Abstract:Olpidiopsis disease is one of the main diseases affecting laver cultivation in the sea, often causing large-scale rot and serious economic losses. Although the oomycetic genus Olpidiopsis has been identified as the pathogen, little is known regarding its mechanisms, including its interaction with epiphytic microbial communities. In the present study, diversities, structures, and major interactions of epiphytic microbial communities were analyzed using Neopyropia yezoensis in sea infected by Olpidiopsis. The N. yezoensis used in the experiment had different health statuses, including no infection (PyOlpH), partial infection (PyOlpM), and serious infection (PyOlpS). The results showed that no significant difference was observed for the α diversity indices among microbial communities associated with the three groups of N. yezoensis, but those of PyOlpM were higher than the other two. Shared operational taxonomic units (OTUs) among the three groups of communities only accounted for 22.7% of the total OTUs, in addition to significant community dissimilarity (permutational multivariate analysis of variance, R2=0.405, P<0.05). More microbial taxa were obtained when communities associated with more seriously infected N. yezoensis compared to those associated with PyOlpH. In total, 208 genera belonging to 23 phyla were annotated, and α-Proteobacteria, γ-Proteobacteria, and Firmicutes were dominant in all samples. Sixteen of the top 20 genera were also assigned to the three groups, with their relative abundances increasing or decreasing across the infection status from none to severe. Among them, genera Cupriavidus and Sphingomonas were the most connected bacterial taxa in the co-occurrence network, and negative interactions were determined between the two taxa and their positively interacting bacterial taxa. This study provides primary datasets for clarifying the microbial ecological mechanisms and searching for probiotics for Olpidiopsis disease.
