Different aspects of bacterial communication signals

The communication or quorum-sensing signal molecules (QSSM) are specialized molecules used by numerous gram-negative bacterial pathogens of animals and plants to regulate or modulate bacterial virulence factor production. In plant-associated bacteria, genes encoding the production of these signal molecules, QSSMs, were discovered to be linked with the phenotype of bacterium, because mutation of these genes typically disrupts some behaviors of bacteria. There are other regulator genes which respond to the presence of signal molecule and regulate the production of signal molecule as well as some virulence factors. The synthesis and regulator genes (collectively called quorum-sensing genes hereafter) are repressed in low bacterial population but induced when bacteria reach to high cell density. Multiple regulatory components have been identified in the bacteria that are under control of quorum sensing. This review describes different communication signal molecules, and the various chemical, physical and genomic factors known to synthesize signals. Likewise, the role of some signal-degrading enzymes or compounds and the interaction of QSSMs with eukaryotic metabolism will be discussed here.     

Association of the <Emphasis Type="Italic">rs1870634</Emphasis> Variant in Long Intergenic Non-protein Coding RNA 841 with Coronary Artery Disease: A GWAS-Replication Study in an Iranian Population

Recent genome-wide association studies (GWAS) identified a list of single-nucleotide polymorphisms (SNPs) associated with coronary artery disease (CAD). Replication of GWAS findings in different population corroborated the observed association in the parent GWAS. In this study, we aimed to replicate the association of rs1870634, a GWAS identified SNP, to CAD in an Iranian population. The study population consisted of 267 subjects undergoing coronary angiography coronary angiography including 155 CAD patients and 112 non-CAD age- and gender-matched controls. The genotype determination of rs1870634 SNP performed using high-resolution melting analysis (HRM) technique. Our results revealed that the GG genotype frequency was significantly higher in CAD patients compared with controls (P?=?0.03). The results of binary logistic regression suggested that this genotype was significantly associated with CAD risk adjustment for age, BMI, sex, TC, and LDL-C lipid levels (OR of 2.78, 95% CI (1.10–7.01), P?=?0.03). Moreover, our results showed that the GG+TG genotypes were 2.52 times more likely to develop CAD (95% CI 1.05–6.03) than TT genotype carriers after adjusting for age, sex, and lipid profiles (P?=?0.037). These data showed that the GG genotype could be associated with increased risk of CAD in a sample of Iranian population.     

A survey on basal resistance and riboflavin-induced defense responses of sugar beet against Rhizoctonia solani

We examined basal defense responses and cytomolecular aspects of riboflavin-induced resistance (IR) in sugar beet-Rhizoctonia solani pathsystem by investigating H(2)O(2) burst, phenolics accumulation and analyzing the expression of phenylalanine ammonia-lyase (PAL) and peroxidase (cprx1) genes. Riboflavin was capable of priming plant defense responses via timely induction of H(2)O(2) production and phenolics accumulation. A correlation was found between induction of resistance by riboflavin and upregulation of PAL and cprx1 which are involved in phenylpropanoid signaling and phenolics metabolism. Application of peroxidase and PAL inhibitors suppressed not only basal resistance, but also riboflavin-IR of sugar beet to the pathogen. Treatment of the leaves with each inhibitor alone or together with riboflavin reduced phenolics accumulation which was correlated with higher level of disease progress. Together, these results demonstrate the indispensability of rapid H(2)O(2) accumulation, phenylpropanoid pathway and phenolics metabolism in basal defense and riboflavin-IR of sugar beet against R. solani.     

The role of epiphytic Pseudomonas and Pantoea population diversity on prevalence of fire blight disease

Several microbial populations on plants interact with each other and their host through the actions of secreted metabolites. However, the role of diverse microorganisms and their metabolites on plant health has yet to be fully appreciated. Here, we investigated the population diversity of two dominant epiphytic bacterial genuses in different area and their role in biological control of fire blight disease. To do so, we isolated and calculated population diversity of different Pantoea spp. and Pseudomonas spp. using serial dilution methods. The growth inhibition of Erwinia amylovora in vitro by some of these bacteria indicated the ecological significance of secondary metabolites produced by these bacteria and discuss how they might contribute to biological control of fire blight disease. Although, we did not work on the ability of these bacteria on induction of disease resistance but it could be considered for future, because they represent very different but important types of secondary metabolites. We also described how the weather conditions in different geographical regions can effect on the population of these epiphytic bacterial phenotypes leading to plant health promotion. In conclusion, we demonstrated the role of Pantoea and Pseudomonas population diversity on prevalence of fire blight in different area of north-east of Iran.     

The role of a periplasmic gluconolactonase (PpgL)-like protein in <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">syringae</Emphasis> B728a

The communication or quorum-sensing signal molecules (QSSM) are specialized molecules used by numerous gram-negative bacterial pathogens of animals and plants to regulate or modulate bacterial virulence factor production. In plant-associated bacteria, genes encoding the production of these signal molecules, QSSMs, were discovered to be linked with the phenotype of bacterium, because mutation of these genes typically disrupts some behaviors of bacteria. There are other regulator genes which respond to the presence of signal molecule and regulate the production of signal molecule as well as some virulence factors. The synthesis and regulator genes (collectively called quorum-sensing genes hereafter) are repressed in low bacterial population but induced when bacteria reach to high cell density. Multiple regulatory components have been identified in the bacteria that are under control of quorum sensing. This review describes different communication signal molecules, and the various chemical, physical and genomic factors known to synthesize signals. Likewise, the role of some signal-degrading enzymes or compounds and the interaction of QSSMs with eukaryotic metabolism will be discussed here.     

Protective effect of selenium on vincristine-induced peripheral neuropathy in PC12 cell line

Cytotechnology - Vincristine-induced peripheral neuropathy (VIPN) is the main side effect and major reason for neuropathic pain in cancer survivors treated with vincristine. Vincristine, a...     

Phenotypic and genome-wide analysis of an antibiotic-resistant small colony variant (SCV) of Pseudomonas aeruginosa

Background

Small colony variants (SCVs) are slow-growing bacteria, which often show increased resistance to antibiotics and cause latent or recurrent infections. It is therefore important to understand the mechanisms at the basis of this phenotypic switch.

Methodology/Principal Findings

One SCV (termed PAO-SCV) was isolated, showing high resistance to gentamicin and to the cephalosporine cefotaxime. PAO-SCV was prone to reversion as evidenced by emergence of large colonies with a frequency of 10⁻⁵ on media without antibiotics while it was stably maintained in presence of gentamicin. PAO-SCV showed a delayed growth, defective motility, and strongly reduced levels of the quorum sensing Pseudomonas quinolone signal (PQS). Whole genome expression analysis further suggested a multi-layered antibiotic resistance mechanism, including simultaneous over-expression of two drug efflux pumps (MexAB-OprM, MexXY-OprM), the LPS modification operon arnBCADTEF, and the PhoP-PhoQ two-component system. Conversely, the genes for the synthesis of PQS were strongly down-regulated in PAO-SCV. Finally, genomic analysis revealed the presence of mutations in phoP and phoQ genes as well as in the mexZ gene encoding a repressor of the mexXY and mexAB-oprM genes. Only one mutation occurred only in REV, at nucleotide 1020 of the tufA gene, a paralog of tufB, both encoding the elongation factor Tu, causing a change of the rarely used aspartic acid codon GAU to the more common GAC, possibly causing an increase of tufA mRNA translation. High expression of phoP and phoQ was confirmed for the SCV variant while the revertant showed expression levels reduced to wild-type levels.

Conclusions

By combining data coming from phenotypic, gene expression and proteome analysis, we could demonstrate that resistance to aminoglycosides in one SCV mutant is multifactorial including overexpression of efflux mechanisms, LPS modification and is accompanied by a drastic down-regulation of the Pseudomonas quinolone signal quorum sensing system.     

Pseudomonas as a frequent and important quorum quenching bacterium with biocontrol capability against many phytopathogens

The aim of the present study was to isolate a variety of quorum quenching bacteria (QB) from the rhizosphere and phyllosphere of three agricultural plants using minimal medium (MM)- and non-minimal medium (NM)-based methods. The members of the Pseudomonas genus constituted the most abundant QB genus, particularly in the rhizospheres of all plant samples and showed the highest quorum quenching (QQ) activity according to a screening assay using a biosensor and 3-oxo-C6-HSL (as an important quorum sensing signal in many phytopathogenic bacteria). In addition, QQ-Pseudomonas were recognised as versatile biocontrol agents against non-bacterial and bacterial plant pathogens, such as Pectobacterium carotovorum subsp. carotovorum (Pcc). Three types of quenching activities, including intracellular and extracellular enzymatic and non-enzymatic activities, were observed in QQ-Pseudomonas. Pseudomonas strains, particularly NM-isolated strains with extracellular activity, are the strongest QQ-based biocontrol agents.