title: Biophysical controls on community succession in stream biofilms.
abstract: Biofilm formation is controlled by an array of coupled physical, chemical, and biotic processes. Despite the ecological relevance of microbial biofilms, their community formation and succession remain poorly understood. We investigated the effect of flow velocity, as the major physical force in stream ecosystems, on biofilm community succession (as continuous shifts in community composition) in microcosms under laminar, intermediate, and turbulent flow. Flow clearly shaped the development of biofilm architecture and community composition, as revealed by microscopic investigation, denaturing gradient gel electrophoresis (DGGE) analysis, and sequencing. While biofilm growth patterns were undirected under laminar flow, they were clearly directed into ridges and conspicuous streamers under turbulent flow. A total of 51 biofilm DGGE bands were detected; the average number ranged from 13 to 16. Successional trajectories diverged from an initial community that was common in all flow treatments and increasingly converged as biofilms matured. We suggest that this developmental pattern was primarily driven by algae, which, as "ecosystem engineers," modulate their microenvironment to create similar architectures and flow conditions in all treatments and thereby reduce the physical effect of flow on biofilms. Our results thus suggest a shift from a predominantly physical control to coupled biophysical controls on bacterial community succession in stream biofilms.
authors.affiliation: Department of Freshwater Ecology, University of Vienna, Althanstr 14, Vienna, Austria.
authors.forename: Katharina
authors.initials: K
authors.lastname: Besemer
authors.forename: Gabriel
authors.initials: G
authors.lastname: Singer
authors.forename: Romana
authors.initials: R
authors.lastname: Limberger
authors.forename: Ann-Kathrin
authors.initials: AK
authors.lastname: Chlup
authors.forename: Gerald
authors.initials: G
authors.lastname: Hochedlinger
authors.forename: Iris
authors.initials: I
authors.lastname: Hödl
authors.forename: Christian
authors.initials: C
authors.lastname: Baranyi
authors.forename: Tom J
authors.initials: TJ
authors.lastname: Battin
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000254:growth & development; D018441:Biofilms / Q000145:classification* / Q000254:growth & development; D004269:DNA, Bacterial / Q000032:analysis; D017753:Ecosystem; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D056890:Eukaryota / Q000145:classification* / Q000235:genetics / Q000254:growth & development; D008969:Molecular Sequence Data; D010802:Phylogeny; D020560:Proteobacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D045483:Rivers / Q000737:chemistry / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014872:Water Movements
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S