No abstract

Severe poisonousness and prolonged instability existing in organic‐inorganic lead‐based perovskite are two matters seriously hindering its potential future application in photocatalysis. Therefore, it is particularly important to explore ecology‐friendly, air‐stable and highly active metal‐halide perovskites. Herein, a new and stable lead‐free perovskite Cs2SnBr6 decorated with reduced graphene oxide (rGO), is synthesized and employed in the photocatalytic organic conversion. The as‐prepared Cs2SnBr6 is ultrastable, exhibiting no clear changes after being placed in the air for six months. The Cs2SnBr6/rGO composite shows excellent photocatalytic activity in photo‐driven‐oxidation of 5‐hydroxymethylfurfural (HMF) to high value enclosed 2,5‐diformylfuran (DFF), achieving>99.5 % conversion of HMF and 88 % DFF selectivity in the presence of green oxidant O2. Comprehensive characterizations disclose a multistep reaction mechanism, demonstrating that the molecular oxygen, photogenerated carriers, ⋅O2− and 1O2 altogether synergistically participate in the effective photo‐driven conversion of HMF to DFF. This work expands the material gallery towards selective organic conversion and environmentally friendly perovskite options for photocatalytic application.

Pseudomonas aeruginosa is capable of causing acute and chronic infections in various host tissues, which depends on its abilities to effectively utilize host-derived nutrients and produce protein virulence factors and toxic compounds. However, the regulatory mechanisms that direct metabolic intermediates towards production of toxic compounds are poorly understood. We previously identified a regulatory protein PvrA that controls genes involved in fatty acid catabolism by binding to palmitoyl-coenzyme A (CoA). In this study, transcriptomic analyses revealed that PvrA activates the Pseudomonas quinolone signal (PQS) synthesis genes, while suppressing genes for production of polyhydroxyalkanoates (PHAs). When palmitic acid was the sole carbon source, mutation of pvrA reduced production of pyocyanin and rhamnolipids due to defective PQS synthesis, but increased PHA production. We further solved the co-crystal structure of PvrA with palmitoyl-CoA and identified palmitoyl-CoA-binding residues. By using pvrA mutants, we verified the roles of the key palmitoyl-CoA-binding residues in gene regulation in response to palmitic acid. Since the PQS signal molecules, rhamnolipids and PHA synthesis pathways are interconnected by common metabolic intermediates, our results revealed a regulatory mechanism that directs carbon flux from carbon/energy storage to virulence factor production, which might be crucial for the pathogenesis.

NrtR is a Nudix-related transcriptional regulator and controls the NAD cofactor biosynthesis in bacteria. P. aeruginosa NrtR binds to the intergenic region between nadD2 and pncA to repress the expression of the two operons, therefore controlling the NAD biosynthesis. We have previously reported that NrtR controls T3SS expression via the cAMP/Vfr pathway in P. aeruginosa .

Bacterial infectious diseases impose a severe threat to human health. The ability to orchestrate virulence determinant in response to the host environment is critical for the pathogenesis of bacterial pathogens. Pseudomonas aeruginosa is a leading pathogen that causes various infections in humans.