Transcriptome analysis of the production enhancement mechanism of antimicrobial lipopeptides of Streptomyces bikiniensis HD-087 by co-culture with Magnaporthe oryzae Guy11.

The lipopeptides produced by Streptomyces bikiniensis have a significant inhibitory effect on Magnaporthe oryzae, but the low yield limits its application. In this study, the anti-M. oryzae activity of the broth of S. bikiniensis HD-087 co-cultured with M. oryzae Guy11 mycelium has risen by 41.22% compared with pure culture, and under induction conditions of adding Guy11-inducer (cell-free supernatant of M. oryzae Guy11), the activity of strain HD-087 improved 61.76%. The result proved that the enhancement effect of Guy11 on the antimicrobial activity of HD-087 was mainly related to metabolites but mycelium cells. Under optimum induction conditions, NRPS gene expression levels of HD-087 were significantly increased by induction with Guy11-inducer, the biomass of HD-087 had no significant change, but crude extract of lipopeptide (CEL) production was 107.4% higher than pure culture, and TLC result under acid hydrolysis showed that the induced culture has one component more than pure culture. To clarify the regulation mechanism of improving lipopeptide production of HD-087 with Guy11-inducer, transcriptomic analysis was performed using RNAseq to compare the induced culture and pure culture. In the induced culture, 943 genes were up-regulated, while 590 genes were down-regulated in DEGs (differentially expressed genes). KEGG results showed that the expression of genes related to amino acid synthesis, fatty acid metabolism, TCA cycle and pyruvate metabolism pathway were significantly increased. The increased expression of genes related to these metabolic pathways provided sufficient precursors for lipopeptide synthesis. Accordingly, key enzyme genes responsible for the synthesis of lipopeptides Srf and NRPS was significantly increased. Quorum sensing related genes OppA and MppA were significantly up-regulated, and then ComP was activated and promoted lipopeptide synthesis. These results provided a scientific basis for using M. oryzae to induce the increase of the production of Streptomyces lipopeptides, and also laid a foundation for further exploring the co-culture mechanisms among different genera.

Genomic and Biocontrol Potential of the Crude Lipopeptide by Streptomyces bikiniensis HD-087 Against Magnaporthe oryzae.

Rice blast caused by Magnaporthe oryzae is one of the most destructive plant diseases. The secondary metabolites of Streptomyces have potential as biological control agents against M. oryzae. However, no commercial secondary antimicrobial products of Streptomyces have been found by gene prediction, and, particularly relevant for this study, a biocontrol agent obtained from Streptomyces bikiniensis has yet to be found. In this research, genomic analysis was used to predict the secondary metabolites of Streptomyces, and the ability to develop biocontrol pharmaceuticals rapidly was demonstrated. The complete genome of the S. bikiniensis HD-087 strain was sequenced and revealed a number of key functional gene clusters that contribute to the biosynthesis of active secondary metabolites. The crude extract of lipopeptides (CEL) predicted by NRPS gene clusters was extracted from the fermentation liquid of S. bikiniensis HD-087 by acid precipitation followed by methanol extraction, and surfactins, iturins, and fengycins were identified by liquid chromatography-mass spectrometry (LC-MS). In vitro, the CEL of this strain inhibited spore germination and appressorial formation of M. oryzae by destroying membrane integrity and through the leakage of cellular components. In vivo, this CEL reduced the disease index of rice blast by approximately 76.9% on detached leaves, whereas its control effect on leaf blast during pot experiments was approximately 60%. Thus, the S. bikiniensis CEL appears to be a highly suitable alternative to synthetic chemical fungicides for controlling M. oryzae.

Hydrophilicity gradient in covalent organic frameworks for membrane distillation.

Desalination can help to alleviate the fresh-water crisis facing the world. Thermally driven membrane distillation is a promising way to purify water from a variety of saline and polluted sources by utilizing low-grade heat. However, membrane distillation membranes suffer from limited permeance and wetting owing to the lack of precise structural control. Here, we report a strategy to fabricate membrane distillation membranes composed of vertically aligned channels with a hydrophilicity gradient by engineering defects in covalent organic framework films by the removal of imine bonds. Such functional variation in individual channels enables a selective water transport pathway and a precise liquid-vapour phase change interface. In addition to having anti-fouling and anti-wetting capability, the covalent organic framework membrane on a supporting layer shows a flux of 600 l m-2 h-1 with 85 °C feed at 16 kPa absolute pressure, which is nearly triple that of the state-of-the-art membrane distillation membrane for desalination. Our results may promote the development of gradient membranes for molecular sieving.

[Effects of different temperature stress on cell membrane permeability,active oxygen metabolism and accumulation of effective substances in Lonicera japonicea].

The study is aimed to explore the effects of stress at different temperatures( 35,45,55 ℃) on membrane permeability,active oxygen metabolism and accumulation of effective substances in Lonicera japonica,and provide theoretical basis for reducing deterioration and revealing browning mechanism during postharvest processing of L. japonica. The cell membrane permeability( relative conductivity,MDA content),active oxygen metabolism( SOD,POD,PPO,CAT activity) and the accumulation of effective substances( chlorogenic acid,luteolin,neochlorogenic acid,cryptochlorogenic acid,3,5-dicaffeoylquinic acid,3,4-dicaffeoylquinic acid and 4,5-dicaffeoylquinic acid) of L. japonica were all studied by constant temperature drying method,and the results were analyzed by the SPSS 17. 0 statistical software. The results showed that MDA content in L. japonica was increased by 151. 14% at 35 ℃,SOD,POD,PPO and CAT activity were 29. 73%,42. 86%,105. 02% and 10. 74% higher than at 45 ℃,respectively. The order of effective substance content in L. japonica was 35 ℃ >45 ℃ >55 ℃. The changes of membrane permeability,activity of active oxygen metabolizing enzyme and accumulation of active components were significantly affected by different temperature stress. The indexes showed that physiological and active oxygen metabolizing enzyme activity of L. japonica was the highest under 35 ℃ stress,chlorogenic acid and luteolin were effectively accumulated,which provides basic data for solving browning problem in the postharvest processing of L. japonica.