The AhpC and AhpD antioxidant defense system of Mycobacterium tuberculosis

The peroxiredoxin AhpC from Mycobacterium tuberculosis has been expressed, purified, and characterized. It differs from other well characterized AhpC proteins in that it has three rather than one or two cysteine residues. Mutagenesis studies show that all three cysteine residues are important for catalytic activity. Analysis of the M. tuberculosis genome identified a second protein, AhpD, which has no sequence identity with AhpC but is under the control of the same promoter. This protein has also been cloned, expressed, purified, and characterized. AhpD, which has only been identified in the genomes of mycobacteria and Streptomyces viridosporus, is shown here to also be an alkylhydroperoxidase. The endogenous electron donor for catalytic turnover of the two proteins is not known, but both can be turned over with AhpF from Salmonella typhimurium or, particularly in the case of AhpC, with dithiothreitol. AhpC and AhpD reduce alkylhydroperoxides more effectively than H(2)O(2) but do not appear to interact with each other. These two proteins appear to be critical elements of the antioxidant defense system of M. tuberculosis and may be suitable targets for the development of novel anti-tuberculosis strategies.     

Microbial eco-physiological profiles to estimate the biological restoration of a trichloroethylene-contaminated soil

In the present study, the effectiveness of two plants, Medicago sativa L. and Dittrichia viscosa L., and a biostimulation method based on the use of an olive waste vermicompost, to restore the original quality of a trichloroethylene-contaminated soil was evaluated using eco-physiological profiles. These were designed in form of sun-ray plots by combining soil enzyme activities (dehydrogenase, alkaline phosphatase, β-glucosidase, urease and o-diphenol oxidase), bacterial population size via real-time PCR, Shannon diversity index values for PCR-denaturing gradient gel electrophoresis profiles, and genetic diversity θ_(π) of the sequenced Proteobacteria of the different treatments. The eco-physiological profiles coupling biochemical and molecular parameters could be used as a valuable index for monitoring the success of a restoration scheme, estimating the quality of both contaminated and restored soils. Particularly remarkable was the interaction between vermicompost and D. viscosa, the only treatment that improved biochemical and microbiological restoration in such a way that an eco-physiological profile greater than that of the uncontaminated soil was noticed. The results showed the need to combine chemical analysis and microbiological measurements for evaluating the efficacy of soil remediation techniques.     

Antimicrobial peptides and plant disease control

Several diseases caused by viruses, bacteria and fungi affect plant crops, resulting in losses and decreasing the quality and safety of agricultural products. Plant disease control relies mainly on chemical pesticides that are currently subject to strong restrictions and regulatory requirements. Antimicrobial peptides are interesting compounds in plant health because there is a need for new products in plant protection that fit into the new regulations. Living organisms secrete a wide range of antimicrobial peptides produced through ribosomal (defensins and small bacteriocins) or non-ribosomal synthesis (peptaibols, cyclopeptides and pseudopeptides). Several antimicrobial peptides are the basis for the design of new synthetic analogues, have been expressed in transgenic plants to confer disease protection or are secreted by microorganisms that are active ingredients of commercial biopesticides.     

CORAL: Building up QSAR models for the chromosome aberration test

A high level of chromosomal aberrations in peripheral blood lymphocytes may be an early marker of cancer risk, but data on risk of specific cancers and types of chromosomal aberrations are limited. Consequently, the development of predictive models for chromosomal aberrations test is important task. Majority of models for chromosomal aberrations test are so-called knowledge-based rules system. The CORAL software (http://www.insilico.eu/coral, abbreviation of “CORrelation And Logic”) is an alternative for knowledge-based rules system. In contrast to knowledge-based rules system, the CORAL software gives possibility to estimate the influence upon the predictive potential of a model of different molecular alerts as well as different splits into the training set and validation set. This possibility is not available for the approaches based on the knowledge-based rules system. Quantitative Structure–Activity Relationships (QSAR) for chromosome aberration test are established for five random splits into the training, calibration, and validation sets. The QSAR approach is based on representation of the molecular structure by simplified molecular input-line entry system (SMILES) without data on physicochemical and/or biochemical parameters. In spite of this limitation, the statistical quality of these models is quite good.     

Ocean Acidification and Increased Temperature Have Both Positive and Negative Effects on Early Ontogenetic Traits of a Rocky Shore Keystone Predator Species

The combined effect of ocean acidification and warming is expected to have significant effects on several traits of marine organisms. The gastropod Concholepas concholepas is a rocky shore keystone predator characteristic of the south-eastern Pacific coast of South America and an important natural resource exploited by small-scale artisanal fishermen along the coast of Chile and Peru. In this study, we used small juveniles of C. concholepas collected from the rocky intertidal habitats of southern Chile (39°S) to evaluate under laboratory conditions the potential consequences of projected near-future levels of ocean acidification and warming for important early ontogenetic traits. The individuals were exposed long-term (5.8 months) to contrasting pCO₂ (ca. 500 and 1400 μatm) and temperature (15 and 19°C) levels. After this period we compared body growth traits, dislodgement resistance, predator-escape response, self-righting and metabolic rates. With respect to these traits there was no evidence of a synergistic interaction between pCO₂ and temperature. Shell growth was negatively affected by high pCO₂ levels only at 15°C. High pCO₂ levels also had a negative effect on the predator-escape response. Conversely, dislodgement resistance and self-righting were positively affected by high pCO₂ levels at both temperatures. High tenacity and fast self-righting would reduce predation risk in nature and might compensate for the negative effects of high pCO₂ levels on other important defensive traits such as shell size and escape behaviour. We conclude that climate change might produce in C. concholepas positive and negative effects in physiology and behaviour. In fact, some of the behavioural responses might be a consequence of physiological effects, such as changes in chemosensory capacity (e.g. predator-escape response) or secretion of adhesive mucous (e.g. dislodgement resistance). Moreover, we conclude that positive behavioural responses may assist in the adaptation to negative physiological impacts, and that this may also be the case for other benthic organisms.     

Pili of Pasteurella multocida of porcine origin

Abstract Using electron microscopy, pili with at least two distinct morphologies were observed on strains of Pasteurella multocida isolated from pigs with atrophic rhinitis. Rigid pili were found on 60–80% of all cells observed. These pili had a strong tendency to lie flat along the side of the outer cell membrane of P. multocida and as a result frequently were difficult to see. After growth in vitro, piliated P. multocida cells produced few pili (approx. 3–5 per cell). Heavily piliated cells were occasionally observed. The second type of pili were curly and also were difficult to visualize. Cells from cultures containing piliated cells failed to attach to red blood cells and to immobilized mucus.     

Nitrogen-Cycling Genes in Epilithic Biofilms of Oligotrophic High-Altitude Lakes (Central Pyrenees,Spain)

Microbial biofilms in oligotrophic environments are the most reactive component of the ecosystem. In high-altitude lakes, exposed bedrock, boulders, gravel, and sand in contact with highly oxygenated water and where a very thin epilithic biofilm develops usually dominate the littoral zone. Traditionally, these surfaces have been considered unsuitable for denitrification, but recent investigations have shown higher biological diversity than expected, including diverse anaerobic microorganisms. In this study, we explored the presence of microbial N-cycling nirS and nirK (denitrification through the conversion of NO₂ ^? to NO), nifH (N₂ fixation), anammox (anaerobic ammonium oxidation), and amoA (aerobic ammonia oxidation, both bacterial and archaeal) genes in epilithic biofilms of a set of high-altitude oligotrophic lakes in the Pyrenees. The concentrations of denitrifying genes determined by quantitative PCR were two orders of magnitude higher than those of ammonia-oxidizing genes. Both types of genes were significantly correlated, suggesting a potential tight coupling nitrification-denitrification in these biofilms that deserves further confirmation. The nifH gene was detected after nested PCR, and no signal was detected for the anammox-specific genes used. The taxonomic composition of denitrifying and nitrogen-fixing genes was further explored by cloning and sequencing. Interestingly, both microbial functional groups were richer and more genetically diverse than expected. The nirK gene, mostly related to Alphaproteobacteria (Bradyrhizobiaceae), dominated the denitrifying gene pool as expected for oxygen-exposed habitats, whereas Deltaproteobacteria (Geobacter like) and Cyanobacteria were the most abundant among nitrogen fixers. Overall, these results suggest an epilithic community more metabolically diverse than previously thought and with the potential to carry out an active role in the biogeochemical nitrogen cycling of high-altitude ecosystems. Measurements of activity rates should be however carried out to substantiate and further explore these findings.     

P2X7: a receptor with a split personality that raises new hopes for anti-cancer therapy

Purinergic Signalling -