A complex immune response to flagellin epitope variation in commensal communities

1. Download : Download high-res image (196KB)
2. Download : Download full-size image

     

Purification and biochemical characterization of an organic solvent-tolerant and detergent-stable lipase from Staphylococcus capitis

A mesophilic bacterial culture, producing an extracellular alkaline lipase, was isolated from the gas-washing wastewaters generated from the Sfax phosphate plant of the Tunisian Chemical Group and identified as Staphylococcus capitis strain. The lipase, named S. capitis lipase (SCL), has been purified to homogeneity from the culture medium. The purified enzyme molecular weight was around 45 kDa. Specific activities about 3,900 and 500 U/mg were measured using tributyrin and olive oil emulsion as substrates, respectively at 37°C and pH 8.5. Interestingly, the SCL maintained more than 60% of its initial activity over a wide pH values ranging from 5 to 11 with a high stability between pH 9 and 11 after 1 hr of incubation at room temperature. The lipase activity was enhanced in the presence of 2 mM of Mg²⁺, Ca²⁺, and K⁺. SCL showed significant stability in the presence of detergents and organic solvents. Altogether, these features make the SCL useful for industrial applications. Besides, SCL was compatible with commercially available detergents, and its incorporation increases lipid degradation performances making it a potential candidate in detergent formulation.     

Maastrichtian-early Paleocene foraminiferal palaeobathymetry and depositional sequences at Gebel El Sharawna,south Luxor,Egypt

Maastrichtian-early Paleocene foraminiferal palaeobathymetry, palaeodiversity and vertical facies changes of Gebel El Sharawna, south Luxor, Egypt have been studied to determine the depositional sequences, their relationships to global records and/or tectonic signatures. Five benthonic assemblages are recorded and replicated in the present study reflect fluctuation in palaeo-water depth from restricted marginal marine to outer shelf palaeoenvironments. Four sequence boundaries that coincide with the Campanian/Maastrichtian, intra-early Maastrichtian, Early/Late Maastrichtian, Cretaceous/Palaeogene (K/Pg) and intra-Danian were recognized based upon sharp vertical facies changes, foraminiferal assemblage changes, hiatuses, mineral hard ground and reworking. The K/Pg unconformity reveals an unexpected ca. 4.2 Myr time gap as indicated by the absence of the CF2 Zone through lower part of the P1c Zone. It is easily distinguished in the field by conglomeration and winnowing of phosphate and glauconite in the lower Paleocene. These sequence boundaries defined five third-order depositional sequences mainly developed as the result of the eustatic sea-level changes, coupled with the Arabian–Nubian shield tectonic uplift at the southern edge of the Tethys Ocean.     

Downregulation of neutral ceramidase by gemcitabine: Implications for cell cycle regulation

Gemcitabine (GMZ) is a chemotherapeutic agent with well established effects on cell growth arrest and apoptosis. In this study, we investigated the potential roles of bioactive sphingolipids in mediating the growth suppressing effects of GMZ on a polyoma middle T transformed murine endothelial cell line. After 12-hour GMZ (0.6 μM) treatment, cell growth was arrested at the G₀/G₁ phase as detected by flow cytometric cell cycle analysis and MTT cell viability analysis, and this was accompanied by dephosphorylation of the retinoblastoma protein (Rb). Furthermore, GMZ treatment resulted in increased levels of specifically the very long chain ceramides as determined by mass spectrometry. Mechanistically, GMZ did not appear to affect the activities of many enzymes of ceramide metabolism; however, GMZ caused a selective reduction in the protein levels of neutral ceramidase (NCDase), as indicated by Western blot analysis, with a concomitant decrease in NCDase activity. The significance of NCDase loss on cell cycle regulation was investigated by specific knockdown of the enzyme using small interfering RNA (siRNA). Interestingly, NCDase siRNA transfection was sufficient to induce a cell cycle arrest at G₀/G₁ and an increase in total ceramide levels, with significant elevation in very long chain ceramides (C_24:1 and C_24:0). NCDase siRNA also induced Rb dephosphorylation. These data provide evidence for a novel mechanism of action for GMZ and highlight downregulation of NCDase as a critical step in GMZ-mediated ceramide elevation and cell cycle arrest.