ISOLATION, CHARACTERIZATION AND ECOLOGICAL DYNAMICS OF TROPICAL FRESHWATER CYANOPHAGES

Abstract

Cyanobacteria are one of the dominant autotrophs in tropical freshwater communities, yet phages infecting them remain poorly characterized. In this thesis, 4 novel cyanophages were isolated from a tropical freshwater lake in Singapore and characterized. With novel cyanophage genome available, qPCR was employed to examine the abundances of cyanophage PA-SR01, S-SRP01, S-SRP02 and S-SRM01 in the same lake from July to November 2019. The result demonstrated the ecological importance and key roles of the cyanophage not only as regulators of the cyanobacterial community, but also as promoters of certain cyanotoxin production. With metagenomic sequencing of viral and bacterial samples further enhancing the study, taxonomic annotation of the viral population uncovered diverse and novel viral population dominated by bacteriophages. Virus-host interaction between assembled bacterial and viral genomes suggests cyanophages infecting Raphidiopsis to be the main driver in CHAB deterioration.