Ecological Linkages between a Biofilm Ecosystem and Reactor Performance: The Specificity of Biofilm Development Phases

In biofilm-based engineered ecosystems,
the reactor performance
was closely linked to interspecies interactions within a biofilm ecosystem,
whereas the ecological processes underpinning such linkage were still
unenlightened. Herein, the principles of community succession and
assembly were integrated to capture the ecological laws of biofilm
development by molecular ecological networks and assembly model analysis
based on the 16S rRNA sequencing analysis and metagenomics in a well-controlled
moving bed biofilm reactor. At the initial colonization phase (days
0–2, driven by initial colonizers), interspecific cooperation
(74.18%) facilitated initial biofilm formation, whereas some pioneers,
and keystone species disappeared at later phases. At the accumulation
phase (days 3–30, rapid biofilm development), interspecific
cooperation (81.41 ± 5.07%) contributed to rapid biofilm development
and keystone species were mainly involved in quorum sensing or positively
correlated with extracellular polymeric substance production. At the
maturation phase (days 31–106, a well-adapted quasi-equilibrium
state), increased interspecific competition (32.74 ± 4.77%) and
higher small-world property facilitated the rapid information transportation
and pollutant treatment, and keystone species were positively correlated
with the removal of COD and NH4+-N. Homogenizing
dispersal diminished the contemporary community dissimilarities, while
turnover but rather nestedness governed the temporal variations in
the biofilm succession period. This study highlighted the specificity
of ecological processes at distinct biofilm development phases, which
would advance our understanding on the development-to-function linkages
in biofilm-based treatment processes.