Effects of pure n-alkanes and crude oil on bacterial phospholipid classes and molecular species determined by electrospray ionization mass spectrometry

Phospholipids are major components of bacterial membrane. Furthermore, the growth in vitro on xenobiotics such as n-alkanes, aromatic compounds or alkanols bring about to a bacterial membrane adaptive response. Concerning this work, we studied the membrane lipid composition of a hydrocarbon-degrading gram-positive bacterium (Corynebacterium sp.) on a soluble substrate and we detected four different phospholipid classes: phosphatidylglycerol, phosphatidylinositol, cardiolipin and acyl phosphatidylglycerol. In addition, a study of the lipid composition was performed after an in vitro culture on either pure n-alkane or crude oil. The growths on such hydrophobic substrates showed major qualitative and quantitative modifications. In the case of a growth on either heneicosane or crude oil, an increase of odd-numbered fatty acids was observed. Furthermore, the phospholipid polar head group composition was highly influenced by the crude oil addition. These modifications were, respectively, interpreted as the consequence of hydrocarbon assimilation and membrane fluidity adaptation. Finally, Corynebacterium sp. was taken back on the initial ammonium acetate substrate in order to determine its restoration abilities after a petroleum contamination.     

Enhanced resolution of random amplified polymorphic DNA genotyping of Pseudomonas aeruginosa

AIMS: To develop a rapid, sensitive and reproducible screening test for the detection of nosocomial spreading of Pseudomonas aeruginosa. METHODS AND RESULTS: Ps. aeruginosa genomic DNA extraction, RAPD-PCR, electrophoresis on acrylamide gel and silver staining were performed by using standardized reagents and conditions. The results were compared with the agarose gel electrophoresis followed by ethidium bromide staining. CONCLUSIONS: The coupling of acrylamide gel electrophoresis and silver staining gave about 80% more DNA bands than the traditional method, allowing a finer discrimination among different Ps. aeruginosa strains. SIGNIFICANCE AND IMPACT OF THE STUDY: By enhancing the resolution of the electrophoretic separation and the sensitivity of the staining, random amplification could be easily applied to the surveillance and prevention of nosocomial infections by clinical microbiology laboratories.     

Lipid metabolism in lipoatrophic diabetes

Some aspects of lipid metabolism were studied in 4 patients with a congenital lipoatrophic diabetes (LAD) associated to a type IV hyperlipoproteinemia. The analysis of lipoprotein composition, expressed as mg/dl, demonstrates a significant increase of VLDL mass and a significant reduction of HDL mass. The analysis of lipoprotein composition, expressed as per cent of total mass demonstrates an increase of the triglyceride content in all fractions and a significant reduction of the cholesterol and phospholipid content in HDL2 particles. Apo C-II, C-III0, C-III1 and C-III2 levels in lipoprotein fractions were normal in LAD patients. Lipoprotein lipase activity in omental adipose tissue, collected during laparoscopy in one patient was undetectable. The serum of this patient did not fully activate the lipoprotein lipase eluted from normal adipose tissue. In all patients the adipose tissue lipoprotein lipase activity in post-heparin plasma was blunted or near absent. Thus a reduced peripheral clearance of triglyceride-rich lipoprotein could be an important determinant of lipoprotein abnormalities in lipoatrophic diabetes.