Extracellular proteolytic activity ofCryptococcus neoformans

Abstract

Eight strains of Cryptococcus neoformans var. neoformans isolated from AIDS patients in the Infectious Disease Institute, University of Turin, Italy, were examined for growth and extracellular proteolytic activity in culture with solid and liquid media. All of the strains grew well on Yeast Carbon Base (YCB) agar medium supplemented with both 0.1% (w/v) bovine serum albumin (BSA) and 0.01% (w/v) polypeptone (Pp), and produced a clear proteolytic zone around their colonies, whereas they exhibited less growth and proteolytic activity on YCB medium supplemented with BSA alone. Strain #8 with a strong proteolytic activity was cultured in three different liquid media. Its growth was limited in YCB medium supplemented with 0.1% BSA, but was moderate in that with 0.01% Pp. Enhanced growth was supported by the addition of both BSA and Pp to the YCB medium. The relative value of the final cellular yields obtained with the above YCB-0.1% BSA, YCB-0.01% Pp and YCB-0.1% BSA-0.01% Pp media was approximately 1:10:20. In the culture with YCB medium containing both BSA and Pp, a rapid decrease in the amount of BSA was demonstrated by a spectrophotometric assay and gel electrophoresis of the culture supernatant after the log-to-stationary phase. The proteolytic activity in the culture supernatant became detectable after the log phase when tested with skim milk agarose plates. These results allowed us to conclude that Cr. neoformans var. neoformans is able to secrete protease and to utilize protein as a source of nitrogen.

Cryptococcus neoformans Gene Expression during Experimental Cryptococcal Meningitis

“…Therefore, C. neoformans may secrete proteases for the assimilation of carbon and nitrogen to enable growth in the relatively nutrient-deficient CSF. There is evidence to support the supposition that C. neoformans secretes proteases to use proteins as a nitrogen source (8). In addition, we identified tags for glutamine synthetase and glutamine-dependent NAD ϩ synthase (both categorized under the GO heading amino acid metabolism; see Table 2).…”

Infecções oportunistas por leveduras e perfil enzimático dos agentes etiológicos

“…Testes preliminares de patogenicidade foram desenvolvidos através da detecção da enzima protease utilizando-se meio indutor contendo soro de albumina bovina (BSA, fração V, Sigma, St Louis, MO) como substrato 1 . As leveduras isoladas foram suspensas em 1,0mL de água destilada esterilizada e contadas em câmara de Neubauer obtendo-se concentração de 106 células/ mL.…”

Purification and Characterization of a 43-Kilodalton Extracellular Serine Proteinase from Cryptococcus neoformans

“…Since then much experimental evidence has accumulated pointing to extracellular proteinases as the most important virulence factors for this fungus (15,17). In contrast to C. albicans, the proteolytic activity of C. neoformans has been only superficially investigated (1,3,4; Goodley and Hamilton, Abstr. 2nd Int.…”

“…Little is known about the proteins it secretes or releases, despite evidence that they elicit substantial immune responses (4). Several proteins of C. neoformans have been investigated (1,3,8,9,18,19,23,24; J. M. Goodley and A. J. Hamilton, Abstr. 2nd Int.…”