Isolation and Characterization of Thermophilic Bacterial Strains with Inulinase Activity

Nine bacterial strains growing on inulin as the sole carbon and energy source were isolated from soil samples by enrichment culture on a mineral medium. Four of the strains were thermophilic and belong to the genus Bacillus. The thermophilic strains synthesized a β-fructosidase that was active on both inulin and sucrose. The presence of inulin in the culture medium is necessary for enzyme synthesis. Most of the activity on inulin was recovered in the culture medium, and the enzyme was synthesized during cell growth.     

Characterization and molecular cloning of thermostable alpha-amylase from Streptomyces sp.To1

Summary A new thermophilic Streptomyces sp. TO1, isolated from Tunisian soil, produced a thermostable alpha-amylase and pullulanase. The gene encoding for the alpha-amylase activity was cloned into the multicopy cloning plasmid pLM1 using S. lividans ZX1 as host strain. The ZX1 / pLM1 strain has the same activity than the initial TO1 strain and about 25 fold higher activity than the ZX1 strain. This alpha-amylase has an optimum of pH and temperature at 6 and 70 °C respectively.     

Differentiation of Fanconi anemia and aplastic anemia using mitomycin C test in Tunisia

Fanconi anemia (FA) is a recessive chromosomal instability syndrome that is clinically characterized by multiple symptoms. Chromosome breakage hypersensitivity to alkylating agents is the gold standard test for FA diagnosis. In this study, we provide a detailed laboratory protocol for accurate assessment of FA diagnosis based on mitomycin C (MMC) test. Induced chromosomal breakage study was successful in 171 out of 205 aplastic anemia (AA) patients. According to the sensitivity of MMC at 50 ng/ml, 38 patients (22.22%) were diagnosed as affected and 132 patients (77.17%) as unaffected. Somatic mosaicism was suspected in an 11-year-old patient with a FA phenotype. Twenty-six siblings of FA patients were also evaluated and five of them (19.23%) were diagnosed as FA. From this study, a standard protocol for diagnosis of FA was developed. It is routinely used as a diagnostic test of FA in Tunisia.     

Glycine inhibitory dysfunction turns touch into pain through PKCgamma interneurons

Dynamic mechanical allodynia is a widespread and intractable symptom of neuropathic pain for which there is a lack of effective therapy. During tactile allodynia, activation of the sensory fibers which normally detect touch elicits pain. Here we provide a new behavioral investigation into the dynamic component of tactile allodynia that developed in rats after segmental removal of glycine inhibition. Using in vivo electrophysiological recordings, we show that in this condition innocuous mechanical stimuli could activate superficial dorsal horn nociceptive specific neurons. These neurons do not normally respond to touch. We anatomically show that the activation was mediated through a local circuit involving neurons expressing the gamma isoform of protein kinase C (PKCgamma). Selective inhibition of PKCgamma as well as selective blockade of glutamate NMDA receptors in the superficial dorsal horn prevented both activation of the circuit and allodynia. Thus, our data demonstrates that a normally inactive circuit in the dorsal horn can be recruited to convert touch into pain. It also provides evidence that glycine inhibitory dysfunction gates tactile input to nociceptive specific neurons through PKCgamma-dependent activation of a local, excitatory, NMDA receptor-dependent, circuit. As a consequence of these findings, we suggest that pharmacological inhibition of PKCgamma might provide a new tool for alleviating allodynia in the clinical setting.     

Effect of chronic lead exposure on kidney function in male and female rats: determination of a lead exposure biomarker

Several cytotoxic chemical pollutants inducing peroxidative damages are liable to induce kidney failure. Among these pollutants we find heavy metals such as: lead, nickel, cadmium, vanadium and mercury. Lead is one of the most dangerous metals because it is widely spread in the environment, and because it may be a source of several nervous diseases. The aim of this study is to provide evidence concerning the effect of this metal on the renal function and to try to determine a storage corner in the organism which serves as an indicator of a lead intoxication. Lead acetate was administered by oral route in the drinking water to adult rats aged three months at the rate of 0.3% (P1) and 0.6% (P2). Reference rats received distilled water to drink under the same conditions. The treatment continued for 15, 30, 45, 60 and 90 days. The creatinemia, uremia, glycemia and creatinuria are determined by colorimetric techniques. Lead concentration in blood as well as the lead content of the tail are determined by atomic absorption after nitroperchloric mineralization at the liquid stage. The results showed an increase of creatinemia on the 30th day of the experiment for both sexes in (P1 and P2). The same happened for ureamia. The increase of these two parameters would indicate a renal deficiency which is confirmed by a decrease of creatinuria and urinary pH observed mainly on and after the 45th day of the experiment. An increase of the renal relative weight was noticed in P1 and P2 on the 30th day of the treatment. The determination of the concentration of lead in the blood shows that this factor increases among treated subjects in a constant way, independently of the dose and the duration of the treatment. Nevertheless, the rate increase of lead in the tail seems to be dose-dependent. In conclusion, lead administered by oral route causes a renal deficiency to the rat without distinction between males and females. In addition, the tail seems to be a reliable exposure biomarker that demonstrates lead intoxication. The tail seems to be a dosimeter of lead bio-accumulation. It constitutes an endogenous source of lead impregnation. The concentration of lead in the blood is only an indicator of recent exposure.     

Aluminum mediates compositional alterations of polar lipid classes in maize seedlings

Changes in lipid composition were investigated on maize roots and shoots under aluminum stress. After 4d exposure to 100 microM Al, root growth was inhibited while shoot growth was not affected. In roots, the decrease of the DBI (double bond index) of total fatty acids may signal a decrease in membrane fluidity. The total lipids (TL) decreased by 49%, but phospholipids (PL), phosphatidylcholine (PC) and phosphatidylinositol (PI) increased to approximately 3-fold. The MGDG increased to 2-fold but no significant change was found in the DGDG. The steryl lipids (SL) increased by 69%. The SL/PL ratio decreased from 2.64 to 1.52 and the MGDG/DGDG ratio increased from 0.45 to 1.06 in roots of Al-stressed plants. Al leads to oxidative stress in roots of treated plants as indicated by the increase of malondialdehyde (MDA) concentrations. In shoots, changes in fatty acid composition were associated with an increase of the DBI in all lipid classes except that of the DGDG decreased. The PG was the lipid class which shows the large variation of fatty acid composition. No significant changes were found either for TL, PL, SL or MDA concentrations in shoots of Al-treated plants. While PE levels did not show significant change, PI and PG increased and PC decreased. However, the Al caused 87% decrease in the GL levels. The MGDG and DGDG decreased to 19- and 8-fold, respectively. The deleterious effects of Al on polar lipids could be caused by a direct intervention of Al on plasma membrane and/or alteration of cell metabolism.     

Impact of green tea on oxidative stress induced by ammonium metavanadate exposure in male rats

Transitional metals, as vanadium, are known to exert noxious effects by generating oxidative stress. Addition of antioxidants in the diet could decrease the cytotoxic effect related to the oxidative stress. The present study, carried out in Wistar rats, is a contribution to the evaluation of protective effects of green tea Camellia sinensis, which is known to be rich in antioxidant compounds (polyphenols...). Rats were divided into four groups: (C) was control, (V) was given ammonium metavanadate (AMV), (TH) was given herbal tea as drink (66 g/l) and TH + V was given tea and metavanadate. Group (TH) was given herbal tea one month before vanadium treatment. Metavanadate was daily i.p. injected (5 mg NH4VO3/kg body weight) for 10 days. (C) and (TH) groups received i.p. injections of 0.9% NaCl during the same period. Changes in lipid peroxidation levels (TBARS) in kidney, liver and testes, serum concentrations of vitamins E and A and superoxidismutase (SOD) and catalase (CAT) activities in blood cells were determined. One month pre-treatment with green tea, followed by 10 days of treatment (TH) did not change TBARS in liver and testes as compared to controls, but induced a clear decrease of TBARS in kidneys. Intraperitoneal administration of AMV to rats (V) induced a time-dependant increase of TBARS in kidney, liver and testes that was lowered in rats (V + TH) drinking tea. Vitamin E concentrations were found to be drastically decreased from day 1 to 10 in rats (V). Vitamin A concentration was decreased at day 10 only. Drinking tea lowered AMV inhibitory effects in rats (V + TH), and conversely an increase of vitamins A and E concentrations were found at day 10. SOD and catalase activities were found increased in the blood cells from day 1 to day 5 and conversely decreased at day 10. In contrast, associated to green tea, AMV did not affect SOD and catalase activities compared to controls.     

Toxicity assessment of the puffer fish Lagocephalus lagocephalus from the Tunisian coast

This study was undertaken to assess the risk of poisoning due to consumption of the puffer fish Lagocephalus lagocephalus collected along the Tunisian coast. Wistar rats were daily intraperitoneally injected, for 10 days, with acidic extracts of liver or flesh (muscles + skin) of L. lagocephalus. Control rats received injections of NaCl (0.9%). No mortality and no evident signs of neurotoxicity were recorded in treated rats. Conversely, treatment led to: (1) diarrhoea and body and organ (liver, kidney) weights loss; (2) oxidative stress evidenced by an increase in lipid peroxidation (TBARS) and conversely a decrease in antioxidant enzyme activities (SOD, catalase, GSH-Px) in tissues (blood cells, liver, kidneys); (3) a decrease in alanine aminotransferase (ALT) and alkaline phosphatase (ALP) activities in blood plasma.     

Characterization of the mineral phosphate solubilizing activity of <Emphasis Type="Italic">Serratia marcescens</Emphasis> CTM 50650 isolated from the phosphate mine of Gafsa

The mineral phosphate solubilizing (MPS) ability of a Serratia marcescens strain, namely CTM 50650, isolated from the phosphate mine of Gafsa, was characterized on a chemically defined medium (NBRIP broth). Various insoluble inorganic phosphates, including rock phosphate (RP), calcium phosphate (CaHPO₄), tri-calcium phosphate (Ca₃(PO₄)₂) and hydroxyapatite were tested as sole sources of phosphate for bacterial growth. Solubilization of these phosphates by S. marcescens CTM 50650 was very efficient. Indeed, under optimal conditions, the soluble phosphorus (P) concentration it produced reached 967, 500, 595 and 326 mg/l from CaHPO₄, Ca₃(PO₄)₂, hydroxyapatite and RP, respectively. Study of the mechanisms involved in the MPS activity of CTM 50650, showed that phosphate solubilization was concomitant with significant drop in pH. HPLC-analysis of culture supernatants revealed the secretion of gluconic acid (GA) resulting from direct oxidation pathway of glucose when the CTM 50650 cells were grown on NBRIP containing glucose as unique carbon source. This was correlated with the simultaneous detection by PCR for the first time in a S. marcescens strain producing GA, of a gene encoding glucose dehydrogenase responsible for GA production, as well as the genes pqqA, B, C and E involved in biosynthesis of its PQQ cofactor. This study is expected to lead to the development of an environmental-friendly process for fertilizer production considering the capacity of S. marcescens CTM 50650 to achieve yields of P extraction up to 75% from the Gafsa RP.