Effect of Starvation on Induction of Quinoline Degradation for a Subsurface Bacterium in a Continuous-Flow Column

Abstract

Differences in the induction response and the initial two reactions of quinoline degradation between short-term (2 days)and long-term (60 to 80 days)-starved cells of a subsurface Pseudonwnas cepacia strain were examined by using continuous-flow columns. The ability of bacteria that are indigenous to oligotrophic environments to respond to a contaminant was assessed by using long-term starvation to induce a cell physiology that simulates the in situ physiology of the bacteria. With quinoline concentrations of 39 and 155 ,uM, long-term-starved cells converted quinoline to degradation products more efficiently than did short-term-starved cells. Quinoline concentrations of 155 ,uM and, to a greater extent, 775 ,uM had an inhibitory effect on induction in long-term-starved cells. However, only the length of the induction process was affected with these quinoline concentrations; degradation of quinoline at the steady state for long-term-starved cells was equal to or better than that for short-term-starved cells. The induction time for short-term-starved cells did not increase progressively with increasing quinoline concentration. Experiments with starved cells are important for the development of accurate predictive models of contaminant transport in the subsurface because starvation, which induces a cell physiology that simulates the in situ physiology of many bacteria, may affect the induction process.

The influence of physical heterogeneity on microbial degradation and distribution in porous media

“…P. cepacia sp. can strongly adhere to porous media through the production of extracellular polysaccarides [Truex et al, 1992]; however, approximately half of the biomass eluted during the initial 48-hour rinse (denoted -48 to 0 hours on graph, Figure 5a). The initial biomass measured by PLFA after the 48-hour rinse, but before the injection of benzoate substrate (e.g., t = 0), was 5.2 x 10 s CFU/g (protein equivalent is 0.85 mg/L).…”

Modeling contaminant transport and biodegradation in a layered porous media system

“…bly transported there by the processes of advection and dispersion during these initial experiments. Although previous experiments [Truex et al, 1992] and monitoring of the flow cell effluent showed that at velocities similar to those present in the biodegradation experiment, the microorgan. ism 866A remains strongly attached to the porous medium, ...... • ................... eventually levels off because oxygen limitations prevent further transformation, as indicated by the lack of oxygen in the system at these locations (Figures 4a and 4b).…”

“…term on the right-hand side of each equation represents the source or sink due to reactions, and are given by equations (2). At the velocities used for these experiments, the microorganism used in this research remains strongly attached to the solid phase[Truex et al, 1992]; therefore transport is neglected for the microbial phase…”

Effects of Microbial Metabolic Lag in Contaminant Transport and Biodegradation Modeling

“…Native subsurface organisms are often in nutrient-poor environments and may have to overcome cell damage when they first encounter a new substrate [e.g., Morita, 1988;Truex et al, 1992]. Furthermore, many of the contaminants of interest in groundwater hydrology are refractory compounds; as a result, it is not unusual for there to be a lag between the time of arrival of the substrate and the time that degradation of substrate begins.…”

“…Furthermore, many of the contaminants of interest in groundwater hydrology are refractory compounds; as a result, it is not unusual for there to be a lag between the time of arrival of the substrate and the time that degradation of substrate begins. In porous media systems, lag times of days to weeks have been observed for some compounds [e.g., Bouwer and McCaray, 1983;Kuhn et al, 1985;Truex et al, 1992;Alvarez, 1992]. Microbial metabolic lag may result in significantly less degradation of the substrate than might be otherwise expected [e.g., Wood and Dawson, 1992]; thus, accounting for microbial lag may be particularly important for predicting the biodegradation of refractory substances.…”