Corniculate Cell surface protrusions in morphotype II of theBlastocaulis-Planctomyces group of budding and appendaged bacteria

Abstract

Natural water samples and dilute-peptone enrichment cultures, containing budding and appendaged bacteria assigned to morphotype II of theBlastocaulis-Planctomyces group of nonprosthecately stalked prokaryotes, have been examined by transmission electron microscopy. When stained with 0.5% potassium phosphotungstate, the usual appendages of morphotype II (a flat, multifibrillar, ribbon-like stalk; peritrichous pili; and several cephalotrichous flagella) were observed, as were the crateriform structures found scattered over the surface of the cell. In 1.0% uranyl acetate stains, the crateriform structures were no longer visible; instead, unusual corniculate structures (“cornicula”) protruded at seemingly the same loci. These protrusions whowed a substructure, possibly in a helical arrangement. No definitive origin or function can yet be assigned to these cornicula.