Functional Comparison of Three Chitinases from Symbiotic Bacteria of Entomopathogenic Nematodes

Abstract

Xenorhabdus and Photorhabdus, bacterial symbionts of entomopathogenic nematodes Steinernema and Heterorhabditis, respectively, have several biological activities including insecticidal and antimicrobial activities. Thus, XnChi, XhChi, and PtChi, chitinases of X. nematophila, X. hominickii, and P. temperata isolated from Korean indigenous EPNs S. carpocapsae GJ1-2, S. monticolum GJ11-1, and H. megidis GJ1-2 were cloned and expressed in Escherichia coli BL21 to compare their biological activities. Chitinase proteins of these bacterial symbionts purified using the Ni-NTA system showed different chitobiosidase and endochitinase activities, but N-acetylglucosamidinase activities were not shown in the measuring of chitinolytic activity through N-acetyl-D-glucosarmine oligomers. In addition, the proteins showed different insecticidal and antifungal activities. XnChi showed the highest insecticidal activity against Galleria mellonella, followed by PtChi and XhChi. In antifungal activity, XhChi showed the highest half-maximal inhibitory concentration (IC50) against Fusarium oxysporum with 0.031 mg/mL, followed by PtChi with 0.046 mg/mL, and XnChi with 0.072 mg/mL. XhChi also showed the highest IC50 against F. graminearum with 0.040 mg/mL, but XnChi was more toxic than PtChi with 0.055 mg/mL and 0.133 mg/mL, respectively. This study provides an innovative approach to the biological control of insect pests and fungal diseases of plants with the biological activity of symbiotic bacterial chitinases of entomopathogenic nematodes.

Gene Cloning, Heterologous Expression, and In Silico Analysis of Chitinase B from Serratia marcescens for Biocontrol of Spodoptera frugiperda Larvae Infesting Maize Crops

“…In another study by Downing et al [32], enhanced biocontrol of the sugarcane borer Eldana saccharina was achieved by co-introducing the cry1Ac7 gene from B. thuringiensis strain 234 and the chiA gene from S. marcescens into strains of Pseudomonas fluorescens. Insecticidal activity of three chitinases isolated from symbiotic bacteria nematodes was evaluated against Galleria mellonela [33]. Chitinase and endotoxins derived from Bacillus thuringiensis have been successfully used in the biological control of Spodoptera exigua and Helicoverpa armigera larvae.…”

“…Such findings suggest that chitinases can be appropriately utilized as green insecticides to prevent and control S. frugiperda in the future [33,40]. Concerns about the environmental release of transgenic bacteria led to the further improvement of the crude extract of chitinase B, which was then utilized as a pathogenic agent against S. frugipedra.…”