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)

Monitoring associations between clade-level variation, overall community structure and ecosystem function in enhanced biological phosphorus removal (EBPR) systems using terminal-restriction fragment length polymorphism (T-RFLP)

The role of Candidatus "Accumulibacter phosphatis" (Accumulibacter) in enhanced biological phosphorus removal (EBPR) is well established but the relevance of different Accumulibacter clades to the performance of EBPR systems is unknown. We developed a terminal-restriction fragment length polymorphism (T-RFLP) technique to monitor changes in the relative abundance of key members of the bacterial community, including Accumulibacter clades, in four replicate mini-sequencing batch reactors (mSBRs) operated for EBPR over a 35-day period. The ability of the T-RFLP technique to detect trends was confirmed using fluorescence in situ hybridisation (FISH). EBPR performance varied between reactors and over time; by day 35, performance was maintained in mSBR2 whilst it had deteriorated in mSBR1. However, reproducible trends in structure function relationships were detected in the mSBRs. EBPR performance was strongly associated with the relative abundance of total Accumulibacter. A shift in the ratio of the dominant Accumulibacter clades was also detected, with Type IA associated with good EBPR performance and Type IIC associated with poor EBPR performance. Changes in ecosystem function of the mSBRs in the early stages of the experiment were more closely associated with changes in the abundance of (unknown) members of the flanking community than of either Accumulibacter or Candidatus "Competibacter phosphatis". This study therefore reveals a hitherto unrecorded and complex relationship between Accumulibacter clades, the flanking community and ecosystem function of laboratory-scale EBPR systems. (C) 2010 Elsevier Ltd. All rights reserved

Phenotypic and molecular characterization of V-factor (NAD)-independent haemophilus paragallinarum

In South Africa from early 1989 onward, strains of Haemophilus paragallinarum not requiring nicotinamide adenine dinucleotide (NAD) have been isolated from commercial chickens suffering from infectious coryza. Fifteen of these field isolates were characterized by biochemical typing, serotyping, restriction endonuclease analysis (REA), and ribotyping. The chosen isolates represented diversity in geographic location, time of disease outbreak, and type of flock. All were typical of the species in biochemical properties, except that they were NAD-independent, and all were Page serovar A. REA was performed with three enzymes: HindIII, HpaII, and SspI. All isolates gave identical REA profiles with all three enzymes. Ribotyping was performed using a probe that consisted of the plasmid pUC19 into which the 16S rRNA operon of H. paragallinarum had been inserted. All 15 isolates gave the same ribotyping profile using each of the three enzymes. As a group, the NAD-independent strains gave REA profiles and ribotypes that were very different from a range of classic South African strains isolated before 1989. Our results strongly suggest that the NAD-independent isolates are clonal in nature