Bacterial conjugation plays a major role in the dissemination of antibiotic resistance and virulence traits through horizontal transfer of plasmids. Robust measurement of conjugation frequency of plasmids between bacterial strains and species is therefore important for understanding the transfer dynamics and epidemiology of conjugative plasmids. In this study, we present a streamlined experimental approach for fluorescence labelling of low-copy-number conjugative plasmids that allows plasmid transfer frequency during filter mating to be measured by flow cytometry. A blue fluorescent protein gene is inserted into a conjugative plasmid of interest using a simple homologous recombineering procedure. A small non-conjugative plasmid, which carries a red fluorescent protein gene with a toxin-antitoxin system that functions as a plasmid stability module, is used to label the recipient bacterial strain. This offers the dual advantage of circumventing chromosomal modifications of recipient strains and ensuring that the red fluorescent protein gene-bearing plasmid can be stably maintained in recipient cells in an antibiotic-free environment during conjugation. A strong constitutive promoter allows the two fluorescent protein genes to be strongly and constitutively expressed from the plasmids, thus allowing flow cytometers to clearly distinguish between donor, recipient, and transconjugant populations in a conjugation mix for monitoring conjugation frequencies more precisely over time.
The shape of newly laid eggs of the wasps Microplitis mediator is different from that of the eggs in the calyx region, due to mechanical press while they pass through the ovipositors, which initiates the development of the embryos. Six hours after oviposition, the embryo attains the germ band stage, and a serosal membrane is observed. Hatching occurs at 32～34 h. Immediately after hatching, the cells from the upper serosal membrane of the embryo disperse to form teratocytes in the haemocoele of the host, while those from the lower part are released gradually. The 1st instar larva has a pair of sclerotized mandibles, which are used as a weapon to fight with its con species competitors. A caudal sac is well developed after the larva enters its 2nd instar at 108～113 h. The surface of a mature teratocyte (6 days after parasitization) is covered with numerous microvilli. A vesiculated endoplasmic reticulum system disperses throughout the cytoplasm in which many Golgi complexes exist too. The nucleus is extensively ramified.
Breast cancer is the most common malignancy in females. The emergence of endocrine resistance is frustrating for estrogen receptor (ER)-positive breast cancer patients even the efficacy of endocrine therapy is acceptable. Our previous study has shown that tumor-associated macrophages (TAMs) are associated with endocrine resistance, yet the mechanism remains unclear. This article is dedicated to discuss the role of TAMs in the endocrine resistance of breast cancer. It was found that tamoxifen-resistant MCF-7 cells induced more macrophages polarized into TAMs. Conversely, TAMs increased the expression of cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2), which promoted tamoxifen resistance through the activation of the PI3K/Akt/mTOR signaling pathway in MCF-7 cells. Furthermore, clinical analysis supported that five-year progression-free survival (PFS) of breast cancer patients with abundant COX-2 expression in TAMs was shorter (p<0.05). Therefore, these results show a positive feedback loop between TAMs and breast cancer cells, suggesting that TAMs and COX-2 may be new therapeutic targets for breast cancer patients suffering from endocrine resistance.
Abstract Horizontal gene transfer (HGT) mediated by the spread of plasmids fuels evolution in prokaryotes. Although plasmids provide bacteria with new adaptive genes, they also produce physiological alterations that often translate into a reduction in bacterial fitness. The fitness costs associated with plasmids represent an important limit to plasmid maintenance in bacterial communities, but their molecular origins remain largely unknown. In this work, we combine phenomics, transcriptomics and metabolomics to study the fitness effects produced by a collection of diverse plasmids in the opportunistic pathogen Pseudomonas aeruginosa PAO1. Using this approach, we scan the physiological changes imposed by plasmids and test the generality of some main mechanisms that have been proposed to explain the cost of HGT, including increased biosynthetic burden, reduced translational efficiency, and impaired chromosomal replication. Our results suggest that the fitness effects of plasmids have a complex origin, since none of these mechanisms could individually provide a general explanation for the cost of plasmid carriage. Interestingly, our results also showed that plasmids alter the expression of a common set of metabolic genes in PAO1, and produce convergent changes in host cell metabolism. These surprising results suggest that there is a common metabolic response to plasmids in P. aeruginosa PAO1.
Abstract CRISPR/Cas12a (Cpf1) is a single RNA-guided endonuclease that provides new opportunities for targeted genome engineering through the CRISPR/Cas9 system. Only AsCpf1 have been developed for insect genome editing, and the novel Cas12a orthologs nucleases and editing efficiency require more study in insect. We compared three Cas12a orthologs nucleases, AsCpf1, FnCpf1, and LbCpf1, for their editing efficiencies and antiviral abilities in vitro . The three Cpf1 efficiently edited the BmNPV genome and inhibited BmNPV replication in BmN-SWU1 cells. The antiviral ability of the FnCpf1 system was more efficient than the SpCas9 system after infection by BmNPV. We created FnCpf1×gIE1 and SpCas9×sgIE1 transgenic hybrid lines and evaluated the gene editing efficiency of different systems at the same target site. We improved the antiviral ability using the FnCpf1 system in transgenic silkworm. This study demonstrated use of the CRISPR/Cpf1 system to achieve high editing efficiencies in the silkworm, and illustrates the use of this technology for increasing disease resistance. Author Summary Genome editing is a powerful tool that has been widely used in gene function, gene therapy, pest control, and disease-resistant engineering in most parts of pathogens research. Since the establishment of CRISPR/Cas9, powerful strategies for antiviral therapy of transgenic silkworm have emerged. Nevertheless, there is still room to expand the scope of genome editing tool for further application to improve antiviral research. Here, we demonstrate that three Cpf1 endonuclease can be used efficiency editing BmNPV genome in vitro and in vivo for the first time. More importantly, this Cpf1 system could improve the resistance of transgenic silkworms to BmNPV compare with Cas9 system, and no significant cocoons difference was observed between transgenic lines infected with BmNPV and control. These broaden the range of application of CRISPR for novel genome editing methods in silkworm and also enable sheds light on antiviral therapy.
GaN epitaxial films were grown on c-face sapphire substrates by metalorganic chemical vapor deposition (MOCVD) with an in situ SiNx deposition insert ed into the normal growth process. The in situ SiNx deposition makes a nanomask on GaN, followed by the epitaxial lateral overgrowth on it. Raman spe ctra and photoluminescence are used to study the stress state of the resulting G aN film. The formation of SiNx nanomask leads to a 2D-3D growth mode transition, which ends in the total coalesce of the GaN film. The distribution o f stress state in this kind of GaN film is more uniform than that of films grown by the conventional epitaxial lateral overgrowth. The data about the relaxation of the stress deduced by the Raman spectra match well with those obtained by ph otoluminescence. These data also show that the more residual stress in the GaN f ilm grown on the SiNx nanomask is relaxed when the time of in situ Si Nx deposition is increased. This is because with the increasing time of in situ SiNx deposition, the wing area of epitaxial lateral overgr owth becomes larger, which will reduce the stress in the GaN thin film grown on it.
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