Research progress of bacterial biofilm eradication agents based on modifications of natural products / 药学学报

Bacterial biofilm widely exists in all kinds of bacteria, and is related to about 80 percent of bacterial infections. It is one of the main reasons for bacterial tolerance and resistance to existing antibiotics. Therefore, there is unmet clinical need for new anti-biofilm drugs. At present, there are three kinds of anti-biofilm agents under research, including biofilm inhibitors, biofilm dispersal agents and biofilm eradication agents. Among them, the biofilm eradication agent is unique, which can not only kill bacteria in biofilm but also eliminate biofilm as a monotherapy. Based on modifications of natural products with antibacterial activity, a variety of compounds with biofilm eradicating activities have been obtained, such as, acyldepsipeptides, pyrrolomycins, halogenated phenazines and halogenated 8-hydroxyquinolines. In this review, we summarize several major biofilm eradication agents above according to their structures and mechanisms.

Study on the antifungal activity of phenazine derivatives / 药学实践杂志

Objective To study the antifungal activity of phenazines derivatives. Methods The anti-fungal activity of phenazine compounds was evaluated initially with micro-liquid dilution. No significant antifungal activity against Candida albicans was found. Then, with the combination of phenazine compounds and fluconazole, the anti-fungal activity against fluconazole-resistant C. albicans was detected. Results The phenazine-17 had significant antifungal activity when combined with fluconazole through the inhibition of hyphae formation. Conclusion This study provides a new idea for the development of antifungal drugs and the solution of antifungal drug resistance.

Effects of combination of phenazine-1-carboxylic acid from Streptomyces kebangsaanensis with amphotericin B on clinical Fusarium solani species

Aim@#A novel endophyte, Streptomyces kebangsaanensis was isolated from the stem of a Malaysian ethnomedicinal plant, Portulaca oleracea in 2013. Studies on S. kebangsaanensis crude extract showed that it had antifungal activities and further work led to isolation of a novel compound, phenazine-1-carboxylic acid (PCA). This study investigated the combinatorial effect of PCA isolated from S. kebangsaanensis with amphotericin B on the growth of four clinical Fusarium solani isolates. @*Methodology and results@#Disk diffusion assay showed that the crude extract of S. kebangsaaneesis inhibited growth of all four F. solani isolates. Whereas, the compound PCA from this extract inhibited two of the tested F. solani isolates, UZ541/12, and UZ667/13 at minimum inhibitory concentration of 18.00 µg/mL Combinations of this compound with amphotericin B, reduced the minimum inhibitory concentration of amphotericin B for these two isolates from 8 to 0.13 µg/mL and 4 to 0.03 µg/mL respectively. Analysis of fractional inhibitory concentration index showed that a borderline synergism is present between the compound and amphotericin B. @*Conclusion, significance and impact of the study@#These results indicate PCA may be useful in improving actions of available drugs against antimicrobial resistant microorganisms.

Bioactive phenazines from an earwig-associated Streptomyces sp / 中国天然药物

Three new phenazine-type compounds, named phenazines SA-SC (1-3), together with four new natural products (4-7), were isolated from the fermentation broth of an earwig-associated Streptomyces sp. NA04227. The structures of these compounds were determined by extensive analyses of NMR, high resolution mass spectroscopic data, as well as single-crystal X-ray diffraction measurement. Sequencing and analysis of the genome data allowed us to identify the gene cluster (spz) and propose a biosynthetic pathway for these phenazine-type compounds. Additionally, compounds 1-5 exhibited moderate inhibitory activity against acetylcholinesterase (AChE), and compound 3 showed antimicrobial activities against Micrococcus luteus.

Survival elongation of Pseudomonas aeruginosa improves power output of microbial fuel cells / 生物工程学报

The secondary metabolites, phenazine products, produced by Pseudomonas aeruginosa can mediate the electrons transfer in microbial fuel cells (MFCs). How increase the total electricity production in MFCs by improving the characteristics of Pseudomonas aeruginosa is one of research hot spots and problems. In this study, P. aeruginosa strain SJTD-1 and its knockout mutant strain SJTD-1 (ΔmvaT) were used to construct MFCs, and the discharge processes of the two MFCs were analyzed to determine the key factors to electricity yields. Results indicated that not only phenazine but also the viable cells in the fermentation broth were essential for the discharge of MFCs. The mutant strain SJTD-1 (ΔmvaT) could produce more phenazine products and continue discharging over 160 hours in MFCs, more than that of the wild-type SJTD-1 strain (90 hours discharging time). The total electricity generated by SJTD-1 (ΔmvaT) strain could achieve 2.32 J in the fermentation process, much higher than the total 1.30 J electricity of the wild-type SJTD-1 strain. Further cell growth analysis showed that the mutant strain SJTD-1 (ΔmvaT) could keep a longer stationary period, survive much longer in MFCs and therefore, discharge more electron than those of the wild-type SJTD-1 strain. Therefore, the cell survival elongation of P. aeruginosa in MFCs could enhance its discharging time and improve the overall energy yield. This work could give a clue to improve the characteristics of MFCs using genetic engineering strain, and could promote related application studies on MFCs.

Expression of phenazine biosynthetic genes during the arbuscular mycorrhizal symbiosis of Glomus intraradices

To explore the molecular mechanisms that prevail during the establishment of the arbuscular mycorrhiza symbiosis involving the genus Glomus, we transcriptionally analysed spores of Glomus intraradices BE3 during early hyphal growth. Among 458 transcripts initially identified as being expressed at presymbiotic stages, 20% of sequences had homology to previously characterized eukaryotic genes, 30% were homologous to fungal coding sequences, and 9% showed homology to previously characterized bacterial genes. Among them, GintPbr1a encodes a homolog to Phenazine Biosynthesis Regulator (Pbr) of Burkholderia cenocepacia, an pleiotropic regulatory protein that activates phenazine production through transcriptional activation of the protein D isochorismatase biosynthetic enzyme phzD (Ramos et al., 2010). Whereas GintPbr1a is expressed during the presymbiotic phase, the G. intraradices BE3 homolog of phzD (BGintphzD) is transcriptionally active at the time of the establishment of the arbuscular mycorrhizal symbiosis. DNA from isolated bacterial cultures found in spores of G. intraradices BE3 confirmed that both BGintPbr1a and BGintphzD are present in the genome of its potential endosymbionts. Taken together, our results indicate that spores of G. intraradices BE3 express bacterial phenazine biosynthetic genes at the onset of the fungal-plant symbiotic interaction.

Optimal Model Design for High Production of Phenazine-1-Caboxylic Acid (PCA) by Pseudomas. spp M18G / 中国生物工程杂志

Phenazine-1-carboxylic acid(PCA)is one of the major antifungal compounds produced by plant growth-promoting rhizosphere(PGPR)pseudomonads and has been shown to contribute to the biological control of soil-borne plant pathogens.Model on secondary metabolite phenazine-1-carboxylic acid(PCA)fermentation nutrition conditions of gacA inactivate mutant Pseudomonas sp.M18G was constructed by Plackett-Burman design(PB)and Response Surface Method(RSM).In PB design four key components selected from 12 different factors have shown to play an important role for promoting PCA production.Center Composite Design(CCD)was adopted to establish a fermentation model for the four nutrition components using RSM.The optimal concentration of the four components based on analysis of regression equation were determined that soybean meal 33.4 g/L,glucose 12.7 g/L,soy peptone10.9 g/L,ethanol13.8 g/L,and the highest PCA production could reached 1.89 g/L after 60h fermentation and the yield increased to 6 fold over that before optimization.The contour graphs depicted interactions of the two nutrition components showed that soybean meal and ethanol played an even more crucial role for the highest production of PCA in fermentation.It establishes a method for high PCA production and lays a foundation for the further PCA commercial development.

Construction and Characterization of a ppbR gene Mutant of Pseudomonas sp. M18 / 微生物学通报

Pseudomonas sp. M18, one of plant-growth-promoting rhizobacteria, can produce secondary metabolites including phenazine-1-carboxylic acid (PCA) and pyoluteorin (Plt). PA2572 gene coding protein is a probable two-component response regulator in Pseudomonas according to homologous speculations. In order to investigate its genetic function, PA2572 homologous gene, ppbR, was amplified from M18 genome, inactivated by inserting a Gm cassette. The resulting reconstruct was introduced into the M18 genome using homologous recombination technique, so as to obtain the null mutant M18P. The results showed that the M18P has less flagellar swimming and swarming motility, and yielded fewer PCA. The production of PCA was only 50% of the wild type. However, there was no remarkable difference between mutant and wild type in producing pyoluteorin in KMB medium.