Diversity and Spatiotemporal Distribution of Fungal Endophytes Associated with Salvia multicaulis

Diversity of endophytic bacteria in Paris Polyphylla var. yunnanensis and their correlation with polyphyllin content

BACKGROUND

Paris polyphylla var. yunnanensis (PPY) is commonly used in traditional Chinese medicine formulas and folk families. Nearly more than 100 chemical substances with medicinal values have been reported in PPY, among which steroidal saponins are the main active components. Due to its long growth cycle, the resource of PPY has become too scarce, and the current production capacity of PPY is still far from meeting the market demand. Numerous studies have shown that endophytic bacteria not only promote the production of secondary metabolites in the host plant, but some of them are also able to produce the same secondary metabolites as the host. However, little is known about the endophytic bacteria associated with PPY in different geographic conditions and tissues. In order to compare the endophytic bacterial communities associated with PPY in different geographic conditions and plant tissues, the endophytic bacteria from roots, stems, and leaves of PPY collected from five locations were isolated, and the diversity, richness, and homogeneity of bacterial communities were analyzed, and the dominant genera correlation with polyphyllin content was further investigated.

RESULTS

A total of 268 endophytic bacterial strains were isolated and identified from PPY. The experimental results showed that the isolates belonged to 5 phyla, 7 classes, 14 orders and 39 genera of bacteria, of which the dominant order was Bacillariophyta and the dominant genera were Bacillus, Pseudomonas and Agrobacterium. In general, the differences in the distribution pattern and diversity of endophytic bacteria in PPY were characterized by the highest diversity and richness index of endophytic bacterial communities in Er yuan Qisheng (QS) and the highest evenness index in Dali Fengyi (FY). The diversity, richness and evenness of bacterial communities in terms of tissue state showed a hierarchical pattern of root > stem > leaf. The three optimal genera were positively correlated with polyphyllin content.

CONCLUSION

The distribution pattern and diversity of endophytic bacteria in PPY were influenced by tissue type and habitat. In addition, three endophytic bacteria (Pseudomonas, Bacllius and Agrobacterium) were positively correlated with the content of polyphylin.

Response of endophytic fungi communities with high antioxidant capacity in riparian plants Salix variegate to water flooding

Riparian plants exhibit strong antioxidant capacity due to the constant periodic flooding and the resulted oxidative stress. The aim of this study was to determine whether the endophytes are involved in oxidative stress pathway of the host. In the study, we isolated the endophytic fungi from a shrub of Salix variegate before and after natural flooding, and characterized through taxonomical characterization of 18S ITS sequences. By means of total antioxidant capacity (TAC) method, we assessed the antioxidant activity of all isolates. Under different oxygen supply levels, a total of 115 culturable fungi were obtained from various tissues, grouped into 6 classes and 26 genera, showing abundant biodiversity. Aspergillus spp. and Penicillium spp. constituted the dominant population. However, the endophyte community was significantly affected by flooding stress. The fungi in post-flooding population were more numerous and biodiverse, especially the genus Aspergillus. The dominant genera had relatively higher activity than others whether in means or maxima, especially in the genera of Aspergillus after flooding. Our results indicated that flooding would change the population composition of endophyte strains with high antioxidant activity and enhance the antioxidant capacity of Aspergillus, which maybe conversely participate the oxidative pathway in the host.

Spatiotemporal diversity of bacterial endophyte microbiome of mandarin (Citrus reticulata) in the northern Persian Gulf and its HCN production and N2 fixation

Endophytes are symbionts that live in healthy plants and potentially improve the health of plant holobionts. Here, we investigated the bacterial endophyte community of Citrus reticulata grown in the northern Persian Gulf. Bacteria were isolated seasonally from healthy trees (root, stem, bark, trunk, leaf, and crown tissues) in four regions of Hormozgan province (i.e., Ahmadi, Siyahoo, Sikhoran, Roudan), a subtropical hot region in Iran. A total of 742 strains from 17 taxa, 3 phyla, and 5 orders were found, most of which belonged to Actinobacteria (Actinobacteriales) as the dominant group, followed by Firmicutes (Bacillales), Proteobacteria (Sphingomonadales, Rhizobiales), and Cyanobacteria (Synechoccales). The genera included Altererythrobacter, Arthrobacter, Bacillus, Cellulosimicrobium, Curtobacterium, Kocuria, Kytococcus, Methylopila, Mycobacterium, Nocardioides, Okiabacterium, Paracraurococcus, and Psychrobacillus. The most frequently occurring species included Psychrobacillus psychrodurans, Kytococcus schroetri, and Bacillus cereus. In addition, the overall colonization frequency and variability of endophytes were higher on the trunks. The leaves showed the lowest species variability in all sampling periods. The frequency of endophyte colonization was also higher in summer. The Shannon-Wiener (H') and Simpson indices varied with all factors, i.e., region, season, and tissue type, with the maximum in Roudan. Furthermore, 52.9% of the strains were capable of nitrogen fixation, and 70% produced antagonistic hydrogen cyanide (HCN). Thus, C. reticulata harbors a variety of bioactive bacterial endophytes that could be beneficial for host fitness in such harsh environments.

Biotransformation of Sclareol by a Fungal Endophyte of Salvia sclarea

Microbial endophytes are known as versatile producers of useful metabolites, which have extensive applications in pharmacy, fragrance, agriculture and food. This study aims to screen sclareol-biotransforming microorganisms from Salvia sclarea, an untapped source of diverse endophytes. In this study, 50 culturable endophytes were isolated from S. sclarea grown in Xinjiang using sclareol as the sole carbon source and screened for their potential to transform sclareol into analogues. A fungal endophyte, identified as the generally recognized as safe (GRAS) strain Aspergillus tubingensis, can produce labd-14-ene-3β,8α,13β-triol and 8α,13β-dihydroxylabd-14-en-3-one from sclareol, involving hydroxylation and carbonylation at the C3 site. Structures of the two metabolites were elucidated by HR-ESI-MS and NMR analysis. S. sclarea was proven to be a good source of endophytes that are prospective producers of secondary metabolites with valuable chemical and biological properties. This study is the first report regarding the isolation of endophytes from S. sclarea.

Seasonal Diversity and Occurrence of Filamentous Fungi in Smallholder Dairy Cattle Feeds and Feedstuffs in South Africa

This study investigated 65 (35 in summer and 30 in winter) smallholder dairy cattle feeds from Free State and Limpopo provinces in South Africa from 2018 to 2019 for fungal contamination and assessed the impacts of seasonal variation on fungal contamination levels, isolation frequency, and diversity. Samples were examined for fungal contamination using macro- and microscopic approaches, and their identities were confirmed by molecular means. A total of 217 fungal isolates from 14 genera, including Aspergillus, Fusarium, and Penicillium, were recovered from feeds from both seasons. The most prevalent fungal species recovered were A. fumigatus and P. crustosum. Mycological analyses showed that 97% of samples were contaminated with one or more fungal isolates, with the summer fungal mean level (6.1 × 103 to 3.0 × 106 CFU/g) higher than that of feeds sampled during winter (mean level: 1.1 × 103 to 4.1 × 105 CFU/g). Independent sample t-test revealed that the isolation frequencies of the genera Aspergillus and Fusarium were significantly (p ≤ 0.05) higher in summer than winter, while Penicillium prevalence in both seasons was not statistically (p > 0.05) different. Furthermore, the Shannon−Weiner diversity index (H′) revealed a higher fungal diversity in summer (H′ = 2.8) than in winter (H′ = 2.1). This study on fungal contamination could be used for future fungal control and mycotoxin risk management in South Africa.

Endophytic fungus Mucor circinelloides DF20 promote tanshinone biosynthesis and accumulation in Salvia miltiorrhiza root

As a traditional Chinese medicine, Salvia miltiorrhiza rhizome is mainly used to treat cardiovascular diseases. Symbiosis of endophytic fungi with their host plants, is an effectively regulatory means to promote the growth and secondary metabolism of medicinal plants. Here, an endophytic fungus Mucor circinelloides DF20 was co-cultivated with the sterile seedlings of S. miltiorrhiza, to clarify the promoting mechanism on tanshinone biosynthesis and accumulation in S. miltiorrhiza root. The assay of promoting-growth activities in vitro showed that DF20 have the ability to produce IAA and siderophores. DF20 could significantly promote the biosynthesis and accumulation of tanshinones in the root of S. miltiorrhiza, especially the content of tanshinone ⅡA, reaching 4.630 ± 0.342 mg/g after 56 days of DF20 treatment, which is 22-fold of the control group. The result also showed that the hyphae of M. circunelloides DF20 mainly colonized in the root tissue interspace of S. miltiorrhiza, and a small amount of hyphae were located inside the cells. The results of florescent real-time quantitative RT-PCR showed that DF20 colonization significantly increase the expression level of some key enzyme genes (DXS, DXR, HMGR, GGPPS) in tanshinone biosynthesis pathway, but the regulatory effect mainly occurred in the early stage of co-culture, while the expression level decreased in different degrees in the later stage. In conclusion, the endophytic fungus M. circunelloides DF20 can form an interaction relationship with its host, then to promote the biosynthesis and accumulation of tanshinones in root by upregulating the key enzyme genes expression levels of the biosynthesis pathway.