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Stabilizing Effects of Bacterial Biofilms: EPS Penetration and Redistribution of Bed Stability Down the Sediment Profile
Author(s) -
Chen X. D.,
Zhang C. K.,
Zhou Z.,
Gong Z.,
Zhou J. J.,
Tao J. F.,
Paterson D. M.,
Feng Q.
Publication year - 2017
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2017jg004050
Subject(s) - sediment , extracellular polymeric substance , penetration (warfare) , biofilm , porosity , chemical engineering , chemistry , materials science , soil science , mineralogy , environmental science , geology , geotechnical engineering , geomorphology , bacteria , engineering , paleontology , operations research
Abstract Biofilms, consisting of microorganisms and their secreted extracellular polymeric substances (EPSs), serve as “ecosystem engineers” stabilizing sedimentary environments. Natural sediment bed provides an excellent substratum for biofilm growth. The porous structure and rich nutrients allow the EPS matrix to spread deeper into the bed. A series of laboratory‐controlled experiments were conducted to investigate sediment colonization of Bacillus subtilis and the penetration of EPS into the sediment bed with incubation time. In addition to EPS accumulation on the bed surface, EPS also penetrated downward. However, EPS distribution developed strong vertical heterogeneity with a much higher content in the surface layer than in the bottom layer. Scanning electron microscope images of vertical layers also displayed different micromorphological properties of sediment‐EPS matrix. In addition, colloidal and bound EPSs exhibited distinctive distribution patterns. After the full incubation, the biosedimentary beds were eroded to test the variation of bed stability induced by biological effects. This research provides an important reference for the prediction of sediment transport and hence deepens the understanding of the biologically mediated sediment system and broadens the scope of the burgeoning research field of “biomorphodynamics.”