Available online 13 September 2022, 126358

SG1 is an abundant bacterium in the gut and venom glands of Vaejovis smithi scorpions.

SG1 is intracellular, located inside secretory vesicles in secretory cells in the venom glands.

SG1 is highly divergent and has a reduced genome with a low GC content.

SG1 is a taxonomic novelty.

Scorpions were among the first animals on land around 430 million years ago. Like many arachnids, scorpions have evolved complex venoms used to paralyze their prey and for self-defense. Here we sequenced and analyzed the metagenomic DNA from venom glands from Vaejovis smithi scorpions. A metagenome-assembled genome (MAG) of 624,025 bp was obtained corresponding to the previously reported Scorpion Group 1 (SG1). The SG1 genome from venom glands had a low GC content (25.78%) characteristic of reduced genomes, many hypothetical genes and genes from the reported minimal set of bacterial genes. Phylogenomic reconstructions placed the uncultured SG1 distant from other reported bacteria constituting a taxonomic novelty. By PCR we detected SG1 in all tested venom glands from 30 independent individuals. Microscopically, we observed SG1 inside epithelial cells from the venom glands using FISH and its presence in scorpion embryos suggested that SG1 is transferred from mother to offspring.

symbiosis

scorpion microbiota

Mollicutes

Mycoplasmatales

polyamines

glycerol

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