Reduction in Exopolysaccharide Viscosity as an Aid to Bacteriophage Penetration through Pseudomonas aeruginosa Biofilms

To cause an infection, bacteriophages must penetrate the alginate exopolysaccharide of Pseudomonas aeruginosa to reach the bacterial surface. Despite a lack of intrinsic motility, phage were shown to diffuse through alginate gels at alginate concentrations up to 8% (wt/vol) and to bring about a 2-log reduction in the cell numbers in 20-day-old biofilms of P. aeruginosa. The inability of alginate to act as a more effective diffusional barrier suggests that phage may cause a reduction in the viscosity of the exopolysaccharide. Samples (n = 5) of commercial alginate and purified cystic fibrosis (CF) alginate were incubated with 2 × 10⁸ purified phage per ml for 24 h at 37°C. After incubation the samples and controls were subjected to rheological analysis with a Carrimed controlled stress rheometer. The viscosities of phage-treated samples were reduced by up to 40% compared to those of controls incubated in the absence of phage. The experiment was repeated by using phage concentrations of 10¹⁰ and 10¹² phage per ml and samples taken for analysis at intervals up to 4 h. The results indicated that there was a time- and concentration-dependent reduction in viscosity of up to 40% compared to the viscosities of the controls. Commercial and purified CF alginate samples, both phage treated and untreated, were subjected to gel filtration chromatography by using Sephacryl High Resolution S-400 medium in order to obtain evidence of degradation. The results demonstrated that alginate treated with phage had a lower molecular weight than untreated alginate. The data suggest that bacteriophage migration through P. aeruginosa biofilms may be facilitated by a reduction in alginate viscosity brought about by enzymic degradation and that the source of the enzyme may be the bacterial host itself.     

A 1,100-year-old founder effect mutation in IL12B gene is responsible for Mendelian susceptibility to mycobacterial disease in Tunisian patients

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare disorder predisposing apparently healthy individuals to infections caused by weakly virulent mycobacteria such as bacille Calmette–Guerin (BCG), environmental mycobacteria, and poorly virulent Salmonella strains. IL-12p40 deficiency is the first reported human disease due to a cytokine gene defect and is one of the deficiencies that cause MSMD. Nine mutant alleles only have been identified in the IL12B gene, and three of them are recurrent mutations due to a founder effect in specific populations. IL-12p40 deficiency has been identified especially in countries where consanguinity is high and where BCG vaccination at birth is universal. We investigated, in such settings, the clinical, cellular, and molecular features of six IL-12p40-deficient Tunisian patients having the same mutation in IL12B gene (c.298_305del). We found that this mutation is inherited as a common founder mutation arousing ~1,100 years ago. This finding facilitates the development of a preventive approach by genetic counseling and prenatal diagnosis especially in affected families.     

MLPA Subtelomere Analysis in Tunisian Mentally Retarded Patients

Subtelomeric rearrangements significantly contribute to idiopathic mental retardation and result in several mental retardation syndromes; however, most subtelomeric defects lack a characteristic phenotype. Thirty patients with unexplained mental retardation, a normal R banded karyotype at the 550 band, and no clinically recognizable syndrome were screened by Multiplex ligation-dependent probe amplification (MLPA). Four anomalies were identified: deletion 17q, duplications (4q), and associated duplications 15q and Xq. This duplication was found in two sisters of the proband. Anomalies were unidentified by the conventional technique. The prevalence of subtelomeric imbalances in our cohort of moderate to severe mental retardation is around 13% and is consistent with the literature. The sensitivity of the MLPA technique was characterized on cytogenetically verified positive and negative controls. MLPA is a fast, reliable, and relatively inexpensive technique to detect subtelomeric rearrangement in comparison with the fluorescence in situ hybridization (FISH) technique.     

Improvement of fermentative decolorization of olive mill wastewater by Lactobacillus paracasei by cheese whey's addition

The effect of the cheese whey's (CW) addition on the fermentative decolorization of olive mill wastewater (OMW) by Lactobacillus paracasei, with and without pH adjustment by lime, was investigated. Mixtures OMW/CW at different proportions were fermented. The highest colour removal (47%) and total phenolic reduction (22.7%) of OMW were obtained after cofermentation of OMW/CW at proportions of 10/90, respectively. The decrease of pH after cofermentation of the two wastewaters, induced the precipitation of whey proteins with phenolic compounds and, so, improves decolorization. These removal yields reached 64% and 34%, respectively after precipitation by adjustment of pH at 7 with lime at the end of cofermentation. These improvements were correlated to a clarification of wastewaters by precipitation of whey proteins with phenolic compounds. An enhanced decolorization (up to 93%) and a total phenolic reduction (50%) of the mixture were obtained when cofermentation sequentially pH corrected by lime addition was investigated.     

Effect of osmotic stress on <Emphasis Type="Italic">Myrtus communis</Emphasis> germination

The effects of water potential on germination were studied in four provenances of Myrtus from different bioclimatic zones in Tunisia. Water potential between 0 and −10 bars were obtained using polyethylene glycol 6000 (PEG-6000) solutions. Seeds were planted in Petri dishes full of sterile perlite, and kept for one month under 1500 lux light with 16h photoperiod and at 25°C. A low water potential induced a reduction in germination percentage and germination speed. Significant variations between the provenances were found even under control conditions, especially at the speed germination level. The provenances from humid regions were the most susceptible to water stress, and their germination percentage showed significant reductions at −8 bars. These differences in germination ability of provenances might be attributed to intraspecific variations resulting from the effects of natural selection and genetic pool background.     

Draft Genome Sequence of Tsukamurella sp. Strain 1534

A draft genome sequence of Tsukamurella sp., an aerobic bacterium isolated from a human sputum specimen, is described here. A new virus or provirus, TPA4, was characterized.     

Modeling growth and photosynthetic response in <Emphasis Type="Italic">Arthrospira platensis</Emphasis> as function of light intensity and glucose concentration using factorial design

Combined effect of light intensity and glucose concentration on Arthrospira platensis growth and photosynthetic response was evaluated using a 3² factorial design. This design was carried out with light levels of 50, 100, and 150 μmol photons m⁻² s⁻¹ and glucose concentrations of 0.5, 1.5, and 2.5 g L⁻¹. Results from the response surface methodology were that the highest level of light intensity and glucose concentration improved biomass (1.33 g L⁻¹), maximum specific growth rate (0.49 day⁻¹), and net photosynthetic rate (139.89 μmol O₂ mg Chl⁻¹ h⁻¹). Furthermore, the interaction of both factors showed that at low light, glucose had a low effect on maximum biomass and maximal net photosynthetic rate. However, at the highest light levels, the effect of glucose was more sensitive and the increase of glucose concentration increased the levels of all responses. The rates of the instantaneous relative growth, net photosynthesis, and dark respiration of growth cultures showed two different phases in mixotrophic condition. The first was distinguished by the preponderance of the photoautotrophic mode; the second was based mainly on photoheterotrophy.     

Mitochondrial disease patients with novel ND4 12058A > C and ND1 m.3911A > G variations: implications for a role in the phenotype following a bioinformatic investigation

Molecular Biology Reports - Mitochondrial diseases include a wide group of clinically heterogeneous disorders caused by a dysfunction of the mitochondrial respiratory chain and can be related to...     

A Rat Model of Neonatal Candidiasis Demonstrates the Importance of Lipases as Virulence Factors for <Emphasis Type="Italic">Candida albicans</Emphasis> and <Emphasis Type="Italic">Candida parapsilosis</Emphasis>

The host factors that contribute to the increased susceptibility of preterm neonates to invasive candidiasis have not been fully identified. In addition, there has been a lack of suitable models to study this problem. We show that rat pups, similar to premature neonates, display increased susceptibility to experimental Candida albicans infection. Further, we find that both C. albicans and Candida parapsilosis lipase disruptant mutants exhibit decreased virulence in rat pups, demonstrating the utility of the model to evaluate the impact of specific genes in disease pathogenesis. Our findings highlight the contribution of lipases to the virulence of C. albicans and C. parapsilosis and provide a new system to study the increased susceptibility of neonates to Candida infections.     

Myocardial fibrosis and TGFB expression in hyperhomocysteinemic rats

Hyperhomocysteinemia, characterized by an elevated plasma homocysteine concentration, leads to several clinical manifestations and particularly cardiovascular diseases. Experimental models of hyperhomocysteinemia revealed several tissue injuries including heart fibrosis and ventricular hypertrophy. In order to analyze the molecular mechanisms link to these morphological alterations, a mild hyperhomocysteinemia was induced in rats via a chronic methionine administration. Effects of methionine administration were examined by histological analysis with Sirius red staining, histomorphometric analysis, zymography, and immunoblotting. Hyperhomocysteinemia due to methionine administration produces an interstitial myocardial fibrosis and a ventricular cardiomyocyte hypertrophy, which were associated with increased expression of transforming growth factor-beta1 (TGFβ1), tissue inhibitors of metalloproteinase (TIMP) 2, and JNK activation. However, the matrix metalloproteinase 2 activity was decreased in the hearts of hyperhomocysteinemic rats. Moreover, the TIMP1 protein expression was decreased, and the TIMP1-MMP1 balance was shifted. Remodeling in cardiac tissue observed in rat model of mild hyperhomocysteinemia is associated with a dysregulation in extracellular matrix degradation which results, at least in part, from enhancement of TGFβ1 level.