Immuno-enzymatic evaluation of the recombinant TSSA-II protein of Trypanosoma cruzi in dogs and human sera: a tool for epidemiological studies

The rTSSA-II (recombinant Trypomastigote Small Surface II) antigen was evaluated by ELISA to detect anti-Trypanosoma cruzi antibodies in sera from naturally infected dogs and humans. For this evaluation ELISA-rTSSA-II was standardized and groups were classified according to the results obtained through xenodiagnosis, ELISA and PCR. Sensitivity (Se), Specificity (Sp), Kappa index (KI) and area under curve (AUC) were determined. The Se was determined by using 14 sera from dogs infected with T. cruzi VI (TcVI) whereas Sp was determined by using 95 non-chagasic sera by xenodiagnosis, ELISA-Homogenate and PCR. The performance of ELISA-rTSSA-II in dog sera was high (AUC=0·93 and KI=0·91). The Se was 92·85% (1 false negative) and Sp was 100%. Two sera from dogs infected with TcI and 1 with TcIII were negative. For patients infected with T. cruzi, reactivity was 87·8% (36/41), there was only 1 indeterminate, and Sp was 100%. Fifty-four sera from non-chagasic and 68 sera from patients with cutaneous leishmaniasis did not react with rTSS-II. ELISA-rTSSA-II showed a high performance when studying sera from naturally infected dogs and it also presented 100% Sp. This assay could be an important tool to carry out sero-epidemiological surveys on the prevalence of T. cruzi circulating lineages in the region.     

Toxin-Antitoxin Systems in the Mobile Genome of Acidithiobacillus ferrooxidans

Toxin-antitoxin (TA) systems are genetic modules composed of a pair of genes encoding a stable toxin and an unstable antitoxin that inhibits toxin activity. They are widespread among plasmids and chromosomes of bacteria and archaea. TA systems are known to be involved in the stabilization of plasmids but there is no consensus about the function of chromosomal TA systems. To shed light on the role of chromosomally encoded TA systems we analyzed the distribution and functionality of type II TA systems in the chromosome of two strains from Acidithiobacillus ferrooxidans (ATCC 23270 and 53993), a Gram-negative, acidophilic, environmental bacterium that participates in the bioleaching of minerals. As in other environmental microorganisms, A. ferrooxidans has a high content of TA systems (28-29) and in twenty of them the toxin is a putative ribonuclease. According to the genetic context, some of these systems are encoded near or within mobile genetic elements. Although most TA systems are shared by both strains, four of them, which are encoded in the active mobile element ICEAfe1, are exclusive to the type strain ATCC 23270. We demostrated that two TA systems from ICEAfe1 are functional in E. coli cells, since the toxins inhibit growth and the antitoxins counteract the effect of their cognate toxins. All the toxins from ICEAfe1, including a novel toxin, are RNases with different ion requirements. The data indicate that some of the chromosomally encoded TA systems are actually part of the A. ferrooxidans mobile genome and we propose that could be involved in the maintenance of these integrated mobile genetic elements.     

Genomic comparison between members of the Salinibacteraceae family,and description of a new species of Salinibacter (Salinibacter altiplanensis sp. nov.) isolated from high altitude hypersaline environments of the Argentinian Altiplano

The application of tandem MALDI-TOF MS screening with 16S rRNA gene sequencing of selected isolates has been demonstrated to be an excellent approach for retrieving novelty from large-scale culturing. The application of such methodologies in different hypersaline samples allowed the isolation of the culture-recalcitrant Salinibacter ruber second phylotype (EHB-2) for the first time, as well as a new species recently isolated from the Argentinian Altiplano hypersaline lakes. In this study, the genome sequences of the different species of the phylum Rhodothermaeota were compared and the genetic repertoire along the evolutionary gradient was analyzed together with each intraspecific variability. Altogether, the results indicated an open pan-genome for the family Salinibacteraceae, as well as the codification of relevant traits such as diverse rhodopsin genes, CRISPR-Cas systems and spacers, and one T6SS secretion system that could give ecological advantages to an EHB-2 isolate. For the new Salinibacter species, we propose the name Salinibacter altiplanensis sp. nov. (the designated type strain is AN15^T = CECT 9105^T = IBRC-M 11031^T).     

Photomixotrophic cultures of blueberries (<Emphasis Type="Italic">Vaccinium corymbosum</Emphasis>) accumulate or release phenylpropanoids via inductive treatments

The in vitro production of phenylpropanoids has been studied in temporary immersion bioreactors (TIBs) cultures of blueberries (Vaccinum corymbosum) supplemented with 0.4 MPa CO₂, light intensity of 150 μM/m²/s, and induced with ABA (4 mM) and H₂O₂ (5 mM). Results demonstrated differences in the accumulation and/or the release of patterns of metabolites. In TIBs plus ABA, a reddish-maroon color was consistent with the accumulation of phenolics, where shoots formed clusters without internodal segments. While in TIBs plus H₂O₂, the phenylpropanoids were released into the culture medium. In both cases, experimental treatments with sucrose-reduced medium displayed the highest phenylpropanoids values, in contrast with the controls (conventional culture). Altogether, differential expressions of genes, linked to key pathways as photosynthesis, phenylpropanoids, and oxidative burst, could corroborate for the increase in the phenolics production in parallel with an improvement of photosynthesis in photomixotrophic culture.     

Formate hydrogenlyase and formate secretion ameliorate H2 inhibition in the hyperthermophilic archaeon Thermococcus paralvinellae

Some hyperthermophilic heterotrophs in the genus Thermococcus produce H₂ in the absence of S° and have up to seven hydrogenases, but their combined physiological roles are unclear. Here, we show which hydrogenases in Thermococcus paralvinellae are affected by added H₂ during growth without S°. Growth rates and steady‐state cell concentrations decreased while formate production rates increased when T. paralvinallae was grown in a chemostat with 65 µM of added H_2(aq). Differential gene expression analysis using RNA‐Seq showed consistent expression of six hydrogenase operons with and without added H₂. In contrast, expression of the formate hydrogenlyase 1 (fhl1) operon increased with added H₂. Flux balance analysis showed H₂ oxidation and formate production using FHL became an alternate route for electron disposal during H₂ inhibition with a concomitant increase in growth rate relative to cells without FHL. T. paralvinellae also grew on formate with an increase in H₂ production rate relative to growth on maltose or tryptone. Growth on formate increased fhl1 expression but decreased expression of all other hydrogenases. Therefore, Thermococcus that possess fhl1 have a competitive advantage over other Thermococcus species in hot subsurface environments where organic substrates are present, S° is absent and slow H₂ efflux causes growth inhibition.     

Improvement of photovoltaic performance by substituent effect of donor and acceptor structure of TPA-based dye-sensitized solar cells

We report a computational study of a series of organic dyes built with triphenylamine (TPA) as an electron donor group. We designed a set of six dyes called (TPA-n, where n?=?0–5). In order to enhance the electron-injection process, the electron-donor effect of some specific substituent was studied. Thus, we gave insights into the rational design of organic TPA-based chromophores for use in dye-sensitized solar cells (DSSCs). In addition, we report the HOMO, LUMO, the calculated excited state oxidized potential E^dye*(eV) and the free energy change for electron-injection ΔG_inject(eV), and the UV-visible absorption bands for TPA-n dyes by a time-dependent density functional theory (TDDFT) procedure at the B3LYP and CAM-B3LYP levels with solvent effect. The results demonstrate that the introduction of the electron-acceptor groups produces an intramolecular charge transfer showing a shift of the absorption wavelengths of TPA-n under studies.

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Graphical Abstract Several organic dyes TPA-n with different donors and acceptors are modeled. A strong conjugation acrros the donor and anchoring groips (TPA-n) bas been studied. Candidate TPA-3 shows a promising results.

     

Immunodiffusion Analysis of Isolates of Xanthomonas cyamopsidis

Immunodiffusion analysis of intact, sonically treated, and sonically treated and heat-treated cell antigen preparations of isolates of races 0 and 1 of Xanthomonas cyamopsidis of guar, Cyamopsis tetragonoloba, indicated that these races differ from one another antigenically. The differentiating precipitin reactions are believed to have been brought about by specific heat-stable surface antigens, possibly similar to lipopolysaccaride somatic antigens of other slime-producing xanthomonads. Because differences in host reaction to inoculation with the two isolates of race 1 were known to be minor, these isolates are considered to represent serotypes of the race rather than distinct separate races. This conclusion is supported by the antigenic behavior of isolates 14 and 19 to antiserum 19. The applicability of immunodiffusion analysis for the study of pathogenic variability in X. cyamopsidis is demonstrated.