THE ARTHROMITUS STAGE OF BACILLUS-CEREUS - INTESTINAL SYMBIONTS OF ANIMALS

In the guts of more than 25 species of arthropods we observed filament s containing refractile inclusions previously discovered and named ''A rthromitus'' in 1849 by Joseph Leidy [Leidy, J, (1849) Proc, Acad, Nar , Sci. Philadelphia 4, 225-233]. We cultivated these microbes from boi led intestines of 10 different species of surface-cleaned soil insects and isopod crustaceans, Literature review and these observations lead us to conclude that Arthromitus are spore-forming, variably motile, c ultivable bacilli, As long rod-shaped bacteria, they lose their flagel la, attach by fibers or fuzz to the intestinal epithelium, grow filame ntously, and sporulate from their distal ends, When these organisms ar e incubated in culture, their life history stages are accelerated by l ight and inhibited by anoxia, Characterization of new Arthromitus isol ates from digestive tracts of common sow bugs (Porcellio scaber), roac hes (Gromphodorhina portentosa, Blaberus giganteus) and termites (Cryp totermes brevis, Kalotermes flavicollis) identifies these flagellated, spore-forming symbionts as a Bacillus sp, Complete sequencing of the 16S rRNA gene from four isolates (two sow bug, one hissing roach, one death's head roach) confirms these as the low-G+C Gram-positive eubact erium Bacillus cereus, We suggest that B. cereus and its close relativ es, easily isolated from soil and grown on nutrient agar, enjoy filame ntous growth in moist nutrient-rich intestines of healthy arthropods a nd similar habitats.