Chromosomal DNA Fragment Research Articles

The whole-genome sequence of Bacillus sp. KICET-3, isolated from doenjang.

Bacillus sp. KICET-3, isolated from doenjang, a traditional Korean fermented food, has a single chromosomal DNA fragment of 4,616,861 bp, and the G+C content is 45.52%. It is estimated to have 4,450 predicted coding DNA sequences, 84 tRNAs, and 24 rRNAs.

Chemotherapeutic effect of baicalein/epirubicin combination against liver cell carcinoma in-vitro: Inducing apoptosis and autophagy

Flavonoids have a pivotal cytotoxic effect against hepatocellular carcinoma (HCC). The current study aimed to investigate which flavonoid isolated from Physalis pubescens L. leaves has the most cytotoxic effect against Hep-G2 liver cancer cells and if it could ameliorate epirubicin efficacy and safety. Baicalein trimethyl ether (BTME), rutin, quercitrin and myricitrin were isolated from Physalis Pubescens L. leaves. Hep-G2 cells were treated with the isolated flavonoids as well as a combination of BTME and epirubicin. Cell viability and the chromosomal DNA fragmentation in Hep-G2 cells were assessed. BTME showed the best cytotoxic effect against Hep-G2 cells. Combination of epirubicin with (200 μg/mL) BTME significantly decreased the IC50 of epirubicin from 2.79 ± 0.626 μg/mL to 0.76 ± 0.258 μg/mL. Moreover, the same combination significantly increased the IC50 of BTME against WI-38 normal cells. DNA fragmentation as well as the concentration of beclin 1 and Bax were significantly increased in Hep-G2 cells treated with BTME and BTME+epirubicin compared to untreated cells. Besides, BTME and BTME+epirubicin significantly decreased the gene expression of TGFβ1 whereas increased ATG-7 gene expression. Conclusions: BTME (200μg/mL) significantly enhanced epirubicin's cytotoxicity against Hep-G2 cells and ameliorated its safety profile. BTME could exert anti-hepatocarcinoma effect by enhancing apoptosis and autophagy.

Kolistin direncinin moleküler tespitinde yanlış tanı: kolistine duyarlı Acinetobacter baumannii izolatlarında yanlış mcr-1-PCR pozitifliği

Purpose: The aim of this study was to investigate the presence of the mcr-1 gene, which is responsible for colistin resistance, in carbapenem-resistant Gram-negative bacteria that cause difficult-to-treat infections in a research hospital in Turkey. 
 Materials and Methods: The mcr-1 gene was examined using PCR in 103 carbapenem-resistant isolates, including 75 Acinetobacter baumannii, 19 Pseudomonas aeruginosa, and 9 Klebsiella pneumoniae. DNA sequencing was performed to confirm the mcr-1 positivity. Other antimicrobial resistance genes were investigated in isolates that were found to be mcr-1-positive by PCR and colistin-resistant isolates. 
 Results: Four (3.9% of the 103 carbapenem-resistant isolates and 5.3% of the 75 A. baumannii isolates) A. baumannii isolates, all susceptible to colistin, were found to be mcr-1-positive by PCR, whereas mcr-1 was not detected in four colistin-resistant isolates, one in A. baumannii and three in K. pneumoniae. DNA sequencing analysis determined that none of the amplification products was the targeted fragment, but they matched more than 70% with the chromosomal DNA fragments of A. baumannii strains. Therefore, these results were considered false-positive. Although these false-positive isolates were susceptible to colistin, they were extensively drug-resistant (XDR). Two of them were found to carry blaOXA23-like and blaTEM genes, another blaOXA23-like, blaTEM and blaOXA48-like genes, and the fourth one to have blaOXA23-like and blaCTXM genes. 
 Conclusion: Although the specificity of the primers used to detect the mcr-1 gene by PCR was reported as 100% in most studies, we concluded that PCR tests are insufficient yet to use alone or with antibiotic susceptibility tests in rapid routine diagnosis. Confirming at least PCR-positive samples using DNA sequence analysis would be appropriate for a certain period.

In vitro toxicological assessment of PhSeZnCl in human liver cells

Phenylselenenylzinc chloride (PhSeZnCl) is an air-stable selenolate, easily synthesizable through oxidative insertion of elemental zinc into the Se-halogen bond of the commercially available phenylselenyl chloride. PhSeZnCl was shown to possess a marked GPx-like activity both in NMR and in vitro tests, and to effectively react with cellular thiols, and was supposed for a potential use in the chemotherapy of drug-resistant cancers. However, activity of PhSeZnCl in hepatic cells has never been tested before now. In this in vitro approach, we evaluated the cytotoxic, genotoxic, and apoptotic activities, as well as the effects on cell cycle of PhSeZnCl in two preclinical hepatic models, namely HepG2 and HepaRG cells. Results showed that cell viability of HepG2 and HepaRG cells decreased in a dose-dependent manner, with a more marked effect in HepG2 tumour cells. Moreover, treatment with 50 µg/mL PhSeZnCl caused an increase of primary DNA damage (4 h) and a statistically significant increase of HepG2 cells arrested in G2/M phase. In addition, it altered mitochondrial membrane potential and induced chromosomal DNA fragmentation (24 h). In HepaRG cells, PhSeZnCl was able to determine a cell cycle-independent induction of apoptosis. Particularly, 50 µg/mL induced mitochondrial membrane depolarization after 24 h and apoptosis after 4 h treatment. Futhermore, all PhSeZnCl concentrations tested determined a significant increase of apoptotic cells after 24 h. Apoptosis was also highlighted by the detection of active Caspase-3 by Western Blot analysis after 24 h exposure. In conclusion, this first toxicological assessment provides new insights into the biological activity of PhSeZnCl in preclinical hepatic models that will be useful in future safety assessment investigation of this compound as a potential pharmaceutical.

Extruded small extracellular vesicles: splinters of circulating tumour cells may promote cancer metastasis?

We speculate ruptured circulating tumour cells (CTC) in capillaries could release a large number of small extracellular vesicle-like vesicles, namely mechanically extruded sEV (sEVme), which can encapsulate chromosomal DNA fragments. These sEVme have similar physicochemical properties compared to small extracellular vesicles spontaneously secreted by living cells (sEVss), and thus sEVme and sEVss cannot be effectively distinguished based on their size or membrane protein markers. Meanwhile, these sEVme derived from CTC inherit oncogenic payloads, deliver cargo through the bloodstream to recipient cells, and thus may promote cancer metastasis. The validation of this speculation could facilitate our understanding of EV biogenesis and cancer pathology. The potential finding will also provide a theoretical foundation for burgeoning liquid biopsy using DNA fragments derived from harvested sEV.

Working with Phage P22.

Transduction experiments in Escherichia coli and Salmonella are usually performed with virulent phage variants. A widely used P1 mutant, called P1 vir, carries one or more uncharacterized mutations that prevent formation of lysogens. In the case of P22, by far the most frequently used variant is named P22 HT105/1 int-201 This phage has a high transducing (HT) frequency due to a mutant nuclease with lower specificity for the pac sequence. As a result, ∼50% of the P22 HT phage heads carry random transducing fragments of chromosomal DNA. The int mutation reduces the formation of stable lysogens. The basic steps in handling the P22 HT105/1 int-201 phage and in performing transduction experiments in Salmonella are described here.

Evolution of an Apomixis-Specific Allele Class in Supernumerary Chromatin of Apomictic Boechera.

Asexual reproduction through seeds in plants (i.e., apomixis) is a heritable trait, and apomixis- linked loci have been identified in multiple species. However, direct identification of genomic elements is typically hindered as apomixis-linked loci and are commonly found in recombination-suppressed and repetitive regions. Heterochromatinized elements, such as B chromosomes and other supernumerary chromosomal DNA fragments have long been known to be associated with asexuality in both plants and animals and are prime candidate regions for the evolution of multiple apomixis factors controlling the individual elements of apomixis. Here, we examined molecular evolution, gene regulation, and chromosomal location of a male apomeiosis factor (UPG2), a long noncoding RNA gene, in sexual and apomictic Boechera with and without male apomeiosis (i.e., balanced and unbalanced apomicts). We revealed the origin of the gene in the apomixis genome on an apomixis-specific, supernumerary heterochromatic Boechera chromosome (Boe1). The UPG2 is active in the tapetum at male meiosis. We found allele classes specific to apomictic and sexual Boechera accessions and a third class that shares the features of both and points to a convergent transition state. Sex alleles are found only in some of the sexual accessions and have higher nucleotide divergence and lower transcriptional activity compared to apo alleles. These data demonstrate selective pressure to maintain the function of UPG2 for unreduced pollen formation in apomicts as the occasional transmission of the allele from unbalanced apomicts into sexual organisms that lead to pseudogenization and functional decay of copies in sexual organisms.

GATA2 deficiency associated with copy number variation: A reference for considering inborn errors of immunity

Deletions and duplications of chromosomal DNA fragments, alongside inversions and translocations, are collectively termed copy number variants (CNVs). A significant contribution to human genome variability can be attributed to CNVs, which are estimated to account for 4.8% to 9.7% of the human genome.1 Copy number variants have three potential implications: no phenotypic effect, an adaptive trait, or underlying disease. Mechanisms implicated in CNV-associated disease include gene dosage, gene disruption, gene fusion, and long-range regulation effects.

WWOX regulates UV/cold shock‐mediated calcium influx and nuclear bubbling in frostbite

UV/cold shock‐mediated frostbite involves non‐apoptotic nuclear bubbling cell death (BCD) and participation of functional WWOX in cells (WWOXf). In contrast, cells with WWOX deficiency or dysfunction (WWOXd) undergo pop‐out explosion death (POD). Here, by time‐lapse microscopy, when WWOXf cells were exposed to UV or UV/cold shock and then incubated at room temperature, these cells rapidly and sequentially underwent: 1) loss of mitochondrial membrane potential, 2) formation of a nitric oxide (NO)‐containing nuclear bubble per cell, 3) WWOX‐dependent increase in calcium (Ca2+) influx, 4) shutdown of mRNA and protein synthesis machinery, as determined by RT/PCR and gene chip analysis, and 5) eventual cell death without caspase activation, stress fiber formation and chromosomal DNA fragmentation. In contrast, WWOXd cells exhibited a faster kinetics of stress fiber formation, explosion and death without NO production. Ectopic WWOX restored calcium influx and nuclear bubbling in WWOXd cells. In hairless mice, UV/cold shock rapidly downregulated protein expression in the skin and then liver, which may lead to organ damages. UV/cold shock induced complex formation of antiapoptotic TRAF2 and proapoptotic WWOX and their co‐translocation to the nucleus, where the complex dissociation occurred. The observations suggest that WWOX and TRAF2 dissociation is needed for nuclear bubbling and death.

Assessing PfGARP-Mediated Apoptosis of Blood-Stage Plasmodium falciparum Parasites.

Apoptosis is conventionally regarded as an evolutionarily conserved and genetically controlled process of programmed cell death confined to metazoan organisms. However, recently, conserved features of apoptosis have also been demonstrated in unicellular eukaryotes (Holzmuller et al. Parasitology 132:S19-S32, 2006; Le Chat et al. Mol Biochem Parasitol 153:41-47, 2007; Madeo et al. Curr Opin Microbiol 7:655-660, 2004; Welburn et al. Parasitology 132:S7-S18, 2006; Jensen et al. Science 216:1230-1233, 1982) including malaria parasites (Al-Olayan et al. Int J Parasitol 32:1133-1143, 2002; Ch'ng et al. Cell Death Dis 1:e26, 2010; Meslin et al. J Infect Dis 195:1852-1859, 2007; Picot et al. Trans R Soc Trop Med Hyg 91:590-591, 1997; Raj et al. Nature 582:104-108, 2020). P. falciparum glutamic-acid-rich protein (PfGARP) is an antigen of 80kDa that is uniquely expressed on the exofacial surface of red blood cells (RBCs) infected by early-to-late-trophozoite-stage P. falciparum parasites (Raj et al. Nature 582:104-108, 2020). We have recently demonstrated that antibodies against PfGARP bind to the PfGARP displayed on the surface of P. falciparum trophozoite-infected RBCs and trigger apoptosis in the intracellular parasites (Raj et al. Nature 582:104-108, 2020). This is the first demonstration of antibody-induced apoptosis in blood-stage malaria parasites and is characterized by several conserved features such as crisis form morphology, loss of mitochondrial membrane potential, loss of integrity of food vacuole, activation of caspase-like cysteine proteases, and fragmentation of chromosomal DNA. Here we describe the assays used to detect these features of apoptosis in the mature blood stage of malaria parasites.

SCO6992, a Protein with β-Glucuronidase Activity, Complements a Mutation at the absR Locus and Promotes Antibiotic Biosynthesis in Streptomyces coelicolor.

Streptomyces coelicolor is a filamentous soil bacterium producing several kinds of antibiotics. S. coelicolor abs8752 is an abs (antibiotic synthesis deficient)-type mutation at the absR locus; it is characterized by an incapacity to produce any of the four antibiotics synthesized by its parental strain J1501. A chromosomal DNA fragment from S. coelicolor J1501, capable of complementing the abs- phenotype of the abs8752 mutant, was cloned and analyzed. DNA sequencing revealed that two complete ORFs (SCO6992 and SCO6993) were present in opposite directions in the clone. Introduction of SCO6992 in the mutant strain resulted in a remarkable increase in the production of two pigmented antibiotics, actinorhodin and undecylprodigiosin, in S. coelicolor J1501 and abs8752. However, introduction of SCO6993 did not show any significant difference compared to the control, suggesting that SCO6992 is primarily involved in stimulating the biosynthesis of antibiotics in S. coelicolor. In silico analysis of SCO6992 (359 aa, 39.5 kDa) revealed that sequences homologous to SCO6992 were all annotated as hypothetical proteins. Although a metalloprotease domain with a conserved metal-binding motif was found in SCO6992, the recombinant rSCO6992 did not show any protease activity. Instead, it showed very strong β-glucuronidase activity in an API ZYM assay and toward two artificial substrates, p-nitrophenyl-β-D-glucuronide and AS-BI-β-D-glucuronide. The binding between rSCO6992 and Zn2+ was confirmed by circular dichroism spectroscopy. We report for the first time that SCO6992 is a novel protein with β-glucuronidase activity, that has a distinct primary structure and physiological role from those of previously reported β-glucuronidases.

Methyl Jasmonate Effect on Betulinic Acid Content and Biological Properties of Extract from Senna obtusifolia Transgenic Hairy Roots.

It is known that Senna obtusifolia has been used in medicine since ancient times due to the content of many valuable compounds with a pro-health effect. One of them is betulinic acid, which is a pentacyclic triterpene with antimalarial, antiviral, anti-inflammatory and anticancer properties. In this work, a continuation of our previous research, an attempt was made to increase the level of betulinic acid accumulation by the cultivation of transgenic hairy roots that overexpress the squalene synthase gene in a 10 L sprinkle bioreactor with methyl jasmonate elicitation. We present that the applied strategy allowed us to increase the content of betulinic acid in hairy root cultures to the level of 48 mg/g dry weight. The obtained plant extracts showed a stronger cytotoxic effect on the U87MG glioblastoma cell line than the roots grown without elicitors. Additionally, the induction of apoptosis, reduction of mitochondrial membrane potential, chromosomal DNA fragmentation and activation of caspase cascades are demonstrated. Moreover, the tested extract showed inhibition of topoisomerase I activity.

P–142 Comparison of the IVF outcome in the course of ICSI vs PICSI treatment continuation in exactly the same group of HBA abnormal patients

Abstract Study question Does the PICSI have a beneficial effect for men with abnormal HBA on the fertilization rate, blastocysts number and clinical pregnancies in the next attempt? Summary answer Patients with HBA <80% choosing to undergo PICSI after ICSI failure see an increase in blastocyst and pregnancy rates. What is known already Hyaluronic acid (HA) is a main component of cervical mucus and the extracellular matrix of cumulus cells. The formation of HA-binding sites in sperm cell membranes is one of the markers of sperm maturation indicating completion the spermatogenic process of remodelling the plasmatic membrane, cytoplasmic extrusion and nuclear maturity. Spermatozoa selected by the HA-binding technique (the physiologically selected intracytoplasmic sperm injection – PICSI) have a potentially reduced risk of chromosomal aneuploidy or DNA fragmentation. Recent evidence do not show significant benefits in using PICSI. However, it has not been analysed in the course of treatment continuation in the same patients. Study design, size, duration This was a retrospective case-control study. It included exactly the same 58 patients with abnormal HBA, who underwent IVF treatment with ICSI initially and later with PICSI, between January 2014 and October 2020 at INVICTA Fertility Centre, Poland. Median female partner age in PICSI group was 36,2±5,34, without PICSI 35,8 ±5,28. Participants/materials, setting, methods 275 cycles (130 ICSI and 145 PICSI) resulted in 793 and 897 MII respectively. Patients were also divided into two groups <80% and ≥80% depending on the obtained HBA score expressed as the percentage of sperm bound with hyaluronan. The analysis covered the fertilization rate (FR), TQ and total blastocyst rate on day 5 and clinical pregnancy rate. Patients with poor response to stimulation were excluded from the study. Main results and the role of chance FR in ICSI and PICSI groups was not significantly difference (57.00%±31.2 vs 59.87%±30.8) even when taking into account the division of patients according to the obtained HBA score. In the <80% group the FR was 57.04%±29.3 vs 59.54%±30.8 in ICSI vs PICSI group respectively. There were no significant differences when comparing the under HBA ≥80% subgroups for all analysed outcomes. Fertilization rate ​​was 56.88% in the ICSI group vs 61.03% in the PICSI group. The percentage of blastocysts was 28.61% vs 34.45% and the percentage of TQ blastocysts on day 5 was 15.32% vs 16.81% with ICSI and PICSI respectively, in the group consisting of the same patients. In the HBA <80% group significant differences were observed in the percentage of obtained blastocysts 37.81% vs 47.61% by comparing the ICSI and PICSI approaches (p < 0.05). Also, percentage of TQ blastocyst on day 5 also was higher in patients with <80% HBA score after PICSI and was statistically significant (17.07% ICSI vs 23.92% PICSI, p < 0.05). We saw statistically significant (p < 0.01) increase in percentage of clinical pregnancies from 29.03% without PICSI to 69.44% in patient’s subsequent procedures involving PICSI. Limitations, reasons for caution More data is required to confirm that improved results of PICSI procedure are consistent and possible to reproduce in a larger group – and as a result could be included as part of the standard treatment process. Wider implications of the findings: The presented results show that in patients with normal HBA score, PICSI does not bring a measurable benefit and this may be important factor to consider in decision-making for couples seeking assistance. Trial registration number Not applicable

Does maternal exposure to nicotine affect the oocyte quality and reproductive capacity in adult offspring?

Gonadal development begins in the intrauterine phase and females from most species are born with an established oocyte reserve. Exposure to drugs during gestation can compromise the offspring health, also affecting the gametes quality. Nicotine, the main component of cigarettes, is an oxidant agent capable of altering the fertility in men and women. As female gametes are susceptible to oxidative stress, this drug can damage the oolemma and affect oocyte maturation, induce errors during chromosomal segregation and DNA fragmentation. Oocyte mitochondria are particularly susceptible to injuries, contributing to the oocyte quality loss and embryonic development disruption. Thus, considering the high number of women who smoke during pregnancy, while significant events are occurring in the embryo for future fertility of offspring, we seek to verify the quality of the oocytes from adult rats exposed to nicotine during intrauterine phase and breastfeeding. Pregnant Wistar rats received nicotine by osmotic mini-pumps and the female progenies were evaluated in adulthood for oocyte quality (viability, lipid peroxidation, generation of reactive oxygen species and mitochondrial integrity) and reproductive capacity. Embryos (3dpc) and fetuses (20dpc) generated by these rats were also evaluated. The results showed that the dose of 2 mg/kg/day of nicotine through placenta and breast milk does not affect the number of oocytes and the fertility capacity of adult rats. However, it causes some morphological alterations in oocytes, mitochondrial changes, embryonic fragmentation and disruption of fetal development. The malformations in fetuses generated from these gametes can also indicate the occurrence of epigenetic modifications.

Identification and characterization of a hemagglutinin gene from Prevotella intermedia

In this study, we describe the cloning of a gene encoding hemagglutinin from Prevotella intermedia to characterize hemagglutinin function and elucidate its possible role in the infectious process mediated by the organism. We screened genomic libraries created in Escherichia coli JM109, using antibodies against P . intermedia , and the positive clones were subsequently tested for their hemagglutinating activity, using rabbit red blood cells. We isolated a clone of strain 0543 in which, a 3.6-kb P. intermedia chromosomal DNA fragment was inserted into the pUC18 plasmid. Our deletion analysis-based subcloning procedures identified a hemagglutinin gene―designated phg. The open-reading frame of phg encoded a 35-kDa protein, and the expression of a recombinant protein of the predicted size was observed in a fusion protein expression system. While the DNA analysis of phg revealed no homology to known DNA sequences, the putative promoter, ribosome binding, and transcriptional termination sequence were found in the flanking DNA regions. In the N-terminus of the deduced amino acid sequence, we found a consensus leader peptide sequence for secretory proteins. These findings indicate that hemagglutinin might be expressed on the surface of P. intermedia to mediate its function.

Nanoparticles: Weighing the Pros and Cons from an Eco-genotoxicological Perspective.

The exponential growth of nanotechnology and the industrial production have raised concerns over its impact on human and environmental health and safety (EHS). Although there has been substantial progress in the assessment of pristine nanoparticle toxicities, their EHS impacts require greater clarification. In this review, we discuss studies that have assessed nanoparticle eco-genotoxicity in different test systems and their fate in the environment as well as the considerable confounding factors that may complicate the results. We highlight key mechanisms of nanoparticle-mediated genotoxicity. Then we discuss the reliability of endpoint assays, such as the comet assay, the most favored assessment technique because of its versatility to measure low levels of DNA strand breakage, and the micronucleus assay, which is complementary to the former because of its greater ability to detect chromosomal DNA fragmentation. We also address the current recommendations on experimental design, including environmentally relevant concentrations and suitable exposure duration to avoid false-positive or -negative results. The genotoxicity of nanoparticles depends on their physicochemical features and the presence of co-pollutants. Thus, the effect of environmental processes (e.g., aggregation and agglomeration, adsorption, and transformation of nanoparticles) would account for when determining the actual genotoxicity relevant to environmental systems, and assay procedures must be standardized. Indeed, the engineered nanoparticles offer potential applications in different fields including biomedicine, environment, agriculture, and industry. Toxicological pathways and the potential risk factors related to genotoxic responses in biological organisms and environments need to be clarified before appropriate and sustainable applications of nanoparticles can be established.

Photodynamic therapy: When van der Waals heterojunction meets tumor

• The vdW heterostructure of graphitic carbon nitride and metallic molybdenum disulfide (CNMS) was fabricated. • CNMS was employed as nano-photosensitizer for efficient photodynamic therapy. • Both O 2 and H 2 O molecules were utilized for light responsive ROS production. • Outstanding biocompatibility and biosafety were guaranteed. Clinically approved photodynamic therapy (PDT) has emerged as an alternative treatment for cancers and malignant diseases; however, high quality PDT agents were still in great demand. Herein, the van der Waals (vdW) heterostructure of graphitic carbon nitride (g-C 3 N 4 , abbreviated as CN here) and metallic molybdenum disulfide (1T-MoS 2 , abbreviated as MS here) was fabricated, PEGylated, and then investigated. By making use of the extraordinary antenna effect and the ultrafast electron transfer rate of metallic molybdenum disulfide, as well as the efficient separation of photogenerated electron-hole pairs of the final heterojunction, massive reactive oxygen species (ROS) can be generated under 670 nm laser irradiation together with the as-synthesized g-C 3 N 4 @1T-MoS 2 vdW nanostructure (CNMS), which should be largely owed to the appealing photocatalytic water splitting property of the CNMS structure. It was well proved by the in vitro studies that the intracellularly produced ROS can result in cell death, by the way of inducing cell apoptosis and/or necrosis through mediating phosphatidylserine ectropion, mitochondrial depolarization, and chromosomal DNA fragmentation, as well as up-regulating the expression of apoptosis-related proteins and unbalancing intracellular redox homeostasis. In vivo exploration also gave out satisfactory results that the tumor growth could be significantly inhibited by the photodynamic therapy. Additionally, outstanding biocompatibility and biosafety were also guaranteed. All these results provided compelling evidences for that the CNMS vdW heterostructure is an aussichtsreich nano-photosensitizer, and may provide some fresh ideas for the developing of nanomedicine for PDT application.

CdSe/ZnS Core-Shell-Type Quantum Dot Nanoparticles Disrupt the Cellular Homeostasis in Cellular Blood–Brain Barrier Models

Two immortalized brain microvascular endothelial cell lines (hCMEC/D3 and RBE4, of human and rat origin, respectively) were applied as an in vitro model of cellular elements of the blood–brain barrier in a nanotoxicological study. We evaluated the impact of CdSe/ZnS core-shell-type quantum dot nanoparticles on cellular homeostasis, using gold nanoparticles as a largely bioorthogonal control. While the investigated nanoparticles had surprisingly negligible acute cytotoxicity in the evaluated models, a multi-faceted study of barrier-related phenotypes and cell condition revealed a complex pattern of homeostasis disruption. Interestingly, some features of the paracellular barrier phenotype (transendothelial electrical resistance, tight junction protein gene expression) were improved by exposure to nanoparticles in a potential hormetic mechanism. However, mitochondrial potential and antioxidant defences largely collapsed under these conditions, paralleled by a strong pro-apoptotic shift in a significant proportion of cells (evidenced by apoptotic protein gene expression, chromosomal DNA fragmentation, and membrane phosphatidylserine exposure). Taken together, our results suggest a reactive oxygen species-mediated cellular mechanism of blood–brain barrier damage by quantum dots, which may be toxicologically significant in the face of increasing human exposure to this type of nanoparticles, both intended (in medical applications) and more often unintended (from consumer goods-derived environmental pollution).

Bacterial Conjugation Protocol for Ruminant Mycoplasmas.

In Mycoplasma agalactiae, two simultaneous processes of DNA transfer have been described that require direct cell-to-cell contact and are similar to conjugation. One involves the self-transmission of an integrative conjugative element (ICE) while the second concerns the horizontal transfer of large and small fragments of chromosomal DNA. Here, we describe an optimized conjugation protocol for the horizontal transfer of ICE or chromosomal DNA carrying antibiotic resistance markers (i.e., tetracycline, gentamicin, puromycin) from donor to recipient mycoplasma cells. Calculation of the conjugation frequencies, selection and characterization of transconjugants are detailed. This protocol has been developed with M. agalactiae but has been successfully used for M. bovis and can be adapted to other related mycoplasma species.

Transmission of Chromosomal MDR DNA Fragment Encoding Ciprofloxacin Resistance by a Conjugative Helper Plasmid in Salmonella.

Resistance to ciprofloxacin, a treatment choice for Salmonella infections, has increased dramatically in recent years in particular in serotype Salmonella Derby with most of strains carrying chromosome-encoded multiple plasmid-mediated quinolone resistance (PMQR) genes. In this work, we discovered a conjugative plasmid, pSa64-96kb, in a Salmonella Derby isolate, namely Sa64, which could extract and fuse to a multiple drug resistance (MDR) DNA fragment containing two PMQR genes, aac(6’)-Ib-cr, and qnrS2 located on the chromosome of the Salmonella strain. This process led to the formation of a new 188 kb fusion plasmid, which could be then subsequently transmitted to recipient strain Escherichia coli J53. The chromosomal MDR DNA fragment was shown to be flanked by one copy of IS26 element at each end and could be excised from the chromosome to form circular intermediate, which was then fused to pSa64-96kb and form a single plasmid through IS26 mediated homologous recombination. The role of IS26 on enhancing the efficacy of fusion and transmission of this chromosomal MDR DNA fragment was further proven in other Salmonella strains. These findings showed that dynamic interaction between specific chromosomal fragment and plasmids may significantly enhance resistance development and transferability of mobile resistance-encoding elements among bacterial pathogens.