Dispersal limitation of rare species by increasing nutrient availability leads to the spatial community uniformity among biofilms.

Aim: Nutrient availability can influence microbial dispersal across local habitats. This study investigated how varying nutrient concentrations affect biofilm metacommunity assembly.

Methods and results: Biofilms were developed from a bacterial polyculture on glass beads regularly arranged within experimental plates. Biofilm communities were analyzed using quantitative PCR and high-throughput sequencing. Bacterial abundance increased, following a positive power-law relationship with rising nutrient concentration (0.5-5.0 g l-1 of the R2A medium), peaking at 3.0 g l-1. Conversely, species richness and diversity exhibited unimodal patterns, with peaks at 1.0 g l-1. Dominant phylotypes (Stenotrophomonas, Acinetobacter, Pseudomonas, and Enterobacter) increased in abundance with increasing nutrient availability, whereas rare phylotypes (e.g. Massilia) declined. Community analyses revealed significant shifts in bacterial community structure with increasing nutrient availability, particularly pronounced between 0.5 and 1.0 g l-1. Spatial heterogeneity in both abundance and community composition decreased markedly from 0.5 to 1.0 g l-1, then showed a slight increase at higher nutrient concentrations. Additionally, lower-ranked individual phylotypes exhibited greater spatial heterogeneity at concentrations ≥1.0 g l-1. Finally, network size and complexity displayed a unimodal pattern with nutrient availability, peaking at 1.0 g l-1.

Conclusion: Nutrient availability is a pivotal ecological factor shaping microbial dispersal, community assembly, and interspecies interactions within biofilm metacommunities.