Recombinant production of a diffusible signal factor inhibits Salmonella invasion and animal carriage.

The complex chemical environment of the intestine is defined largely by the metabolic products of the resident microbiota. Enteric pathogens, elegantly evolved to thrive in the gut, use these chemical products as signals to recognize specific niches and to promote their survival and virulence. Our previous work has shown that a specific class of quorum-sensing molecules found within the gut, termed diffusible signal factors (DSF), signals the repression of Salmonella tissue invasion, thus defining a means by which this pathogen recognizes its location and modulates virulence to optimize its survival. Here, we determined whether the recombinant production of a DSF could reduce Salmonella virulence in vitro and in vivo. We found that the most potent repressor of Salmonella invasion, cis-2-hexadecenoic acid (c2-HDA), could be recombinantly produced in E. coli by the addition of a single exogenous gene encoding a fatty acid enoyl-CoA dehydratase/thioesterase and that co-culture of the recombinant strain with Salmonella potently inhibited tissue invasion by repressing Salmonella genes required for this essential virulence function. Using the well characterized E. coli Nissle 1917 strain and a chicken infection model, we found that the recombinant DSF-producing strain could be stably maintained in the large intestine. Further, challenge studies demonstrated that this recombinant organism could significantly reduce Salmonella colonization of the cecum, the site of carriage in this animal species. These findings thus describe a plausible means by which Salmonella virulence may be affected in animals by in situ chemical manipulation of functions essential for colonization and virulence.

Despite our best efforts, infections of agricultural animals with Salmonella persist, posing threats to food safety. Few, if any, measures have proven effective in reducing Salmonella carriage in animals used for food, a major source of this pathogen. Antibiotics are ineffective at curtailing infection and have served only to exacerbate the global crisis of antimicrobial resistance. The alternative then is to seek novel means to reduce Salmonella disease and carriage by preventing its colonization of livestock and poultry. Here we describe an approach targeting invasion, a function essential for Salmonella carriage and disease in animals. We show that a potent chemical inhibitor of invasion, the diffusible signal factor cis-2 hexadecenoic acid, can be produced by recombinant E. coli strains capable of stably colonizing the animal intestine, providing a means to directly affect the virulence of Salmonella within an animal host. These studies may thus provide a route to reduce the carriage of this pathogen in production animals and thus the spread of disease to humans.

Mechanistic insight into the electrocatalytic performance of reduced graphene oxide supported palladium, silver and palladium-silver nanodeposits toward electro-dehalogenation of halocarbons in room temperature ionic liquids.

Herein, we report the results from our extensive voltammetric investigations designed to explore, assess and explain the electrocatalytic performance of reduced graphene oxide supported metal nano-deposits toward the electro-dehalogenation of halocarbons in room temperature ionic liquids (RTILs). Specifically, we investigated the electro-reductive dechlorination of the model halocarbon, carbon tetrachloride over glassy carbon electrode (GCE) and palladium-graphene (Pd-Gr), silver-graphene (Ag-Gr) and palladium-silver-graphene (PdAg-Gr) nanocomposites in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][NTf2]). Analysis of the voltammetric data in light of Marcus-Hush formulation reveals that the electro-reductive cleavage of the C-Cl bond of CCl4 over GCE in [BMIM][NTf2] follows a sticky dissociative electron transfer (SDET) pathway. The significantly stronger interaction energy between electrogenerated Cl- and CCl3˙ (radical) fragments in RTILs makes electroreduction of CCl4 in [BMIM][NTf2] much easier than in organic solvents. The activation-driving force relationship for electro-catalytic dechlorination of CCl4 over Pd-Gr was observed to follow a modified sticky dissociative electron transfer model wherein apart from the ion-radical interaction, the adsorptive interaction of chlorinated species with the electrocatalytic surface needs to be taken into consideration to account for the apparent activation energy-driving force dependence. Interestingly the activation energy-driving force relationships for the electroreduction of CCl4 over Ag-Gr and PdAg-Gr were observed to fit a modified stepwise ET (MSET) pathway. In the MSET pathway, the adsorption and the implied free energy change of the electroreducible halocarbon significantly alter the solvent re-organization energy and the inherent barrier for the heterogeneous ET process. The adsorptive interaction and hence the electrocatalytic performance of PdAg-Gr were observed to be more than that observed for Ag-Gr. This is attributed to the Ag to Pd charge transfer in the PdAg-Gr nanodeposits. Our results besides underlining the positive influence of RTILs in facilitating the electroreductive detoxification of halocarbons, very well establish the mechanistic basis for the electrocatalytic performance of graphene based nanodeposits toward electrodehalogenation of halocarbons.

Transforming micelles into mixed micelles: a promising approach to tune the catalytic performance of imidazolium-based surface active ionic liquids toward degradation of rhodamine B.

Herein, we demonstrate that the catalytic performance of imidazolium-based surface-active ionic liquid (SAIL) micelles can be significantly enhanced through the addition of an appropriate type and amount of intelligently conceived amphiphile to form mixed micelles. Specifically, we show that the catalytic performance of 1-dodecyl-3-methyl imidazolium chloride (DDMIMCl) micelles toward the reductive degradation of rhodamine B (RhB), a carcinogenic dye extensively used in multiple industrial applications, can be appreciably boosted through addition of Brij56, a nonionic surfactant. Detailed kinetic investigations on the catalytic performance of pre- and post-micellar concentrations of DDMIMCl and its mixed micelles with Brij56 over various mole fractions, toward the reductive degradation of RhB, are presented. The data analyzed in light of Berezin's kinetic model suggest that the addition of Brij56 to DDMIMCl micelles significantly enhances their catalytic performance. The catalytic activity exhibited by the DDMIMCl-Brij56 (XBrij56 = 0.2) mixed micellar system is better than that reported for many state-of-the-art nanoparticle/homogenous catalysts. The results explained in light of Berezin's kinetic model are well supported by physico-chemical studies like conductometry, fluorimetry and dynamic light scattering. The presented results anticipate stimulation of extensive research activity for exploiting the mixed micellization approach as a novel avenue for modulating the catalytic performance of SAILs.

Structural-functional integrity of lysozyme in imidazolium based surface active ionic liquids.

The present study was designed to explore the hydrophobicity and concentration dependence of imidazolium based surface active ionic liquids (SAILs) effects on the structural-functional integrity of proteins. Specifically, we investigated the impact of SAILs viz. 1-octyl-3-methylimidazolium dodecylbenzenesulfonate ([OMIM][DBS]) and 1-dodecyl-3-methylimidazolium dodecylbenzenesulfonate ([DDMIM][DBS]) on activity, structure and stability of lysozyme. Activity measurements revealed that, in contrast to [DDMIM][DBS] that renders lysozyme either feebly active or inactive, [OMIM][DBS] significantly enhances the lysozyme activity in the concentration range of critical aggregation concentrations (CAC) to Cs (SAIL saturation concentration of protein backbone) i.e., 0.5 mM-1.35 mM. Tensiometric results in agreement with turbidity measurements inferred significant composition and concentration dependence of the lysozyme-SAIL interactions. Spectroscopic investigations revealed that compared to destabilizing behaviour of [DDMIM][DBS], [OMIM][DBS] significantly enhances both conformational as well as thermal stability of lysozyme in the CAC to Cs concentration regime. Altogether, results obtained do indicate that [OMIM][DBS], in the concentration regime of CAC to Cs, serves as an efficient stabiliser with an ability to appreciably enhance the activity, thermal stability and overall conformational stability of lysozyme. We firmly believe that [OMIM][DBS], at least in the CAC to Cs concentration ranges, can be exploited as a promising stabiliser and activity enhancer for numerous industrially important enzymes.

PdAg Bimetallic Nanoalloy-Decorated Graphene: A Nanohybrid with Unprecedented Electrocatalytic, Catalytic, and Sensing Activities.

Recent reports about the promising and tunable electrocatalytic activity and stability of nanoalloys have stimulated an intense research activity toward the design and synthesis of homogeneously alloyed novel bimetallic nanoelectrocatalysts. We herein present a simple one-pot facile wet-chemical approach for the deposition of high-quality bimetallic palladium-silver (PdAg) homogeneous nanoalloy crystals on reduced graphene (Gr) oxide sheets. Morphological, structural, and chemical characterizations of the so-crafted nanohybrids establish a homogeneous distribution of 1:1 PdAg nanoalloy crystals supported over reduced graphene oxide (PdAg-Gr). The PdAg-Gr nanohybrids exhibit outstanding electrocatalytic, catalytic, and electroanalytical performances. The PdAg-Gr samples were found to exhibit exceptional durability when subjected to repeated potential cycles or long-term electrolysis. In the CVs recorded for fuel cell reactions, viz. methanol oxidation reaction and oxygen reduction reaction, and for detoxification of environmental pollutants, viz. electroreduction of methyl iodide and chloroacetonitrile over PdAg-Gr with potential sweep rate of 25 mVs-1, the peak potentials were observed to be just -0.221, -0.297, (vs Ag/AgCl, 3 M KCl) -1.508, and -1.189 V (vs Fc+/Fc), respectively. The potential of PdAg-Gr nanohybrid for simultaneous and sensitive electrochemical sensing and estimation of hydroxybenzene isomers with very low detection limits (0.05 µM for hydroquinone, 0.06 µM for catechol, 6.7 nM for 4-aminophenol, and 13.7 nM for 2-aminophenol) is demonstrated. Additionally, PdAg-Gr was observed to offer excellent solution-phase catalytic performance in bringing about the reduction of notorious environmental pollutant 4-nitrophenol to pharmaceutically important 4-aminophenol with an apparent rate constant ( kapp) of 3.106 × 10-2 s-1 and a normalized rate constant ( knor) of 6.21 × 102 s-1 g-1. The presented synthetic scheme besides being high yielding, low cost, and easy to carry out results in the production of PdAg-Gr nanohybrids with stability and activity significantly better than most of the nanomaterials purposefully designed and testified so far by various groups.

Oxides in silver-graphene nanocomposites: electrochemical signatures and electrocatalytic implications.

Herein we report an electrochemical approach to establish the presence of silver oxides in silver-reduced graphene oxide (Ag-rGO) nanocomposites synthesised under alkaline conditions. The recorded electrochemical signatures, further supported and validated by UV-Vis spectroscopy, XRD and TEM analysis, clearly establish the presence of an oxide phase of silver in the nanodimensional silver present in Ag-rGO. The Ag-rGO was tested for its electrocatalytic and electrosensing activity for hydroquinone (H2Q) and ascorbic acid (AA). The presented results establish that the electrocatalytic and electrosensing potential of the Ag-rGO for H2Q and AA can be enhanced through electroreduction of the oxide phase of silver in these nanocomposites. Our results prove that the electrocatalytic and electroanalytic activities of electroreduced Ag-rGO for AA are better than most of the electrode materials reported so far in the literature.

Determination of cmc of imidazolium based surface active ionic liquids through probe-less UV-vis spectrophotometry.

In the first of its kind we herein report the results of our studies undertaken on the micellization behaviour of imidazolium based surface active ionic liquids (SAILs) to prove that their critical micelle concentration (cmc) can be estimated through ultraviolet-visible (UV-vis) spectroscopy without using any external probe. Tensiometric and spectrophotometric investigations of a series of freshly prepared SAILs viz. 1-octyl-3-methylimidazolium chloride ([OMIM][Cl]), 1-octyl-3-methylimidazolium dodecylsulphate ([OMIM][DS]), 1-octyl-3-methylimidazolium benzoate ([OMIM][Bz]), 1-octyl-3-methylimidazolium salicylate ([OMIM][Sc]), 1-octyl-3-methylimidazolium acetate ([OMIM][Ac]) are presented as a case study in support of the said claim. The cmcs estimated through spectrophotometric method were found to be close to the values estimated through tensiometry for the said SAILs. The cmcs for the investigated SAILS were found to vary in order of [OMIM][Cl]>[OMIM][Ac]>[OMIM][Bz]>[OMIM][Sc]>[OMIM][DS]. To the best of our knowledge the present communication will be the first report about the synthesis, characterization and micellization behaviour of [OMIM][Bz] and [OMIM][Sc].

Detection and sequencing of plasmid encoded tetracycline resistance determinants (tetA and tetB) from food-borne Bacillus cereus isolates.

OBJECTIVE: To investigate the detection and sequencing of plasmid encoded tetracycline resistance genes (tetA and tetB) from food-borne and standard strains of Bacillus cereus (B. cereus). METHODS: A PCR was carried out to detect the tetracycline resistance genes (tetA and tetB) in food-borne B. cereus strains and the amplified products were sequenced. RESULTS: The phenotypic resistance against tetracycline was observed in 39 of the 118 food-borne isolates and two reference strains (MTCC 430 and MTCC 1307) of B. cereus. Among the phenotypically resistant isolates, tetA was detected in 36 food-borne isolates and two reference strains (MTCC 430 and MTCC 1307), whereas, tetB was detected in 12 food-borne isolates and MTCC 1307 strain. CONCLUSIONS: A close association was therefore found between phenotypic resistance against tetracycline and presence of tetracycline resistance genes. The tetA and tetB gene fragments were amplified, purified and sequenced. The gene sequences of the isolates studied herein were found similar to tetA and tetB gene sequences of other bacteria available in NCBI. The occurrence of tetA and tetB genes in B. cereus indicate the horizontal transfer of antibiotic resistance determinants from other bacteria into B. cereus. The transfer of these resistant determinants to other potentially pathogenic bacteria may be a matter of great concern.

Ruptured heterotopic pregnancy: a rare cause for hemoperitoneum; report of three cases from kashmir, India.

Heterotopic pregnancy has been found in various forms but is still a rare event in the natural conception cycles, occurring in less than 1:30000 pregnancies with the incidence rising to 1:100 to 1:500 pregnancies duo to assisted reproductive technologies. Delay in diagnosing the condition can be fatal for both the mother and the fetus. Three patients aged 28, 31 and 26 years presented with amenorrhea of ten, eight and twelve weeks duration respectively with signs of peritonism and shock. Investigations revealed intra and extra uterine pregnancies in all the three cases with the rupture of the extra uterine pregnancies. All the cases were operated and first two cases were followed up postoperatively till the delivery of the term live babies. The third case is still under our follow up. A high index of suspicion by a general surgeon is needed in arriving at a prompt diagnosis of ruptured heterotopic pregnancy so that rapid resuscitation, heart sparing anesthesia and expeditious surgery is carried out for both maternal and intrauterine fetal wellbeing.

Torsion of vermiform appendix with fecalith: a case report.

INTRODUCTION: Torsion of the vermiform appendix is a rare disorder, which causes abdominal symptoms indistinguishable from acute appendicitis and is found by chance during the laparotomy. CASE PRESENTATION: We report a case (a 76-year-old male) suffering of torsion of the vermiform appendix with fecalith. It was twisted 540 degrees in an anti-clockwise direction. Appendectomy was done. CONCLUSION: Appendiceal torsion may be assocated with the presence of fecalith. This case is the oldest one among the patients with appendiceal torsion reported to literature.