Enzyme release by Trichophyton rubrum depends on nutritional conditions

Abstract

Summary. Enzymes liberated by growing der‐matophytes are of pathogenetic importance in tinea. To investigate the influence of nutrients on this enzyme release, Trichophyton rubrum was grown in media containing peptone, keratin and lipids, to which glucose was added in separate assays. The culture supernatants were compared for extracellular enzyme activities by use of the api‐zym® test. Our results clearly show that the extracellular enzyme activity is dependent on the nutrients supplied. Seven different enzymes were released when keratin was supplied, as compared with only five and two respectively when lipids or peptone were available. Among these enzymes alkaline phosphatase and N‐acetyl‐β‐glucosaminidase were detected in all cultures lacking glucose. Enzyme release was inhibited completely when glucose was added to the media, except for N‐acetyl‐β‐glucosaminidase in peptone cultures. This dependency of enzyme release on fungal nutrition can be expected to occur in vivo too. In addition, it has to be considered for in vitro cultural conditions. Alkaline phosphatase and acetylglucosaminidase may be more important in tinea than has been assumed so far. Zusammenfassung. Von Dermatophyten frei‐gesetzte Enzyme sind bei der Entstehung einer Tinea pathogenetisch relevant. Um den Einfluβ von Nährsubstraten auf die Enzymfreisetzung von Trichophyton rubrum zu untersuchen, wurde dieser Erreger in pepton‐, keratin‐ und lipid‐haltigen Nährmedien gezüchtet, denen in zusätz‐lichen Ansätzen Glucose beigefügt wurde. Die Kulturüberstände wurden mit dem api‐zym® ‐Test auf extrazelluläre Enzymaktivität unter‐sucht. Unsere Ergebnisse zeigen eine eindeutige Abhängigkeit dieser Enzymaktivitäten vom Nährstoffangebot. Bei Wachstum auf Keratin wurden sieben verschiedene Enzyme bestimmt, bei Lipid‐ bzw. Peptonangebot dagegen nur fünf bzw. zwei. Alkalische Phosphatase und N‐Acetyl‐β‐Glucosaminidase waren in alien glucosefreien Nährmedien nachweisbar. Durch Glucosezusatz zu den Nährmedien erfolgte eine vollständige Hemmung der Enzymfreisetzung mit Ausnahme von N‐Acetyl‐β‐Glucosaminidase in der Pepton‐kultur. Diese Nährstoffabhangigkeit der Enzymfreisetzung kann auch in vivo vermutet werden und ist bei der Auswahl von Kulturmedien zu berücksichtigen. Alkalische Phosphatase und Acetylglucosaminidase könnten mehr Bedeutung bei Dermatophytosen besitzen als bisher ange‐nommen.

The host range of dermatophytes, it is at all possible? Phenotypic evaluation of the keratinolytic activity of Trichophyton verrucosum clinical isolates

“…The latter factor supported the observation that proteolytic activity is frequently suppressed by glucose. 26,40,67 Our recent trials have suggested that the use of carbohydrate-free mineral medium for a keratin decomposition assay yields by 25% higher keratinolytic activity than that obtained with the modified Sabouraud medium. In the medium with 0.5% glucose, there was also a trend for longer persistence of the activity of the proteolytic enzymes at high levels at 30 and 60 days of incubation than in the modified Sabouraud medium.…”

The use of global transcriptional analysis to reveal the biological and cellular events involved in distinct development phases of Trichophyton rubrum conidial germination

“…Several homologues of genes related to the cAMP/PKA and RAS GTPase signalling pathways were found related to conidial germination in T. rubrum . However, we also found that glucose only could not trigger the conidia germination and conidia could germinate and grow in nitrogen abundant but fermentable C source absent media such as soy protein liquid medium (SP) and keratin liquid medium (KSP) [42-44]. So, we suppose that the signal transduction modules are different molecular mechanism involved in sensing the external signal and initiation of germination in T. rubrum .…”

Pathogenesis of tinea

“…UV exposure might possibly direct the direction of growth of the hyphae into the depth [10]. Numerous enzymes released by the dermatophytes during growth allow them to degrade and utilize keratins and other proteins as well as lipids and DNA [11][12][13]. To which extent certain enzymes are produced after activation of the respective genes depends greatly on the supply of nutrients [12,13].…”