Gene cassette-associated sequences from phosphorus and non-phosphorus removing microbial communities in aerobic:anaerobic sequencing batch reactors.

Mobile gene elements associated with integrons, including as gene cassettes, have been proposed to play an important role in bacterial evolution by providing an extensive genetic resource. This study hypothesized that critical genes for enzymes involved in EBPR systems, including those involved in polyphosphate, PHA and glycogen synthesis, may be present in mobile gene cassettes. Although no such genes were identified in any of the functional and deteriorated enhanced biological phosphorus removal (EBPR) laboratory-scale SBR systems examined here, many of the open reading frames (ORFs) remained unidentified because of the incompleteness of publicly available databases. An ORF of unknown function (SBR6-2) was encountered in deteriorated EBPR system with an unexpectedly high frequency, comprising 35% of the gene cassette-associated sequences for that system.

Environmental factors contributing to the "G bacteria" population in full-scale EBPR plants.

A survey of several enhanced biological phosphorus removal (EBPR) plants within Australia has demonstrated that a group of bacteria known as the "G" bacteria are able to proliferate under a broad range of plant configurations. The diverse designs and operational parameters of these plants did not permit definitive determination of the factor(s) contributing to the proliferation of G bacteria. Two plants were monitored over time to assess the G bacteria and phosphorus accumulating organisms (PAO) populations in relation to key operational parameters. The mixed liquor biomass and operational parameters were compared to other plants successfully and unsuccessfully reducing phosphorus from the wastewater. Two critical factors recognised in this study were the dissolved oxygen concentration in the aerobic zone and the type and amount of carbon source in the anaerobic zone.

Role of "G-bacteria" in anaerobic substrate uptake in a SBR with no phosphorus removal.

Biomass from an SBR running with no enhanced biological phosphorus removal (EBPR) but which exhibited anaerobic assimilation of glucose and acetate, was dominated by "G-bacteria", cocci in tetrads and clusters. Extracted 16S rDNA was amplified by PCR and then analysed using Denaturing Gradient Gel Electrophoresis (DGGE). Major bands were extracted and their sequences determined. Clone libraries were also prepared, the 16S rDNA extracted, PCR performed and the resultant fragments run by DGGE to aid in identifying the DGGE bands and provide fuller sequences than available by DGGE alone. The two approaches together allowed several bands to be identified. Probes for FISH analyses were designed for some of these in attempts to see to which phylogenetic group "G-bacteria" belonged, and whether they represented the dominant bands detected by DGGE. Then FISH/Microautoradiography (MAR) was used in attempts to see which bacteria there were assimilating substrates anaerobically. Results indicated that the "G-bacteria" were phylogenetically diverse, but mainly alpha-proteobacteria and members of the high G+C% gram-positive bacteria. Not all of these could assimilate glucose and/or acetate anaerobically, and Amaricoccus, the original "G-bacteria" of Cech and Hartman, was not detected.

Genomic fingerprinting of the 16S-23S gene spacer region suggests that novel Acinetobacter isolates are present in activated sludge.

The taxonomic status of the genus Acinetobacteris currently confused and the role of these organisms in activated sludge is poorly understood. Currently unidentified isolates of Acinetobacterfrom activated sludge were fingerprinted by making use of polymorphisms in their 16S-23S rDNA spacer region. The PCR amplified 16S-23S rDNA spacer region was digested with five different restriction enzymes to further differentiate between the isolates. The resulting band patterns were very diverse and the data suggests that the activated sludge isolates are different to the known genomic species of Acinetobacter which are predominantly clinical isolates. The results of this study imply the existence of yet unrecognised species of Acinetobacter in activated sludge.