Influence of different chemical treatments on transport of Alcaligenes paradoxus in porous media

Abstract

Seven chemicals, three buffers, and a salt solution known to affect bacterial attachment were tested to quantify their abilities to enhance the penetration of Alcaligenes paradoxus in porous media. Chemical treatments included Tween 20 (a nonionic surfactant that affects hydrophobic interactions), sodium dodecyl sulfate (an anionic surfactant), EDTA (a cell membrane permeabilizer that removes outer membrane lipopolysaccharides), sodium PP i (a surface charge modifier), sodium periodate (an oxidizer that cleaves surface polysaccharides), lysozyme (an enzyme that cleaves cell wall components), and proteinase K (a nonspecific protease that cleaves peptide bonds). Buffers included MOPS [3-(N-morpholino)propanesulfonic acid], Tris, phosphate, and an unbuffered solution containing only NaCl. Transport characteristics in the porous media were compared by using a sticking coefficient, ␣, defined as the rate at which particles stick to a grain of medium divided by the rate at which they strike the grain. Tween 20 reduced ␣ by 2.5 orders of magnitude, to ␣ ‫؍‬ 0.0016, and was the most effective chemical treatment for decreasing bacterial attachment to glass beads in buffered solutions. Similar reductions in ␣ were achieved in unbuffered solutions by reducing the solution ionic strength to 0.01 mM. EDTA, protease, and other treatments designed to alter cell structures did not reduce ␣ by more than an order of magnitude. The number of bacteria retained by the porous media was decreased by treatments that made A. paradoxus more hydrophobic and less electrostatically charged, although ␣ was poorly correlated with electrophoretic mobility and hydrophobicity index measurements at lower ␣ values. Filtration model calculations indicate that ␣ values of <0.01 are necessary to achieve bacterial transport over distances large enough to facilitate bioremediation of contaminated groundwater aquifers. Chemical treatments that reduce ␣ from 0.61 (1 mM MOPS buffer; ionic strength, 70 mM) to 0.0016 would increase bacterial penetration from 0.16 to 60 m, with only a 2-log reduction in cell concentration under typical groundwater and soil conditions (assuming a water velocity of 1 m day ؊1 and an average soil grain diameter of 500 m).

Effect of low‐concentration rhamnolipid biosurfactant on Pseudomonas aeruginosa transport in natural porous media

“…Chemical treatments have been widely used to modify bacterial surfaces to weaken bacterial attachment and enhance transport of bacteria in porous media for bioaugmentation applications [ Bai et al ., ; Brown and Jaffé , ; Gross and Logan , ; Johnson and Logan , ; Johnson et al ., ; Powelson and Mills , ; Shen et al ., ; Streger et al ., ; Wang et al ., ]. For example, the chemical surfactants, e.g., nonionic surfactants, Tween‐20 and Brij, and anionic surfactants, sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS), were observed to decrease CSH or produce the steric effect, and thus lower cell‐attachment efficiencies and decrease cell retention [ Brown and Jaffé , ; Gross and Logan , ; Johnson et al ., ; Powelson and Mills , ; Streger et al ., ]. Other chemicals, e.g., ethylene diamine tetraacetic acid (EDTA), proteinase‐k, pyrophosphate, sulfate, and phosphate, were also reported to enhance bacterial transport either by modifying cell and sand surface properties (e.g., hydrophobicity and zeta potential) or by releasing previously immobilized cells [ Gross and Logan , ; Johnson et al ., ; Shen et al ., ; Wang et al ., ].…”

“…For example, the chemical surfactants, e.g., nonionic surfactants, Tween‐20 and Brij, and anionic surfactants, sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS), were observed to decrease CSH or produce the steric effect, and thus lower cell‐attachment efficiencies and decrease cell retention [ Brown and Jaffé , ; Gross and Logan , ; Johnson et al ., ; Powelson and Mills , ; Streger et al ., ]. Other chemicals, e.g., ethylene diamine tetraacetic acid (EDTA), proteinase‐k, pyrophosphate, sulfate, and phosphate, were also reported to enhance bacterial transport either by modifying cell and sand surface properties (e.g., hydrophobicity and zeta potential) or by releasing previously immobilized cells [ Gross and Logan , ; Johnson et al ., ; Shen et al ., ; Wang et al ., ]. However, high concentrations of the chemicals are generally required for achieving significant decrease of cell retention.…”

Characterizing the adhesion of motile and nonmotile Escherichia coli to a glass surface using a parallel‐plate flow chamber

“…At the same time, increasing the velocity also enables a larger number of bacteria to pass over the surface in a given time period, a phenomenon that tends to have the opposite eect. A signi®cant amount of research has been done to better understand the eect of¯uid velocity on the adhesion of nonmotile bacteria, involving both speci®c (Dickinson and Cooper, 1995;Mohamed et al, 1999Mohamed et al, , 2000 and nonspeci®c (Gannon et al, 1991;Gross and Logan, 1995;Meinders et al, 1992Meinders et al, , 1994Wollum and Cassel, 1978) interactions. However, because approximately 80% of bacteria studied so far are motile (Aizawa, 1996), we are primarily interested in understanding how¯uid velocity aects the transport and adhesion of motile bacteria in comparison to their nonmotile counterparts.…”

A novel approach to investigate biofilm accumulation and bacterial transport in porous matrices

“…Fields which depend on accurate knowledge of bacterial transport and biofilm growth in porous media include: pathogen migration to groundwater (Abuashour et al ., 1994); subsurface bioremediation using emplacement or enhancement of indigenous bacteria (Gross and Logan, 1995) and; prediction of the location of populations of microorganisms in oil reservoirs. Biofilm growth can block oil‐bearing rock pores reducing permeability and water and oil flow (MacLeod et al ., 1988; Bass and Lappin‐Scott, 1997) or contaminate crude oil with hydrogen sulphide (Ligthelm et al ., 1991; Sunde et al ., 1993).…”