Quantitative image analysis for the characterization of microbial aggregates in biological wastewater treatment : a review

Quantitative image analysis techniques have gained an undeniable role in several fields of research during the last decade. In the field of biological wastewater treatment (WWT) processes, several computer applications have been developed for monitoring microbial entities, either as individual cells or in different types of aggregates. New descriptors have been defined that are more reliable, objective, and useful than the subjective and time-consuming parameters classically used to monitor biological WWT processes. Examples of this application include the objective prediction of filamentous bulking, known to be one of the most problematic phenomena occurring in activated sludge technology. It also demonstrated its usefulness in classifying protozoa and metazoa populations. In high-rate anaerobic processes, based on granular sludge, aggregation times and fragmentation phenomena could be detected during critical events, e.g., toxic and organic overloads. Currently, the major efforts and needs are in the development of quantitative image analysis techniques focusing on its application coupled with stained samples, either by classical or fluorescent-based techniques. The use of quantitative morphological parameters in process control and online applications is also being investigated. This work reviews the major advances of quantitative image analysis applied to biological WWT processes.The authors acknowledge the financial support to the project PTDC/EBB-EBI/103147/2008 and the grant SFRH/BPD/48962/2008 provided by Fundacao para a Ciencia e Tecnologia (Portugal)

Towards understanding the taxonomy of some of the filamentous bacteria causing bulking and foaming in activated sludge plants

Several filamentous bacteria obtained in pure culture from activated sludge plants were characterised using their 16S rDNA sequences to determine their phylogenetic relationship to other bacteria. ''Microthrix parvicella'' was shown to be an unusual actinomycete, while the Gram negative bacteria Type 0092, Type 0411 and Type 1863 all belong to the Flexibacter-Cytophaga-Bacteroides phylum, and Type 0803 is a member of the beta subclass of the Proteobacteria. The practical value of obtaining this information is discussed. Copyright (C) 1996 IAWQ

16S rRNA analysis of isolates obtained from gram-negative, filamentous bacteria micromanipulated from activated sludge

Individual filaments of the Gram negative, bulking filamentous morphotypes Eikelboom Type 0092, Type 0411, TT;pe 0803 and Herpetosiphon sp. were identified in activated sludge mixed liquors and specifically isolated by micromanipulation. Although their isolation and partial phenotypic description have previously been reported, we sought them to determine their phylogenetic position and to compare our data with the previous descriptions. Direct cell lysis procedures and the polymerase chain reaction were used to obtain their 16S rRNA genes, These were sequenced and the data were analysed to phylogenetically place the filaments into their respective lines of descent in the domain Bacteria. Type 0803 is a member of the Rubrivivax subgroup of the beta proteobacterial subclass; Herpetosiphon sp. belongs in the Chloroflexus subdivision of the green non-sulfur lineage and its sequence is most similar to that of H. aurantiacus; while Type 0092 and Type 0411 belong in the Flexibacter-Cytophaga-Bacteroides phylum. The contemporary ''identification'' of these organisms is ambiguous and relies on subjective morphological criteria and staining reactions. However, the sequence data reported here are being examined for morphotype-specific regions to be exploited for RNA-directed, DNA probes for rapid, unequivocal, in situ identification of each filament type

The filamentous morphotype Eikelboom Type 1863 is not a single genetic entity

Five isolates of a filamentous bacterial morphotype with the distinctive diagnostic microscopic features of Eikelboom Type 1863 were obtained from activated sludge sewage treatment plants in Victoria, Australia. On the basis of phenotypic evidence and 16S rDNA sequence data, these isolates proved to be polyphyletic. Two (Ben 06 and Ben 06C) are from the Chryseobacterium subgroup which is in the Cytophaga group, subdivision I of the Flexibacter-Cytophaga-Bacteroides phylum. Two (Ben 56 and Ben 59) belong to the genus Acinetobacter, and one (Ben 58) is a Moraxella sp., closest to Mor. osloensis. The significance of these findings to the reliance on microscopic features for identification of these filamentous bacteria in activated sludge is discussed

Metabolic model for the filamentous 'Candidatus Microthrix parvicella' based on genomic and metagenomic analyses

‘Candidatus Microthrix parvicella’ is a lipid-accumulating, filamentous bacterium so far found only in activated sludge wastewater treatment plants, where it is a common causative agent of sludge separation problems. Despite attracting considerable interest, its detailed physiology is still unclear. In this study, the genome of the RN1 strain was sequenced and annotated, which facilitated the construction of a theoretical metabolic model based on available in situ and axenic experimental data. This model proposes that under anaerobic conditions, this organism accumulates preferentially long-chain fatty acids as triacylglycerols. Utilisation of trehalose and/or polyphosphate stores or partial oxidation of long-chain fatty acids may supply the energy required for anaerobic lipid uptake and storage. Comparing the genome sequence of this isolate with metagenomes from two full-scale wastewater treatment plants with enhanced biological phosphorus removal reveals high similarity, with few metabolic differences between the axenic and the dominant community ‘Ca. M. parvicella’ strains. Hence, the metabolic model presented in this paper could be considered generally applicable to strains in full-scale treatment systems. The genomic information obtained here will provide the basis for future research into in situ gene expression and regulation. Such information will give substantial insight into the ecophysiology of this unusual and biotechnologically important filamentous bacterium