The filamentous bacterial morphotype 'Nostocoida limicola' I contains at least two previously described genera in the low G+C gram positive bacteria.

Isolates of eight bacterial filaments fitting the published morphological description of 'Nostocoida limicola' I were obtained from the mixed liquor of four different Australian and one Czech Republic activated sludge plants by micromanipulation. On the basis of their near complete (Ben 200 and Ben 201), or partial (Ben 77, Ben 78, Ben 202, Ben 203, Ben 204 and Ben 205) 16S rRNA gene sequences, six of these isolates were 99.3-100% similar to Lactosphaera pasteurii and Trichococcus flocculiformis, a bulking filament only reported previously in Germany. The other two (Ben 203 and Ben 204) were 99.9% similar to Streptococcus suis. Hence, all are in the low mol % G+C gram-positive bacteria division of the Bacteria. On this evidence 'N. limicola' I is phylogenetically unrelated to 'Nostocoida limicola' II, which is now known to be in the Actinobacteria, even though these two filamentous bacteria appearing in activated sludge systems have been considered to be closely related to each other historically.

Fighting foam with phages?

Seventeen (17) phages infective for the mycolata were isolated from six samples of activated sludge using 21 prospective hosts from the genera Dietzia, Gordonia, Nocardia, Rhodococcus, Tsukamurella and Mycobacterium. Their morphology indicated that they were all members of the viral family Siphoviridae, but they varied in the size of the icosahedral head and length of non-contractile tail, suggesting they were different. This was confirmed by host-range studies with 47 strains of mycolata, which showed that each phage had a unique host-range, and this was polyvalent in the majority (15/17) of cases, with 12 phages infective for hosts representing two or three of the genera Gordonia, Nocardia and Rhodococcus. The potential for use of these phages in the control of foaming and other applications is discussed.

Diversity of isolates of Acinetobacter from activated sludge systems based on their whole cell protein patterns.

Whole cell protein extracts from strains of the currently recognized genomic species of Acinetobacter, together with those from a range of isolates of several genomic species identified using the Biolog system and obtained from a biological nutrient-removal activated sludge plant were analysed by SDS-PAGE. The dendrograms obtained after numerical analysis for the known genomic species generally supported the taxonomic relationships suggested from earlier DNA-DNA hybridisation data. In some cases the activated sludge isolates identified to genomic species level clustered closely with the corresponding genomic species reference strains, although isolates 5 and 8/9 were scattered throughout the dendrogram. Considerable variations were seen in the protein patterns of the 27 different environmental isolates of genomic species 7 that were analysed. Three unidentified Acinetobacter isolates examined formed their own subcluster.

The opportunistic pathogen Nocardia farcinica is a foam-producing bacterium in activated sludge plants.

A Gram-positive unicellular coccal-diphtheroid rod causing foam in an activated sludge plant was successfully isolated by micromanipulation. Phenotypic characterization and 16S rDNA sequencing identified it as Nocardia farcinica. This is the first report that this opportunistic pathogen is a foam-causing bacterium in activated sludge, and the clinical implications of these observations are discussed.

Microbiology of the 'G-bacteria' in activated sludge.

This review discusses a group of bacteria, the 'G-bacteria', which have a distinctive morphology of cocci in tetrads, sheets or clusters, that are seen in large numbers in many activated sludge biomass samples. Isolates of 'G-bacteria' that have been grown axenically are phylogenetically diverse. The Gram-negative members include several alpha- and beta-proteobacteria, among which is the genus Amaricoccus, while the Gram-positive 'G-bacteria' contain several members of the actinobacteria. It is probable that other, as yet uncharacterized, 'G-bacteria' exist in activated sludge. The hypothesis that these 'G-bacteria' are detrimental to the process of enhanced biological phosphate removal by competing for substrates anaerobically with the phosphate-accumulating bacteria in such systems, based as it is largely on mixed-culture studies, receives little support from studies using those available in pure culture. The evidence on which these conclusions are founded is discussed, as are the arguments used to explain why these 'G-bacteria' all appear to thrive under conditions found in certain activated sludge systems.

Friedmanniella spumicola sp. nov. and Friedmanniella capsulata sp. nov. from activated sludge foam: gram-positive cocci that grow in aggregates of repeating groups of cocci.

Two Gram-positive, non-motile, non-spore-forming, strictly aerobic, pigmented cocci, strains Ben 107T and Ben 108T, growing in aggregates were isolated from activated sludge samples by micromanipulation. Both possessed the rare type A3 gamma' peptidoglycan. Major menaquinones of strain Ben 107T were MK-9(H4) and MK-7(H2), and the main cellular fatty acid was 12-methyltetradecanoic acid (ai-C15:0). In strain Ben 108T, MK-9(H4), MK-9(H2) and MK-7(H4) were the menaquinones and again the main fatty acid was 12-methyltetradecanoic acid (ai-C15:0). Polar lipids in both strains consisted of phosphatidyl inositol, phosphatidyl glycerol and diphosphatidyl glycerol with two other unidentified glycolipids and phospholipids also present in both. These data, together with the 16S rDNA sequence data, suggest that strain Ben 107T belongs to the genus Friedmanniella which presently includes a single recently described species, Friedmanniella antarctica. Although the taxonomic status of strain Ben 108T is far less certain, on the basis of its 16S rRNA sequence it is also adjudged to be best placed in the genus Friedmanniella. The chemotaxonomic characteristics and DNA-DNA hybridization data support the view that Ben 107T and Ben 108T are novel species of the genus Friedmanniella. Hence, it is proposed that strain Ben 107T (= ACM 5121T) is named as Friedmanniella spumicola sp. nov. and strain Ben 108T (= ACM 5120T) as Friedmanniella capsulata sp. nov.