Bacteria acid-fast organisms

Of all the acid-fast bacteria, Mycobacteria have been studied most extensively thus, most of our knowledge of glycolipids concerns Mycobacteria, and only occasional mention of Coiynebacteria or other acid-fast micro-organisms can be found. 

Ziehl-Neelsen acid-fast stain A differential stain for organisms that are not decolorized by acid in alcohol, such as the bacteria that cause Hansen s disease (leprosy) and tuberculosis. 

When Urel is expressed in Xenopus oocytes, there is a large increase in urea uptake that is pH dependent. There is no increase at neutral pH but a large increase with acidification down to pH 4.0, the limit of survival of oocytes. The pH-transport curve can be overlaid on the pH-urease activity curve of intact bacteria. Half-maximal transport occurs at a medium pH of 5.9. The increased uptake is energy independent, temperature independent, and nonsaturable, properties indicating that Urel is a urea channel. This allows extremely fast transport of urea across the inner membrane of the bacteria. Complementation of Urel deletion mutants with wild-type Urel in H. pylori also restore urease activation at acidic pH, showing that Urel is a urea transporter in both the heterologous oocyte expression system and in the native organism. 

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