Chemotaxis Increases the Residence Time of Bacteria in Granular Media Containing Distributed Contaminant Sources

Abstract

The use of chemotactic bacteria in bioremediation has the potential to increase access to, and the biotransformation of, contaminant mass within the subsurface. This laboratory-scale study aimed to understand and quantify the influence of chemotaxis on the residence times of pollutant-degrading bacteria within homogeneous treatment zones. Focus was placed on a continuous-flow sand-packed column in which a uniform distribution of naphthalene crystals created distributed sources of dissolved-phase contaminant. A 10 mL pulse of Pseudomonas putida G7, which is chemotactic to naphthalene, and Pseudomonas putida G7 Y1, a nonchemotactic mutant strain, were simultaneously introduced into the sand-packed column at equal concentrations. Breakthrough curves obtained from experiments conducted with and without naphthalene were used to quantify the effect of chemotaxis on transport parameters. In the presence of the chemoattractant, longitudinal dispersion of PpG7 increased by a factor of 3, and percent recovery decreased by 43%. In contrast, PpG7 Y1 transport was not influenced by the presence of naphthalene. The results imply that pore-scale chemotaxis responses are evident at an interstitial velocity of 1.8 m/day, which is within the range of typical groundwater flow. Within the context of bioremediation, chemotaxis may work to enhance bacterial residence times in zones of contamination, thereby improving treatment.

Influence of 3-Chloroaniline on the Biofilm Lifestyle of Comamonas testosteroni and Its Implications on Bioaugmentation

“…Compared with the control, the cells exposed to 3-CA had a lower dispersion coefficient (1.406 Ϯ 0.033 cm 2 /h versus 1.487 Ϯ 0.168 cm 2 /h), a lower retardation factor (R; 1.003 Ϯ 0.023 versus 1.245 Ϯ 0.017; P Ͻ 0.05), and lower irreversible retention (k m ; 0.151 Ϯ 0.032 h Ϫ1 versus 0.237 Ϯ 0.043 h Ϫ1 ; P Ͻ 0.05). Lower R and k m values for cells exposed to 3-CA suggest that both the reversible and irreversible retention of C. testosteroni cells in the bioreactors were reduced (23). The 3-CA-treated cells also exhibited a shorter mean travel time, which suggested 3-CA would decrease the residence time of bacterial cells in the bioreactors.…”

“…The breakthrough curves of the treated and control groups were obtained based on cell density in the effluents. The bacterial transport process was modeled using the following one-dimensional advection-dispersion equation (22,23):…”

Surface-Adsorbed Contaminants Mediate the Importance of Chemotaxis and Haptotaxis for Bacterial Transport Through Soils

“…Tetracycline (CAS 60-54-8) was added to the Pf5RL culture at a concentration of 10 mg L −1 . Cultures were grown to stationary phase (optical density of 1.0 at a wavelength of 600 nm), centrifuged at 1,000 g for 10 min, and re-suspended in 500 ml of 10% random motility buffer (RMB) (background solution) (Adadevoh et al, 2015). Cellsurface hydrophobicity was derived from the contact angles (θ w ) of water drops on the bacterial lawns using a goniometer microscope (Krüss GmbH, Germany).…”

“…As a representative of polycyclic aromatic hydrocarbons (PAHs), naphthalene is one of the most prevalent groundwater contaminants at sites contaminated with PAHs (Mihelcic and Luthy, 1991;Ghoshal et al, 1996;Marx and Aitken, 1999). Although naphthalene-induced bacterial migration has been well studied as a chemotactic phenomenon, the majority of studies were conducted in homogeneous model porous media by placing pure crystalline naphthalene somewhere in the porous media to observe the induced change in bacterial deposition (Marx and Atiken, 2000;Law and Aitken, 2003;Velasco-Casal et al, 2008;Adadevoh et al, 2015). This strategy creates macroscopic concentration gradients for straightforward observation of chemotactic movement in the liquid phase.…”

In silico analysis of the chemotactic system of Agrobacterium tumefaciens

“…Chemotaxis can help micro-organisms under nutrition stress search for suitable living environments, and is important for host–microbe symbiotic processes, such as host invasion [1], biofilm formation [2] and cell adhesion [3]. The movement of bacteria towards degradable environmental pollutants is related to chemotaxis, and could improve the degradation rates and bioavailability of some pollutants, and effectively promote bioremediation of environmental pollutants [4, 5]. The chemotactic system of bacteria (often called the Che system) is composed of a chemoreceptor and core proteins.…”