Superior Protection from Live-Attenuated Vaccines Directed against Johne's Disease.

Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) is the etiological agent of Johne's disease in ruminants.

IraL is an RssB anti-adaptor that stabilizes RpoS during logarithmic phase growth in Escherichia coli and Shigella.

Unlabelled: RpoS (σ(S)), the general stress response sigma factor, directs the expression of genes under a variety of stressful conditions. Control of the cellular σ(S) concentration is critical for appropriately scaled σ(S)-dependent gene expression. One way to maintain appropriate levels of σ(S) is to regulate its stability.

Tuning the biological activity profile of antibacterial polymers via subunit substitution pattern.

Binary nylon-3 copolymers containing cationic and hydrophobic subunits can mimic the biological properties of host-defense peptides, but relationships between composition and activity are not yet well understood for these materials. Hydrophobic subunits in previously studied examples have been limited mostly to cycloalkane-derived structures, with cyclohexyl proving to be particularly promising. The present study evaluates alternative hydrophobic subunits that are isomeric or nearly isomeric with the cyclohexyl example; each has four sp(3) carbons in the side chains.

Effects of Cyclic vs. Acyclic Hydrophobic Subunits on the Chemical Structure and Biological Properties of Nylon-3 Co-Polymers.

Nylon-3 co-polymers containing both hydrophobic and cationic subunits can mimic the activity profile of host-defense peptides, if subunit identity and proportion are carefully selected. These sequence- and stereo-random co-polymers inhibit bacterial growth at relatively low concentrations, apparently via disruption of bacterial membranes, but they are relatively non-disruptive toward eukaryotic cell membranes (low hemolytic activity). In all previous examples, the hydrophobic subunits have contained cycloalkyl groups that incorporate the backbone Cα-Cβ bond.

Transcription of the Escherichia coli fatty acid synthesis operon fabHDG is directly activated by FadR and inhibited by ppGpp.

In Escherichia coli, FadR and FabR are transcriptional regulators that control the expression of fatty acid degradation and unsaturated fatty acid synthesis genes, depending on the availability of fatty acids. In this report, we focus on the dual transcriptional regulator FadR. In the absence of fatty acids, FadR represses the transcription of fad genes required for fatty acid degradation.

The dksA promoter is negatively feedback regulated by DksA and ppGpp.

Escherichia coli DksA is an RNA polymerase (RNAP)-binding protein required for the regulation of a number of promoters, including those for the biosynthesis of rRNA, many ribosomal proteins, components of the flagellum, and several amino acids. Previous work demonstrated that DksA protein levels do not vary greatly in different growth conditions. We show here that DksA is a stable protein whose levels are kept constant by a negative feedback loop in which transcription from the dksA promoter is inhibited by DksA protein in conjunction with its cofactor ppGpp.

Direct regulation of Escherichia coli ribosomal protein promoters by the transcription factors ppGpp and DksA.

We show here that the promoters for many of the Escherichia coli ribosomal protein operons are regulated directly by two transcription factors, the small RNA polymerase-binding protein DksA and the nutritional stress-induced nucleotide ppGpp. ppGpp and DksA work together to inhibit transcription initiation from ribosomal protein promoters in vitro and in vivo. The degree of promoter regulation by ppGpp/DksA varies among the r-protein promoters, but some are inhibited almost as much as rRNA promoters.

DksA and ppGpp directly regulate transcription of the Escherichia coli flagellar cascade.

The components of the Escherichia coli flagella apparatus are synthesized in a three-level transcriptional cascade activated by the master regulator FlhDC. The cascade co-ordinates the synthesis rates of a large number of gene products with each other and with nutritional conditions. Recent genome-wide studies have reported that flagellar transcription is altered in cells lacking the transcription regulators DksA or ppGpp, but some or all reported effects could be indirect, and some are contradictory.

Effects of DksA, GreA, and GreB on transcription initiation: insights into the mechanisms of factors that bind in the secondary channel of RNA polymerase.

Escherichia coli DksA, GreA, and GreB have similar structures and bind to the same location on RNA polymerase (RNAP), the secondary channel. We show that GreB can fulfil some roles of DksA in vitro, including shifting the promoter-open complex equilibrium in the dissociation direction, thus allowing rRNA promoters to respond to changes in the concentration of ppGpp and NTPs. However, unlike deletion of the dksA gene, deletion of greB had no effect on rRNA promoters in vivo.