<Emphasis Type="Italic">In vivo</Emphasis>site-specific biotinylation of proteins within the secretory pathway using a single vector system

Background  

Due to its extremely high strength, the interaction between biotin and (strept)avidin has been exploited for a large number of biotechnological applications. Site-specific biotinylation of proteins in vivo can be achieved by co-expressing in mammalian cells the protein of interest fused to a 15 amino acid long Biotin Acceptor Peptide (BAP) and the bacterial biotin-protein ligase BirA, which specifically recognizes and attaches a biotin to the single lysine residue of the BAP sequence. However, this system is mainly based on the contemporaneous use of two different plasmids or on induction of expression of two proteins through an IRES-driven mechanism.     

The role of sigma factor RpoH1 in the pH stress response of <Emphasis Type="Italic">Sinorhizobium meliloti</Emphasis>

Background  

Environmental pH stress constitutes a limiting factor for S. meliloti survival and development. The response to acidic pH stress in S. meliloti is versatile and characterized by the differential expression of genes associated with various cellular functions. The purpose of this study was to gain detailed insight into the participation of sigma factors in the complex stress response system of S. meliloti 1021 using pH stress as an effector.     

A new strategy for isolating genes controlling dosage compensation in <Emphasis Type="Italic">Drosophila</Emphasis>using a simple epigenetic mosaic eye phenotype

Background  

The Drosophila Male Specific Lethal (MSL) complex contains chromatin modifying enzymes and non-coding roX RNA. It paints the male X at hundreds of bands where it acetylates histone H4 at lysine 16. This epigenetic mark increases expression from the single male X chromosome approximately twofold above what gene-specific factors produce from each female X chromosome. This equalises X-linked gene expression between the sexes. Previous screens for components of dosage compensation relied on a distinctive male-specific lethal phenotype.     

Rapid acid treatment of <Emphasis Type="Italic">Escherichia coli</Emphasis>: transcriptomic response and recovery

Background  

Many E. coli genes show pH-dependent expression during logarithmic growth in acid (pH 5–6) or in base (pH 8–9). The effect of rapid pH change, however, has rarely been tested. Rapid acid treatment could distinguish between genes responding to external pH, and genes responding to cytoplasmic acidification, which occurs transiently following rapid external acidification. It could reveal previously unknown acid-stress genes whose effects are transient, as well as show which acid-stress genes have a delayed response.     

LTR retrotransposons and the evolution of dosage compensation in <Emphasis Type="Italic">Drosophila</Emphasis>

Background  

Dosage compensation in Drosophila is the epigenetic process by which the expression of genes located on the single X-chromosome of males is elevated to equal the expression of X-linked genes in females where there are two copies of the X-chromosome. While epigenetic mechanisms are hypothesized to have evolved originally to silence transposable elements, a connection between transposable elements and the evolution of dosage compensation has yet to be demonstrated.     

Study on roles of anaplerotic pathways in glutamate overproduction of <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis> by metabolic flux analysis

Background  

Corynebacterium glutamicum has several anaplerotic pathways (anaplerosis), which are essential for the productions of amino acids, such as lysine and glutamate. It is still not clear how flux changes in anaplerotic pathways happen when glutamate production is induced by triggers, such as biotin depletion and the addition of the detergent material, Tween 40. In this study, we quantitatively analyzed which anaplerotic pathway flux most markedly changes the glutamate overproduction induced by Tween 40 addition.     

Characterization of the iron-regulated <Emphasis Type="Italic">desA</Emphasis> promoter of <Emphasis Type="Italic">Streptomyces pilosus</Emphasis> as a system for controlled gene expression in actinomycetes

Background  

The bioavailability of iron is quite low since it is usually present as insoluble complexes. To solve the bioavailability problem microorganisms have developed highly efficient iron-scavenging systems based on the synthesis of siderophores that have high iron affinity. The systems of iron assimilation in microorganisms are strictly regulated to control the intracellular iron levels since at high concentrations iron is toxic for cells. Streptomyces pilosus synthesizes the siderofore desferrioxamine B. The first step in desferrioxamine biosynthesis is decarboxylation of L-lysine to form cadaverine, a desferrioxamine B precursor. This reaction is catalyzed by the lysine decarboxylase, an enzyme encoded by the desA gene that is repressed by iron.     

Influence of short chain fatty acids and lysine on Salmonella typhimurium cadA expression

In Salmonella typhimurium, cadA has a role in virulence expression and is an inducible gene that responds to external lysine concentration. In this study, a strain of S. typhimurium carrying a cadA: lacZ fusion was used to determine if the induction of cadA occurred under different lysine concentrations and mildly acid conditions in the presence of short chain fatty acids. Aliquots of an 18-h culture of S. typhimurium were placed on fresh media containing different lysine concentrations at pH 5.8 adjusted by addition of HCl or by 1 M short chain fatty acids (SCFA, acetic, propionic and butyric acid) stock solution. After an induction period of 2 h, -galactosidase activities were assayed. Expression of cadA in rich medium was significantly higher than that of minimal medium at neutral pH and different lysine concentrations. In contrast, at pH 5.8, there was a significant increase in cadA expression, particularly when pH was adjusted using HCl at all lysine levels. Addition of a mixture of organic acids yielded an overall lower cadA expression at all lysine levels studied when compared to HCl. However, each SCFA challenge (individual or as a mixture) caused a high level of expression, both at neutral and acidic pH. Based on these results it is apparent that in the presence of external lysine, SCFA and nutrient availability can influence cadA expression in S. typhimurium.     

The structure of a reduced form of OxyR from <Emphasis Type="Italic">Neisseria meningitidis</Emphasis>

Background  

Survival of the human pathogen, Neisseria meningitidis, requires an effective response to oxidative stress resulting from the release of hydrogen peroxide by cells of the human immune system. In N. meningitidis, expression of catalase, which is responsible for detoxifying hydrogen peroxide, is controlled by OxyR, a redox responsive LysR-type regulator. OxyR responds directly to intracellular hydrogen peroxide through the reversible formation of a disulphide bond between C199 and C208 in the regulatory domain of the protein.     

<Emphasis Type="Italic">Brucella abortus ure2</Emphasis> region contains an acid-activated urea transporter and a nickel transport system

Background  

Urease is a virulence factor that plays a role in the resistance of Brucella to low pH conditions, both in vivo and in vitro. Brucella contains two separate urease gene clusters, ure1 and ure2. Although only ure1 codes for an active urease, ure2 is also transcribed, but its contribution to Brucella biology is unknown.