and Panax quinquefolius, 13% and 49% of OTUs, respectively, were ubiquitous in leaf, stem and root. Proteobacteria, Bacteroidetes, Actinobacteria and Acidobacteria were the most abundant phyla in Ginkgo biloba while Proteobacteria, Bacteroidetes, Actinobacteria, Plantomycetes and Acidobacteria were the most abundant phyla in Panax quinquefolius. Functional prediction of these bacterial communities using MicrobiomeAnalyst revealed 5843 and 6251 KEGG orthologs in Ginkgo biloba and Panax quinquefolius, respectively. A number of these KEGG pathways were predicted at significantly different levels between tissues. These findings demonstrate the heterogeneity, niche specificity and functional diversity of plant-associated bacteria.