Classification and molecular characteristics of tet(X)-carrying plasmids in Acinetobacter species.

The rapid dissemination of plasmid-mediated tet(X) genes in Acinetobacter species has compromised the clinical effectiveness of tigecycline, one of the last-resort antibiotics. However, the classification strategy and homology group of tet(X)-positive Acinetobacter spp. plasmids remain largely unknown. In this study, we classified them by genome-based replicon typing, followed by analyses of structural characteristics, transferability and in vivo effect. A total of 34 plasmids distributed in at least nine Acinetobacter species were collected, including three tet(X3)-positive plasmids and one tet(X6)-positive plasmid from our genome sequencing results. Among them, there were 28 plasmids carrying Rep_3 superfamily replicase genes and classified into six homology groups, consisting of GR31 (82.1%), GR26 (3.6%), GR41 (3.6%), GR59 (3.6%), and novel groups GR60 (3.6%) and GR61 (3.6%). Our tet(X3)-positive plasmids pYH16040-1, pYH16056-1, and pYH12068-1 belonged to the dominant GR31 group, whereas the tet(X6)-positive plasmid pYH12068-2 was unclassified. Structurally, all tet(X)-positive GR31 plasmids shared similar plasmid replication (repB), stability (parA and parB) and accessory modules [tet(X) and sul2], and 97.6% of plasmid-mediated tet(X) genes in Acinetobacter species were adjacent to ISCR2. Conjugation and susceptibility testing revealed pYH16040-1, pYH16056-1, and pYH12068-2, carrying plasmid transfer modules, were able to mediate the mobilization of multiple antibiotic resistance. Under the treatment of tigecycline, the mortality rate of Galleria mellonella infected by pYH16040-1-mediated tet(X3)-positive Acinetobacter spp. isolate significantly increased when compared with its plasmid-cured strain (p < 0.0001). The spread of such plasmids is of great clinical concern, more effects are needed and will facilitate the future analysis of tet(X)-positive Acinetobacter spp. plasmids.

Photoelectric effect of hybrid ultraviolet-sensitized phototransistors from an n-type organic semiconductor and an all-inorganic perovskite quantum dot photosensitizer.

Low-dimensional all-inorganic perovskite quantum dots (QDs) have been increasingly developed as photo-sensing materials in the field of photodetectors because of their strong light-absorption capability and broad bandgap tunability. Here, solution-processed hybrid phototransistors built by a dithienothiophenoquinoid (DTTQ) n-type organic semiconductor transport channel mixing with a colloidal CsPbBr3 perovskite QD photosensitizer are demonstrated by manipulating the relative volume ratio from 10 : 0 to 9 : 1, 7 : 3, 5 : 5, 3 : 7, 1 : 9, and 0 : 10. This results in a significantly enhanced photodetection performance owing to the advantages of a high UV absorption cross-section based on the perovskite QDs, efficient carrier transport abilities from the DTTQ semiconductor, and the photogating effect between the bulk heterojunction photocarrier transfer interfaces. The optimized DTTQ : QD (3 : 7) hybrid phototransistor achieves a high photoresponsivity (R) of 7.1 × 105 A W-1, a photosensitivity (S) of 1.8 × 104, and a photodetectivity (D) of 3.6 × 1013 Jones at 365 nm. Such a solution-based fabrication process using a hybrid approach directly integrated into a sensitized phototransistor potentially holds promising photoelectric applications towards advanced light-stimulated photodetection.

Stable Perovskite Solar Cells Using Molecularly Engineered Functionalized Oligothiophenes as Low-Cost Hole-Transporting Materials.

Triarylamine-substituted bithiophene (BT-4D), terthiophene (TT-4D), and quarterthiophene (QT-4D) small molecules are synthesized and used as low-cost hole-transporting materials (HTMs) for perovskite solar cells (PSCs). The optoelectronic, electrochemical, and thermal properties of the compounds are investigated systematically. The BT-4D, TT-4D, and QT-4D compounds exhibit thermal decomposition temperature over 400 °C. The n-i-p configured perovskite solar cells (PSCs) fabricated with BT-4D as HTM show the maximum power conversion efficiency (PCE) of 19.34% owing to its better hole-extracting properties and film formation compared to TT-4D and QT-4D, which exhibit PCE of 17% and 16%, respectively. Importantly, PSCs using BT-4D demonstrate exceptional stability by retaining 98% of its initial PCE after 1186 h of continuous 1 sun illumination. The remarkable long-term stability and facile synthetic procedure of BT-4D show a great promise for efficient, stable, and low-cost HTMs for PSCs for commercial applications.