The bacterial community structures of phosphate- and non-phosphate-removing activated sludges were compared. Sludge samples were obtained from two sequencing batch reactors (SBRs), and 16S rDNA clone libraries of the bacterial sludge populations were established. Community structures were determined by phylogenetic analyses of 97 and 92 partial clone sequences from SBR1 (phosphate-removing sludge) and SBR2 (non-phosphate-removing sludge), respectively. For both sludges, the predominant bacterial group with which clones were affiliated was the beta subclass of the proteobacteria. Other major groups represented were the alpha proteobacterial subclass, planctomycete group, and Flexibacter-Cytophaga-Bacteroides group. In addition, several clone groups unaffiliated with known bacterial assemblages were identified in the clone libraries. Acinetobacter spp., thought to be important in phosphate removal in activated sludge, were poorly represented by clone sequences in both libraries. Differences in community structure were observed between the phosphate- and non-phosphate-removing sludges; in particular, the Rhodocyclus group within the beta subclass was represented to a greater extent in the phosphate-removing community. Such differences may account for the differing phosphate-removing capabilities of the two activated sludge communities.

https://espace.library.uq.edu.au/view/UQ:245679/UQ245679_OA.pdf

Bacterial community structures of phosphate-removing and non-phosphate- removing activated sludges from sequencing batch reactors

Platforms for energy and nutrient recovery from domestic wastewater: A review.

The purple nonsulfur bacteria (Rhodospirillaceae) comprise different morphological types of photo-trophic bacteria that can photoassimilate simple organic compounds under anaerobic conditions. They are also capable of chemotrophic growth under aerobic conditions, but not all species develop under full atmospheric oxygen tension. At oxygen concentrations between 0.5% and 5%, photosynthesis and oxidative metabolism may function simultaneously. Although several species would grow under aerobic conditions at rates comChapauble to those observed under anaerobic phototrophic conditions, incubation with organic substrates in the light with oxygen excluded is the only way to enrich selectively for the purple nonsulfur bacteria.

Isolation of Members of the Family Rhodospirillaceae

The capacity for chemoautotrophic, mixotrophic and organotrophic growth in the dark was tested with 45 strains of 17 species (11 genera) of the Chromatiaceae. The auxanographic deep agar shake culture method was used; the gas phase contained 5% O2 and 1% CO2 in N2. All strains tested of Chromatium vinosum, C. minus, C. violascens, C. gracile, Thiocystis violacea, Amoebobacter roseus, Thiocapsa roseopersicina gave positive growth responses under chemoautotrophic and mixotrophic conditions (extra carbon source acetate); one strain of Thiocapsa roseopersicina grew also organotrophically on acetate alone. No growth was obtained with the remaining 17 strains of ten species. None of the five type species (three genera) of the Chlorobiaceae grew under chemotrophic conditions. With Thiocystis violacea 2311 a growth yield of 11.3g dry weight per mol thiosulfate consumed was obtained under chemoautotrophic conditions; under mixotrophic conditions with acetate the yield increased to 69g dry weight per mol thiosulfate consumed. With Thiocystis violacea 2311 maximal specific respiration rates were obtained with thiosulfate as electron donor irrespective of the presence or absence of sulfur globules in the cells; organic substrates served as carbon sources only and did not support respiration. With Chromatium vinosum D utilization of thiosulfate was not constitutive; maximal respiration rates on thiosulfate were obtained only with thiosulfate grown cells containing sulfur globules. Respiration rates were further increased by malate, fumarate or propionate; these substrates also served as sole electron donors for respiration. Acetate and pyruvate were used as carbon sources only. The ecological significance of the chemotrophic metabolism is discussed.

Capacity of chromatiaceae for chemotrophic growth. Specific respiration rates of Thiocystis violacea and Chromatium vinosum

Publisher Summary The chapter focuses on the physiological aspects regulating hydrogen metabolism in anoxygenic phototrophic bacteria, along with technical and economical aspects of hydrogen production, with particular reference to purple nonsulfur bacteria. Studies on the growth phase of the organism are considered equally important as studies on hydrogen production by resting cells; hence, the chapter explains in general the physiology related to hydrogen metabolism and other important related areas of research on anoxygenic phototrophic bacteria. Biological hydrogen evolution is still in an exploratory stage in bioenergy production research, unlike methane (biogas) and alcohol production. There is enough justification to carry out further work that now concentrates on process development rather than on strain selection. For this futuristic research, a multi- and interdisciplinary approach is the need of the day.

Anoxygenic Phototrophic Bacteria: Physiology and Advances in Hydrogen Production Technology

In all purification stages of a biological sewage treatment plant, phototrophic bacteria were detected by the method of viable cell counts. The predominant species identified belonged to the genus Rhodopseudomonas of purple nonsulfur bacteria. The number of phototrophic bacteria was highest in wastewater containing sludge. In activated sludge, an average of 10(5) viable cells/ml was found; the number depended upon concentration of sludge rather than on seasonal changes in light conditions in the course of a year. Bacteriochlorophyll a was extracted from activated sludge. Relative to the viable counts of phototrophic bacteria, the content of bacteriochlorophyll a was 5- to 10-fold higher than that of three representative pure cultures. By incubation of activated and digester sludge under different environmental conditions, it was shown that phototrophic bacteria can complete with other bacteria only under anaerobic conditions in the light.

Phototrophic purple and green bacteria in a sewage treatment plant.

Inallpurification stages ofabiological sewage treatment plant, phototrophic bacteria weredetected bythemethodofviable cell counts. Thepredominant species identified belonged tothegenus Rhodopseudomonas ofpurple nonsulfur bacteria. Thenumberofphototrophic bacteria washighest inwastewater containing sludge. Inactivated sludge, anaverage of105viable cells/ml wasfound; thenumberdepended uponconcentration ofsludge rather thanonseasonal changes inlight conditions inthecourse ofayear. Bacteriochlorophyll awas

R. L. Irgens

Papers

Phototrophic purple and green bacteria in a sewage treatment plant.

Phototrophic Purple andGreenBacteria ina Sewage Treatment Plant