0000000000362561
AUTHOR
Tanja Arras
Availability of O 2 as a Substrate in the Cytoplasm of Bacteria under Aerobic and Microaerobic Conditions
ABSTRACT The growth rates of Pseudomonas putida KT2442 and mt-2 on benzoate, 4-hydroxybenzoate, or 4-methylbenzoate showed an exponential decrease with decreasing oxygen tensions (partial O 2 tension [pO 2 ] values). The oxygen tensions resulting in half-maximal growth rates were in the range of 7 to 8 mbar of O 2 (corresponding to 7 to 8 μM O 2 ) (1 bar = 10 5 Pa) for aromatic compounds, compared to 1 to 2 mbar for nonaromatic compounds like glucose or succinate. The decrease in the growth rates coincided with excretion of catechol or protocatechuate, suggesting that the activity of the corresponding oxygenases became limiting. The experiments directly establish that under aerobic and micr…
Role of glutathione in the formation of the active form of the oxygen sensor FNR ([4Fe-4S]·FNR) and in the control of FNR function
The oxygen sensor regulator FNR (fumarate nitrate reductase regulator) of Escherichia coli is known to be inactivated by O2 as the result of conversion of a [4Fe-4S] cluster of the protein into a [2Fe-2S] cluster. Further incubation with O2 causes loss of the [2Fe-2S] cluster and production of apoFNR. The reactions involved in cluster assembly and reductive activation of apoFNR isolated under anaerobic or aerobic conditions were studied in vivo and in vitro. In a gshA mutant of E. coli that was completely devoid of glutathione, the O2 tension for the regulatory switch for FNR-dependent gene regulation was decreased by a factor of 4–5 compared with the wild-type, suggesting a role for glutat…