Entomopathogenic efficacy of the chitinolytic bacteria: Aeromonas hydrophila isolated from Siwa Oasis, Egypt

Abstract

Thirty-four bacterial isolates were isolated from soil samples collected from the North Western Coast and a water sample collected from brackish water at Siwa Oasis, Matrouh Governorate, Egypt. Only six isolates showed chitinase activity when screened on colloidal chitin agar medium. The highest chitinolytic activity was achieved by a bacterial isolate labeled as A.S. This isolate was identified as Aeromonas hydrophila based on analysis of 16S rRNA gene sequence and morphological, physiological, and biochemical characteristics. Optimization of the cultural conditions for maximum chitinase production by A. hydrophila revealed that the highest level of chitinase was recorded when the bacterium was grown in malt nitrogen-based medium containing 1% colloidal chitin at pH7 for 48 h incubation at 30°C. Crude chitinase from isolate A. hydrophila was evaluated against first instar larvae of the greater wax moth; Galleria mellonella L. (Lepidoptera: Pyralidae) at different concentrations of 0, 185, 205, 235, 265, 295 U/mg protein. It increased larval and pupal mortality rates in a concentration-dependent manner. The tested crude chitinase significantly induced a decrease in adults' emergence rate and their fecundity.

Physiological Effects of Crude Chitinase From Aeromonas Hydrophila on the Greater Wax Moth; Galleria Mellonella L. (Lepidoptera: Pyralidae)

“…Aeromonas hydrophila was isolated from brackish water sample collected from Siwa Oasis, Egypt. The pathogenic activity of this bacterial species against Galleria mellonella, its potentiality for chitinase production and the LC50 value of the crude chitinase were determined (Korany et al, 2019). According to the later authors, the LC50 of crude chitinase was found to be 135.0 U/mg protein and had been used through this study.…”

Extraction of chitin from edible crab shells of Callinectes sapidus and comparison with market purchased chitin

“…From 85 isolates only 27 isolates (35.29%) showed vivid zone of chitin hydrolysis. Korany et al (Korany et al, 2019) reported that among the thirty four isolates only four isolates produced zones of clearance (hydrolysis) on chitin agar medium. Similarly Ajayi et al ( 2016) had isolated 36 chitinolytic isolates but selected 24 on the basis of highest chitnolytic index.…”