[Remote Sensing Monitoring on Spatial Differentiation of Suspended Sediment Concentration in a River-Lake System Based on Sentinel-2 MSI Imaging:A Case for Shengjin Lake and Connected Yangtze River Section in Anhui Province].

Carrying out monitoring of suspended sediment concentration in river and lake systems is of great significance for understanding the laws of sediment transport in water and formulating policies on water environmental control. Taking Shengjin Lake and the connected Yangtze river section in Anhui province as the study area, band reflectance of a Sentinel-2 MSI sensor is simulated according to field spectral datasets, and the retrieval model is established by statistical regression from the synchronized suspended sediment concentration measurements. Then, the retrieved results from 28 scene MSI images during 2017-2019 are used to analyze the spatiotemporal variation of suspended sediment concentration in rivers and lakes, and the influence of water level variation on their spatial differentiation is also discussed. The results show that:① The retrieval model established by the ratio of the sixth band to the third band of the MSI sensor is suitable for high-turbidity water type, with high accuracy (R2=0.863, RMSE=22.211 mg·L-1). ② Spatially, the suspended sediment concentration near the lake entrances, northwestern parts of the upper and middle lake areas, and the lower lake is relatively higher, and that of Shengjin Lake is lower than that of the Yangtze River overall except for in summer. Temporally, the suspended sediment concentration in Shengjin Lake is relatively lower in summer and higher in other seasons, while the connected Yangtze River section exhibits the opposite intra-annual variation. ③ The water level, which is caused by the connectivity of rivers and lakes under the influence of the sluice, is the key factor affecting the spatial differentiation of suspended sediment concentration in the river and lake system. The suspended sediment concentration in Shengjin Lake contributes to the Yangtze River in dry and normal water periods, and that in the normal water period is more significant. In contrast, during the flood period, the correlation between suspended sediment concentration in the Yangtze River and that in Shengjin Lake is not obvious.

Heterologous and Engineered Biosynthesis of Nematocidal Polyketide-Nonribosomal Peptide Hybrid Macrolactone from Extreme Thermophilic Fungi.

Fungal polyketide-nonribosomal peptide (PK-NRP) hybrid macrolactones are a growing family of natural products with biomedical and agricultural activities. One of the most important families is the thermolides, which are produced by extreme thermophilic fungi and exhibit strong nematocidal activity. We show here that the genes ThmABCE from Talaromyces thermophilus NRRL 2155 are critical for thermolide synthesis. Two separate single-module hrPKS (ThmA) and NRPS (ThmB) enzymes collaborate to synthesize the core macrolactone backbone (6 or 7), and the NRPS ThmB-CT domain catalyzes the key macrocyclization step in PK-NRP intermediate release via ester bond formation, representing a novel function of fungal NRPS C domains. We also show that heterologous and engineered expression of the Thm genes in the type strains of Aspergillus nidulans and Escherichia coli not only dramatically enhances the yields of thermolides but also affords different esterified analogues, such as butyryl- (thermolides J and K, 15 and 16), hexanoyl-, and octanyl- derivatives or mixed thermolides. Thermolides L and M (18 and 19), discovered via genome mining-based combinatorial biosynthesis, represent the first l-phenylalanine-based thermolides. Our work shows a unique biosynthetic mechanism of PK-NRP hybrid macrolactones from extremophiles, which led to the discovery of novel compounds and furthers our biosynthetic knowledge.

Chamiside A, a Cytochalasan with a Tricyclic Core Skeleton from the Endophytic Fungus Chaetomium nigricolor F5.

Chamiside A (1), a novel cytochalasan with a new 6/6/5-fused tricyclic core skeleton, was isolated from an endophytic fungus, Chaetomium nigricolor F5, harbored in the medicinal plant Mahonia fortunei. Its structure was unambiguously determined by extensive spectroscopic analyses, measurement of single-crystal X-ray diffraction, and electronic circular dichroism calculation. A biosynthetic pathway for the unique ring system in 1 was proposed. Compound 1 exhibited moderate antibacterial activity against Staphylococcus aureus.

Induced production of steroids by co-cultivation of two endophytes from Mahonia fortunei.

A new ergosterol derivative, 23R-hydroxy-(20Z,24R)-ergosta-4,6,8(14),20(22)-tetraen-3-one (1), and a biosynthetically related known compound, (22E,24R)-ergosta-4,6,8(14),22-tetraen-3-one (2), were isolated from the co-culture between endophytic fungus Pleosporales sp. F46 and endophytic bacterium Bacillus wiedmannii Com1 both inhibiting in the medicinal plant Mahonia fortunei. The structure of the new compound 1 was determined by extensive spectroscopic analysis using HRMS and NMR, together with the modified Mosher's ester method. This is the first example of isolation of a ergosterol derivative with a Δ20(22)-double bond in the side chain. Compound 1 exhibited moderate antibacterial efficacy against Staphylococcus aureus and no obvious cytotoxic activities against the cancer cell lines A549, MDA-MB-231 and Hct116. Our results not only reveal that compound 1 is a potent antibacterial lead compound, but also highlight the powder of co-cultivation for inducing the production of cryptic natural products from endophytes derived from the same host plant.