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ABSTRACT Soil salinization usually occurs in arid and semi-arid climate areas from 37 to 50 degrees north latitude and 73 to 123 degrees east longitude. These regions are inhabited by a large number of Coleopteran insects, which play an important role in the ecological cycle. However, little is known about the endosymbiotic microbial taxa and their biological characteristics in these insects. A study of endosymbiotic microorganisms of Coleoptera from Xinjiang, a typical arid and inland saline area, revealed that endosymbiont bacteria with salinity tolerance are common among the endosymbionts of Coleoptera. Functional prediction of the microbiota analysis indicated a higher abundance of inorganic ion transporters and metabolism in these endosymbiont strains. Screening was conducted on the tolerable 11% NaCl levels of Brevibacterium casei G20 (PRJNA754761), and differential metabolite and proteins were performed. The differential metabolites of the strain during the exponential and plateau phases were found to include benzene compounds, organic acids, and their derivatives. These results suggest that the endosymbiotic microorganisms of Coleoptera in this environment have adaptive evolution to extreme environments, and this group of microorganisms is also one of the important resources for mining saline and alkaline-tolerant chassis microorganisms and high-robustness enzymes.IMPORTANCEColeoptera insects, as the first largest order of insect class, have the characteristics of a wide variety and wide distribution. The arid and semi-arid climate makes it more adaptable. By studying the endosymbiont bacteria of Coleoptera insects, we can systematically understand the adaptability of endosymbiont bacteria to host and special environment. Through the analysis of endosymbiont bacteria of Coleoptera insects in different saline-alkali areas in arid and semi-arid regions of Xinjiang, it was found that bacteria in different host samples were resistant to saline-alkali stress. These results suggest that bacteria and their hosts co-evolved in response to this climate. Therefore, this study is of great significance for understanding the endosymbiont bacteria of Coleoptera insects and obtaining extremophile resources (Saline-alkali-resistant chassis strains with modification potential for the production of bulk chemicals and highly robust industrial enzymes).