Intracellular growth of Bdellovibrio bacteriovorus 6-5-S in heat-killed Spirillum serpens VHL

If cells of Spirillum serpens (strain VHL) are heat-killed at 56C for 90 min the cells retain their original morphology remarkably well. When actively motile cells of Bdellovibrio bacteriovorus (strain 6-5-S) are inoculated into a suspension of S. serpens heat-killed at this temperature, B. bacteriovorus attacks and penetrates the dead cells, and undergoes a cycle of growth and replication similar to that which occurs in living cells. Intracellular growth of B. bacteriovorus in nonviable cells has not previously been reported.