Oxygen-regulated stimulons of Salmonella typhimurium identified by Mu d(Ap lac) operon fusions

Abstract

Using the technique of Mu dl(Ap lac)-directed lacZ operon fusions, several oxygen-regulated genetic loci were identified in SalmoneUa typhimurum. Thirteen anaerobically inducible and six aerobically inducible operon fusions were identified. Based on control by the oxrA and oxrB regulatory loci, the ani-lacZ fusions were grouped into three classes: class I loci were regulated by both oxr loci, class H genes were regulated by oxrA only, and class m loci were not affected by either regulatory locus. Several of the ani-lacZ fusions required growth in complex medium before they exhibited the inducible phenotype. While the expression of some of these loci was repressed when organisms were grown in nitrate, others were stimulated by nitrate. Fusions into the hyd and phs loci were identified among the Isolated ani-lacZ fusions. Six oxygen-inducible (oxi) operon fusions were also identified. Two of the oxi loci mapped near oxygen-regulatory loci: oxiC near oxrA and oxiE near oxyR. However, neither fusion appeared to occur within the regulatory locus. The data presented serve to further define the aerobic and anaerobic stimulons of S. typhimurium but indicate additional regulatory circuits above those already defined.

Anaerobically expressed Escherichia coli genes identified by operon fusion techniques

“…The gene fusion strategy which we used to study genes regulated by anaerobiosis is similar to those described by Winkelman and Clark (31) and Aliabadi et al (1) except that they used the indirect indicator lactose-MacConkey agar rather than XG (5-bromo-4-chloro-3-indolyl-,-D-galactopyranoside) the direct chromogenic substrate for 3-galactosidase. Our fusions are different from those which they identified, perhaps reflecting a different level of indicator sensitivity.…”

Novel regulatory loci controlling oxygen- and pH-regulated gene expression in Salmonella typhimurium

“…Various oxr mutants were subjected to two-dimensional polyacrylamide electrophoretic analysis of anaerobiosis-inducible proteins. Several pathways of anaerobic control were observed by means of these techniques.There have been several reports identifying genes in Salmonella typhimurium and Escherichia coli whose expressions are controlled by the presence or absence of molecular oxygen (1,10,35,37). Anaerobiosis-inducible genes with unidentified products have been referred to as ani (1) and oxd (35).…”

“…There have been several reports identifying genes in Salmonella typhimurium and Escherichia coli whose expressions are controlled by the presence or absence of molecular oxygen (1,10,35,37). Anaerobiosis-inducible genes with unidentified products have been referred to as ani (1) and oxd (35).…”

“…Mutations in fnr prevent the anaerobic induction of several respiratory enzymes, such as the nitrate and fumarate reductases, hydrogenase 2, dimethyl sulfoxide reductase, and glycerol-3-phosphate dehydrogenase (3,7,23,25,34 (1,11,18,19,30,35). The molecular mechanism(s) controlling the expressions of these genes remains obscure.…”

“…Anaerobiosis-inducible genes with unidentified products have been referred to as ani (1) and oxd (35). These genes were discovered by generating random lacZ operon fusions in the chromosome with Mu d(Ap lac) phage.…”