Comparative genomics analyses on EPS biosynthesis genes required for floc formation of Zoogloea resiniphila and other activated sludge bacteria.

Homogenization of activated sludge greatly increased the apparent bacterial count obtained by plating on a solid medium, and for this reason facilitated the isolation of the predominant flora by liberating the bacteria from the interior of the sludge flocs. The ordinary domestic cream-making machine was found to be quite effective for this purpose.The high counts obtained indicated that there are probably several hundred thousand million bacteria per gram of dry matter in activated sludge.Aeration of sewage was found to result in an increase in the total count of bacteria, and a high count was maintained for a considerable time. After aeration for several days fairly rapid and apparently fairly complete separation of the sludge occurred on allowing the liquid to stand, but the supernatant liquor contained large numbers of bacteria. When a fresh quantity of sewage was added to the small quantity of sludge which settled and a second period of aeration commenced, the bacteria were found to associate more quickly with the sludge than they had during the first aeration. Coliform bacteria and spore-forming aerobes formed only a small fraction of the total number of micro-organisms concerned in these changes, and moulds and yeasts never accounted for a large proportion. The predominant bacteria did not produce acid from glucose.Various media were tested in investigating the bacteriology of activated sludge. None showed any superiority to nutrient agar. Coliform bacteria and aerobic spore-formers were encountered in negligible numbers. The morphological and physiological characters of seventy-one strains of the predominant bacteria were determined. The majority were Gram-negative rods with no action on carbohydrates and were members of the genera Achromobacterium, Chromobacterium, and Pseudomonas. Those isolated from activated sludge soon after its formation from aerated sewage were found to be non-proteolytic, but a proteolytic flora was established after the sludge had been built up for a period of 4 weeks. The characters of the predominant bacteria indicate that they are water types derived from the water supply or the drainage water which enters sewage. Intestinal bacteria appear to be unimportant.The experiments described in this paper were carried out as part of the programme of the Water Pollution Research Board of the Department of Scientific and Industrial Research, and the results are published by permission of the Department.

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The bacteriology of activated sludge.

Agar plating media containing solely activated sludge extracts yielded, in general, higher viable counts of activated sludge bacteria than any other culture medium tested Activated sludge extracts made from different treatment plants varied in efficacy in evoking maximal viable counts Frequently, homologous plating, ie, plating inocula of activated sludges on extracts made from the same activated sludges, tended to yield lower counts than the heterologous platings tried in this investigation The counts obtained by homologous plating of activated sludge were not significantly lower and sometimes were even significantly higher than the counts obtained on standard Nutrient Agar, which had been found by previous workers to be a good medium for counting activated sludge bacteria The higher counts obtained with activated sludge extracts set objectives for formulating reproducible or defined culture media for the enumeration of activated sludge bacteria

Aerobic Heterotrophic Bacterial Populations of Sewage and Activated Sludge I. Enumeration

Bacteria of the genus Zoogloea have historically been differentiated from other obligately aerobic, Gram-negative, nonsporeforming, rod-shaped bacteria that grow in aquatic habitats on the basis of the presence of a characteristic gelatinous matrix, often called a “zoogloeal matrix”, that surrounds clumps of cells when they are found in their aquatic habitat or in unshaken liquid culture in the laboratory (Butterfield, 1935; Butterfield, Ruchhoft, and McNamee, 1937; Wattie, 1943). The name Zoogloea is derived from Greek and means animal glue. This has been the primary trait used to distinguish Zoogloea from other bacteria which can be confused with Zoogloea on the basis of similar metabolic and biochemical capabilities, e.g., lack of sugar fermentation, metabolic by-product formation.

C. T. Butterfield

Papers

Studies of Sewage Purification. VI. Biochemical Oxidation by Sludges Developed by Pure Cultures of Bacteria Isolated from Activated Sludge.

Studies of Sewage Purification. IX. Total Purification, Oxidation, Adsorption, and Synthesis of Nutrient Substrates by Activated Sludge.

Studies of Sewage Purification. VII. Biochemical Oxidation by Activated Sludge.