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Cuticle‐degrading proteases and toxins as virulence markers of Beauveria bassiana (Balsamo) Vuillemin
Author(s) -
Cito Annarita,
Barzanti Gian Paolo,
Strangi Agostino,
Francardi Valeria,
Zanfini Assunta,
Dreassi Elena
Publication year - 2016
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/jobm.201600022
Subject(s) - beauveria bassiana , beauvericin , bassiana , proteases , microbiology and biotechnology , biology , beauveria , virulence , enzyme , biological pest control , food science , biochemistry , botany , mycotoxin , gene
Beauveria bassiana is one of the most known entomopathogenic fungal species and its entomopathogenic mechanism involves several bioactive metabolites, mainly cuticle‐degrading enzymes and toxic molecules, which are predicted to play a key role as virulence factors. In this study six Beauveria bassiana strains (B 13/I03, B 13/I11, B 13/I49, B 13/I57, B 13/I63, and B 13/I64) were assayed against Tenebrio molitor larvae. Enzymatic activity of total proteases and specifically Pr 1 and Pr 2, as well as the production of toxic compounds were investigated in each fungal strain. Toxins were detected both in vitro —in medium filtrates and mycelia—and in vivo —in Tenebrio molitor larvae infected by the fungal strains tested. B 13/I11 and B 13/I63 strains showed the most significant entomopathogenic activity against Tenebrio molitor larvae (cumulative mortality rate 100 and 97%, respectively; average survival time 5.85 and 6.74 days, respectively). A widely variable and fungal strain‐dependent enzymatic activity of total proteases, Pr 1 and Pr 2 was found. Beauvericin, beauvericin A and bassianolide resulted the most prevalent toxins detected in the substrates analyzed. It has been found that an increase of beauvericin content in vivo resulted significantly correlated to a decrease of Tenebrio molitor larvae average survival time in entomopathogenic bioassay (inverse correlation). The involvement of beauvericin in B. bassiana entomopathogenic process is confirmed; in vitro analysis of cuticle degrading proteases activity and toxins production in relation to the methods adopted resulted insufficient for a rapid screening to determine the virulence of B. bassiana strains against Tenebrio molitor larvae.