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Helicobacter pylori

Helicobacter pylori - Gram-negative, spiral to pleomorphic, spiral rod prokaryote. Magnification 2,200, Scanning electron microscope. This bacterium can move by means of tiny flagella at the end of the cell. There are many strains of H. pylori which are distinguished by the human disease with which they cause. H. pylori infection is the main cause of chronic superficial gastritis and it is associated with both gastric and duodenal ulcers. It lives in the interface between the surface of gastric epithelial cells (the lining of the stomach). It often clusters at the junctions of epithelial cells. Courtesy of Dennis Kunkel.

Pichia pastoris

Pichia pastoris, a methylotrophic yeast. Magnification 1600, scanning electron microscopy. This methylotrophic yeast was isolated from nature and can consume methanol as a sole carbon source when glycerol or glucose is not found as a food source. It is a recombinant organism that is used to produce large quantities of specialized proteins. To metabolize methanol Pichia pastoris has an alcohol oxidase (AOX) gene. The P. pastoris expression system uses the methanol-induced alcohol oxidase promoter (AOX1) which controls the gene that codes for the expression of alcohol oxidase (the enzyme which catalyzes the fist step in the metabolism of methanol). Using genetic techniques genes for pharmaceutical proteins can be inserted next to the AOX-gene in Pichia allowing the yeast to produce the protein. A number of proteins have been produced using this system, including tetanus toxin fragment, Bordatella pertussus petactin, human serum albumin and lysozyme. Courtesy of Dennis Kunkel.

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