Dependence of the superficial layers of Spirillum putridiconchylium on Ca²⁺ or Sr²⁺

Chelating agents disrupted the superficial layers on Spirillum putridiconchylium and adsorption of cationized ferritin indicated that both upper and lower surfaces of superficial layer fragments, as well as the outer membrane surface, possessed areas which were negatively charged. Growth of the bacterium in 1% casamino acids (vitamin free) resulted in cells which were devoid of the superficial layers, and negative staining of these cells revealed an amorphous precipitate together with a vesicular outer membrane component extruding from their surfaces into the medium. Addition of either 1 mM Ca 2+ or 1 mM Sr 2+ to the growth medium produced the typical regularly structured cell surface, whereas addition of equal concentrations of Li + , Na + , K + , Mg 2+ , Ba 2+ , Mn 2+ , Fe 3+ , or three polyamines produced the structureless surface.