The role of bacteriophages in mixed microbial communities and populations of Pseudomonas aeruginosa

• Main Author: Muhammad Hafiz Ismail
• Other Authors: Scott Rice
• Format: Theses and Dissertations
• Language: English
• Published: 2019
• Subjects: DRNTU::Science::Biological sciences::Microbiology::Microbial ecology; DRNTU::Science::Biological sciences::Molecular biology
• Online Access: https://hdl.handle.net/10356/83268; http://hdl.handle.net/10220/48129
• Institution: Nanyang Technological University

Bacteriophages can impact bacterial communities, not just through predation, but also through the regulation of host genes that can improve biofilm development. Bacterial communities are essential in the function of most ecosystems including engineered systems such as activated floccular sludges of water reclamation plants. Activated floccular sludge is often used to cultivate aerobic granules and the formation of such granules is normally achieved by selection through physical parameters. However, these granules are unstable and have long initiation times. It has been hypothesized that bacteriophages are important in the formation of granules. In this study, a metagenomics approach was used to monitor the abundance of bacteriophage and bacterial communities of granulating sludge. Analysis suggested that Inoviridae and Microviridae influence the bacterial community change the most during initiation of granulation. Additionally, the changes in the abundance of bacteria, especially ‘Candidatus Accumulibacter’, and physical factors such as settling time and biomass discharge are also important in this process. To better define the impacts of filamentous phage on a bacterial host, a model phage-host system was chosen, based on Pseudomonas aeruginosa and its endogenous filamentous phages, Pf4 and Pf6. Transcriptomics revealed that in the presence of Pf4, virulence factor associated genes were upregulated, in agreement with the previous observation that the wild type P. aeruginosa is more virulent than the phage deletion mutant. This is likely due to a DNA-binding protein, repressor C, which was also found to prevent reinfection by Pf4. Collectively, this supports the hypothesis that filamentous phages might play an important role in biofilm development and begins to shed information on the role of filamentous phage in a more complex community, as found in aerobic granules.