Activated sludge flocs suspended in wet mounts on microscope slides were observed to sprout, finger-like, bacterial zoogloeae as a consequence of the outgrowth of bacteria from flocs. Photomicrographic and fluorescent antibody studies revealed that the bacterial zoogloeae consisted of the progeny of specific zoogloea-forming bacteria. Purified exopolymers of Zoogloea strains and domestic activated sludge contained two amino sugars, one of which was identified as glucosamine. Zoogloea exopolymer was not fibrilar or cellulosic and contained approximately 17 to 19 per cent amino sugar and about one per cent hexoses, uronic acids and ether soluble substances on a dry weight of polymer basis. Amino sugar production was found to parallel zoogloea formation by Zoogloea sp. Calcium ion appeared to augment flocculation of bacterial cells capable of undergoing natural coalescence. Two cell types, described as rough and smooth colony-forming, were found in some strains of Zoogloea. Rough cells readily flocculated in agitated cultures whereas smooth cells produced relatively turbid cultures under similar growth conditions.

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