Regulation of Raoultella terrigena comb.nov. phytase expression.

Phytases catalyze the release of phosphate from phytate (myo-inositol hexakisphosphate) to inositol polyphosphates. Raoultella terrigena comb.nov.

On the origin of plasmid-borne, extended-spectrum, antibiotic resistance mutations in bacteria.

Many antibiotic resistance mutations arise in pathogenic bacteria that harbor plasmids (R-plasmids). Resistance to third generation cephalosporins, for instance, largely occurs by one or more point mutations in plasmid bla genes that expand the resistance spectrum of beta-lactamases. Here I review relevant evidence underlying the worldwide emergence of extended spectrum beta-lactamases (ESBLs).

An IS4 insertion at the glnA control region of Escherichia coli creates a new promoter by providing the -35 region of its 3'-end.

An insertion element (IS)4 insertion selected as suppressor of the rpoN73::Tn5 alelle was located inside the control region of the glnA gene in Escherichia coli. In the rpoN73::Tn5 background the IS4 insertion promotes glnA transcription at a low constitutive level sufficient to sustain glutamine-independent growth. The IS4 insertion mutation in either rpoN73::Tn5 or wild-type backgrounds promotes glnA transcription from a new start site located two bases downstream of the glnAp2 start site.

Nitrogen regulation in an Escherichia coli strain with a temperature sensitive glutamyl-tRNA synthetase.

Escherichia coli cells carrying the gltX351 allele are unable to grow at 42 degrees C (Ts phenotype) due to an altered glutamyl-tRNA synthetase. We found that gltX351 cells display a new phenotype termed Gsd-, i.e.

Mutations affecting the Shine-Dalgarno sequences of the untranslated region of the Escherichia coli gltBDF operon.

Individual mutations which affected each of the two Shine-Dalgarno sequences at the 5' untranslated region of the gltB gene of Escherichia coli were characterized. They were isolated in plasmids carrying a gltB'-'lacZ protein fusion preceded by the regulatory region of the gltBDF operon. Subcloning and nucleotide sequencing of approximately 1,206 bp of DNA encompassing the gltBDF regulatory region showed that the mutations affected the first base at each of the two identical Shine-Dalgarno sequences, SD1 and SD2, located 40 and 8 bases, respectively, upstream from the putative gltB open reading frame.