The role of bacteriophage in granulation

Abstract

Aerobic granulation technologies are important in water reclamation processes due to their capability to remove nutrient and toxins efficiently. The formation of granules has traditionally been done by selection through physical parameters, such as hydrolic retention time and shear force. However this selection is done without a clear understanding of how the selection works. Granules represent a suspended biofilm for which the developmental stages have been shown to be analogous to that of surface associated biofilms. The aim of this thesis is to investigate the role of bacteriophage in granular systems, in attempt to create a better understanding in its developmental process. A multi-pronged approach was used to tackle this challenge, Pf phage and Pseudomonas aeruginosa was used the model to establish a better understanding of phage-host interactions during biofilm development and a granulation reactor will be operated to allow for the monitoring of virus production and the study of the viral community shift with respect to the different phases of granular development. Results from the transcriptomic analyses of the ΔPf4 mutant revealed the up regulation of genes from the filamentous phage correlates to the up regulated of genes essential for variant formation, biofilm development and virulence. Phage population dynamics experiments carried out in this study also demonstrated that the Pf4 phage has a suppressive effect on a secondary prophage (Pf6). The metagenomics study of the viral fraction allowed for reconstruction of 81 novel viral genomes and the monitoring of viral abundance and diversity. And the metatranscriptomics study on the microbial population of the granulation reactor allowed for the tracking of transcribed viral genes. It was observed that there was relatively higher expression of filamentous phage genes during the granule development phase and high abundance of filamentous phage during the granule maintenance phase. Supporting the notion that filamentous phage might play an important role in biofilm development and stability.