Monothiol Glutaredoxin Is Essential for Oxidative Stress Protection and Virulence in Pseudomonas aeruginosa.

Glutaredoxins (Grxs), ubiquitous redox enzymes belonging to the thioredoxin family, catalyze the reduction of thiol-disulfide exchange reactions in a glutathione-dependent manner. A Pseudomonas aeruginosa Δ mutant exhibited hypersensitivity to oxidative stress-generating agents, such as paraquat (PQ) and cumene hydroperoxide (CHP). studies showed that P.

Inactivation of the ActSR system affects resistance to multiple stresses with increased HO sensitivity due to reduced expression of .

The ActSR two-component regulatory system is a member of a homologous group of global redox-responsive regulatory systems that adjust the expression of energy-consuming and energy-supplying metabolic pathways in order to maintain cellular redox balance. In this study, the transcriptional organization of the locus was determined and the effect of system inactivation on stress resistance was investigated. It was found that is transcribed as a monocistronic mRNA and is transcribed along with as a bicistronic mRNA, while is also transcribed as a monocistronic message.

Identification of a repressor and an activator of azoreductase gene expression in Pseudomonas putida and Xanthomonas oryzae.

Genes responsible for the production of azoreductase enzymes in 2 gram-negative bacteria, the soil bacterium Pseudomonas putida (AzoP) and the plant pathogen Xanthomonas oryzae (AzoX), were identified. The deduced amino acid sequences of AzoP and AzoX, share 46% amino acid identity to each other. Two different bacterial transcription factors, a repressor (AzoPR) and an activator (AzoXR), in P.

Specific detection of the pesticide chlorpyrifos by a sensitive genetic-based whole cell biosensor.

The Sinorhizobium meliloti chpA promoter is highly induced in the presence of the pesticide chlorpyrifos (CPF) through the action of the transcriptional activator, ChpR. A whole-cell biosensor for the detection of CPF was developed and is composed of an Escherichia coli strain carrying a chpR expression vector and a chpA promoter-atsBA transcriptional fusion plasmid encoding sulfatase (atsA) and formylglycine generating enzyme (atsB) from Klebsiella sp. The sulfatase is posttranslationally activated by formylglycine generating enzyme (FGE) and then converts 4-methylumbelliferyl sulfate (4-MUS) to the fluorescent product, 4-methyllumbelliferone (4-MU).

Cloning of Toluene 4-Monooxygenase Genes and Application of Two-Phase System to the Production of the Anticancer Agent, Indirubin.

Indirubin is a strong inhibitor of several eukaryotic cell signaling pathways and shows promise as a treatment for myelocytic leukemia and Alzheimer's disease. The tmoABCDEF operon, encoding the components of a novel toluene 4-monooxygenase from the paint factory soil isolate, Pseudomonas sp. M4, was cloned and expressed in Escherichia coli.

Peroxide-sensing transcriptional regulators in bacteria.

The ability to maintain intracellular concentrations of toxic reactive oxygen species (ROS) within safe limits is essential for all aerobic life forms. In bacteria, as well as other organisms, ROS are produced during the normal course of aerobic metabolism, necessitating the constitutive expression of ROS scavenging systems. However, bacteria can also experience transient high-level exposure to ROS derived either from external sources, such as the host defense response, or as a secondary effect of other seemingly unrelated environmental stresses.

The hdhA gene encodes a haloacid dehalogenase that is regulated by the LysR-type regulator, HdhR, in Sinorhizobium meliloti.

The plasmid pSymA, in the nitrogen-fixing soil bacterium, Sinorhizobium meliloti, carries a 750-bp ORF (SMa1978) designated, hdhA, which encodes a novel dehalogenase that can detoxify haloacid compounds, showing a preference for haloacetic acids. Purified His-tagged HdhA demonstrated the apparent ability to dehalogenate chloroacetic acid and trifluoroacetic acid. In addition, upstream of hdhA, a gene encoding a lysR-type transcription regulator denoted, hdhR (SMa1979), has been identified to be a transcriptional repressor of hdhA expression.

ChpR is a chlorpyrifos-responsive transcription regulator in Sinorhizobium meliloti.

The broad-spectrum organophosphate insecticide chlorpyrifos (CPF)-inducible locus, chpAB, was identified on the endogenous plasmid pSymB in Sinorhizobium meliloti. The S. meliloti chpA promoter was highly induced by CPF and was induced at much lower levels by diazinon and ethion.

Peroxiredoxins in bacterial antioxidant defense.

Peroxiredoxins constitute an important component of the bacterial defense against toxic peroxides. These enzymes use reactive cysteine thiols to reduce peroxides with electrons ultimately derived from reduced pyridine dinucleotides. Studies examining the regulation and physiological roles of AhpC, Tpx, Ohr and OsmC reveal the multilayered nature of bacterial peroxide defense.

HpdR is a transcriptional activator of Sinorhizobium meliloti hpdA, which encodes a herbicide-targeted 4-hydroxyphenylpyruvate dioxygenase.

Sinorhizobium meliloti hpdA, which encodes the herbicide target 4-hydroxyphenylpyruvate dioxygenase, is positively regulated by HpdR. Gel mobility shift and DNase I footprinting analyses revealed that HpdR binds to a region that spans two conserved direct-repeat sequences within the hpdR-hpdA intergenic space. HpdR-dependent hpdA transcription occurs in the presence of 4-hydroxyphenylpyruvate, tyrosine, and phenylalanine, as well as during starvation.

Challenging Xanthomonas campestris with low levels of arsenic mediates cross-protection against oxidant killing.

Xanthomonas encounters highly toxic reactive oxygen species (ROS) from many sources, such as those generated by plants against invading bacteria, other soil bacteria and from aerobic respiration. Thus, conditions that alter intracellular ROS levels such as exposure to toxic metalloids would have profound effects on bacterial physiology. Here, we report that exposure of Xanthomonas campestris pv.

ohrR and ohr are the primary sensor/regulator and protective genes against organic hydroperoxide stress in Agrobacterium tumefaciens.

The genes involved in organic hydroperoxide protection in Agrobacterium tumefaciens were functionally evaluated. Gene inactivation studies and functional analyses have identified ohr, encoding a thiol peroxidase, as the gene primarily responsible for organic hydroperoxide protection in A. tumefaciens.

Chemical modulation of physiological adaptation and cross-protective responses against oxidative stress in soil bacterium and phytopathogen, Xanthomonas.

Soil bacteria need to adapt quickly to changes in the environmental conditions. Physiological adaptation plays an important role in microbial survival, especially under stressful conditions. Here the abilities of chemicals and pesticides to modulate physiological adaptive and cross-protective responses, that make the bacteria more resistant to oxidative stress, are examined in the soil bacterium and phytopathogen, Xanthomonas.

Effector-mediated interaction of CbbRI and CbbRII regulators with target sequences in Rhodobacter capsulatus.

In Rhodobacter capsulatus, genes encoding enzymes of the Calvin-Benson-Bassham reductive pentose phosphate pathway are located in the cbb(I) and cbb(II) operons. Each operon contains a divergently transcribed LysR-type transcriptional activator (CbbR(I) and CbbR(II)) that regulates the expression of its cognate cbb promoter in response to an as yet unidentified effector molecule(s). Both CbbR(I) and CbbR(II) were purified, and the ability of a variety of potential effector molecules to induce changes in their DNA binding properties at their target promoters was assessed.

Regulators of nonsulfur purple phototrophic bacteria and the interactive control of CO2 assimilation, nitrogen fixation, hydrogen metabolism and energy generation.

For the metabolically diverse nonsulfur purple phototrophic bacteria, maintaining redox homeostasis requires balancing the activities of energy supplying and energy-utilizing pathways, often in the face of drastic changes in environmental conditions. These organisms, members of the class Alphaproteobacteria, primarily use CO2 as an electron sink to achieve redox homeostasis. After noting the consequences of inactivating the capacity for CO2 reduction through the Calvin-Benson-Bassham (CBB) pathway, it was shown that the molecular control of many additional important biological processes catalyzed by nonsulfur purple bacteria is linked to expression of the CBB genes.

Interactions of the cbbII promoter-operator region with CbbR and RegA (PrrA) regulators indicate distinct mechanisms to control expression of the two cbb operons of Rhodobacter sphaeroides.

In a previous study (Dubbs, J. M., Bird, T.

Differential expression of the CO2 fixation operons of Rhodobacter sphaeroides by the Prr/Reg two-component system during chemoautotrophic growth.

In Rhodobacter sphaeroides, the two cbb operons encoding duplicated Calvin-Benson Bassham (CBB) CO2 fixation reductive pentose phosphate cycle structural genes are differentially controlled. In attempts to define the molecular basis for the differential regulation, the effects of mutations in genes encoding a subunit of Cbb3 cytochrome oxidase, ccoP, and a global response regulator, prrA (regA), were characterized with respect to CO2 fixation (cbb) gene expression by using translational lac fusions to the R. sphaeroides cbb(I) and cbb(II) promoters.