Chongxi Liu

Nonomuraea solani sp. nov., an actinomycete isolated from eggplant root (Solanum melongena L.)

A novel actinomycete, designated strain NEAU-Z6(T), was isolated from eggplant (Solanum melongena L.) root. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain NEAU-Z6(T) belonged to the genus Nonomuraea, with highest sequence similarity to Nonomuraea monospora PT 708(T) (98.83 %), Nonomuraea rosea GW 12687(T) (98.55 %) and Nonomuraea rhizophila YIM 67092(T) (98.02 %). Sequence similarities between strain NEAU-Z6(T) and other species of the genus Nonomuraea ranged from 97.94 % (Nonomuraea candida HMC10(T)) to 96.30 % (Nonomuraea wenchangensis 210417(T)). Key morphological, physiological and chemotaxonomic characteristics of strain NEAU-Z6(T) were congruent with the description of the genus Nonomuraea. The G+C content of the genomic DNA was 64.51 mol%. DNA-DNA relatedness and comparative analysis of physiological, biochemical and chemotaxonomic data allowed genotypic and phenotypic differentiation of strain NEAU-Z6(T) from closely related species. Thus, strain NEAU-Z6(T) represents a novel species of the genus Nonomuraea, for which the name Nonomuraea solani sp. nov. is proposed. The type strain is NEAU-Z6(T) ( = CGMCC 4.7037(T) = DSM 45729(T)).

A new prenylated indole derivative from endophytic actinobacteria Streptomyces sp. neau-D50

A new prenylated indole derivative 3-acetonylidene-7-prenylindolin-2-one (1) was isolated from the endophytic actinobacterium Streptomyces sp. neau-D50, together with four known hybrid isoprenoids, 7-isoprenylindole-3-carboxylic acid (2), 3-cyanomethyl-6-prenylindole (3), 6-isoprenylindole-3-carboxylic acid (4) and 7,4′-dihydroxy-5-methoxy-8-(γ,γ-dimethylallyl)-flavanone (5). The structures of these compounds were elucidated on the basis of extensive spectroscopic analysis and comparison with data from the literature. Compounds 1 and 2 demonstrated strong cytotoxic activities against human lung adenocarcinoma cell line A549 with an IC50 of 3.3 and 5.1 μg mL− 1, respectively, which are comparable to that of the positive control doxorubicin (4.2 μg mL− 1). Furthermore, compounds 1–4 exhibited potent antifungal activity against phytopathogenic fungi Colletotrichum orbiculare, Phytophthora capsici, Corynespora cassiicola and Fusarium oxysporum.

Streptomyces harbinensis sp. nov., an endophytic, ikarugamycin-producing actinomycete isolated from soybean root [Glycine max (L.) Merr].

A novel ikarugamycin-producing actinomycete, designated strain NEAU-Da3(T), was isolated from soybean root [Glycine max (L.) Merr.] and characterized using a polyphasic approach. 16S rRNA gene sequence similarity studies showed that strain NEAU-Da3(T) belonged to the genus Streptomyces, and was most closely related to Streptomyces carpaticus NRRL B-16359(T) (99.5 %), Streptomyces cheonanensis VC-A46(T) (99.3 %) and Streptomyces xiamenensis MCCC 1A01550(T) (97.2 %); similarities to other type strains of species of the genus Streptomyces were lower than 97.1 %. The maximum-likelihood phylogenetic tree based on 16S rRNA gene sequences showed that the isolate formed a distinct phyletic line with S. carpaticus NRRL B-16359(T), S. cheonanensis VC-A46(T) and S. xiamenensis MCCC 1A01550(T). This branching pattern was also supported by the tree reconstructed with the neighbour-joining method. A comparative study between strain NEAU-Da3(T) and the type strains of the closest related species of the genus Streptomyces revealed that it differed from them in morphological, physiological and biochemical characteristics. Therefore, it is proposed that strain NEAU-Da3(T) represents a novel species of the genus Streptomyces, for which the name Streptomyces harbinensis sp. nov. is proposed. The type strain is NEAU-Da3(T) ( = CGMCC 4.7047(T) = DSM 42076(T)).

Streptomyces zhaozhouensis sp. nov., an actinomycete isolated from candelabra aloe (Aloe arborescens Mill).

A novel endophytic actinomycete, designated strain NEAU-LZS-5(T), was isolated from the leaf of candelabra aloe (Aloe arborescens Mill) and characterized using a polyphasic approach. Analysis of the 16S rRNA gene sequence showed that strain NEAU-LZS-5(T) belongs to the genus Streptomyces and exhibited 99.51 and 97.37 % similarity to Streptomyces sedi YIM 65188(T) and Streptomyces specialis GW41-1564(T), respectively, whereas low similarity values (<97 %) distinguished strain NEAU-LZS-5(T) from all other species of the genus Streptomyces with validly published names. Two tree-making algorithms also supported the position that strain NEAU-LZS-5(T) formed a distinct clade with Streptomyces sedi YIM 65188(T) and Streptomyces specialis GW41-1564(T). However, levels of DNA-DNA relatedness between strain NEAU-LZS-5(T) and Streptomyces sedi YIM 65188(T) and Streptomyces specialis GW41-1564(T) were 45.59 and 31.90 %, respectively. A comparative study between strain NEAU-LZS-5(T) and the type strains of closest related species of the genus Streptomyces revealed that it differed from them in morphological, physiological and biochemical characteristics. Therefore, strain NEAU-LZS-5(T) represents a novel species of the genus Streptomyces, for which the name Streptomyces zhaozhouensis sp. nov. is proposed. The type strain is NEAU-LZS-5(T) ( = CGMCC 4.7095(T) = DSM 42101(T)).

Xiangella phaseoli gen. nov., sp. nov., a member of the family Micromonosporaceae

A novel endophytic actinomycete, designated strain NEAU-J5(T) was isolated from roots of snap bean (Phaseolus vulgaris L.). Comparative analysis of the 16S rRNA gene sequence indicated that NEAU-J5(T) is phylogenetically related to members of the family Micromonosporaceae. The whole-cell sugars were galactose, mannose and glucose. The predominant menaquinones were MK-9(H4) and MK-9(H6). The major fatty acids were C16:0, C18:0, C17:1ω7c, iso-C15:0 and C17:0. The phospholipids were phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol and phosphatidylinositol mannoside. The DNA G+C content was 72.2 mol%. On the basis of the morphological and chemotaxonomic characteristics, phylogenetic analysis and characteristic patterns of 16S rRNA gene signature nucleotides, strain NEAU-J5(T) represents a novel species of a new genus within the family Micromonosporaceae, for which the name Xiangella phaseoli gen. nov., sp. nov. is proposed. The type strain of Xiangella phaseoli is strain NEAU-J5(T) (=CGMCC 4.7038(T)=DSM 45730(T)).

Novel cyclopentenone derivatives produced by a rare actinobacterial strain Actinoalloteichus nanshanensis sp. nov. NEAU 119

Four novel cyclopentenone derivatives (1–4), characterising a cyclopentenone ring conjugated with a 1,8-dioxadecalin, were isolated from rare actinobacterial strain Actinoalloteichus nanshanensis sp. nov. NEAU 119. The structures of these compounds were elucidated on the basis of extensive spectroscopic analysis. Bioassays indicated that compounds 1–4 showed low cytotoxicities against human leukaemia cell line K562 and human renal carcinoma cell line ACHN. To the best of our knowledge, this is the first example of isolation of C11 cyclopentenones from actinomycetes.

Borrelidin, a potent antifungal agent: insight into the antifungal mechanism against Phytophthora sojae.

Borrelidin has high and specific antifungal activity against Phytophthora sojae . To explore the antifungal mechanism of borrelidin against P. sojae , the relationship between the antifungal activity of borrelidin and the concentration of threonine was evaluated. The results demonstrated that the growth-inhibitory effect of borrelidin on the growth of P. sojae was antagonized by threonine in a dose-dependent manner, suggesting that threonyl-tRNA synthetase (ThrRS) may be the potential target of borrelidin. Subsequently, the inhibition of the enzymatic activity of ThrRS by borrelidin in vitro was confirmed. Furthermore, the detailed interaction between ThrRS and borrelidin was investigated using fluorescence spectroscopy and circular dichroism (CD), implying a tight binding of borrelidin to ThrRS. Taken together, these results suggest that the antifungal activity of borrelidin against P. sojae was mediated by inhibition of ThrRS via the formation of the ThrRS-borrelidin complex.

Micromonospora polyrhachis sp. nov., an actinomycete isolated from edible Chinese black ant (Polyrhachis vicina Roger)

A novel actinomycete, designated strain NEAU-ycm2(T), was isolated from edible Chinese black ants (Polyrhachis vicina Roger) and characterized using a polyphasic approach. The organism was found to have morphological and chemotaxonomic characteristics typical of the genus Micromonospora. The 16S rRNA gene sequence of strain NEAU-ycm2(T) showed highest similarity to those of Micromonospora sonneratiae 274745(T) (99.12%), Micromonospora pattaloongensis TJ2-2(T) (98.85%), Micromonospora pisi GUI 15(T) (98.76%), Polymorphospora rubra TT 97-42(T) (98.42%) and Micromonospora eburnea LK2-10(T) (98.21%). Phylogenetic analysis based on the 16S rRNA gene and gyrB gene demonstrated that strain NEAU-ycm2(T) is a member of the genus Micromonospora and supported the close phylogenetic relationship to M. sonneratiae 274745(T), M. pattaloongensis JCM 12833(T) and M. pisi GUI 15(T). Furthermore, a combination of DNA-DNA hybridization and some physiological and biochemical properties indicated that the novel strain could be readily distinguished from its closest phylogenetic relatives. Therefore, it is proposed that NEAU-ycm2(T) represents a novel species of the genus of Micromonospora, for which the name Micromonospora polyrhachis sp. nov. is proposed. The type strain is NEAU-ycm2(T) ( = CGMCC 4.7100(T) = DSM 45886(T)).

Two new piperidine alkaloids from Streptomyces sp. NEAU-Z4

Two new piperidine alkaloids, streptazones E (1) and F (2), were isolated from Streptomyces sp. NEAU-Z4. Their structures were elucidated on the basis of MS and NMR analysis.

Antifungal Activity of Borrelidin Produced by a Streptomyces Strain Isolated from Soybean

In this study, an endophytic Streptomyces sp. neau-D50 with strong antifungal activity against Phytophthora sojae was isolated from healthy soybean root, using an in vitro screening technique. A bioactivity-guided approach was then employed to isolate and determine the chemical identity of bioactive constituents with antifungal activity from strain neau-D50. The structure of the antifungal metabolite was elucidated as borrelidin on the basis of spectral analysis. To our knowledge, this is the first report that borrelidin has strong antifungal activity against dominant race 1 of P. sojae with EC(50) and EC(95) of 0.0056 and 0.026 mg/L, respectively. The values were respectively 62.5- and 262.3-fold lower than those of the commercial fungicide metalaxyl, which has been used to treat soybean seed for the control of P. sojae . The in situ bioassays demonstrated that borrelidin at 10 mg/L reduced P. sojae race 1 lesions on soybean seedlings by 94.72% without affecting root growth. Thus, borrelidin might be a promising candidate for new antifungal agents against P. sojae.