The stringent response regulates the poly-β-hydroxybutyrate (PHB) synthesis in Azotobacter vinelandii.

The stringent response exerted by (p)ppGpp and RNA-polymerase binding protein DksA regulates gene expression in diverse bacterial species. To control gene expression (p)ppGpp, synthesized by enzymes RelA and SpoT, interacts with two sites within the RNA polymerase; site 1, located in the interphase between subunits β' and ω (rpoZ), and site 2 located in the secondary channel that is dependent on DksA protein. In Escherichia coli, inactivation of dksA results in a reduced sigma factor RpoS expression.

The Azotobacter vinelandii AlgU regulon during vegetative growth and encysting conditions: A proteomic approach.

In the Pseduomonadacea family, the extracytoplasmic function sigma factor AlgU is crucial to withstand adverse conditions. Azotobacter vinelandii, a closed relative of Pseudomonas aeruginosa, has been a model for cellular differentiation in Gram-negative bacteria since it forms desiccation-resistant cysts. Previous work demonstrated the essential role of AlgU to withstand oxidative stress and on A.

Defining the regulatory mechanisms of sigma factor RpoS degradation in Azotobacter vinelandii and Pseudomonas aeruginosa.

In several Gram-negative bacteria, the general stress response is mediated by the alternative sigma factor RpoS, a subunit of RNA polymerase that confers promoter specificity. In Escherichia coli, regulation of protein levels of RpoS involves the adaptor protein RssB, which binds RpoS for presenting it to the ClpXP protease for its degradation. However, in species from the Pseudomonadaceae family, RpoS is also degraded by ClpXP, but an adaptor has not been experimentally demonstrated.

The ribosome rescue pathways SsrA-SmpB, ArfA, and ArfB mediate tolerance to heat and antibiotic stresses in Azotobacter vinelandii.

Bacteria have a mechanism to rescue stalled ribosomes known as trans-translation consisting of SsrA, a transfer-messenger RNA (tmRNA), and the small protein SmpB. Other alternative rescue mechanisms mediated by ArfA and ArfB proteins are present only in some species. Ribosome rescue mechanisms also play a role in tolerance to antibiotics and various stresses such as heat.

PsrA positively regulates the unsaturated fatty acid synthesis operon fabAB in Azotobacter vinelandii.

In Pseudomonas spp. PsrA, a transcriptional activator of the rpoS gene, regulates fatty acid catabolism by repressing the fadBA5 β-oxidation operon. In Azotobacter vinelandii, a soil bacterium closely related to Pseudomonas species, PsrA is also an activator of rpoS expression, although its participation in the regulation of lipid metabolism has not been analyzed.

Cyclic di-GMP-Mediated Regulation of Extracellular Mannuronan C-5 Epimerases Is Essential for Cyst Formation in Azotobacter vinelandii.

The genus belonging to the family, is characterized by the formation of cysts, which are metabolically dormant cells produced under adverse conditions and able to resist desiccation. Although this developmental process has served as a model for the study of cell differentiation in Gram-negative bacteria, the molecular basis of its regulation is still poorly understood. Here, we report that the ubiquitous second messenger cyclic dimeric GMP (c-di-GMP) is critical for the formation of cysts in Upon encystment induction, the levels of c-di-GMP increased, reaching a peak within the first 6 h.

The evolution of opioid-related mortality and potential years of life lost in Spain from 2008 to 2017: differences between Spain and the United States.

To investigate the evolution of opioid-related mortality and potential years of life lost in Spanish general population from 2008 to 2017. To evaluate the differences between Spain and the US. A descriptive study using retrospective annual data from 2008 to 2017 in Spanish and US general population.

Outer membrane protein I is associated with poly-β-hydroxybutyrate granules and is necessary for optimal polymer accumulation in on solid medium.

is a soil bacterium that is able to synthesize poly-β-hydroxybutyrate (PHB), a polymer used to produce biodegradable plastic. PHB is stored in the cytoplasm as granules surrounded by several proteins such as the major phasin PhbP, PHB synthase and PHB depolymerase, among others. Many studies have reported the presence of membrane proteins on PHB granules due to contamination during the polymer extraction procedures.

Expression of the sRNAs CrcZ and CrcY modulate the strength of carbon catabolite repression under diazotrophic or non-diazotrophic growing conditions in Azotobacter vinelandii.

Azotobacter vinelandii is a nitrogen-fixing bacterium of the Pseudomonadaceae family that prefers the use of organic acids rather than carbohydrates. Thus, in a mixture of acetate-glucose, glucose is consumed only after acetate is exhausted. In a previous work, we investigated the molecular basis of this carbon catabolite repression (CCR) process under diazotrophic conditions.

The pyrophosphohydrolase RppH is involved in the control of RsmA/CsrA expression in Azotobacter vinelandii and Escherichia coli.

In bacteria, the 5'-end-dependent RNA degradation is triggered by the RNA pyrophosphohydrolase RppH converting tri/diphosphate to monophosphate transcripts. This study shows that in the soil bacterium Azotobacter vinelandii, inactivation of rppH gene negatively affected the production of bioplastic poly-β-hydroxybutyrate (PHB) by reducing the expression at the translational level of PhbR, the specific transcriptional activator of the phbBAC biosynthetic operon. The effect of RppH on the translation of phbR seemed to be exerted through the translational repressor RsmA, as the inactivation of rsmA in the rppH mutant restored the phbR expression.

LEA proteins are involved in cyst desiccation resistance and other abiotic stresses in Azotobacter vinelandii.

Late embryogenesis abundant (LEA) proteins constitute a large protein family that is closely associated with resistance to abiotic stresses in multiple organisms and protect cells against drought and other stresses. Azotobacter vinelandii is a soil bacterium that forms desiccation-resistant cysts. This bacterium possesses two genes, here named lea1 and lea2, coding for avLEA1 and avLEA2 proteins, both containing 20-mer motifs characteristic of eukaryotic plant LEA proteins.

Unphosphorylated EIIA induces ClpAP-mediated degradation of RpoS in Azotobacter vinelandii.

The nitrogen-related phosphotransferase system (PTS ) is composed of the EI , NPr and EIIA proteins that form a phosphorylation cascade from phosphoenolpyruvate. PTS is a global regulatory system present in most Gram-negative bacteria that controls some pivotal processes such as potassium and phosphate homeostasis, virulence, nitrogen fixation and ABC transport activation. In the soil bacterium Azotobacter vinelandii, unphosphorylated EIIA negatively regulates the expression of genes related to the synthesis of the bioplastic polyester poly-β-hydroxybutyrate (PHB) and cyst-specific lipids alkylresorcinols (ARs).

GacA regulates the PTSNtr-dependent control of cyst formation in Azotobacter vinelandii.

Azotobacter vinelandii forms cysts resistant to desiccation and produces polyhydroxybutyrate (PHB), alginate and alkylresorcinols (ARs) that are components of mature cysts. The expression of genes involved in the synthesis of these compounds is under the control of the GacA-RsmA global regulatory system where the RsmA protein represses the translation of mRNAs involved in the synthesis of these polymers. The synthesis of PHB and ARs is also controlled by the Nitrogen-regulated phosphotransferase system (PTS) global regulatory system.

The GacS/A-RsmA Signal Transduction Pathway Controls the Synthesis of Alkylresorcinol Lipids that Replace Membrane Phospholipids during Encystment of Azotobacter vinelandii SW136.

Azotobacter vinelandii is a soil bacterium that undergoes a differentiation process that forms cysts resistant to desiccation. During encystment, a family of alkylresorcinols lipids (ARs) are synthesized and become part of the membrane and are also components of the outer layer covering the cyst, where they play a structural role. The synthesis of ARs in A.

The unphosphorylated EIIA(Ntr) protein represses the synthesis of alkylresorcinols in Azotobacter vinelandii.

Upon encystment induction, Azotobacter vinelandii produces the phenolic lipids alkylresorcinols (ARs) that are structural components of the cysts. The enzymes responsible for the ARs synthesis are encoded in the arsABCD operon, whose expression is activated by ArpR. The transcription of arpR is initiated from an RpoS dependent promoter.

A small heat-shock protein (Hsp20) regulated by RpoS is essential for cyst desiccation resistance in Azotobacter vinelandii.

In Azotobacter vinelandii, a cyst-forming bacterium, the alternative sigma factor RpoS is essential to the formation of cysts resistant to desiccation and to synthesis of the cyst-specific lipids, alkylresorcinols. In this study, we carried out a proteome analysis of vegetative cells and cysts of A. vinelandii strain AEIV and its rpoS mutant derivative AErpoS.

Posttranscriptional regulation of PhbR, the transcriptional activator of polyhydroxybutyrate synthesis, by iron and the sRNA ArrF in Azotobacter vinelandii.

Azotobacter vinelandii is a Gram-negative bacterium able to synthesize poly-β-hydroxybutyrate (PHB), a biodegradable plastic of industrial interest. The phbBAC operon encodes the enzymes of PHB synthesis and is activated by the transcriptional regulator PhbR and the sigma factor RpoS. Iron limitation has been previously reported to increase PHB accumulation in A.

Expression of alginases and alginate polymerase genes in response to oxygen, and their relationship with the alginate molecular weight in Azotobacter vinelandii.

The transcription of genes involved in alginate polymerization and depolymerization, as well as the alginase activity (extracellular and intracellular) under oxygen-limited and non oxygen-limited conditions in cultures of A. vinelandii, was studied. Two levels of dissolved oxygen tension (DOT) (1% and 5%, oxygen-limited and non-oxygen-limited, respectively) strictly controlled by gas blending, were evaluated in a wild type strain.

Sigma factor RpoS controls alkylresorcinol synthesis through ArpR, a LysR-type regulatory protein, during encystment of Azotobacter vinelandii.

Azotobacter vinelandii is a bacterium which undergoes a differentiation process leading to the formation of metabolically dormant cysts. During the encystment process, A. vinelandii produces alkylresorcinol lipids (ARs) that replace the membrane phospholipids and are also components of the layers covering the cyst.

Alginate synthesis in Azotobacter vinelandii is increased by reducing the intracellular production of ubiquinone.

Azotobacter vinelandii, a soil nitrogen fixing bacterium, produces alginate a polysaccharide with industrial and medical relevant applications. In this work, we characterized a miniTn5 mutant, named GG101, that showed a 14-fold increase in the specific production of alginate when grown diazotrophically on solid minimal medium comparing to the parental E strain (also named AEIV). Quantitative real-time reverse transcription PCR analysis indicated that this increased alginate production was due to higher expression levels of several biosynthetic alg genes such as algD.

RsmA post-transcriptionally controls PhbR expression and polyhydroxybutyrate biosynthesis in Azotobacter vinelandii.

In Azotobacter vinelandii the two-component GacS/GacA system is required for synthesis of polyhydroxybutyrate (PHB) and of the exopolysaccharide alginate. The RsmA protein was shown to interact with the alginate biosynthetic algD mRNA, acting as a translational repressor, and GacA was found to activate transcription of the rsmZ1 and rsmZ2 genes that encode small RNAs interacting with RsmA to counteract its repressor activity. The phbBAC operon encodes the enzymes of PHB synthesis and is activated by the transcriptional regulator PhbR.

Transcriptional activation of the Azotobacter vinelandii polyhydroxybutyrate biosynthetic genes phbBAC by PhbR and RpoS.

We previously showed that in Azotobacter vinelandii, accumulation of polyhydroxybutyrate (PHB) occurs mainly during the stationary phase, and that a mutation in phbR, encoding a transcriptional regulator of the AraC family, reduces PHB accumulation. In this study, we characterized the roles of PhbR and RpoS, a central regulator during stationary phase in bacteria, in the regulation of expression of the PHB biosynthetic operon phbBAC and phbR. We showed that inactivation of rpoS reduced PHB accumulation, similar to the phbR mutation, and inactivation of both rpoS and phbR resulted in an inability to produce PHB.

Roles of RpoS and PsrA in cyst formation and alkylresorcinol synthesis in Azotobacter vinelandii.

Azotobacter vinelandii is a soil bacterium that undergoes differentiation to form cysts that are resistant to desiccation. Upon induction of cyst formation, the bacterium synthesizes alkylresorcinols that are present in cysts but not in vegetative cells. Alternative sigma factors play important roles in differentiation.

Isolation and characterization of Azotobacter vinelandii mutants impaired in alkylresorcinol synthesis: alkylresorcinols are not essential for cyst desiccation resistance.

During encystment of Azotobacter vinelandii, a family of alkylresorcinols (ARs) and alkylpyrones (APs) are synthesized. In the mature cyst, these lipids replace the membrane phospholipids and are also components of the layers covering the cyst. In this study, A.

The Azotobacter vinelandii AlgE mannuronan C-5-epimerase family is essential for the in vivo control of alginate monomer composition and for functional cyst formation.

The industrially widely used polysaccharide alginate is a co-polymer of beta-D-mannuronic acid and alpha-L-guluronic acid (G), and the G residues originate from a polymer-level epimerization process catalysed by mannuronan C-5-epimerases. In the genome of the alginate-producing bacterium Azotobacter vinelandii genes encoding one periplasmic (AlgG) and seven secreted such epimerases (AlgE1-7) have been identified. Here we report the generation of a strain (MS163171) in which all the algE genes were inactivated by deletion (algE1-4 and algE6-7) or interruption (algE5).