Probiotic characterization of Enterococcus mundtii isolated from larval gut of Diamondback moth, Plutella xylostella

Authors: LI, WENHONG - Guizhou Academy Of Agricultural Sciences; ZHANG, JIE - Institute Of Plant Protection - China; Zhu, Yu Cheng; LI, FENGLIANG - Guizhou Academy Of Agricultural Sciences

Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2021
Publication Date: 4/10/2021
Citation: Li, W., Zhang, J., Zhu, Y., Li, F. 2021. Probiotic characterization of Enterococcus mundtii isolated from larval gut of Diamondback moth, Plutella xylostella. Journal of Kansas Entomological Society. 93(3):196-210. https://doi.org/10.2317/0022-8567-93.3.196.
DOI: https://doi.org/10.2317/0022-8567-93.3.196

Interpretive Summary: Gut bacterium Enterococcus mundtii is one of the predominant bacterial species in the larval gut of the diamondback moth (DBM). To understand the potential probiotic property of this bacterium, antimicrobial activity against other gut bacteria, cell surface properties in forming colony, hydrophobicity, carbon use ability, and the pH and osmotic environment adaptability of this bacterium were also examined in this study. Results showed that E. mundtii was capable to inhibit other three gut bacteria, including some pathogenic bacteria of the host insect DBM. Enterococcus mundtii exhibited a high auto-aggregation score and a hydrophilic cell surface. The bacterium can effectively use carbon sources and other organic acids and carbohydrates. It had a wide range of adaptabilities and could still show active metabolism in a wide variety and concentration range of several osmolytes. However, its metabolic activity was limited by some chemicals at certain concentrations. In a wide pH range of 5-10, this gut bacterium still exhibited active deaminase activity but no decarboxylase activity. Therefore, the probiotic characterization of E. mundtii in this study provided a valuable information regarding the adaptability of the bacterium in gut environments of the host species, which might be explored to modulate gut microbials for insect pest management.

Technical 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.