20 research outputs found
Benthic Biofilm Controls on Fine Particle Dynamics in Streams
Este artÃculo contiene 15 páginas, 7 figuras, 3 tablas.Benthic (streambed) biofilms metabolize a substantial fraction of particulate organic matter
and nutrient inputs to streams. These microbial communities comprise a significant proportion of overall
biomass in headwater streams, and they present a primary control on the transformation and export of
labile organic carbon. Biofilm growth has been linked to enhanced fine particle deposition and retention, a
feedback that confers a distinct advantage for the acquisition and utilization of energy sources. We
quantified the influence of biofilm structure on fine particle deposition and resuspension in experimental
stream mesocosms. Biofilms were grown in identical 3 m recirculating flumes over periods of 18–47 days to
obtain a range of biofilm characteristics. Fluorescent, 8 mm particles were introduced to each flume, and
their concentrations in the water column were monitored over a 30 min period. We measured particle
concentrations using a flow cytometer and mesoscale (10 mm to 1 cm) biofilm structure using optical
coherence tomography. Particle deposition-resuspension dynamics were determined by fitting results to a
stochastic mobile-immobile model, which showed that retention timescales for particles within the
biofilm-covered streambeds followed a power-law residence time distribution. Particle retention times
increased with biofilm areal coverage, biofilm roughness, and mean biofilm height. Our findings suggest
that biofilm structural parameters are key predictors of particle retention in streams and rivers.This study was
funded by a Marie Curie Intra-
European Fellowship to WRH (FP7-
PEOPLE-2011-IEF-302297) and an
Austrian Science Fund grant to T.J.B.
(START Y420-B17). K.R.R. was
supported by a CUAHSI Pathfinder
fellowship and U.S. NSF Graduate
Research Fellowship. J.D.D. was
supported by a Fulbright-Spain
fellowship. The modeling effort was
supported by U.S. NSF grants EAR-
1215898 and EAR-1344280 to AIP.
Supporting data are provided at
doi:10.6084/m9.figshare.4252193.Peer reviewe
Focus on the physics of biofilms
Bacteria are the smallest and most abundant form of life. They have traditionally been considered as primarily planktonic organisms, swimming or floating in a liquid medium, and this view has shaped many of the approaches to microbial processes, including for example the design of most antibiotics. However, over the last few decades it has become clear that many bacteria often adopt a sessile, surface-associated lifestyle, forming complex multicellular communities called biofilms. Bacterial biofilms are found in a vast range of environments and have major consequences on human health and industrial processes, from biofouling of surfaces to the spread of diseases. Although the study of biofilms has been biologists' territory for a long time, a multitude of phenomena in the formation and development of biofilms hinges on physical processes. We are pleased to present a collection of research papers that discuss some of the latest developments in many of the areas to which physicists can contribute a deeper understanding of biofilms, both experimentally and theoretically. The topics covered range from the influence of physical environmental parameters on cell attachment and subsequent biofilm growth, to the use of local probes and imaging techniques to investigate biofilm structure, to the development of biofilms in complex environments and the modeling of colony morphogenesis. The results presented contribute to addressing some of the major challenges in microbiology today, including the prevention of surface contamination, the optimization of biofilm disruption methods and the effectiveness of antibiotic treatments