A Novel 4H-Chromen-4-One Derivative from Marine Streptomyces ovatisporus S4702T as Potential Antibacterial and Anti-Cancer Agent

Enantioselective Reduction and Sulfenylation of Isoflavanone Derivatives via Bisguanidinium Hypervalent Silicate

In this work, we describe an enantioselective reduction and sulfenylation of isoflavanone derivatives by an ion pair strategy. The chiral cationic catalyst bisguanidinium (BG) is capable of chiral induction in catalytic systems. Silane hydride works as a reductant and helps to form an anionic hypervalent silicate complex and intermediates with substrates to pair with chiral catalyst. A series of umpolung sulfur reagents accomplish electrophilic attack in the presence of a silicate anion. Both chemoselectivity and enantioselectivity are good to excellent to afford a wide scope of 4-oxo-4H-chromene-3-carbonitrile and S-electrophilic reagents. Further transformations were completed to introduce more applications.

Whole genome analysis of Flavobacterium aziz-sancarii sp. nov., isolated from Ardley Island (Antarctica), revealed a rich resistome and bioremediation potential

Despite being one of the most isolated regions in the world, Antarctica is at risk of increased contamination with potentially toxic elements and other toxic chemicals through anthropogenic interventions. In this study, a psychrotolerant bacterium was isolated using the lake water collected from Ardley Island (Antarctica), which can grow at temperatures between 4 and 30 °C and pH values between 6.0 and 9.0. The isolate, named AC, had protease, amylase, and lipase activities with no NaCl tolerance and could degrade 1-5% diesel fuel. Multilocus sequence analysis (MLSA) using 16S rRNA, gyrB, tuf, and rpoD genes resulted in 92.91-98.6% sequence similarities between the isolate AC and other Flavobacterium spp. Whole genome analysis indicated that the genome length of Flavobacterium sp. AC is 5.8 Mbp with a GC content of 34.04% and 1274 genes predicted. The strain AC branched independently from other Flavobacterium spp. in the phylogenetic and phylogenomic trees and ranked a new species named Flavobacterium aziz-sancarii. Genome mining identified several cold-inducible genes, including stress-associated genes such as cold-shock proteins, chaperones, carotenoid biosynthetic genes, or oxidative-stress response genes. In addition, virulence, gliding motility, and biofilm-related genes were determined. Its genome contains 35 and 88 open-reading frames related to potentially toxic element and antibiotic resistance, respectively. F. aziz-sancarii showed a remarkable tolerance of Cr and Ni, with minimal inhibitory concentration values of 2.88 and 2.81 mM, respectively. Pb, Cu, and Zn exposure resulted in moderate toxicity (2.14-2.41 mM), while Cd showed the highest inhibitory effect in bacterial growth (0.74 mM). Antibiotic susceptibility testing indicated multidrug-resistant phenotype in correlation to in silico prediction of antibiotic resistance genes. Overall, our results contribute to biodiversity of Antarctica and provide new insights into resistome profile of Antarctic microorganisms. Additionally, the diesel degradation feature of F. aziz-sancarii offers potential use for the bioremediation of hydrocarbon-contaminated polar ecosystems.