Characterisation of bacteriophages that infect Acaryochloris

Abstract

The cyanobacterium Acaryochloris marina was isolated in 1996 and solved a 50 year old mystery as to the origin of the pigment chlorophyll d, which was thought to be a pigment of red algae or a breakdown product of the universal chlorophyll, chlorophyll a. Over the next decade, new Acaryochloris spp. were isolated from all over the world as the genus received international interest from the scientific community, with the majority of research directed towards understanding the mechanisms of photosynthesis of this uniquely pigmented cyanobacterium, using A. marina as the model organism of the genus. During this project, characterisation of different aspects of photosynthesis in Acaryochloris spp. was performed including an investigation of pigment adaptation and composition and the growth and characterisation of A. marina biofilms. However, the main focus of the thesis concerns the isolation and characterisation of cyanophages A-HIS1 and AHIS2, which infect A. marina as a basis to investigate and understand the impact of phage on host physiology in this new model system. A-HIS1 and A-HIS2 were characterised by their morphology, growth behaviour and genomes. Experiments were designed and implemented to investigate interactions between the phages and host. Interestingly, an analysis of novel genes in these phages revealed a surprising evolutionary history of phages A-HIS1 and A-HIS2 providing new insights into the origin of DNA polymerase, which is found only in the mitochondria of eukaryotes