Physical constraints affecting bacterial habitats and activity in unsaturated porous media – a review

Or, Dani; Smets, Barth F.; Wraith, Jon M.; Dechesne, Arnaud; Friedman, Shmulik P.

doi:10.1016/j.advwatres.2006.05.025

Cited by 519 publications

(419 citation statements)

References 172 publications

Supporting

Mentioning

408

Contrasting

Unclassified

Order By: Relevance

“…The fragmentation of aqueous microhabitat has been identified as a key factor promoting the microbial diversity found in soil [Curtis and Sloan, 2005;Dion, 2008;Or et al, 2007], nevertheless, the degree of fragmentation in 3-D soil pore networks has not been quantified as of yet. We express the degree of fragmentation of connected aqueous habitats as the ratio of the largest connected aqueous cluster size to the system size (this definition follows concepts from percolation theory [Sahimi, 1994;Tsang and Tsang, 1999;Wang and Or, 2012]).…”

Section: Aqueous Phase Fragmentation-comparisons With Percolation Theorymentioning

confidence: 99%

“…Other forms of motility such as swarming, gliding, twitching, and sliding are limited to a few species [Harshey, 2003;Dechesne et al, 2008]. Microbial life in natural soils under most climatic conditions is characterized by motion in small pores and in thin liquid films governed by low Reynolds numbers that also limit the role of passive (advective) transport to a few rare events where the soil becomes very wet [Purcell, 1977;Bitton and Harvey, 1992;Fenchel, 2002;Berg, 2005;Or et al, 2007]. In heterogeneous systems, bacterial motility is often biased by chemotaxis that guides bacteria toward higher concentrations of nutrients (or away from toxic compounds) [Fenchel, 2002;Stocker et al, 2008].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Microbial dispersal in unsaturated porous media: Characteristics of motile bacterial cell motions in unsaturated angular pore networks

Ebrahimi

2014

Water Resources Research

109

View full text Add to dashboard Cite

The dispersal rates of self-propelled microorganisms affect their spatial interactions and the ecological functioning of microbial communities. Microbial dispersal rates affect risk of contamination of water resources by soil-borne pathogens, the inoculation of plant roots, or the rates of spoilage of food products. In contrast with the wealth of information on microbial dispersal in water replete systems, very little is known about their dispersal rates in unsaturated porous media. The fragmented aqueous phase occupying complex soil pore spaces suppress motility and limits dispersal ranges in unsaturated soil. The primary objective of this study was to systematically evaluate key factors that shape microbial dispersal in model unsaturated porous media to quantify effects of saturation, pore space geometry, and chemotaxis on characteristics of principles that govern motile microbial dispersion in unsaturated soil. We constructed a novel 3-D angular pore network model (PNM) to mimic aqueous pathways in soil for different hydration conditions; within the PNM, we employed an individual-based model that considers physiological and biophysical properties of motile and chemotactic bacteria. The effects of hydration conditions on first passage times in different pore networks were studied showing that fragmentation of aquatic habitats under dry conditions sharply suppresses nutrient transport and microbial dispersal rates in good agreement with limited experimental data. Chemotactically biased mean travel speed of microbial cells across 9 mm saturated PNM was $3 mm/h decreasing exponentially to 0.45 mm/h for the PNM at matric potential of 215 kPa (for 235 kPa, dispersal practically ceases and the mean travel time to traverse the 9 mm PNM exceeds 1 year). Results indicate that chemotaxis enhances dispersal rates by orders of magnitude relative to random (diffusive) motions. Model predictions considering microbial cell sizes relative to available liquid pathways sizes were in good agreement with experimental results for unsaturated soils. The new modeling platform enables quantitative consideration of key biophysical factors (e.g., pore space heterogeneities and hydration conditions) governing microbial interactions in 3-D soil pore spaces.

show abstract

Section: Aqueous Phase Fragmentation-comparisons With Percolation Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microbial dispersal in unsaturated porous media: Characteristics of motile bacterial cell motions in unsaturated angular pore networks

Ebrahimi

2014

Water Resources Research

109

View full text Add to dashboard Cite

show abstract

“…Soil bacteria inhabit complex and heterogeneous pore spaces where water and nutrient resources essential for bacterial life may significantly vary across micrometeric spatial scales or entirely change within a single bacterial generation (Crawford et al, 2005;Mitchell and Kogure, 2006;Or et al, 2007;Banavar and Maritan, 2009). Hydration status and pore-space characteristics are critical factors shaping nutrient fields and bacterial motility, and are thus key to understanding bacterial interactions in soil and other porous media such as dry food products (Barton and Ford, 1997;Dens and Van Impe, 2000;Wilson et al, 2002;Chang and Halverson, 2003;Or et al, 2007;Chen and Jin, 2011).…”

Section: Introductionmentioning

confidence: 99%

Hydration dynamics promote bacterial coexistence on rough surfaces

Wang

2012

The ISME Journal

View full text Add to dashboard Cite

Identification of mechanisms that promote and maintain the immense microbial diversity found in soil is a central challenge for contemporary microbial ecology. Quantitative tools for systematic integration of complex biophysical and trophic processes at spatial scales, relevant for individual cell interactions, are essential for making progress. We report a modeling study of competing bacterial populations cohabiting soil surfaces subjected to highly dynamic hydration conditions. The model explicitly tracks growth, motion and life histories of individual bacterial cells on surfaces spanning dynamic aqueous networks that shape heterogeneous nutrient fields. The range of hydration conditions that confer physical advantages for rapidly growing species and support competitive exclusion is surprisingly narrow. The rapid fragmentation of soil aqueous phase under most natural conditions suppresses bacterial growth and cell dispersion, thereby balancing conditions experienced by competing populations with diverse physiological traits. In addition, hydration fluctuations intensify localized interactions that promote coexistence through disproportional effects within densely populated regions during dry periods. Consequently, bacterial population dynamics is affected well beyond responses predicted from equivalent and uniform hydration conditions. New insights on hydration dynamics could be considered in future designs of soil bioremediation activities, affect longevity of dry food products, and advance basic understanding of bacterial diversity dynamics and its role in global biogeochemical cycles.

show abstract

“…In contrast to water-replete environments where flagellar motility is essentially unrestricted, there exists strong physical limitations to flagellar motility in partially saturated media where aquatic microhabitats are often fragmented and connected only by thin liquid films of bacterial size or smaller (9). The limitations to bacterial motility in thin liquid films have, thus, long been posited but never directly quantified or described biophysically beyond the general notion that flagellar motility requires hydrated pathways.…”

mentioning

confidence: 99%

Hydration-controlled bacterial motility and dispersal on surfaces

Dechesne

Wang

Gulez

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

171

237

View full text Add to dashboard Cite

Flagellar motility, a mode of active motion shared by many prokaryotic species, is recognized as a key mechanism enabling population dispersal and resource acquisition in microbial communities living in marine, freshwater, and other liquid-replete habitats. By contrast, its role in variably hydrated habitats, where water dynamics result in fragmented aquatic habitats connected by micrometric films, is debated. Here, we quantify the spatial dynamics of Pseudomonas putida KT2440 and its nonflagellated isogenic mutant as affected by the hydration status of a rough porous surface using an experimental system that mimics aquatic habitats found in unsaturated soils. The flagellar motility of the model soil bacterium decreased sharply within a small range of water potential (0 to −2 kPa) and nearly ceased in liquid films of effective thickness smaller than 1.5 μm. However, bacteria could rapidly resume motility in response to periodic increases in hydration. We propose a biophysical model that captures key effects of hydration and liquid-film thickness on individual cell velocity and use a simple roughness network model to simulate colony expansion. Model predictions match experimental results reasonably well, highlighting the role of viscous and capillary pinning forces in hindering flagellar motility. Although flagellar motility seems to be restricted to a narrow range of very wet conditions, fitness gains conferred by fast surface colonization during transient favorable periods might offset the costs associated with flagella synthesis and explain the sustained presence of flagellated prokaryotes in partially saturated habitats such as soil surfaces.flagella | biophysics | liquid film | fitness | motility D ispersal is recognized as a key ecological process enabling populations' access to new sites and pools of resources (1), thereby affecting structure and productivity of ecosystems (2, 3). Active bacterial motion (motility) takes on many forms that require various appendages (4). If surface-associated modes of motility such as twitching, gliding, or swarming seem restricted to some species (5), the ability to swim by rotating one or more flagella is shared by a large diversity of prokaryotes. This swimming motility has attracted considerable attention, primarily aimed at resolving the biophysical functioning of flagella and to a lesser degree, exploring its adaptive value. In marine environments, a large fraction of bacterial populations are flagellated (6), and swimming motility is often coupled with chemotaxis, conferring a clear benefit to these cells by allowing them to outswim diffusion and exploit transient substrate gradients (7,8).In contrast to water-replete environments where flagellar motility is essentially unrestricted, there exists strong physical limitations to flagellar motility in partially saturated media where aquatic microhabitats are often fragmented and connected only by thin liquid films of bacterial size or smaller (9). The limitations to bacterial motility in thin liquid films have, thus, l...

show abstract

Physical constraints affecting bacterial habitats and activity in unsaturated porous media – a review

Cited by 519 publications

References 172 publications

Microbial dispersal in unsaturated porous media: Characteristics of motile bacterial cell motions in unsaturated angular pore networks

Microbial dispersal in unsaturated porous media: Characteristics of motile bacterial cell motions in unsaturated angular pore networks

Hydration dynamics promote bacterial coexistence on rough surfaces

Hydration-controlled bacterial motility and dispersal on surfaces

Contact Info

Product

Resources

About