The relationship between bacterial composition, environment and the underlying principles of bacterial community assembly has triggered great debates in the field of microbial ecology for decades. Two interactive mechanisms "niche process” and “neutral process” have been classified as the main processes to determine bacterial community structures.  

Bacterioplankton and epiphytes are two forms of bacterial community; however, epiphytes are believed to be more important in modifying macrophytes growth and development. They can affect the nutrient cycling and photosynthetic activity of their host plants. Despite this, the knowledge of the effects of epiphytic bacteria on community ecology and dynamics is still poorly understood, especially the relations among bacteria, plants host and environment. 

The research team, consisted of Wuhan Botanical Garden and Fairy Lake Botanical Garden, used two contrasting artificial water environments (eutrophic and oligotrophic) for reciprocal transplant experiment of Myriophyllum spicatum to examine the colonization of epiphytic bacteria accompanied with plants growth.  

The species diversity was higher in epiphytic bacteria than in bacterioplankton, which might be because of the interface between water and plant hosts which endowed epibiotic bacteria with competitive advantages to acquire nutrients from both media, especially for carbon sources through the plants in productivity and element cycling. The highest microbiome richness occurred in sediment. 

Both plant status (i.e. branch number, net photosynthesis rate etc.) and water conditions (i.e. total phosphate, total nitrogen, pH etc.) were probed to be the driving forces on the bacteria communities, with the plant status in priority. 16S rRNA gene sequencing further indicated that the epiphytic assemblies were motivated by functionalization and interplay with hosts as a whole.   

This study provides more valuable perspectives on bacteria and macrophytes, taking the interaction with water condition into account. The efforts could also facilitate the integrative framework for ecological theory.  

This work is supported by the National Key R & D Program of China and the National Natural Science Foundation of China. It has been published in Current Microbiology with the title of “Structural Variability and Functional Prediction in the Epiphytic Bacteria Assemblies of Myriophyllum spicatum”.  

Summary of the triadic relationships among macrophyte hosts, bacteria (epiphytic bacteria and environment bacteria) and the environments (Image by WBG)