Probiotic Characterization of Enterococcus mundtii Isolated from Larval Gut of the Diamondback Moth, Plutella xylostella

Abstract: Gut bacterium Enterococcus mundtii is one of the predominant bacterial species in the larval gut of the diamondback moth, Plutella xylostella. Probiotic characterization in auto-aggregation and hydrophobicity, carbon use ability, and pH and osmotic environment adaptability of this bacterium were analyzed. Results exhibited that E. mundtii showed inhibition against Micrococcus luteus, Bacillus thuringiensis and Escherichia coli. It revealed a high auto-aggregation score and a hydrophilic cell surface. It metabolized 24.21% of the tested carbon sources with informative utilization patterns in organic acids and carbohydrates. It had a wide range of adaptabilities, and could still metabolize in osmolytes with up to 6% potassium chloride, 6% sodium chloride, 20% ethylene glycol, 5% sodium sulfate, 2% sodium lactate, 7% urea, 200 mM sodium phosphate (pH 7.0), 20 mM sodium benzoate (pH 5.2), 100 mM ammonium sulfate (pH 8.0), and 100 mM sodium nitrate; while it could not metabolize sodium lactate ranging from 3% to 12%, sodium formate ranging from 1% to 6%, or sodium nitrite ranging from 10 to 100 mM. Enterococcus mundtii exhibited active metabolism under pH values between 5 and 10, active deaminase activity but no decarboxylase activity. The probiotic characterization of E. mundtii increased our knowledge of adaptability in gut environments.