Unveiling Diversity and Function: Venom-Associated Microbes in Two Spiders, Heteropoda venatoria and Chilobrachys guangxiensis.

Spiders are natural predators of agricultural pests, primarily due to the potent venom in their venom glands. Spider venom is compositionally complex and holds research value. This study analyzes the diversity of symbiotic bacteria in spider venom glands and venom, as well as the biological activity of culturable symbiotic bacteria. Focusing on the venom glands and venom of Heteropoda venatoria and Chilobrachys guangxiensis, we identified a diverse array of microorganisms. High-throughput sequencing detected 2151 amplicon sequence variants (ASVs), spanning 31 phyla, 75 classes, and 617 genera. A total of 125 strains of cultivable bacteria were isolated. Using the Oxford cup method, crude extracts from 46 of these strains exhibited inhibitory effects against at least one indicator bacterium. MTT (Thiazolyl blue) assays revealed that the crude extracts from 43 strains had inhibitory effects on tumor cell line MGC-803 growth. Additionally, DAPI (4',6-diamidino-2'-phenylindole) staining and flow cytometry were employed to detect cell apoptosis. The anti-inflammatory activity of nine bacterial strains was assessed using a NO assay kit and enzyme-linked immunosorbent assay (ELISA). This study further investigated the biological activity of venom, exploring the relationship between the venom and the functional activity of venom-associated bacteria.