The Genus Zoogloea

Abstract

Bacteria of the genus Zoogloea have historically been considered members of the family Pseudomonadaceae but have been differentiated from other obligately aerobic, Gram-negative, nonsporeforming, rod-shaped bacteria that grow in aquatic habitats on the basis of their production of a characteristic gelatinous matrix. The ?zoogloeal matrix? surrounds clumps of cells found in natural aquatic habitats or when grown in unshaken liquid culture in the laboratory (Butterfield, 1935; Butterfield et al., 1937; Wattie, 1943). The name Zoogloea, which was derived from the Greek word meaning animal glue, refers to the primary trait, the zoogloeal matrix, that is used to distinguish Zoogloea from other metabolically similar bacteria. The two species of Zoogloea, Z. ramigera and Z. filipendula, have been isolated from sewage or from sewage-treatment systems that employ oxidative methods, i.e., activated sludge systems, trickling filters, or oxidation ponds (Butterfield et al., 1937; Butterfield and Wattie, 1941; McKinney and Horwood, 1952; McKinney and Weichlein, 1953). Both species produce branched, finger-like projections or outgrowths from the floc (i.e., clumps of cells that grow in an aggregated form that settles or ?flocs? from aqueous suspension) when grown under quiescent culture conditions but have been differentiated from each other on the basis of cell size, biochemical reactions, and appearance of the zoogloeal matrix.