Ultrastructural changes during encystment and germination of Bdellovibrio sp.

Abstract

Under proper conditions, Bdellovibrio sp. strain W cells develop into bdellocysts in appropriate prey bacteria. After attachment and penetration of the prey cell, the encysting bdellovibrio began to accumulate inclusion material and increase in size, and was surrounded by an outer layer of amorphous electrondense material. The cytoplasm of the encysting cell appeared more electron dense, and the nuclear areas appeared more compact. During germination of bdellocysts, the outer wall was uniformly broken down, the inclusion material changed shape and affinity for the heavy metal stain, and the nuclear areas expanded. As the outer wall was dissolved, outgrowth began with the elongation of the germinant as it emerged from the prey ghost as an actively motile cell.