Optimizing Cyanobacteria Detection for Comparing Lichenized and Environmental Cyanobacterial Communities

Cyanolichens are symbiotic associations between fungi and cyanobacteria. When lichenized fungi reproduce sexually, the fungal spores are dispersed without the cyanobacteria, and they must find a new partner to form a cyanolichen thallus. However, how common these potential cyanobacterial partners are in the substrates where the cyanolichens grow is unknown. A robust sequencing procedure is necessary to compare the communities of lichenized and environmental cyanobacteria. This study aims to optimize the procedure for sequencing 1800 environmental samples from Alberta, Canada. We tested the sensitivity of the 16S rRNA and rbcLX genetic markers for cyanobacteria detection and the role of substrate depth on cyanobacterial community composition. The rbcLX genetic marker is more variable but is single-copy, while the 16S rRNA gene is less variable but exists in multiple copies. Sequencing the 16S rRNA gene may be better for detecting trace amounts of cyanobacteria in environmental samples. Additionally, cyanobacteria are expected to be more diverse in top substrate layers because they need light for photosynthesis, so sampling from deeper depths may not be necessary. We sequenced the two markers from 112 environmental samples, including 12 with known taxonomic compositions. The remaining 100 samples have unknown compositions and include both top and bottom substrate layers. We will use the sequence data to compare the detection sensitivity of the two genetic markers. Preliminary results favor the 16S rRNA gene. The results will inform the procedure for large-scale characterization of environmental cyanobacteria to understand the formation of the cyanolichen symbiosis.