High dietary salt decreases antioxidant defenses in the liver of fructose-fed insulin-resistant rats

In this study we investigated the hypothesis that a high-salt diet to hyperinsulinemic rats might impair antioxidant defense owing to its involvement in the activation of sodium reabsorption to lead to higher oxidative stress. Rats were fed a standard (CON), a high-salt (HS), or a high-fructose (HF) diet for 10 weeks after which, 50% of the animals belonging to the HF group were switched to a regimen of high-fructose and high-salt diet (HFS) for 10 more weeks, while the other groups were fed with their respective diets. Animals were then euthanized and their blood and liver were examined. Fasting plasma glucose was found to be significantly higher (approximately 50%) in fructose-fed rats than in the control and HS rats, whereas fat liver also differed in these animals, producing steatosis. Feeding fructose-fed rats with the high-salt diet triggered hyperinsulinemia and lowered insulin sensitivity, which led to increased levels of serum sodium compared to the HS group. This resulted in membrane perturbation, which in the presence of steatosis potentially enhanced hepatic lipid peroxidation, thereby decreasing the level of antioxidant defenses, as shown by GSH/GSSG ratio (HFS rats, 7.098±2.1 versus CON rats, 13.2±6.1) and superoxide dismutase (HFS rats, 2.1±0.05 versus CON rats, 2.3±0.1%), and catalase (HFS rats, 526.6±88.6 versus CON rats, 745.8±228.7 U/mg ptn) activities. Our results indicate that consumption of a salt-rich diet by insulin-resistant rats may lead to regulation of sodium reabsorption, worsening hepatic lipid peroxidation associated with impaired antioxidant defenses.     

Identification of the Anabaena sp. strain PCC7120 cyanophycin synthetase as suitable enzyme for production of cyanophycin in gram-negative bacteria like Pseudomonas putida and Ralstonia eutropha

The cyanophycin synthetase gene cphA1 encoding the major cyanophycin synthetase (CphA) of Anabaena sp. strain PCC7120 was expressed in Escherichia coli conferring so far the highest specific CphA activity to E. coli (6.7 nmol arginine per min and mg protein). CphA1 and cphA genes of Synechocystis sp. strains PCC6803 and PCC6308 and Synechococcus strain MA19 were also expressed in wild types and polyhydroxyalkanoate-negative (PHA) mutants of Pseudomonas putida and Ralstonia eutropha. Recombinant strains of these bacteria expressing cphA1 accumulated generally more cyanophycin (23.0 and 20.0% of cellular dry matter, CDM, respectively) than recombinants expressing any other cphA (6.8, 9.0, or 15.8% of CDM for P. putida strains and 7.3, 12.6, or 14.1% of CDM for R. eutropha). Furthermore, PHA-negative mutants of P. putida (9.7, 10.0, 17.5, or 24.0% of CDM) and R. eutropha (8.9, 13.8, 16.0, or 22.0% of CDM) accumulated generally more cyanophycin than the corresponding PHA-positive parent strains (6.8, 9.0, 15.8, and 23.0% of CDM for P. putida strains and 7.3, 12.6, 14.1, or 20.0% of CDM for R. eutropha strains). Recombinant strains of Gram-positive bacteria (Bacillus megaterium, Corynebacterium glutamicum) were not suitable for cyanophycin production due to accumulation of less cyanophycin and retarded release of cyanophycin. PHA-negative mutants of P. putida and R. eutropha expressing cphA1 of Anabaena sp. strain PCC7120 are therefore preferred candidates for industrial production of cyanophycin.     

Antimicrobial resistance and biotechnological potential of plastic-associated bacteria isolated from an urban estuary

Plastics have quickly become one of the major pollutants in aquatic environments worldwide and solving the plastic pollution crisis is considered a central goal of modern society. In this study, 10 different plastic samples, including high- and low-density polyethylene and polypropylene, were collected from a deeply polluted urban estuary in Brazil. By employing different isolation and analysis approaches to investigate plastic-associated bacteria, a predominance of potentially pathogenic bacteria such as Acinetobacter, Aeromonas, and Vibrio was observed throughout all plastic samples. Bacteria typically found in the aquatic environment harboured clinically relevant genes encoding resistance to carbapenems (bla_KPC) and colistin (such as mcr-3 and mcr-4), along with genetic determinants associated with potentially active gene mobilization. Whole genome sequencing and annotation of three plastic-associated Vibrio strains further demonstrated the carriage of mobile genetic elements and antimicrobial resistance and virulence genes. On the other hand, bacteria isolated from the same samples were also able to produce esterases, lipases, and bioemulsifiers, thus highlighting that the plastisphere could also be of special interest from a biotechnological perspective.     

Exploring patterns of interspecific variation in quantitative traits using sequential phylogenetic eigenvector regressions

A number of metrics have been developed for estimating phylogenetic signal in data and to evaluate correlated evolution, inferring broad-scale evolutionary and ecological processes. Here, we proposed an approach called phylogenetic signal-representation (PSR) curve, built upon phylogenetic eigenvector regression (PVR). In PVR, selected eigenvectors extracted from a phylogenetic distance matrix are used to model interspecific variation. In the PSR curve, sequential PVR models are fitted after successively increasing the number of eigenvectors and plotting their R(2) against the accumulated eigenvalues. We used simulations to show that a linear PSR curve is expected under Brownian motion and that its shape changes under alternative evolutionary models. The PSR area, expressing deviations from Brownian motion, is strongly correlated (r= 0.873; P < 0.01) with Blomberg's K-statistics, so nonlinear PSR curves reveal if traits are evolving at a slower or higher rate than expected by Brownian motion. The PSR area is also correlated with phylogenetic half-life under an Ornstein-Uhlenbeck process, suggesting how both methods describe the shape of the relationship between interspecific variation and time since divergence among species. The PSR curve provides an elegant exploratory method to understand deviations from Brownian motion, in terms of acceleration or deceleration of evolutionary rates occurring at large or small phylogenetic distances.     

Replication slippage may cause parallel evolution in the secondary structures of mitochondrial transfer RNAs

Presence of the dihydrouridine (D) stem in the mitochondrial cysteine tRNA is unusually variable among lepidosaurian reptiles. Phylogenetic and comparative analyses of cysteine tRNA gene sequences identify eight parallel losses of the D-stem, resulting in D-arm replacement loops. Sampling within the monophyletic Acrodonta provides no evidence for reversal. Slipped-strand mispairing of noncontiguous repeated sequences during replication or direct replication slippage can explain repeats observed within cysteine tRNAs that contain a D-arm replacement loop. These two mechanisms involving replication slippage can account for the loss of the cysteine tRNA D-stem in several lepidosaurian lineages, and may represent general mechanisms by which the secondary structures of mitochondrial tRNAs are altered.      

Thirty‐five years of spatial autocorrelation analysis in population genetics: an essay in honour of Robert Sokal (1926–2012)

We could not start this review, literally from the beginning, without expressing our sadness over the passing of Professor Robert R. Sokal. We are sure, nevertheless, that the importance of his scientific achievements will ensure he is long remembered. In this modest tribute to Professor Sokal, we highlight his contributions to the field of population genetics and spatial statistical methods. Specifically, we discuss how two papers, co‐authored with Professor N. L. Oden and published in the pages of the Biological Journal of the Linnean Society in 1978, revolutionized the field of analytical population genetics. In these papers, Sokal and Oden created an elegant framework for inferring evolutionary processes (e.g. isolation‐by‐distance, demic diffusion, selection gradients, genetic drift) from the spatial autocorrelation analysis of genetic variation patterns. We also highlight the pivotal importance of Sokal's work to the development of emerging fields (e.g. landscape and conservation genetics). We hope this virtual issue containing the papers that Professor Sokal published in BJLS, and later, related papers by other researchers, will help to remember his work and maintain his legacy of spatial analysis in genetics, ecology, and evolutionary biology. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

The hypervariable domain of the mitochondrial control region in Atlantic spiny lobsters and its potential as a marker for investigating phylogeographic structuring

Atlantic spiny lobsters support major fisheries in northeastern Brazilian waters and in the Caribbean Sea. To avoid reduction in diversity and elimination of distinct stocks, understanding their population dynamics, including structuring of populations and genetic diversity, is critical. We here explore the potential of using the hypervariable domain in the control region of the mitochondrial DNA as a genetic marker to characterize population subdivision in spiny lobsters, using Panulirus argus as the species model. The primers designed on the neighboring conserved genes have amplified the entire control region (approx. 780 bases) of P. argus and other closely related species. Average nucleotide and haplotype diversity within P. argus were found to be high, and population structuring was hypothesized. The data suggest a division of P. argus into genetically different phylogeographic groups. The hypervariable domain seems to be useful for determining genetic differentiation of geographically distinct stocks of P. argus and other Atlantic spiny lobsters.     

Synthesis and antimicrobial activity of novel amphiphilic aromatic amino alcohols

We report in this work the preparation and in vitro antimicrobial evaluation of novel amphiphilic aromatic amino alcohols synthesized by reductive amination of 4-alkyloxybenzaldehyde with 2-amino-2-hydroxymethyl-propane-1,3-diol. The antibacterial activity was determined against four standard strains (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa) and 21 clinical isolates of methicillin-resistant Staphylococcus aureus. The antifungal activity was evaluated against four yeast (Candida albicans, Candida tropicalis, Candida glabrata and Candida parapsilosis). The results obtained showed a strong positive correlation between the lipophilicity and the antibiotic activity of the tested compounds. The best activities were obtained against the Gram-positive bacteria (MIC = 2–16 μg ml^?1) for the five compounds bearing longer alkyl chains (4c–g; 8–14 carbons), which were also the most active against Candida (MIC = 2–64 μg ml^?1). Compound 4e exhibited the highest levels of inhibitory activity (MIC = 2–16 μg ml^?1) against clinical isolates of MRSA. A concentration of twice the MIC resulted in bactericidal activity of 4d against 19 of the 21 clinical isolates.