The Anti-Sigma Factor MucA of Pseudomonas aeruginosa: Dramatic Differences of a mucA22 vs. a ΔmucA Mutant in Anaerobic Acidified Nitrite Sensitivity of Planktonic and Biofilm Bacteria in vitro and During Chronic Murine Lung Infection

Mucoid mucA22 Pseudomonas aeruginosa (PA) is an opportunistic lung pathogen of cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) patients that is highly sensitive to acidified nitrite (A-NO2-). In this study, we first screened PA mutant strains for sensitivity or resistance to 20 mM A-NO2- under anaerobic conditions that represent the chronic stages of the aforementioned diseases. Mutants found to be sensitive to A-NO2- included PA0964 (pmpR, PQS biosynthesis), PA4455 (probable ABC transporter permease), katA (major catalase, KatA) and rhlR (quorum sensing regulator). In contrast, mutants lacking PA0450 (a putative phosphate transporter) and PA1505 (moaA2) were A-NO2- resistant. However, we were puzzled when we discovered that mucA22 mutant bacteria, a frequently isolated mucA allele in CF and to a lesser extent COPD, were more sensitive to A-NO2- than a truncated ΔmucA deletion (Δ157–194) mutant in planktonic and biofilm culture, as well as during a chronic murine lung infection. Subsequent transcriptional profiling of anaerobic, A-NO2--treated bacteria revealed restoration of near wild-type transcript levels of protective NO2- and nitric oxide (NO) reductase (nirS and norCB, respectively) in the ΔmucA mutant in contrast to extremely low levels in the A-NO2--sensitive mucA22 mutant. Proteins that were S-nitrosylated by NO derived from A-NO2- reduction in the sensitive mucA22 strain were those involved in anaerobic respiration (NirQ, NirS), pyruvate fermentation (UspK), global gene regulation (Vfr), the TCA cycle (succinate dehydrogenase, SdhB) and several double mutants were even more sensitive to A-NO2-. Bioinformatic-based data point to future studies designed to elucidate potential cellular binding partners for MucA and MucA22. Given that A-NO2- is a potentially viable treatment strategy to combat PA and other infections, this study offers novel developments as to how clinicians might better treat problematic PA infections in COPD and CF airway diseases

Application of AHP for Selection of Environmentally Friendly Crop Cultivation in Mae Hong Son Province

ABSTRACT          The purpose of this research was to analyze alternative plant models under environmentally friendly production systems through participatory processes of the communities in Mae Hong Son province.  The 140 samples consisting of farmers and stakeholders were selected by using purposive sampling method.  The analytical hierarchy process (AHP) was used as a tool for decision making. Under the criterions of physical characteristic, and sustainability aspect, there were nine feasible environmentally friendly crops that could be cultivated in the Mae Hong Son province which were separated into three crop types such as field crops, horticulture, and vegetable.  The results shown that tiger peanut, garlic, and cabbage were the first priorities of each crop type.  In addition, under the conditions of waste control, waste treatment, reduce, reuse and recycle, pollution prevention, and water conservation, tiger peanut should be planted in the Mueang and Pang Mapha districts, garlic should by grown in the Pai and Khun Yuam districts, and cabbage should be cultivated in the Sop Moei and Pang Mapha districts.  The findings of this research were used for creating environmentally friendly alternative crop production manuals and policy recommendations for sustainable natural resource management in the Mae Hong Son province

An Overview of Infections in Cystic Fibrosis Airways and the Role of Environmental Conditions on Pseudomonas aeruginosa Biofilm Formation and Viability

In this chapter, the authors review a major complication associated with cystic fibrosis (CF), problematic bacterial infections of the lungs. Infection by organisms such as Staphylococcus aureus, Burkholderia cepacia complex, and Pseudomonas aeruginosa (a major player in CF related infections) results in complications due to increased inflammation and production of virulence factors produced by the bacteria. In addition to these more canonical organisms associated with CF infection, emergingbacterial species have been found in the CF, including anaerobes that have only within the past 5-10 years have been reported to exist in the lungs. P. aeruginosa has long been a cause of devastating infections, and is often seen as the“hallmark”organism associated with the disease. The authors describe the P. aeruginosa infection, including its conversion to a mucoid phenotype, as well as its ability to utilize the thicker airway surface layer associated with CF to grow in “mode two biofilms.” Finally, the authors discuss treatments for bacterial infections, and some of the new advances that offerhope for treatment of CF symptoms and infections by multi-drug resistant organisms. Among these new treatments is the application of acidified nitrite, a non-antibiotic treatment that has been found to be effective at killing nonmucoid and mucoid variants of P. aeruginosa

Oxidation of a single active site suffices for the functional inactivation of the dimeric Bacillus subtilis OhrR repressor in vitro

Bacillus subtilis OhrR is a dimeric repressor that senses organic peroxides and regulates the expression of the OhrA peroxiredoxin. Derepression results from oxidation of an active site cysteine which ultimately results in formation of a mixed disulfide with a low molecular weight thiol, a cyclic sulfenamide, or overoxidation to the sulfinic or sulfonic acids. We expressed a single-chain OhrR (scOhrR) in which the two monomers were connected by a short amino-acid linker. scOhrR variants containing only one active site cysteine were fully functional as repressors and still responded, albeit with reduced efficacy, to organic peroxides in vivo. Biochemical analyses indicate that oxidation at a single active site is sufficient for derepression regardless of the fate of the active site cysteine. scOhrR with only one active site cysteine in the amino-terminal domain is inactivated at rates comparable to wild-type whereas when the active site is in the carboxyl-terminal domain the protein is inactivated much more slowly. The incomplete derepression noted for single active site variants of scOhrR in vivo is consistent with the hypothesis that protein reduction regenerates active repressor and that, in the cell, oxidation of the second active site may also contribute to derepression

BdlA, DipA and Induced Dispersion Contribute to Acute Virulence and Chronic Persistence of Pseudomonas aeruginosa

The human pathogen Pseudomonas aeruginosa is capable of causing both acute and chronic infections. Differences in virulence are attributable to the mode of growth: bacteria growing planktonically cause acute infections, while bacteria growing in matrix-enclosed aggregates known as biofilms are associated with chronic, persistent infections. While the contribution of the planktonic and biofilm modes of growth to virulence is now widely accepted, little is known about the role of dispersion in virulence, the active process by which biofilm bacteria switch back to the planktonic mode of growth. Here, we demonstrate that P. aeruginosa dispersed cells display a virulence phenotype distinct from those of planktonic and biofilm cells. While the highest activity of cytotoxic and degradative enzymes capable of breaking down polymeric matrix components was detected in supernatants of planktonic cells, the enzymatic activity of dispersed cell supernatants was similar to that of biofilm supernatants. Supernatants of non-dispersing Delta bdlA biofilms were characterized by a lack of many of the degradative activities. Expression of genes contributing to the virulence of P. aeruginosa was nearly 30-fold reduced in biofilm cells relative to planktonic cells. Gene expression analysis indicated dispersed cells, while dispersing from a biofilm and returning to the single cell lifestyle, to be distinct from both biofilm and planktonic cells, with virulence transcript levels being reduced up to 150-fold compared to planktonic cells. In contrast, virulence gene transcript levels were significantly increased in non-dispersing Delta bdlA and Delta dipA biofilms compared to wild-type planktonic cells. Despite this, bdlA and dipA inactivation, resulting in an inability to disperse in vitro, correlated with reduced pathogenicity and competitiveness in cross-phylum acute virulence models. In contrast, bdlA inactivation rendered P. aeruginosa more persistent upon chronic colonization of the murine lung, overall indicating that dispersion may contribute to both acute and chronic infections

Exploiting Thiol Modifications

Molecular oxygen may be necessary for life but with its beneficial properties comes formation of potentially toxic reactive oxygen species. One of the ways in which bacteria protect themselves is explaine

Control and regulation of S‐Adenosylmethionine biosynthesis by the regulatory β subunit and quinolone‐based compounds

Methylation is an underpinning process of life and provides control for biological processes such as DNA synthesis, cell growth, and apoptosis. Methionine adenosyltransferases (MAT) produce the cellular methyl donor, S‐Adenosylmethionine (SAMe). Dysregulation of SAMe level is a relevant event in many diseases, including cancers such as hepatocellular carcinoma and colon cancer. In addition, mutation of Arg264 in MATα1 causes isolated persistent hypermethioninemia, which is characterized by low activity of the enzyme in liver and high level of plasma methionine. In mammals, MATα1/α2 and MATβV1/V2 are the catalytic and the major form of regulatory subunits, respectively. A gating loop comprising residues 113–131 is located beside the active site of catalytic subunits (MATα1/α2) and provides controlled access to the active site. Here, we provide evidence of how the gating loop facilitates the catalysis and define some of the key elements that control the catalytic efficiency. Mutation of several residues of MATα2 including Gln113, Ser114, and Arg264 lead to partial or total loss of enzymatic activity, demonstrating their critical role in catalysis. The enzymatic activity of the mutated enzymes is restored to varying degrees upon complex formation with MATβV1 or MATβV2, endorsing its role as an allosteric regulator of MATα2 in response to the levels of methionine or SAMe. Finally, the protein–protein interacting surface formed in MATα2:MATβ complexes is explored to demonstrate that several quinolone‐based compounds modulate the activity of MATα2 and its mutants, providing a rational for chemical design/intervention responsive to the level of SAMe in the cellular environment

Global regulation of gene expression by OxyR in an important human opportunistic pathogen

Most bacteria control oxidative stress through the H2O2-responsive transactivator OxyR, a member of the LTTR family (LysR Type Transcriptional Regulators), which activates the expression of defensive genes such as those encoding catalases, alkyl hydroperoxide reductases and superoxide dismutases. In the human opportunistic pathogen Pseudomonas aeruginosa, OxyR positively regulates expression of the oxidative stress response genes katA, katB, ahpB and ahpCF. To identify additional targets of OxyR in P. aeruginosa PAO1, we performed chromatin immunoprecipitation in combination with whole genome tiling array analyses (ChIP-chip). We detected 56 genes including all the previously identified defensive genes and a battery of novel direct targets of OxyR. Electrophoretic mobility shift assays (EMSAs) for selected newly identified targets indicated that ∼70% of those were bound by purified oxidized OxyR and their regulation was confirmed by quantitative real-time polymerase chain reaction. Furthermore, a thioredoxin system was identified to enzymatically reduce OxyR under oxidative stress. Functional classification analysis showed that OxyR controls a core regulon of oxidative stress defensive genes, and other genes involved in regulation of iron homeostasis (pvdS), quorum-sensing (rsaL), protein synthesis (rpsL) and oxidative phosphorylation (cyoA and snr1). Collectively, our results indicate that OxyR is involved in oxidative stress defense and regulates other aspects of cellular metabolism as well

A Novel OxyR Sensor and Regulator of Hydrogen Peroxide Stress with One Cysteine Residue in Deinococcus radiodurans

In bacteria, OxyR is a peroxide sensor and transcription regulator, which can sense the presence of reactive oxygen species and induce antioxidant system. When the cells are exposed to H2O2, OxyR protein is activated via the formation of a disulfide bond between the two conserved cysteine residues (C199 and C208). In Deinococcus radiodurans, a previously unreported special characteristic of DrOxyR (DR0615) is found with only one conserved cysteine. dr0615 gene mutant is hypersensitive to H2O2, but only a little to ionizing radiation. Site-directed mutagenesis and subsequent in vivo functional analyses revealed that the conserved cysteine (C210) is necessary for sensing H2O2, but its mutation did not alter the binding characteristics of OxyR on DNA. Under oxidant stress, DrOxyR is oxidized to sulfenic acid form, which can be reduced by reducing reagents. In addition, quantitative real-time PCR and global transcription profile results showed that OxyR is not only a transcriptional activator (e.g., katE, drb0125), but also a transcriptional repressor (e.g., dps, mntH). Because OxyR regulates Mn and Fe ion transporter genes, Mn/Fe ion ratio is changed in dr0615 mutant, suggesting that the genes involved in Mn/Fe ion homeostasis, and the genes involved in antioxidant mechanism are highly cooperative under extremely oxidant stress. In conclusion, these findings expand the OxyR family, which could be divided into two classes: typical 2-Cys OxyR and 1-Cys OxyR