Epiphytic microbiota of kai Cladophora sp. from Nan River, Nan Province, Thailand

Cladophora is a cosmopolitan green algal genus in northern Thailand, commonly known as Kai or Sa Rai Kai, which the local people use for culinary and medicinal purposes. In nature, Cladophora acts as an ecological engineer in the ecosystem by creating, modifying, and maintaining the habitat by providing oxygen and microhabitats for several organisms, including prokaryotes and eukaryotes, namely epiphytic microbiota. These epiphytic microbiota living on the algal host's surface might exhibit crucial roles in the ecosystem. However, most understandings of the Cladophora microbiota were from the USA. Therefore, this study aims to investigate the Cladophora microbiota collected from Nan River, Nan Province, Thailand, by using amplicon-based metagenomic analysis. Results revealed a total of 575 eukaryotic genera and 698 bacterial genera, which were present variedly in the study sites. Among the identified bacterial taxa, 227 genera were shared taxa, taxa commonly present in all sites. Some were highly abundant taxa, which might be involved in various processes, e.g., cellulose degradation, vitamin B12 biosynthesis, and nitrogen fixation. Among the shared taxa, 17 genera were core taxa, taxa present in Cladophora microbiota of this and other previous studies. Some were bioinformatically inferred to play crucial roles in freshwater Cladophora microbiome, e.g., vitamin B12 biosynthesis (Flavobacterium and Pseudomonas), extracellular polymeric substance secretion (Terrimonas), and denitrification (Acidovorax and Methylotenera). These findings allow us to understand more of the taxonomic composition and the putative ecological functions of Cladophora sp. microbiome.