Effect of carbon starvation on toluene degradation activity by toluene monooxygenase-expressing bacteria

Abstract

Subsurface bacteria commonly exist in a starvation state with only periodic exposure to utilizable sources of carbon and energy. In this study, the effect of carbon starvation on aerobic toluene degradation was quantitatively evaluated with a selection of bacteria representing all the known toluene oxygenase enzyme pathways. For all the investigated strains, the rate of toluene biodegradation decreased exponentially with starvation time. First-order deactivation rate constants for TMO-expressing bacteria were approximately an order of magnitude greater than those for other oxygenase-expressing bacteria. When growth conditions (the type of growth substrate and the type and concentration of toluene oxygenase inducer) were varied in the cultures prior to the deactivation experiments, the rate of deactivation was not significantly affected, suggesting that the rate of deactivation is independent of previous substrate/inducer conditions. Because TMO-expressing bacteria are known to efficiently detoxify TCE in subsurface environments, these findings have significant implications for in situ TCE bioremediation, specifically for environments experiencing variable growth-substrate exposure conditions.

Species-specific patterns in the vulnerability of ­carbon-starved bacteria to protist grazing

“…(Kjelleberg 1993, McDougald et al 2001, Entero bacteria (Jenkins et al 1988, Galdiereo et al 1994, Brauer et al 2006) and others (Wrangstadh et al 1986, Redon et al 2005, Johnson et al 2006). For these model organisms, the final outcome is so-called nongrowing 'ultramicrobacteria' which are highly resistant to diverse stress factors (e.g.…”

Induction kinetics of aerobic toluene degradation as a function of carbon starvation history

“…In TCEdegrading TMO bacteria, the first-order deactivation rate constant was found to be both organism-specific and independent of previous induction history and/or growth conditions [27].…”

“…When TCE-degrading bacteria are exposed to subthreshold concentration of substrate/inducer such as under carbon starvation conditions, the specific activity of toluene degradation was found to decrease exponentially as the duration of prior carbon starvation was increased [26,27]. A first-order decay expression was therefore employed to express the scaling factor (e Down-shift ) as a function of the duration of carbon starvation (Eq.…”

“…The deactivation rate of TMOcontaining TCE-degrading microbes was found to be more than an order of magnitude greater than that of other oxygenase-containing bacteria [27]. Supplying the TCE-cooxidizing bacteria with a primary substrate for cellular growth and a chemical inducer of the TMO In this study, the effects of carbon starvation history on the induction kinetics of aerobic toluene degradation by Ralstonia pickettii PKO1 were quantitatively explored.…”

Benzene degradation by Ralstonia pickettii PKO1 in the presence of the alternative substrate succinate

“…Furthermore, it has recently been shown that the rate of toluene degradation by PKO1 decreased exponentially during periods of carbon starvation. This deactivation probably resulted from carbon starvation itself and not from the absence of an inducer of the tbu pathway (Johnson et al 2006). …”