An integrated network analysis identifies how ArcAB enables metabolic oscillations in the nitric oxide detoxification network of Escherichia coli

Abstract

The virulences of many pathogens depend on their abilities to detoxify the immune antimicrobial nitric oxide (NO•). The functions of bacterial NO• detoxification machinery depend on oxygen (O ), with O inhibiting some enzymes, whereas others use it as a substrate. Previously, Escherichia coli NO• detoxification was found to be highly attenuated under microaerobic conditions and metabolic oscillations were observed. The oscillations in [NO•] and [O ] were found to result from the inhibitory action of NO• on aerobic respiration, the catalytic inactivation of NO• by Hmp (an NO• dioxygenase), and an imbalanced competition for O between Hmp and cytochrome terminal oxidase activity. Here the authors investigated the role of the ArcAB two component system (TCS) in microaerobic NO• detoxification. The authors observed that wild-type, ΔarcA, and ΔarcB had comparable initial NO• clearance times; however, the mutant cultures failed to exhibit [NO•] and [O ] oscillations. Using an approach that employed experimentation and computational modeling, the authors found that the loss of oscillations in ΔarcA was due to insufficient induction of cytochrome bd-I expression. Collectively, these results establish ArcAB as a TCS that influences NO• detoxification in E. coli within the physiologically-relevant microaerobic regime.

Quantitative Modeling Extends the Antibacterial Activity of Nitric Oxide

“…To quantitatively explore the relationship between delivery dynamics and antimicrobial efficacy, we trained a kinetic model of NO stress in E. coli using the data obtained at 6 and 18 µmol. The model was developed in previous studies (Robinson and Brynildsen, 2013, 2016aRobinson et al, 2014a,b;Sacco et al, 2017) and expanded upon here. Specifically, the model was adjusted to comply with fed-batch systems and cellular growth was incorporated and assumed to depend on the availability of aerobic cytochrome oxidases for respiration.…”

Transcriptional Regulation Contributes to Prioritized Detoxification of Hydrogen Peroxide over Nitric Oxide

“…The H 2 O 2 and NO· biochemical reaction networks of E. coli are complex, and dynamic models have proven useful in quantifying the distributions of these toxic metabolites and exploring system behaviors (29)(30)(31)(32)(33)(34)(35). These previously developed models included detoxification by antioxidants and enzymes, transcriptional regulation and inactivation of enzymes, damage and repair of DNA and Fe-S clusters, and destruction of amino acids by the hydroxyl radical, ·OH, and they were compartmentalized (intracellular, media, and gaseous) to account for the cell-dependent and cell-independent reactions.…”