Arginine aminopeptidase activity of phytopathogenic spiroplasmas.

The arginine aminopeptidase activity of arginine-utilizing phytopathogenic spiroplasmas was investigated with arginine beta-naphthylamide substrate using the fluorometric method. Hydrolysis of this substrate was demonstrated with broth cultures, washed concentrated whole cells, and cell-free extracts of corn stunt spiroplasma (CSS) and Spiroplasma citri. Growing CSS and S. citri in the presence of 47 mM arginine resulted in a reduction in aminopeptidase activity, indicating that synthesis of the enzyme might be subject to control by catabolic repression. Results of these experiments suggest a possible biochemical basis for pathogenicity of phytopathogenic spiroplasmas in vivo.

Preservation and storage of pathogenic Neisseria.

Pathogenic species of Neisseria, especially N. gonorrhoeae are notoriously difficult to maintain in a viable state for long storage periods. Frequent transfer of cultures on artificial media and storage at 4 to 8 C quickly leads to loss of viability and virulence and to changes in antigenicity. Freeze-drying has been reported as a convenient method for long-term storage of these organisms; however, many laboratories are not properly equipped to use this method. A simple, inexpensive, and efficient procedure is described for storage of N. gonorrhoeae or N. meningitidis for 12 and 18 months, respectively. Results of this work may provide the basis for an efficient method of transporting these organisms over long distances via mail.