ELECTRON MICROSCOPE OBSERVATIONS ON THE INTERACTION OF BDELLOVIBRIO BACTERIOVORUS WITH PHORMIDIUM LURIDUM AND SYNECHOCOCCUS SP. (CYANOPHYCEAE)1

The effects of Bdellovibrio bacteriovorus (Stolp & Starr) culture supernatants on Phormidium luridum var. olivacea Boresch and Synechococcus sp. were examined by transmission electron microscopy. Both normal (nonheat-treated) and heat-treated bdellovibrio supernatant caused the formation of intrathylakoidal vesicles in P. luridum in 24–48 h. This vesiculation increased until 96–129 h when the P. luridum showed loss of the mucopeptide layer in the cell envelope and subsequently lysed. Similar treatment of Synechococcus sp. with the bdellovibrio supernatants showed a different ultrastructural pattern with the apparent dissolution of many of the photosynthetic membranes in the bluegreen cells. Myelin-like membranous configurations were seen in some of these treated cells. The results suggest that an autolytic mechanism in P. luridum and Synechococcus sp. is stimulated by the bdellovibrio secretions.