Cell density and non-equilibrium sorption effects on bacterial dispersal in groundwater microcosms

Abstract

The relative importance of dispersion, physical straining, non-equilibrium sorption, and cell density on the dispersal of bacteria was examined in saturated, flow-dynamic sand columns. The bacterial breakthrough as a result of different size distributions of sand particles was followed by measuring the effluent concentration of 3H-adenosine-labelled cells of a Bacillus sp. and an Enterobacter sp. strain suspended in groundwater. The breakthrough curves were compared with theoretical curves predicted from an advective-dispersioe equilibrium sorption model (ADS), an ADS model with a first order sink term for irreversible cell reactions, a two-site model (equilibrium and nonequilibrium sorption sites), and a filtration model. Bacterial sand: water isotherms were linear in the experimental concentration range but had positive intercepts. The partition coefficients ranged from 15 to 0.4 for the Bacillus sp., and 120 to 0.4 for a Pseudomonas sp., and decreased with increasing particle size of the dominant fraction. In a kinetic study, the partition coefficient for the Enterobacter sp. in the smaller particle sand was 63 after one hour, but had decreased to 9 after 19 hours. Bacteria were detected in the effluent after one pore volume, which was earlier than predicted by the sand : water partition coefficients, and displayed an apparent nonequilibrium breakthrough. Dispersion effects and physical straining appeared to be insignificant in the experiments, but tailing of the elution part of the curves indicated slow reversible sorption, and nonequilibrium sorption may have been the main determinant of dispersal retardation. The reversible non-equilibrium sorption invalidated some of the assumptions behind all models except, possibly, the two-site model. Consequently, the models described the large particle sand data better where sorption was of less importance for the dispersal. The dispersal retardation was also affected by the bacterial cell density, both in the pore water and on the sand, suggesting that population characteristics may be an important factor for the bacterial distribution between the water and sand habitats. The retardation factor decreased from 13.7 to 7.8 when the cell density in the loading solution was increased from 3× 10(8) to 1.2 × 10(9) cells ml(-1). Presaturation of the sand with bacteria had a similar effect.

Acid–base properties of cyanobacterial surfaces I: Influences of growth phase and nitrogen metabolism on cell surface reactivity

“…In particular, organic functional groups located in the bacterial cell wall act as highly efficient ligands for the sorption of metals (e.g., Beveridge and Murray, 1980;Beveridge et al, 1982; and/or organic compounds (Baughman and Paris, 1981;Fein and Delea, 1999). Those ligands also determine the overall cell surface charge governing bacterial adherence to solid substrata (van Loosdrecht et al, 1989(van Loosdrecht et al, , 1990Yee et al, 2000), which in turn, impacts on metal mobility in many fluid-rock systems (e.g., McCarthy and Zachara, 1989;Lindgvist and Enfield, 1992;Corapcioglu and Kim, 1995). The sorptive capacity of bacteria additionally alters mineral precipitation and dissolution rates at the bacterial surface (Konhauser et al, 1993;Fortin et al, 1997;Warren and Ferris, 1998).…”

Acid–base properties of cyanobacterial surfaces. II: Silica as a chemical stressor influencing cell surface reactivity

“…doi:10. 1016/j.gca.2007.10.032 solute transport (e.g., McCarthy and Zachara, 1989;Lindgvist and Enfield, 1992;Corapcioglu and Kim, 1995), and redox reactions (for review, see Konhauser, 2006).…”

Interaction of Pseudomonas putida with kaolinite and montmorillonite: A combination study by equilibrium adsorption, ITC, SEM and FTIR

“…The adsorption can significantly alter microbial activity [3,4], the ecological distribution of bacteria [5][6][7], biomineralization, weathering of minerals, and biodegradation of pollutants [8]. Therefore, the understanding of sorption process of bacteria is of great environmental and geological significance.…”