Salt-Tolerant Antifungal and Antibacterial Activities of the Corn Defensin ZmD32

We examined whether the high charge on ZmD32 would allow this defensin to retain activity in media with elevated salt concentrations. ZmD32 inhibited C. albicans, C. auris, C. glabrata, C. krusei, C. parapsilosis, and C. tropicalis growth with IC50 values ranging from 0.7 to 3.0 in ½ PDB medium containing 100 mM NaCl. In contrast, NaD1 was only active against C. parapsilosis and C. tropicalis with IC50 values of 3.4 and 1.3 μM, respectively, in medium with added NaCl. ZmD32 also retained activity against E. coli when NaC1 concentrations were raised to 100 mM while NaD1 did not (Table 1). For C. albicans and C. krusei the IC50 for ZmD32 was slightly higher when the assay was performed with the addition of 100 mM NaCl, for C. glabrata, C. parapsilosis, and C. tropicalis the IC50 was not significantly different at 100 mM NaCl and for C. auris and E. coli. The activity of ZmD32 and NaD1 against C. albicans was also assessed in the presence of 5 mM MgCl2 or 2 mM CaCl2. NaD1 lost activity in the presence of both MgCl2 and CaCl2 while ZmD32 was active in both divalent metal salts but had an sevenfold increase in IC50 (data not shown). The Rate of Fungal Cell Killing by ZmD32 Is Slower in 100 mM NaCl A cell survival assay was used to assess whether ZmD32 was fungistatic or fungicidal against C. albicans. There was a greater than 95% reduction in survival of C. albicans cells after a 30 min exposure to 10 μM ZmD32 and no viable cells after 2 h in ½ PDB me...
Source: Frontiers in Microbiology - Category: Microbiology Source Type: research