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
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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 (IC
50) 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 IC
50 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.
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