Interleukin IL-1B gene polymorphism in Tunisian patients with chronic hepatitis B infection: Association with replication levels

Approaches based on association studies have proven useful in identifying genetic predictors for many diseases, including susceptibility to chronic hepatitis B. In this study we were interested by the IL-1B genetic variants that have been involved in the immune response and we analyzed their role in the susceptibility to develop chronic hepatitis B in the Tunisian population. IL - 1B is a potent proinflammatory cytokine that plays an important role in inflammation of the liver. Polymorphic gene IL-1 ( − 511, +3954) was analyzed in a total of 476 individuals: 236 patients with chronic hepatitis B from different cities of Tunisia recruited in Pasteur Institute between January 2017 and December 2018 and 240 controls. Genomic DNA was obtained using the standard salting-out method and genotyping was performed by polymerase chain reaction (PCR)-restriction fragment length polymorphism. For − 511C>T polymorphism a significant association was found between patients and controls when comparing the genotypic (P = 0.007; χ² = 9.74 and odds ratio [OR] = 0.60; confidence interval [CI] = 0.41–0.89) and allelic (P = 0.001; χ² = 10.60) frequencies. When the viral load was taken into account a highly significant difference was found (P = 9 × 10⁻⁴; χ² = 10.89). For +3954C>T polymorphism a significant association was found between patients and controls when comparing genotypic (P = 0.0058; χ² = 7.60 and OR = 1.67; CI = 1.14–2.46) and allelic (P = 0.0029; χ² = 8.81) frequencies. T allele can be used as a strong marker for hepatitis B virus disease for both polymorphisms.     

Heterologous expression and secretion of an antifungal Bacillus subtilis chitosanase (CSNV26) in Escherichia coli

The aims of the study were the production improvement, the purification, the characterization and the activity investigation of chitosanase CSNV26 of Bacillus subtilis (V26). The gene csnV26 encoding for this protein was amplified and cloned in the pBAD vector then expressed in Escherichia coli (Top10). The SDS-PAGE and zymogram analysis of the recombinant protein showed that it has two active forms sized 27 and 31 kDa, corresponding to the protein with and without signal peptide. This protein has the particularity of being secreted by Top10-pBAD-csnV26 with a high yield of 6.2 g/l. The HPLC purification of CSNV26 from supernatant confirmed the presence of the two sizes. The investigation of the CSNV26 thermostability showed that the pure protein is highly stable keeping 68 % of its activity after 30-min treatment at 100 °C, contrarily to the protein present within the supernatant of E. coli and B. subtilis (V26). The molecular dynamics study of the predicted structure of protein in both forms showed that the presence of the peptide signal in the form of 31 kDa gave it a remarkable thermal stability. The antifungal activity of CSNV26 was evidenced on Rhizopus nigricans and Rhizopus oryzae. Indeed, it has provoked an alteration and embrittlement of their hyphae with onset of protoplast.     

Production of biosurfactant on crude date syrup under saline conditions by entrapped cells of Natrialba sp. strain E21, an extremely halophilic bacterium isolated from a solar saltern (Ain Salah, Algeria)

A bacterial strain E21 was isolated from a sample of water collected in the salt lake located close to Ain Salah, Algeria. The analysis of 16S rRNA gene sequence had indicated that the strain had 93 % sequence similarity with the genus Natrialba sp. strain E21 (GenBank, FR750525.1) and was considered extremely halophilic. Production of biosurfactant by the strain E21 with free and entrapped cells was investigated using soluble starch in the saline conditions. Biosurfactant synthesis was followed by measuring the surface tension and emulsifying index 9 days under optimal conditions (40 °C, pH 7). Some diffusional limitations in alginate and agar beads affected the kinetics of biosurfactant production when compared to that obtained with free cells culture. The minimum values of surface tension were 27 and 30 mN m^?1 achieved after 9 days with free and immobilized cells, respectively, while the corresponding maximum E24 values were 65.3 and 62.3 %, respectively. The re-use of bacterial cells along with the limited cell losses provided by the immobilized system might lead to significant reduction of the biosurfactant production cost.     

Analyse morphométrique semi quantitative de l’histologie testiculaire au cours du vieillissement

Testicular aging is usually studied using sperm and quantitative hormone analysis. Testicular samples are obviously difficult to obtain from a control aging population. Body donations from the Anatomy Department of the Saint-Peres University provided access to testicular samples from deceased men between the ages of 53 to 102 years. We present the first results of a semiquantitative histological morphometric study of testicular aging. We studied a series of 39 subjects. After removal of the sample within the first 24 hours, several investigations were conducted. Macroscopic examination (volume, weight) was followed by histological examination and computer-assisted morphometric analysis: N.I.H images based on the following parameters: (i) transverse sections of the seminiferous tubules (total surface, thickness of the basal membrane, and nuclear density of Sertoli cells, spermatogonia, spermatocytes and spermatozoids; (ii) histological sections were studied for interstitial tissue, number of clusters and the surface occupied by Leydig cells (percentage per parenchyma area), their appearance, size and nuclear density were determined; (iii) this study was completed by visual count of the various cell types in the seminiferous epithelium. The results obtained on a series of 39 subjects aged from 53 to 102 showed various alterations, such as thickening of the tunica albuginea and basal membrane and intertubule hyalinization. The most frequent histological pattern of the aging testis is a mosaic of various seminiferous tubule lesions varying from tubules with complete although reduced spermatogenesis to entirely sclerosed tubules. Individual variations are extremely marked with major alterations of spermatogenesis as early as 60 years old, with atrophied Leydig cells and, on the contrary, preserved spermatogenesis until the age of 95 years.     

A new Tunisian strain of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis><Emphasis Type="Italic">kurstaki</Emphasis> having high insecticidal activity and δ-endotoxin yield

BLB1 is a new Bacillus thuringiensis kurstaki strain, isolated from a Tunisian soil sample. Assay of toxicity of BLB1 crystal proteins resulted in an LC50 of 70.32 ng of toxin per mg of flour against third instar Ephestia kuehniella with confidence limits of (31.6–109.04 ng). This LC50 is less than that of the commercial strains HD1 used as a reference. The characterization of this strain by scanning transmission electron microscopy, analysis of its cry genes content by PCR-sequencing, and analysis of its δ-endotoxin patterns demonstrate that it belongs to the same subgroup than HD1, but ruled out the involvement of cry gene content or protoxin activation in the hypertoxicity of this strain. Taking into account the δ-endotoxin/spore ratio for each strain, and by allowing the estimation of the production level per spore, it might be concluded that BLB1 production is the highest, when compared with that of HD1. On the basis of its toxicity, BLB1 could be considered as a strain of great interest and would allow the production of quantities of bioinsecticides at low cost.     

Rare taxa and dark microbial matter: novel bioactive actinobacteria abound in Atacama Desert soils

An “in house” taxonomic approach to drug discovery led to the isolation of diverse actinobacteria from hyper-arid, extreme hyper-arid and very high altitude Atacama Desert soils. A high proportion of the isolates were assigned to novel taxa, with many showing activity in standard antimicrobial plug assays. The application of more advanced taxonomic and screening strategies showed that strains classified as novel species of Lentzea and Streptomyces synthesised new specialised metabolites thereby underpinning the premise that the extreme abiotic conditions in the Atacama Desert favour the development of a unique actinobacterial diversity which is the basis of novel chemistry. Complementary metagenomic analyses showed that the soils encompassed an astonishing degree of actinobacterial ‘dark matter’, while rank-abundance analyses showed them to be highly diverse habitats mainly composed of rare taxa that have not been recovered using culture-dependent methods. The implications of these pioneering studies on future bioprospecting campaigns are discussed.