Engineering of a calcium-ion binding site into the RC-LH1-PufX complex of Rhodobacter sphaeroides to enable ion-dependent spectral red-shifting

The reaction centre-light harvesting 1 (RC-LH1) complex of Thermochromatium (Tch.) tepidum has a unique calcium-ion binding site that enhances thermal stability and red-shifts the absorption of LH1 from 880 nm to 915 nm in the presence of calcium-ions. The LH1 antenna of mesophilic species of phototrophic bacteria such as Rhodobacter (Rba.) sphaeroides does not possess such properties. We have engineered calcium-ion binding into the LH1 antenna of Rba. sphaeroides by progressively modifying the native LH1 polypeptides with sequences from Tch. tepidum. We show that acquisition of the C-terminal domains from LH1 α and β of Tch. tepidum is sufficient to activate calcium-ion binding and the extent of red-shifting increases with the proportion of Tch. tepidum sequence incorporated. However, full exchange of the LH1 polypeptides with those of Tch. tepidum results in misassembled core complexes. Isolated α and β polypeptides from our most successful mutant were reconstituted in vitro with BChl a to form an LH1-type complex, which was stabilised 3-fold by calcium-ions. Additionally, carotenoid specificity was changed from spheroidene found in Rba. sphaeroides to spirilloxanthin found in Tch. tepidum, with the latter enhancing in vitro formation of LH1. These data show that the C-terminal LH1 α/β domains of Tch. tepidum behave autonomously, and are able to transmit calcium-ion induced conformational changes to BChls bound to the rest of a foreign antenna complex. Thus, elements of foreign antenna complexes, such as calcium-ion binding and blue/red switching of absorption, can be ported into Rhodobacter sphaeroides using careful design processes

Quantifying K, U, and Th contents of marine sediments using shipboard natural gamma radiation spectra measured on DV JOIDES Resolution

During International Ocean Discovery Program (IODP) expeditions, shipboard-generated data provide the first insights into the cored sequences. The natural gamma radiation (NGR) of the recovered material, for example, is routinely measured on the ocean drilling research vessel DV JOIDES Resolution. At present, only total NGR counts are readily available as shipboard data, although full NGR spectra (counts as a function of gamma-ray energy level) are produced and archived. These spectra contain unexploited information, as one can estimate the sedimentary contents of potassium (K), thorium (Th), and uranium (U) from the characteristic gamma-ray energies of isotopes in the ^(40)K, ^(232)Th, and ^(238)U radioactive decay series. Dunlea et al. [2013] quantified K, Th and U contents in sediment from the South Pacific Gyre by integrating counts over specific energy levels of the NGR spectrum. However, the algorithm used in their study is unavailable to the wider scientific community due to commercial proprietary reasons. Here, we present a new MATLAB algorithm for the quantification of NGR spectra that is transparent and accessible to future NGR users. We demonstrate the algorithm's performance by comparing its results to shore-based inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-emission spectrometry (ICP-ES), and quantitative wavelength-dispersive X-ray fluorescence (XRF) analyses. Samples for these comparisons come from eleven sites (U1341, U1343, U1366-U1369, U1414, U1428-U1430, U1463) cored in two oceans during five expeditions. In short, our algorithm rapidly produces detailed high-quality information on sediment properties during IODP expeditions at no extra cost

The Evolution of Host Specialization in the Vertebrate Gut Symbiont Lactobacillus reuteri

Recent research has provided mechanistic insight into the important contributions of the gut microbiota to vertebrate biology, but questions remain about the evolutionary processes that have shaped this symbiosis. In the present study, we showed in experiments with gnotobiotic mice that the evolution of Lactobacillus reuteri with rodents resulted in the emergence of host specialization. To identify genomic events marking adaptations to the murine host, we compared the genome of the rodent isolate L. reuteri 100-23 with that of the human isolate L. reuteri F275, and we identified hundreds of genes that were specific to each strain. In order to differentiate true host-specific genome content from strain-level differences, comparative genome hybridizations were performed to query 57 L. reuteri strains originating from six different vertebrate hosts in combination with genome sequence comparisons of nine strains encompassing five phylogenetic lineages of the species. This approach revealed that rodent strains, although showing a high degree of genomic plasticity, possessed a specific genome inventory that was rare or absent in strains from other vertebrate hosts. The distinct genome content of L. reuteri lineages reflected the niche characteristics in the gastrointestinal tracts of their respective hosts, and inactivation of seven out of eight representative rodent-specific genes in L. reuteri 100-23 resulted in impaired ecological performance in the gut of mice. The comparative genomic analyses suggested fundamentally different trends of genome evolution in rodent and human L. reuteri populations, with the former possessing a large and adaptable pan-genome while the latter being subjected to a process of reductive evolution. In conclusion, this study provided experimental evidence and a molecular basis for the evolution of host specificity in a vertebrate gut symbiont, and it identified genomic events that have shaped this process

Being Moved: Louis XIV’s Triumphant Tenderness and the Protestant Object

This essay examines the place of affect in Le Triomphe de la Religion, a text from 1687 that praises Louis XIV for the Revocation of the Edict of Nantes and the forced conversion of French Protestants. It explores the role of the material object in this text and contrasts it with seventeenth-century Protestant fears about the seductive power of Catholic objects. Drawing on the work of affect theory, it suggest how attention to the strange relation between emotion and the material object might better illuminate our sense of what it meant to be religiously different in absolutist France

Safety of 2-hour IIVs of tacrolimus in the HSCT unit

Pharmacy residents have the opportunity to complete a research project during their residency training, which provides them with skills on how to conduct and manage a research project. Projects often represent an area of interest and need that has been recognized by the host institution’s pharmacy department. Projects are presented as a poster at an annual CSHP Ontario Branch Residency Research Night, and many eventually go on to be published in a peer-reviewed journal.Background: Administering intravenous (IV) tacrolimus by 24-hour continuous IV infusion (CIV), as recommended by the product monograph, poses significant logistical challenges in the allogeneic hematopoietic stem cell transplantation (HSCT) unit because it requires a dedicated central venous catheter lumen. Consequently, at our institution, tacrolimus has been administered via two-hour intermittent IV infusions (IIV) every twelve hours in the HSCT unit. Administration by IIV is not the standard of practice and shorter infusion times are cautioned due to higher rates of nephrotoxicity, neurotoxicity and infusion-related reactions (IRRs), although there is a paucity of data to support this claim. The primary objective of this retrospective study was to evaluate the safety of a two-hour IIV of tacrolimus in an adult HSCT population. Efficacy was evaluated as a secondary endpoint. Methods and Patients: We performed a retrospective chart review of all patients who received IV tacrolimus at our institution from January 2002 – January 2016. We reviewed 104 patients who received 118 tacrolimus treatment courses by IIV (TTC) [median number of doses per TTC=22, range 1 – 158, interquartile range (IQR) = 28]. Primary outcomes collected include rates of nephrotoxicity, neurotoxicity and IRRs that occurred during TTC. The incidence of acute graft-versus-host disease (aGVHD) and disease relapse within 180 days of transplant were collected to evaluate efficacy. Results and Discussion: There were sixteen incidences (13.6%) of nephrotoxicity, defined as a doubling of serum creatinine from baseline. Nephrotoxicity resolved in all but six (5.1%) cases. Precipitating factor for nephrotoxicity unrelated to tacrolimus were identified by the physician in all six cases. There were 40 incidences (34.5%) of neurotoxicity [seizure, posterior reversible encephalopathy syndrome (PRES), tremor, paresthesia, visual disturbance], of which, eight (6.8%) were considered serious (seizure and/or PRES). All neurotoxicity reverted to baseline or resolved completely. One grade 2 infusion reaction occurred and resolved without discontinuation of tacrolimus. In the subset of patients who received tacrolimus for the prevention of aGVHD (n=41), seven patients (17.1%) developed grade II – IV aGVHD. Nine patients (8.7%) experienced relapse of their disease. Conclusions: We propose that a two-hour IIV of tacrolimus is a safe method of administration in the adult HSCT setting. Additional safety and efficacy data from other institutions will provide external validity to this conclusion