Induction of synthesis of an antimicrobial peptide in the skin of the freeze-tolerant frog, Rana sylvatica, in response to environmental stimuli

AbstractAn extract of skin taken from specimens of the freeze-tolerant wood frog, Rana sylvatica, that were collected from cold (<7°C) ponds and maintained at 5°C lacked detectable antimicrobial activity. In contrast, an extract of skin taken from specimens maintained at 30°C for 3 weeks under laboratory conditions contained a high concentration (approximately 4 nmol/g) of a single antimicrobial peptide of the brevinin-1 family (FLPVVAGLAAKVLPSIICAVTKKC). The peptide inhibited growth of Escherichia coli (minimum inhibitory concentration 45 μM) and Staphylococcus aureus (minimum inhibitory concentration 7 μM). The data suggest that synthesis of the peptide is induced when the animal is in an environment that promotes the growth of microorganisms consistent with a role in the animal’s defense strategy