Ultrastructure of Cytophaga johnsonae and C. aquatilis by Freeze-etching

SUMMARY: Cytophaga johnsonae and C. aquatilis (ATCC 29551), examined by frozen-surface replica and freeze-etch techniques, displayed undulated and particulated surfaces. They produced copious amounts of extracellular slime when cultured. Cytophaga aquatilis contained large, complex mesosomes in freeze-etched cells whereas C. johnsonae contained none. In non-cryoprotected freeze-etch preparations, C. aquatilis contained two major fracture planes whereas the C. johnsonae cell envelope fractured in three distinct planes. Linear fibres, such as the peripheral fibrils previously described in Flexibacter columnaris, were not observed in the outer membrane of freeze-etched C. aquatilis. Cytophaga johnsonae contained periplasmic linear fibrils; however, these appeared to be associated with the outer surface of the cytoplasmic membrane or an intermediate layer and not with peripheral fibrils.