Mining novel biosynthetic machineries of secondary metabolites from actinobacteria

Discovery, Antitumor Activity, and Fermentation Optimization of Roquefortines from Penicillium sp. OUCMDZ-1435

Meleagrin and oxaline, which belong to the roquefortine alkaloids with a unique dihydroindole spiroamide framework, have significant bioactivities, especially tumor cell inhibitory activity. In order to discover the requefortine alkaloids, Penicillium sp. OUCMDZ-1435 was fished and identified from marine fungi using molecular probe technology. Meleagrin (1) and oxaline (2) were isolated from it. In addition, we first reported that compounds 1 and 2 could effectively inhibit the proliferation and metastasis of the human HepG2 cell and induce HepG2 cell apoptosis and cell cycle arrest in the G2/M phase. Additionally, the fermentation of Meleagrin (1) was optimized to increase its yield to 335 mg/L. These results provided bioactive inspiration and fungus resources for roquefortine alkaloid development.

Changes in the gut microbiota structure and function in rats with doxorubicin-induced heart failure

Objectives

The rat model of heart failure (HF) induced by doxorubicin (DOX), a broad spectrum and highly effective chemotherapeutic anthracycline with high-affinity to myocardial tissue that causes severe dose-dependent irreversible cardiotoxicity has been widely recognized and applied in HF pathogenesis and drug therapy studies. The gut microbiota (GM) has attracted significant attention due to its potential role in HF, and research in this area may provide beneficial therapeutic strategies for HF. Considering the differences in the route, mode, and total cumulative dose of DOX administration used to establish HF models, the optimal scheme for studying the correlation between GM and HF pathogenesis remains to be determined. Therefore, focusing on establishing the optimal scheme, we evaluated the correlation between GM composition/function and DOX-induced cardiotoxicity (DIC).

Methods

Three schemes were investigated: DOX (at total cumulative doses of 12, 15 or 18 mg/kg using a fixed or alternating dose via a tail vein or intraperitoneal injection) was administered to Sprague Dawley (SD) for six consecutive weeks. The M-mode echocardiograms performed cardiac function evaluation. Pathological changes in the intestine were observed by H&E staining and in the heart by Masson staining. The serum levels of N-terminal pre-B-type natriuretic peptide (NT-proBNP) and cardiac troponin I (cTnI) were measured by ELISA. The GM was analysed by 16S rRNA gene sequencing.

Key findings

Strikingly, based on the severity of cardiac dysfunction, there were marked differences in the abundance and grouping of GM under different schemes. The HF model established by tail vein injection of DOX (18 mg/kg, alternating doses) was more stable; moreover, the degree of myocardial injury and microbial composition were more consistent with the clinical manifestations of HF.

Conclusions

The model of HF established by tail vein injection of doxorubicin, administered at 4mg/kg body weight (2mL/kg) at weeks 1, 3 and 5, and at 2mg/kg body weight (1mL/kg) at weeks 2, 4 and 6, with a cumulative total dose of 18mg/kg, is a better protocol to study the correlation between HF and GM.

Microbes: A Hidden Treasure of Polyunsaturated Fatty Acids

Microbes have gained a lot of attention for their potential in producing polyunsaturated fatty acids (PUFAs). PUFAs are gaining scientific interest due to their important health-promoting effects on higher organisms including humans. The current sources of PUFAs (animal and plant) have associated limitations that have led to increased interest in microbial PUFAs as most reliable alternative source. The focus is on increasing the product value of existing oleaginous microbes or discovering new microbes by implementing new biotechnological strategies in order to compete with other sources. The multidisciplinary approaches, including metabolic engineering, high-throughput screening, tapping new microbial sources, genome-mining as well as co-culturing and elicitation for the production of PUFAs, have been considered and discussed in this review. The usage of agro-industrial wastes as alternative low-cost substrates in fermentation for high-value single-cell oil production has also been discussed. Multidisciplinary approaches combined with new technologies may help to uncover new microbial PUFA sources that may have nutraceutical and biotechnological importance.

Clostridium butyricum affects nutrition and immunology by modulating gut microbiota

The gut microbiota has nutritional and protective functions. In patients with end-stage renal disease, changes in the gut microbiota disrupt their protective functions. Probiotics help maintain normal bowel function. However, their role in patients with end-stage renal disease is controversial. We investigated whether Clostridium butyricum affects the nutrition and immune function of patients with end-stage renal disease undergoing maintenance dialysis between 2014 and 2015; thirty-seven patients were included. The patients were divided into two groups: one in which C. butyricum was administered and one in which it was not. One tablet of the probiotics, which contained 20 mg of C. butyricum, was administered orally three times daily for 2 years in the C. butyricum group. The 16S rRNA genes were sequenced from stool samples of 14 (37.8%) patients in the C. butyricum group and 23 (62.2%) patients in the control group. The differences in the gut microbiota of the two groups were analyzed. The α-diversity index indicated that the C. butyricum group had significantly more operational taxonomic units and higher albumin and transferrin levels than the control group. The effector to target cell ratio was significantly higher in the C. butyricum group. In addition, interleukin-6 levels were significantly lower in the C. butyricum group, and inflammation was less severe in this group. The patients undergoing maintenance dialysis with C. butyricum had abundant gut microbiota. They also had a good nutritional status, low systemic inflammation, and a good immunological status.

New approaches for antituberculosis leads from Actinobacteria

Bioactive metabolites derived from the phylum Actinobacteria represent many of the existing antimicrobial drugs. Compared with other bacterial pathogens, direct preliminary screening by diffusion assays is a limiting factor against Mycobacterium tuberculosis (Mtb) and different methodologies have been used to improve the search for new molecules. However, the concern remains that most of the previously discovered molecules replicate by conventional procedures. The combination of multidisciplinary approaches with new technologies could advance the discovery of new leads against Mtb like considering the unexplored Actinobacteria jointly with selective and integrative procedures.

Taxonomic Characterization, and Secondary Metabolite Analysis of Streptomyces triticiradicis sp. nov.: A Novel Actinomycete with Antifungal Activity

The rhizosphere, an important battleground between beneficial microbes and pathogens, is usually considered to be a good source for isolation of antagonistic microorganisms. In this study, a novel actinobacteria with broad-spectrum antifungal activity, designated strain NEAU-H2^T, was isolated from the rhizosphere soil of wheat (Triticum aestivum L.). 16S rRNA gene sequence similarity studies showed that strain NEAU-H2^T belonged to the genus Streptomyces, with high sequence similarities to Streptomyces rhizosphaerihabitans NBRC 109807^T (98.8%), Streptomyces populi A249^T (98.6%), and Streptomyces siamensis NBRC 108799^T (98.6%). Phylogenetic analysis based on 16S rRNA, atpD, gyrB, recA, rpoB, and trpB gene sequences showed that the strain formed a stable clade with S. populi A249^T. Morphological and chemotaxonomic characteristics of the strain coincided with members of the genus Streptomyces. A combination of DNA-DNA hybridization results and phenotypic properties indicated that the strain could be distinguished from the abovementioned strains. Thus, strain NEAU-H2^T belongs to a novel species in the genus Streptomyces, for which the name Streptomyces triticiradicis sp. nov. is proposed. In addition, the metabolites isolated from cultures of strain NEAU-H2^T were characterized by nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses. One new compound and three known congeners were isolated. Further, genome analysis revealed that the strain harbored diverse biosynthetic potential, and one cluster showing 63% similarity to natamycin biosynthetic gene cluster may contribute to the antifungal activity. The type strain is NEAU-H2^T (= CCTCC AA 2018031^T = DSM 109825^T).