An Exploration of Cell Death and Lysis in an Alkaliphilic Cyanobacterial Consortium using Multi-'Omics Approaches
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2023-12-01
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Abstract
Cyanobacteria are important primary producers in many ecosystems, converting light into chemical energy. Their death plays a vital role in releasing organic carbon and nitrogen into the environment, supporting the life of other, heterotrophic organisms, and facilitating carbon sequestration in sediments. With warming aquatic systems, algal blooms are becoming more frequent, persistent, and larger in size, highlighting the need to understand the mechanisms of their death. Cyanobacterial death, whether via viral predation or other mechanisms such as programmed cell death, remains an underexplored topic in non-marine aquatic ecosystems. In this thesis, cell lysis and death of an alkaliphilic Cyanobacterium, Candidatus Sodalinema alkaliphilum, is explored primarily from the perspective of viral infections. Ca. Sodalinema alkaliphilum was enriched, along with its associated heterotrophic microbial community, from alkaline soda lakes on Cariboo Plateau in British Columbia, Canada. This robust cyanobacterial consortium has also been the focus of biotechnological research aimed at producing sustainable bioproducts. Robustness of this consortium can be defined as its capacity to maintain phototrophic function in spite of (a)biotic disturbances. First, bioinformatic techniques to investigate the viral ecology and dynamics of microbial communities in silico were reviewed in Chapter 2. These included identifying viral sequences, classifying their taxonomy, performing phylogenomic analyses, and predicting their hosts. Methods from Chapter 2 were subsequently applied to characterize viral populations in the alkaliphilic cyanobacterial consortium and to investigate viral dynamics by comparing bacterial defence mechanisms across multiple years. This study was the first metagenomic survey of viruses in an alkaliphilic phototrophic consortium and provided valuable insight into the viral ecology of a phototrophic enrichment culture. Finally, based on findings from Chapter 3, the same cyanobacterial consortium was challenged with threats from its natural environment, the alkaline soda lakes. In Chapter 4, the trigger and mechanism of a sudden and rapid cell lysis of the Ca. Sodalinema alkaliphilum was explored using metagenomic, metatranscriptomics analysis, and transmission electron microscopy. This work enhanced our understanding of viral dynamics within an alkaliphilic phototrophic microbial community and highlighted the complexity of cell death in the natural environment.
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Khot, V. M. (2023). An exploration of cell death and lysis in an alkaliphilic cyanobacterial consortium using multi-'omics approaches (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.