Phylogenetic And Metabolic Characteristics Of Rhodocyclales And Coandidatus Accumulibacter Based On Genomics

The bacteria under Rhodocyclales,including Accumulibacter,play an important role in the key physiological and biochemical functions,such as nitrogen removal,phosphorus removal and the formation of activitated sludge flocs in wastewater treatment.However,due to the lack of comprehensive genomic information currently,there are still many deficiencies even contradictions in the understanding of the phylogeny of Rhodocyclales.So far,the understanding of Accumulibacter genomic diversity is limited to just 6 of the 14 known clades and may still be one-sided.In this study,combined the single gene-based and concatenated core gene-based phylogenetic tree construction methods,94 Rhodocyclales and 21 Accumulibacter genomes,collected from the online database and obtained from our laboratory,were used to perform the phylogenetic reanalysis of the entire Rhodocyclales and Accumulibacter to obtain more robust and reliable classification results.Meanwhile,the analyses of their core genes,pan genes and the metabolic traits of Accumulibacter facilitate our further understanding of the important evolutionary events,from which their special functions were obtained.Results as follow:1)Compared to single gene-based method,phylogenetic analysis based on concatenated core gene method can provide more reliable classification and evolution information.2)Based on phylogenetic analysis of core genes,the classification of Rhodocyclales,from the current three families,can be reclassified into five families:Azonexaceae,Rhodocyclaceae,Zoogloeaceae,Uliginosibacterium_f,Azospira_f.3)Three genomes of Accumulibacter obtained from activated sludge enriched in our laboratory EBPR reactor were identified as three new clades and the existing 14 clades of Accumulibacter were expanded to 17 clades;at the same time we also obtained the first Clade II B genome,expanding the clades which have genome representatives from 6 to 10.4)By analyzing the metabolic pathways of Accumulibacter,the specificity of substrates utilization by different types means that they may be enriched using different substrates,respectively.In this study,we have obtained the most reliable classification and evolution information of Rhodocyclales and Accumulibacter using the most comprehensive genomic information so far,and at the same time provide an important basis for understanding the metabolic characteristics of different Accumulibacter clades at genome level.These results will contribute to the in-depth study of the important functions of Rhodocyclales and Accumulibacter in the wastewater treatment system.