Ji-Hong Jiang

Biodiversity, bioactive natural products and biotechnological potential of plant-associated endophytic actinobacteria

Endophytic actinobacteria, which exist in the inner tissues of living plants, have attracted increasing attention among taxonomists, ecologists, agronomists, chemists and evolutionary biologists. Numerous studies have indicated that these prolific actinobacteria appear to have a capacity to produce an impressive array of secondary metabolites exhibiting a wide variety of biological activity, such as antibiotics, antitumor and anti-infection agents, plant growth promoters and enzymes, and may contribute to their host plants by promoting growth and enhancing their ability of withstanding the environmental stresses. These microorganisms may represent an underexplored reservoir of novel species of potential interest in the discovery of novel lead compounds and for exploitation in pharmaceutical, agriculture and industry. This review focuses on new findings in the isolation methods, bio- and chemical diversity of endophytic actinobacteria and reveals the potential biotechnological application. The facing problems and strategies for biodiversity research and bioactive natural products producing are also discussed.

Abundant and diverse endophytic actinobacteria associated with medicinal plant Maytenus austroyunnanensis in Xishuangbanna tropical rainforest revealed by culture‐dependent and culture‐independent methods

Endophytes are now considered as an important component of biodiversity. However, the diversity of endophytic actinobacteria associated with tropical rainforest native medicinal plants is essentially unknown. In this study, the diversity of endophytic actinobacteria residing in root, stem and leaf tissues of medicinal plant Maytenus austroyunnanensis collected from tropical rainforest in Xishuangbanna, China was investigated with a combination of cultivation and culture-independent analysis on the basis of 16S rRNA gene sequencing. By using different selective isolation media and methods, a total of 312 actinobacteria were obtained, and they were affiliated with the order Actinomycetales (distributed into 21 genera). Based on a protocol for endophytes enrichment, three 16S rRNA gene clone libraries were constructed and 84 distinct operational taxonomic units were identified and they distributed among the orders Actinomycetales and Acidimicrobiales, including eight suborders and at least 38 genera with a number of rare actinobacteria genera. Phylogenetic analysis showed that 32% of the clones in the libraries had lower than 97% similarities with related type strains. Interestingly, six genera from the order Actinomycetales and uncultured clones from Acidimicrobiales have not, to our knowledge, been previously reported as endophytes. Our study confirms abundant endophytic actinobacterial consortium in tropical rainforest native plant and suggests that this special habitat represents an underexplored reservoir of diverse and novel actinobacteria of potential interest for bioactive compounds discovery.

Synthesis and in vitro antifungal efficacy of oleoyl-chitosan nanoparticles against plant pathogenic fungi

An antifungal dispersion system was prepared by oleoyl-chitosan (O-chitosan) nanoparticles, and the antifungal activity against several plant pathogenic fungi was investigated. Under scanning electron microscopy, the nanoparticles formulation appeared to be uniform with almost spherical shape. The particle size of nanoparticles was around 296.962 nm. Transmission electron microscopy observation showed that nanoparticles could be well distributed in potato dextrose agar medium. Mycelium growth experiment demonstrated that Nigrospora sphaerica, Botryosphaeria dothidea, Nigrospora oryzae and Alternaria tenuissima were chitosan-sensitive, while Gibberella zeae and Fusarium culmorum were chitosan-resistant. The antifungal index was increased as the concentration of nanoparticles increased for chitosan-sensitive fungi. Fatty acid analyses revealed that plasma membranes of chitosan-sensitive fungi were shown to have lower levels of unsaturated fatty acid than chitosan-resistant fungi. Phylogenetic analysis based on ITS gene sequences indicated that two chitosan-resistant fungi had a near phylogenetic relationship. Results showed that O-chitosan nanoparticles could be a useful alternative for controlling pathogenic fungi in agriculture.

Pseudonocardia tropica sp. nov., an endophytic actinomycete isolated from the stem of Maytenus austroyunnanensis

A novel strain, designated YIM 61452(T), was isolated from the stem of Maytenus austroyunnanensis collected from the tropical rainforest of Xishuangbanna, Yunnan Province, south-west China. The strain was characterized taxonomically by using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YIM 61452(T) belonged to the genus Pseudonocardia and was most closely related to Pseudonocardia alni IMSNU 20049(T) (99.5 %), Pseudonocardia antarctica DVS 5a1(T) (99.5 %) and Pseudonocardia carboxydivorans Y8(T) (99.4 %). The chemotaxonomic properties of strain YIM 61452(T), for example MK-8(H(4)) as the predominant quinone system and iso-C(16 : 0) and iso-C(16 : 1) H as the major fatty acids, were also consistent with its classification within the genus Pseudonocardia. Strain YIM 61452(T) could be differentiated from closely related species of the genus Pseudonocardia by phenotypic and genotypic analysis. DNA-DNA hybridization experiments between strain YIM 61452(T) and closely related reference strains further confirmed that strain YIM 61452(T) represented a novel taxon of the genus Pseudonocardia. Therefore, strain YIM 61452(T) represents a novel species, for which the name Pseudonocardia tropica sp. nov. is proposed. The type strain is YIM 61452(T) (=DSM 45199(T)=CCTCC AA 208018(T)).

Nocardia endophytica sp. nov., an endophytic actinomycete isolated from the oil-seed plant Jatropha curcas L.

A novel actinomycete, designated strain KLBMP 1256(T), was isolated from a surface-sterilized stem of the oil-seed plant Jatropha curcas L. collected from Sichuan Province, south-west China, and was characterized to determine its taxonomic position. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the isolate was closely related to members of the genus Nocardia in the family Nocardiaceae, being most closely related to Nocardia callitridis CAP 290(T) (98.4 % similarity) and Nocardia nova JCM 6044(T) (97.5 %). Levels of 16S rRNA gene sequence similarity between strain KLBMP 1256(T) and the type strains of other recognized species of the genus Nocardia were less than 97 %. Chemotaxonomic data supported the affiliation of the new isolate to the genus Nocardia. However, the novel strain could be distinguished from its closest phylogenetic neighbour, N. callitridis CAP 290(T), by a range of phenotypic properties. The combination of low DNA-DNA relatedness values and phenotypic differences from N. callitridis CAP 290(T) indicated that strain KLBMP 1256(T) represents a novel species of the genus Nocardia, for which the name Nocardia endophytica sp. nov. is proposed. The type strain is KLBMP 1256(T) ( = KCTC 19777(T)  = CCTCC AA 2010004(T)).

Production of a bioflocculant from Pseudomonas veronii L918 using the hydrolyzate of peanut hull and its application in the treatment of ash-flushing wastewater generated from coal fired power plant.

In this study, bioflocculant produced by Pseudomonas veronii L918 was applied to treat ash-flushing wastewater. The strain L918 could convert the hydrolyzate of peanut hull into bioflocculant, which can effectively reduce the production cost of bioflocculant. The yield of 3.39g/L bioflocculant MBF-L918 was achieved when 300mL/L peanut hull hydrolyzate was used as carbon source. The bioflocculant MBF-L918 contains 77.14% polysaccharides and 4.84% proteins, and the molecular weight (MW) of MBF-L918 is 24.77kDa. Furthermore, MBF-L918 showed good flocculating efficiency of 92.51% to ash-flushing wastewater when 2.83mg/L MBF-L918 was added, and thus achieved the recycling of ash-flushing wastewater. This study reported for the first time that the bioflocculant was produced using peanut hull hydrolyzate and effectively applied in the treatment of coal ash-flushing wastewater.

Schiff base – Chitosan grafted l-monoguluronic acid as a novel solid-phase adsorbent for removal of congo red

A novel modified chitosan adsorbent (GL-SBCS) was synthesized by covalently grafting a Schiff base-chitosan (SBCS) onto the surface of l-monoguluronic acid. Physico-chemical investigation on the adsorption of congo red, an anionic azo dye by GL-SBCS has been carried out. The effect of different weight contents of chitosan in GL-SBCS composite, adsorbent dosage, initial pH and contract time were studied in detail using batch adsorption. Results showed that GL-SBCS exhibited better than normal CS and l-monoguluronic acid. Further investigation demonstrated that the adsorption pattern fitted well with the Langmuir model (R(2)>0.99) but less-satisfied the Freundlich model. Both ionic interaction as well as physical forces is responsible for binding of congo red with GL-SBCS as determined by zeta potential measurement Both sodium chloride and sodium dodecyl sulfate significantly influenced the adsorption process. SBCS would be a good method and resource to increase absorption efficiency for the removal of anionic dyes in a wastewater treatment process.

Study of the anti-sapstain fungus activity of Bacillus amyloliquefaciens CGMCC 5569 associated with Ginkgo biloba and identification of its active components

An endophytic bacterium, designated strain Bacillus amyloliquefaciens CGMCC 5569 was isolated from Chinese medicinal Ginkgo biloba collected from Xuzhou, China. Both the filtrate and the ethyl acetate extract of strain CGMCC 5569 showed growth inhibition activity against the sapstain fungi Lasiodiplodia rubropurpurea, L. crassispora, and L. theobromae obviously (>65%) based on the comparison of the length of zones on the petri dish. From the ethyl acetate extract of the filtrate, the antifungal compounds were obtained as a series of lipopeptides, which including series of fengycin, surfactin and bacillomycin. It showed strong growth inhibition activity in vitro against the L. rubropurpurea, L. crassispora and L. theobromae by about 70.22%, 69.53% and 78.76%, respectively. The strong anti-sapstain fungus activity indicated that the endophytic B. amyloliquefaciens CGMCC 5569 and its bioactive components might provide an alternative bio-resource for the bio-control of sapstain.

Promicromonospora xylanilytica sp. nov., an endophytic actinomycete isolated from surface-sterilized leaves of the medicinal plant Maytenus austroyunnanensis

A novel xylan-degrading actinomycete, strain YIM 61515(T), was isolated from surface-sterilized leaves of the medicinal plant Maytenus austroyunnanensis. Cells were Gram-positive and non-spore-forming, produced primary branches and formed white to yellowish white colonies on the media tested. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YIM 61515(T) was most similar to Promicromonospora aerolata V54A(T) and Promicromonospora vindobonensis V45(T) (99.4 and 99.1% sequence similarity, respectively). The isolate formed a separate lineage in a cluster containing P. aerolata V54A(T). 16S rRNA gene sequence similarity between the isolate and other members of the genus Promicromonospora ranged from 96.3 to 98.4%. Chemotaxonomic data, including major menaquinones, fatty acid compositions and polar lipid profiles, supported the placement of strain YIM 61515(T) in the genus Promicromonospora. DNA-DNA relatedness, physiological and biochemical data showed that strain YIM 61515(T) could be distinguished from members of all known species of the genus Promicromonospora and therefore represented a novel species. The name Promicromonospora xylanilytica sp. nov. is proposed, with YIM 61515(T) (=DSM 21603(T)=CCTCC AA 208046(T)) as type strain.

Selenylation of Polysaccharide from the Sweet Potato and Evaluation of Antioxidant, Antitumor, and Antidiabetic Activities

Interest in sweet potato as a functional food is growing. A polysaccharide (SWP) was isolated from the sweet potato tuber and elucidation of its structure as composed of rhamnose, glucose, and galactose undertaken. To improve its activity, selenylation of this novel polysaccharide (Se-SWP) was undertaken by using microwave synthesis. In vitro evaluation showed that the Se-SWP has excellent antioxidant activity on scavenging free radicals and reducing capacity. In vivo antitumor evaluation showed selenylation polysaccharide could effectively inhibit tumor growth (>50%) and adjust immune factor levels in the mice (IL-2, TNF-α, and VEGF). The antidiabetic potential of Se-SWP was tested in STZ-induced diabetic rats. The results indicated that the Se-SWP treatment significantly reduced the levels of malondialdehyde and other disadvantageous factors that were increased by the STZ treatment. Meanwhile, the Se-SWP treatment caused a significant increase in the activities of enzymatic antioxidants and the levels of nonenzymatic antioxidants in the organs of diabetic rats. All of the activity evaluations indicated that the selenylation method could improve the activity of sweet potato polysaccharide and its efficacy as a potential therapeutic, which will be the focus of further study.