Characterization and Analysis of the Microbiota of Bangia atropurpurea and other Freshwater and Marine Algae in North America

Abstract

Algae are a diverse polyphyletic group of photosynthetic organisms that contribute to forming rich ecosystems within marine and freshwater habitats. Many factors contribute to algal function and growth, such as the chemistry of their aquatic environment as well as interactions with other organisms through competition, parasitism, and mutualism. An often-overlooked symbiotic relationship is between alga and the microbial community that inhabits its surface or intercellular space. In fact, studies investigating the algal microbiome are limited and comparative analyses are rare. This study examines microbial community compositions of Bangia atropurpurea (freshwater Rhodophyta), Bangia fuscopurpurea (marine Rhodophyta), and Cladophora glomerata (freshwater Chlorophyta) to gain more information on bacterial diversity and composition changes across environment, species, and time. Microbial taxonomy was determined through sequencing of the V4 region of 16S rRNA gene. Sequence data was filtered, sorted, and analysed with Qiime2 and R. Using MEGA to construct maximum likelihood phylogenetic trees, the identification of genera within biologically relevant phyla such as Cyanobacteria, Planctomycetes, Verrucomicrobia, and Bacteroidetes were explored. Comparisons of algal microbiota isolated from different host species or geolocations demonstrated that bacterial communities likely assemble in alga-specific and environment-specific patterns. Sampling the microbiota of Bangia atropurpurea 14 years apart showed a significant decrease in bacterial diversity over this time, which may be attributed to loss of certain temporary associations. Future studies can use this data to inform larger metagenomic surveys and further investigate the relationships between bacteria and their algal hosts. This will provide valuable insight into the microbial effect on algal function which may contribute to the mitigation of harmful invasions and blooms that cause damage to the local ecosystem.