Epiphytic bacteria on the surfaces of submerged macrophytes play important roles in the growth of the host plant, nutrient cycling, and the conversion of pollutants in aquatic systems. A knowledge of the epiphytic bacterial community structure could help us to understand these roles. In this study, the abundance, diversity, and functions of the epiphytic bacterial community of Myriophyllum spicatum collected from Baiyangdian Lake in June, August, and October 2019 were studied using quantitative PCR (qPCR), high-throughput sequencing, and the prediction of functions. An analysis using qPCR showed that the epiphytic bacteria were the most abundant in October and the least abundant in August. High-throughput sequencing revealed that Proteobacteria, Gammaproteobacteria, and Aeromonas were the dominant phylum, class, and genus in all the samples. The common analyses of operational taxonomic units (OTUs), NMDS, and LDA showed that the epiphytic bacterial communities were clustered together based on the seasons. The results of a canonical correlation analysis (CCA) showed that the key water quality index that affected the changes of epiphytic bacterial community of M. spicatum was the total phosphorus (TP). The changes in abundance of Gammaproteobacteria negatively correlated with the TP. Predictive results from FAPROTAX showed that the predominant biogeochemical cycle functions of the epiphytic bacterial community were chemoheterotrophy, nitrate reduction, and fermentation. These results suggest that the epiphytic bacterial community of M. spicatum from Baiyangdian Lake varies substantially with the seasons and environmental conditions.

A Gram-stain-variable, aerobic, rod-shaped, endospore-forming strain R196T) was isolated from internal tissues of roots of Cymbidium goeringii. Cells were motile with peritrichous flagella. The colonies were light pink on tryptone soya agar medium. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain R196T fell into a phylogenetic cluster belonging to the genus Paenibacillus . Strain R196T was closely related to Paenibacillus cavernae C4-5T and Paenibacillus contaminans CKOBP-6T with 93.6 and 93.3% sequence similarities, respectively. The major cellular polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, three unidentified phospholipids, two unidentified aminophospholipids and an unidentified aminolipid. The dominant respiratory quinone was MK-7. The main cellular fatty acids were anteiso-C15 : 0 (53.01%), C16 : 0 (13.04%) and iso-C16 : 0 (10.80%). The genome size of R196T was 9.45 Mb, containing 7617 predicted protein-coding genes, with a DNA G+C content of 57.7 mol%. Based on the results of phenotypic, chemotaxonomic and whole-genome analyses, strain R196T represents a novel species of the genus Paenibacillus , for which the name Paenibacillus cymbidii sp. nov. is proposed. The type strain is R196T (=ACCC 61713T=KCTC 33718T).