Isolation of a Urea Degrading Bacteria :: Biology

Isolation of a Urea Degrading Bacteria Introduction Urea was the first organic chemical to be synthetically produced1, previously it was thought that only living creatures could produce organic compounds Urea is naturally produced by the kidneys as waste from the degradation of amino acids. It is because of this that urea is commonly found in soils and is a useful nutrient source for bacteria that are able to utilise it, such as, Helicobacter pylori, Klebsiella pneumonia, all species of Proteus and Micrococcus luteus. These bacteria degrade urea in a reaction catalysed by the urease enzyme, CO(NH2)2 + H2O Ã  CO2 + 2NH3. this process benefits the bacteria in several ways. The bacteria use the ammonia that is produced for respiration, the products also raise the pH of the environment. This promotes the growth of many urea degrading bacteria and inhibits competition from many other bacterial species. M. luteus is commonly found on mammalian skin and it is unusual for a member of the natural human flora to degrade urea. It is believed that M. luteus has this ability as an evolutionary hangover from its life in its ancestral soil habitat. In this environment urea is readily available and the ability to degrade it is a distinct advantage. As the species evolved to live on skin the trait remained, as it had no negative effect on survivability. Micrococcus is a genus within the Micrococcaceae family. With the use of 16s RNA in bacterial taxonomy the genus has recently been revised2. The genus now includes three species, M. luteus, M. lylae and M. antarcticus3. M. luteus is a common yellow gram-positive coccus and roughly 0.5-2.0mm in diameter. Cells appear in pairs, tetrads and irregular clusters but never in chains.4 Method of Isolation * Isolate a variety of organisms from soil and skin. By taking samples from four different sources (three skin and one soil) the chance of urea degrading bacteria being present was increased. * Culture in nutrient broth. This allowed all isolated microbes to grow. * Plate sample onto urea plates. On these plates urea was the only nutrient available, this meant that any bacteria that grew could degrade urea. * Perform urease test. Isolated bacteria are grown in a broth containing phosphate buffer, yeast extract, 2% urea and phenol red. An agar slope of the medium is heavily inoculated and incubated at 370c for at least four hours. If the organism only has low urease activity the phosphate buffer will neutralise the NH3 produced. A red colour indicates that NH3 has been produced and the result is positive5. * Perform Gram stain. This is the most important stain in bacteriology and differentiates between gram positive and gram-negative cell walls, which indicates