CHARACTERIZATION OF Enterobacter Spp. ISOLATED FROM THE GUT OF RICE WEEVIL

Abstract

Rice weevil is the most widely distributed and destructive insect pest found in cereal products.
The insects usually harbour some biologically important bacteria in their guts which may
considerably affect various aspects of their ecology, behaviour, and physiology. The aim of this
research was to characterize the Enterobacter sp. previously isolated from rice weevil and
identified molecularly. These bacteria was investigated based on (i) morphological properties:
(ii) biochemical; its ability to utilize different type of carbon and nitrogen sources (glucose,
sucrose, lactose, starch, casamino acid, nitrate, nitrite and ammonium), (iii) tolerance towards
various heavy metal ions (copper, zinc, manganese, aluminium) and antibiotics. This
Enterobacter sp. was found to be Gram negative, rod-shaped, non-motile bacterium, and showed
positive reaction with catalase, urease and citrate. Based on carbon and nitrogen experiments,
sucrose and casamino acid were found to be suitable carbon and nitrogen source for the growth
of Enterobacter sp. The isolate was also tolerant to aluminium with maximum tolerance
concentration of 800 mg/L with growth rate (μ) of 0.240 h-1. Besides that, this bacterium was
able to grow in 400 mg/L of copper and exhibit intolerance towards zinc at concentration of 200
mg/L to 800 mg/L. In addition, the isolate was able to tolerate well up to 800 mg/L (growth rate:
0.244 h-1) of manganese. The bacterium was also found resistant to erythromycin,
chloramphenicol and ampicillin. Considering the ability of the bacteria to tolerate various types
of heavy metals, they could potentially be used for bioremediation of heavy metal from
environment