Ultrastructural and Immunochemical Changes During the In Vitro Development of Plasmopara halstedii.

ABSTRACT The asexual phase of the life cycle of Plasmopara halstedii, the causal agent of downy mildew of sunflower, plays a key role in the propagation of the disease. We investigated the morphological and ultrastructural changes that occur during the asexual development of the pathogen. Direct examination of infected cotyledons confirmed the presence of sporangiophores.

A morphological transition in the pleomorphic bacterium Ramlibacter tataouinensis TTB310.

We provide microscopic evidence that motile rod-shaped forms of Ramlibacter tataouinensis TTB310 are formed from dividing cyst-like cells. Careful estimation of the size of the two morphotypes was conducted using optical and transmission electron microscopy (TEM). The cyst-like cell was shown to be a sphere with a diameter Dc=850 nm.

Ramlibacter tataouinensis gen. nov., sp. nov., and Ramlibacter henchirensis sp. nov., cyst-producing bacteria isolated from subdesert soil in Tunisia.

Ramlibacter gen. nov. is proposed for two aerobic, chemo-organotrophic, cyst-producing soil bacterial strains.