Antimicrobial Property and Mode of Action of the Skin Peptides of the Sado Wrinkled Frog, <i>Glandirana susurra,</i> against Animal and Plant Pathogens

• Main Authors: Daisuke Ogawa, Manami Suzuki, Yuriko Inamura, Kaito Saito, Itaru Hasunuma, Tetsuya Kobayashi, Sakae Kikuyama, Shawichi Iwamuro
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Antibiotics
• Subjects: Sado wrinkled frog; frog skin; antimicrobial peptides; anti-plant-pathogen activity; ELEBA
• Online Access: https://www.mdpi.com/2079-6382/9/8/457

The Sado wrinkled frog <i>Glandirana susurra</i> has recently been classified as a new frog species endemic to Sado Island, Japan. In this study, we cloned 12 cDNAs encoding the biosynthetic precursors for brevinin-2SSa–2SSd, esculentin-2SSa, ranatuerin-2SSa, brevinin-1SSa–1SSd, granuliberin-SSa, and bradykinin-SSa from the skin of <i>G. susurra</i>. Among these antimicrobial peptides, we focused on brevinin-2SSb, ranatuerin-2SSa, and granuliberin-SSa, using their synthetic replicates to examine their activities against different reference strains of pathogenic microorganisms that infect animals and plants. In broth microdilution assays, brevinin-2SSb displayed antimicrobial activities against animal pathogens <i>Escherichia coli</i>, <i>Salmonella enterica</i>, <i>Pseudomonas aeruginosa</i>, and <i>Candida albicans</i> and plant pathogens <i>Xanthomonas oryzae</i> pv. <i>oryzae</i>, <i>Clavibacter michiganensis</i> subsp. <i>michiganensis</i>, and <i>Pyricularia oryzae</i>. Ranatuerin-2SSa and granuliberin-SSa were active against <i>C. albicans</i> and <i>C. michiganensis</i> subsp. <i>michiganensis</i>, and granuliberin-SSa also was active against the other plant pathogenic microbes. Scanning electron microscopic observations demonstrated that brevinin-2SSb, ranatuerin-2SSa, and granuliberin-SSa induced morphological abnormalities on the cell surface in a wide range of the reference pathogens. To assess the bacterial-endotoxin-binding ability of the peptides, we developed an enzyme-linked endotoxin-binding assay system and demonstrated that brevinin-2SSb and ranatuerin-2SSa both exhibited high affinity to lipopolysaccharide and moderate affinity to lipoteichoic acid.