The Anti-Termite Activity of Bacillus licheniformis PR2 against the Subterranean Termite, Reticulitermes speratus kyushuensis Morimoto (Isoptera: Rhinotermitidae)

Abstract

Subterranean termites of the species Reticulitermes speratus kyushuensis Morimoto (Isoptera: Rhinotermitidae) are notoriously destructive soil-dwelling pests that feed on the cellulosic wood biomass. This leads to tremendous losses of forest trees such as Pinus densiflora Siebold and Zucc. (Pinales: Pinaceae) and precious wooden structures of cultural heritage. This study investigated the efficacy of chitinase and protease produced by Bacillus licheniformis PR2 as cuticle-degrading enzymes for the biocontrol of worker termites. Bacillus licheniformis PR2 produced a strong chitinase and protease activity up to a maximum of 82.3 unit/mL and 35.9 unit/mL, respectively, and caused a lethal effect on termites under laboratory conditions. Treatment of termites with the bacterial broth culture and the crude enzyme fraction of B. licheniformis PR2 resulted in a maximum mortality rate (with a median lethal time (ET50)) of 83.3% (3 h, 36 min) and 88.9% (2 h, 59 min), respectively. The termites treated with B. licheniformis PR2 exhibited loss of setae, disintegration of epicuticle, rupturing of procuticle, and swelling at sockets. The degradation of cuticular chitin and glycoprotein polymers in the termite cuticle by chitinase and protease enzymes produced by B. licheniformis PR2 represents an effective eco-friendly strategy for controlling termite damage in Korean cultural heritage sites and forests.