The global regulator Crc modulates metabolism,susceptibility to antibiotics and virulence in Pseudomonas aeruginosa

The capacity of a bacterial pathogen to produce a disease in a treated host depends on the former's virulence and resistance to antibiotics. Several scattered pieces of evidence suggest that these two characteristics can be influenced by bacterial metabolism. This potential relationship is particularly important upon infection of a host, a situation that demands bacteria adapt their physiology to their new environment, making use of newly available nutrients. To explore the potential cross‐talk between bacterial metabolism, antibiotic resistance and virulence, a Pseudomonas aeruginosa model was used. This species is an important opportunistic pathogen intrinsically resistant to many antibiotics. The role of Crc, a global regulator that controls the metabolism of carbon sources and catabolite repression in Pseudomonas, was analysed to determine its contribution to the intrinsic antibiotic resistance and virulence of P. aeruginosa. Using proteomic analyses, high‐throughput metabolic tests and functional assays, the present work shows the virulence and antibiotic resistance of this pathogen to be linked to its physiology, and to be under the control (directly or indirectly) of Crc. A P. aeruginosa strain lacking the Crc regulator showed defects in type III secretion, motility, expression of quorum sensing‐regulated virulence factors, and was less virulent in a Dictyostelium discoideum model. In addition, this mutant strain was more susceptible to beta‐lactams, aminoglycosides, fosfomycin and rifampin. Crc might therefore be a good target in the search for new antibiotics.     

Arsenic-resistant <Emphasis Type="BoldItalic">Pseudomonas</Emphasis> spp. and <Emphasis Type="BoldItalic">Bacillus</Emphasis> sp. bacterial strains reducing As(V) to As(III), isolated from Alps soils,Italy

Five arsenic-resistant bacterial strains (designated MP1400, MP1400a, MP1400d, APSLA3, and BPSLA3) were isolated from soils collected at the Alps region (Italy), which showed no contamination by arsenic. Phylogenetic analysis of the 16S rRNA gene sequences assigned them to the genera Pseudomonas and Bacillus. Bacillus sp. strain 1400d and Pseudomonas spp. strains APSLA3 and MP1400 showed higher tolerance to As(III), as indicated by minimum inhibitory concentrations of 10 mmol/L. Pseudomonas sp. strain MP1400 exhibited higher tolerance to As(V) (minimum inhibitory concentration of 135 mmol/L). The isolated arsenic-resistant strains were able to reduce As(V) to As(III), especially Pseudomonas sp. strain MP1400 reducing 2 mmol/L of As(V) to As(III) within 24 h. The results suggest that the isolated bacterial strains play a role in the arsenic biogeochemical cycle of arsenic-poor soils in the Alps mount area.     

Fnr (EtrA) acts as a fine-tuning regulator of anaerobic metabolism in <Emphasis Type="Italic">Shewanella oneidensis</Emphasis>MR-1

Background  

EtrA in Shewanella oneidensis MR-1, a model organism for study of adaptation to varied redox niches, shares 73.6% and 50.8% amino acid sequence identity with the oxygen-sensing regulators Fnr in E. coli and Anr in Pseudomonas aeruginosa, respectively; however, its regulatory role of anaerobic metabolism in Shewanella spp. is complex and not well understood.     

Construction and transformation of a <Emphasis Type="Italic">Thermotoga-E. coli</Emphasis>shuttle vector

Background  

Thermotoga spp. are attractive candidates for producing biohydrogen, green chemicals, and thermostable enzymes. They may also serve as model systems for understanding life sustainability under hyperthermophilic conditions. A lack of genetic tools has hampered the investigation and application of these organisms. This study aims to develop a genetic transfer system for Thermotoga spp.     

Crystal structure of nitrogen regulatory protein IIA<Superscript>Ntr</Superscript> from <Emphasis Type="Italic">Neisseria meningitidis</Emphasis>

Background  

The NMB0736 gene of Neisseria meningitidis serogroup B strain MC58 encodes the putative nitrogen regulatory protein, IIA^Ntr (abbreviated to NM-IIA^Ntr). The homologous protein present in Escherichia coli is implicated in the control of nitrogen assimilation. As part of a structural proteomics approach to the study of pathogenic Neisseria spp., we have selected this protein for structure determination by X-ray crystallography.     

Calcium-mediated perception and defense responses activated in plant cells by metabolite mixtures secreted by the biocontrol fungus <Emphasis Type="Italic">Trichoderma atroviride</Emphasis>

Background  

Calcium is commonly involved as intracellular messenger in the transduction by plants of a wide range of biotic stimuli, including signals from pathogenic and symbiotic fungi. Trichoderma spp. are largely used in the biological control of plant diseases caused by fungal phytopathogens and are able to colonize plant roots. Early molecular events underlying their association with plants are relatively unknown.     

<Emphasis Type="Italic">Rhizobium leguminosarum</Emphasis> bv. <Emphasis Type="Italic">trifolii rosR</Emphasis> is required for interaction with clover,biofilm formation and adaptation to the environment

Background  

Rhizobium leguminosarum bv. trifolii is a symbiotic nitrogen-fixing bacterium that elicits nodules on roots of host plants Trifolium spp. Bacterial surface polysaccharides are crucial for establishment of a successful symbiosis with legumes that form indeterminate-type nodules, such as Trifolium, Pisum, Vicia, and Medicago spp. and aid the bacterium in withstanding osmotic and other environmental stresses. Recently, the R. leguminosarum bv. trifolii RosR regulatory protein which controls exopolysaccharide production has been identified and characterized.     

High yield expression of leptospirosis vaccine candidates LigA and LipL32 in the methylotrophic yeast <Emphasis Type="Italic">Pichia pastoris</Emphasis>

Background  

Leptospirosis, a zoonosis caused by Leptospira spp., is recognized as an emergent infectious disease. Due to the lack of adequate diagnostic tools, vaccines are an attractive intervention strategy. Recombinant proteins produced in Escherichia coli have demonstrated promising results, albeit with variable efficacy. Pichia pastoris is an alternative host with several advantages for the production of recombinant proteins.     

Identification of an unusual <Emphasis Type="Italic">Brucella</Emphasis> strain (BO2) from a lung biopsy in a 52 year-old patient with chronic destructive pneumonia

Background  

Brucellosis is primarily a zoonotic disease caused by Brucella species. There are currently ten Brucella spp. including the recently identified novel B. inopinata sp. isolated from a wound associated with a breast implant infection. In this study we report on the identification of an unusual Brucella-like strain (BO2) isolated from a lung biopsy in a 52-year-old patient in Australia with a clinical history of chronic destructive pneumonia.     

Enzymatic,immunological and phylogenetic characterization of <Emphasis Type="Italic">Brucella suis</Emphasis> urease

Background  

The sequenced genomes of the Brucella spp. have two urease operons, ure-1 and ure-2, but there is evidence that only one is responsible for encoding an active urease. The present work describes the purification and the enzymatic and phylogenomic characterization of urease from Brucella suis strain 1330. Additionally, the urease reactivity of sera from patients diagnosed with brucellosis was examined.     

Anti‐Campylobacter and resistance‐modifying activity of Alpinia katsumadai seed extracts

Aims

We tested extracts from Alpinia katsumadai seeds for anti‐Campylobacter activity and investigated the roles of the CmeABC and CmeDEF efflux pumps in Campylobacter resistance to these natural phenolics. Additionally, we investigated an A. katsumadai ethanolic extract (AlpE) and other plant extracts as putative efflux pump inhibitors on Campylobacter isolates and mutants in efflux pump genes.

Methods and Results

AlpE showed antimicrobial activity against sensitive and multidrug‐resistant Campylobacter isolates. CmeB inactivation resulted in the greatest reduction in resistance, while cmeF and cmeR mutations produced only moderate effects on minimal inhibitory concentrations (MICs). The chemical efflux pump inhibitors additionally reduced MICs in isolates and mutants, confirming that active efflux is an important mechanism in resistance to AlpE, with additional contributions of other efflux systems. A notable decrease in resistance to tested antimicrobials in the presence of subinhibitory concentrations of AlpE confirms its modifying activity in Campylobacter spp.

Conclusions

AlpE is important anti‐Campylobacter source of antimicrobial compounds with resistance‐modifying activity. At least two of the efflux systems are involved in the resistance to A. katsumadai antimicrobial seed extracts.

Significance and Impact of the Study

This is the first report of antimicrobial and resistance‐modifying activity of AlpE from A. katsumadai seeds, demonstrating its potential in the control of Campylobacter in the food chain.     

<Emphasis Type="Italic">Leptospira</Emphasis> seroprevalence and associations between seropositivity,clinical disease and host factors in horses

Background  

A cross-sectional study was carried out to determine the seroprevalence of different serovars of Leptospira spp. and their association with clinical disease and host factors in Swedish horses.     

Protective effect of rifampicin and clindamycin impregnated devices against <Emphasis Type="Italic">Staphylococcus</Emphasis>spp. infection after cerebrospinal fluid diversion procedures

Background  

Infection is a major complication of cerebrospinal fluid shunting procedures. The present report assesses the efficacy of such catheters in both shunts and external ventricular drains (EVDs) against infection and particularly against Staphylococcus spp. infection.     

Genome-scale metabolic reconstruction and <Emphasis Type="Italic">in silico</Emphasis> analysis of methylotrophic yeast <Emphasis Type="Italic">Pichia pastoris</Emphasis> for strain improvement

Background  

Pichia pastoris has been recognized as an effective host for recombinant protein production. A number of studies have been reported for improving this expression system. However, its physiology and cellular metabolism still remained largely uncharacterized. Thus, it is highly desirable to establish a systems biotechnological framework, in which a comprehensive in silico model of P. pastoris can be employed together with high throughput experimental data analysis, for better understanding of the methylotrophic yeast's metabolism.     

Potassium deficiency induces the biosynthesis of oxylipins and glucosinolates in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Background  

Mineral fertilization and pest control are essential and costly requirements for modern crop production. The two measures go hand in hand because plant mineral status affects plant susceptibility to pests and vice versa. Nutrient deficiency triggers specific responses in plants that optimize nutrient acquisition and reprogram metabolism. K-deficient plants illustrate these strategies by inducing high-affinity K-uptake and adjusting primary metabolism. Whether and how K deficient plants also alter their secondary metabolism for nutrient management and defense is not known.     

Incidence of and risks associated with <Emphasis Type="Italic">Giardia</Emphasis> infections in herds on dairy farms in the New York City Watershed

Background  

The primary aims of this study were to determine the incidence of Giardia infections in dairy herds on farms in the New York City Watershed region and to evaluate risk factors associated with infections. Because co-infections of Giardia and Cryptosporidium spp. are common in this population, we also evaluated the effect of herd infection status on Giardia infections.     

The molecular evolution of <Emphasis Type="Italic">PL10</Emphasis> homologs

Background  

PL10 homologs exist in a wide range of eukaryotes from yeast, plants to animals. They share a DEAD motif and belong to the DEAD-box polypeptide 3 (DDX3) subfamily with a major role in RNA metabolism. The lineage-specific expression patterns and various genomic structures and locations of PL10 homologs indicate these homologs have an interesting evolutionary history.