Identification of bacteria in the salivary gland of Bactrocera dorsalis (Hendel) and study of their bioactivity

The microbial community within the insect digestive tract can exert a substantial regulatory influence on the behavioral tendencies of the host. The salivary glands, serving as a unique microenvironment upstream of the digestive tract, are potentially implicated in the behavior of attraction. Focusing on the microbial community in the salivary glands of the oriental fruit fly, Bactrocera dorsalis, this study have screened and identified functional bacteria strains and key compounds that exhibit an attracting effect on adult flies. Enterobacter bugandensis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Citrobacter farmeri were isolated and characterized. Behavioral assays demonstrated that both K. pneumoniae and C. farmeri had significant attracting effects on adult flies under indoor conditions. In the wild environment, however, only K. pneumoniae retained a high efficiency in attracting adult flies. By integrating gas chromatography-mass spectrometry (GC-MS) and electroantennogram (EAG) techniques, it was confirmed that phenethyl alcohol in the culture supernatant of K. pneumoniae could specifically elicit an electrophysiological response from the antennae of B. dorsalis. Further indoor attraction experiments revealed that a 0.05 μL/mL phenethyl alcohol solution had a notable attracting effect on adult flies. This study was the first to disclose that K. pneumoniae in the salivary glands of the oriental fruit fly might modulate the fly's behavioral tendency via the metabolite phenethyl alcohol. Simultaneously, the fermentation broth of K. pneumoniae exhibits a remarkable attracting effect in the wild environment. This finding offers a novel strategy and crucial theoretical foundation for the development of green monitoring and control technologies for B. dorsalis.