Insights into the Transposable Mobilome of Paracoccus spp. (Alphaproteobacteria)

Several trap plasmids (enabling positive selection of transposition events) were used to identify a pool of functional transposable elements (TEs) residing in bacteria of the genus Paracoccus (Alphaproteobacteria). Complex analysis of 25 strains representing 20 species of this genus led to the capture and characterization of (i) 37 insertion sequences (ISs) representing 9 IS families (IS3, IS5, IS6, IS21, IS66, IS256, IS1182, IS1380 and IS1634), (ii) a composite transposon Tn6097 generated by two copies of the ISPfe2 (IS1634 family) containing two predicted genetic modules, involved in the arginine deiminase pathway and daunorubicin/doxorubicin resistance, (iii) 3 non-composite transposons of the Tn3 family, including Tn5393 carrying streptomycin resistance and (iv) a transposable genomic island TnPpa1 (45 kb). Some of the elements (e.g. Tn5393, Tn6097 and ISs of the IS903 group of the IS5 family) were shown to contain strong promoters able to drive transcription of genes placed downstream of the target site of transposition. Through the application of trap plasmid pCM132TC, containing a promoterless tetracycline resistance reporter gene, we identified five ways in which transposition can supply promoters to transcriptionally silent genes. Besides highlighting the diversity and specific features of several TEs, the analyses performed in this study have provided novel and interesting information on (i) the dynamics of the process of transposition (e.g. the unusually high frequency of transposition of TnPpa1) and (ii) structural changes in DNA mediated by transposition (e.g. the generation of large deletions in the recipient molecule upon transposition of ISPve1 of the IS21 family). We also demonstrated the great potential of TEs and transposition in the generation of diverse phenotypes as well as in the natural amplification and dissemination of genetic information (of adaptative value) by horizontal gene transfer, which is considered the driving force of bacterial evolution

GRB 130831a: Rise and demise of a magnetar at z = 0.5

Gamma-ray bursts (GRBs) are the brightest explosions in the universe, yet the properties of their energy sources are far from understood. Very important clues, however, can be deduced by studying the afterglows of these events. We present observations of GRB 130831A and its afterglow obtained with Swift, Chandra, and multiple ground-based observatories. This burst shows an uncommon drop in the X-ray light curve at about 100 ks after the trigger, with a decay slope of α 7. The standard Forward Shock (FS) model offers no explanation for such a behaviour. Instead, a model in which a newly born magnetar outflow powers the early X-ray emission is found to be viable. After the drop, the X-ray afterglow resumes its decay with a slope typical of FS emission. The optical emission, on the other hand, displays no clear break across the X-ray drop and its decay is consistent with that of the late X-rays. Using both the X-ray and optical data, we show that the FS model can explain the emission after 100 ks. We model our data to infer the kinetic energy of the ejecta and thus estimate the efficiency of a magnetar “central engine” of a GRB. Furthermore, we break down the energy budget of this GRB into prompt emission, late internal dissipation, kinetic energy of the relativistic ejecta, and compare it with the energy of the accompanying supernova, SN 2013fu

The Fast, Luminous Ultraviolet Transient AT2018cow: Extreme Supernova, or Disruption of a Star by an Intermediate-Mass Black Hole?

Wide-field optical surveys have begun to uncover large samples of fast (t_rise 10 days. The spectrum remains extremely hot throughout its evolution, and the photospheric radius contracts with time (receding below R<10^14 cm after 1 month). This behavior does not match that of any known supernova, although a relativistic jet within a fallback supernova could explain some of the observed features. Alternatively, the transient could originate from the disruption of a star by an intermediate-mass black hole, although this would require long-lasting emission of highly super-Eddington thermal radiation. In either case, AT 2018cow suggests that the population of fast luminous transients represents a new class of astrophysical event. Intensive follow-up of this event in its late phases, and of any future events found at comparable distance, will be essential to better constrain their origins

Prevalence and Correlates of Injecting with Visitors from the United States Among People Who Inject Drugs in Tijuana, Mexico.

Cross-border infectious disease transmission is a concern related to drug tourism from the U.S. to Mexico. We assessed this risk among people who inject drugs (PWID) in Tijuana, Mexico. We measured the prevalence and identified correlates of injecting with PWID visiting from the U.S. among PWID in Tijuana using univariable and multivariable logistic regression. Of 727 participants, 18.5% injected during the past 6&nbsp;months in Mexico with U.S. PWID described mostly as friends (63%) or acquaintances (26%). Injecting with U.S. PWID was independently associated with higher education [adjusted odds ratio (aOR) = 1.13/year], deportation from the U.S. (aOR = 1.70), younger age at first injection (aOR = 0.96/year), more lifetime overdoses (aOR = 1.08), and, in the past 6&nbsp;months, backloading (aOR = 4.00), syringe confiscation by the police (aOR = 3.02) and paying for sex (aOR = 2.98; all p-values &lt; 0.05). Nearly one-fifth of PWID in Tijuana recently injected with U.S. PWID, and their reported risk behaviors could facilitate cross-border disease transmission