ENZYME LOCALIZATION IN Azotobacter Vinelandii

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Abstract
The intracellular localization of several enzymes was studied in A. vinelandii O by isolation of cellular constituents in a buffered lactose menstruum. Criteria are discussed by which valid enzyme distribution in the bacterial cell can be ascertained. The succinoxidase system of the Azotobacter is localized in the particles, the greatest activity being associated with the submicroscopic granules. Adenosine deaminase and alkaline phosphatase are found in the non-particulate cell components, whereas catalase appears associated with both granular and soluble cell material. Distribution results indicate marked similarity of the organization of the microorganism to that of the cells of higher plants and animals, although the presence of a large granule which gives a positive metachromatic reaction for polymetaphosphate may indicate presence of an energy-storage within the microbial cell. Absence of a nuclear particle in these bacterial extracts leads to some problems with regard to cytochemical studies. Although the "soluble" fraction (S) represents to a great degree the ground substance of the cell, presence of DNA in that fraction can result in erroneous conclusions. If there does exist a nuclear particle in bacteria, enzymes bound to it should be recovered in the DNA-containing fraction, namely S. It is still necessary to find a means of isolating the bacterial nucleus free of the cell, so that its biochemical properties may be examined directly.