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

• DOI: 10.1038/ismej.2013.6
• Publication Date: 2013-02-28T11:35:43Z
• Authors: Simon Jon McIlroy; Rikke Kristiansen; Mads Albertsen; Søren Michael Karst; Simona Rossetti; Jeppe Lund Nielsen; Valter Tandoi; Robert James Seviour; Per Halkjær Nielsen
• Keywords: 0301 basic medicine; 570; Evolution; Triacylglycerol; Models, Biological; 1105 Ecology; Water Purification; 12. Responsible consumption; 03 medical and health sciences; Behavior and Systematics; Lipid-accumulating bacteria; 11. Sustainability; Whole genome sequence; Microthrix parvicella; Sewage; 2404 Microbiology; Fatty Acids; wastewater treatment; Microthrix parvicella; bulking and foaming; activated sludge; Filamentous bacteria; 6. Clean water; Actinobacteria; Activated sludge bulking and foaming; Metagenomics; Genome, Bacterial; Metabolic Networks and Pathways

Abstract ‘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.