Comparative Metagenomics of Freshwater Cyanobacteria Bloom and Non-Bloom Sites in Ontario and the Investigation into the Utilization of Conserved Signature Proteins for Identification of Cyanobacteria

Abstract

Cyanobacterial algal blooms have been increasing in frequency and severity over the past few years in Ontario. Depending on the presence of toxigenic Cyanobacteria, these blooms have the potential to release toxins into the water, posing a public and environmental risk to humans and animals. Although traditional methods of studying Cyanobacteria provide important information regarding the microbial community, metagenomic sequencing allows for a more comprehensive examination of microbial diversity and functional capacities as limitations in cultivating organisms is circumvented. Therefore, to gain insight into the community composition of freshwater blooms and to compare them to non-bloom sites within Ontario, we collaborated with the Ministry of the Environment and Climate Change (MOECC) to undergo a high throughput DNA sequencing approach for a comparative metagenomic analysis. In 2015, 108 bloom and non-bloom samples were collected and sent for 16S rRNA sequencing and a subset of these were chosen for shotgun metagenomic sequencing. Our study focuses on comparing community structure and functional differences that may exist between bloom and non-bloom sites as well as analyzing differences in cyanobacterial communities across bloom sites. Our findings reveal differences in the microbial communities between these two environments. At the functional level, large-scale functionalities were conserved across the two groups but differences in specialized functions were revealed. Overall, our results show that metagenomics is a powerful tool for delineating functional and taxonomic analysis of bloom and non-bloom sites across Ontario. The second part of this work studied the utilization of the molecular marker, Conserved Signature Proteins (CSPs), as a valid method for identifying Cyanobacteria to facilitate the problem of cyanobacterial taxonomic classification. It was found that CSPs proved to be reliable in identifying Cyanobacteria within environmental samples when compared to amplicon and shotgun metagenomic sequencing approaches.