Mutants of Escherichia coli K12 Unable to use Fumarate as an Anaerobic Electron Acceptor

Abstract

SUMMARYMutants of Escherichia coli KI 2 strain WGAS-GF+/LF+ were selected for their inability to use fumarate as terminal electron acceptor for supporting growth on glycerol or lactate in an atmosphere of H, plus 5 % COz. Eighty-three mutants were grouped into seven different categories according to their ability to grow on different media and their ability to produce gas during glucose fermentation. Enzymological and genetic studies indicated that the major class (type I), representing nearly 70 % of the isolates, lacked fumarate reductase and corresponded to thefrdA mutants studied previously (Spencer & Guest, 1973, 1974. Members of a second class (type 11) were phenotypically similar to men mutants, blocked in menaquinone biosynthesis. They differed from menA mutants in having lesions in the 4 to 51 min region of the chromosome rather than at 87 min. It was concluded that fumarate reductase and menaquinone are essential for anaerobic growth when fumarate serves as electron acceptor but not when nitrate performs this function. Fumarate reductase and menaquinone are also essential for H,-dependent growth on fumarate. Type 111 mutants, originallyfrdl?, were designated fnr because they were defective in fumarate and nitrate reduction and impaired in their ability to produce gas. The fnr gene was located at 28-5 min by its cotransducibility withpyrF(5-7 to 9.2%) and trpA (2-7 to 5'7%) and the gene order fnr-qmeA-pyrF-tpA was established. It was not possible to assign specific metabolic lesions to the fnr mutants nor to the remaining classes, which all exhibited pleiotropic phenotypes. Nevertheless, the results demonstrate that functional or organizational relationships exist between the fumarate reductase system, nitrate reduction and hydrogen production.

HlyX, the FNR homologue of Actinobacillus pleuropneumoniae, is a [4Fe–4S]‐containing oxygen‐responsive transcription regulator that anaerobically activates FNR‐dependent Class I promoters via an enhanced AR1 contact

“…The ability of the regulators to complement the JRG1728 fnr mutation was assessed by their capacity to restore anaerobic growth on leucine-supplemented glycerol nitrate agar (Lambden and Guest, 1976).…”

Molybdenum effector of fumarate reductase repression and nitrate reductase induction in Escherichia coli

“…The operon is positively controlled by an activator protein encoded by the closely linked narL gene and responding to nitrate as the inducer (38,39). The narC operon is inducible only anaerobically, and its expression also depends on the pleiotropic activator protein encoded by fnr at minute 29 (6,23). Fumarate reductase is encoded by the frdABCD operon at minute 94 (8,9,12,21,24,36).…”

“…Fumarate reductase is encoded by the frdABCD operon at minute 94 (8,9,12,21,24,36). The frd operon is induced anaerobically by fumarate in the absence of nitrate (7,13,16,21,23). Expression of the operon also depends on the Fnr protein (6,23).…”

“…The frd operon is induced anaerobically by fumarate in the absence of nitrate (7,13,16,21,23). Expression of the operon also depends on the Fnr protein (6,23).…”

Regulation and Over-expression of the fnr Gene of Escherichia coli

“…The anaerobic respiratory chains associated with these electron acceptors are generally inducible and are repressed during aerobic growth even in the presence of their inducer (for a general review see Ingledew & Poole, 1984). In addition, synthesis of the reductases (fumarate reductase, nitrate reductase and nitrite reductase) and other components of these respiratory systems depends on the regulatory locus fnr (Lambden & Guest, 1976;Newman & Cole, 1978;Chippaux et al, 1978). Evidence has accumulated to indicate that thefnr gene product (FNR) is a transcriptional activator which regulates the expression of its target genes in response to anaerobiosis.…”