Desulphurisation kinetics of thiophenic compound by sulphur oxidizing Klebsiella oxytoca SOB-1

AIMS

The major aims of this study are to determine the capability of sulphur oxidizing bacterium (SOB-1) to desulphurize dibenzothiophene (DBT) and crude oil, detection of the reaction kinetics and identify the proposed pathway of DBT desulphurization.

METHODS AND RESULTS

The isolate was genetically identified based on 16S rRNA gene sequencing as Klebsiella oxytoca and deposited in the Genebank database under the accession number: MT355440. The HPLC analysis of the remaining DBT concentration revealed that, SOB-1 could desulphurize 90% of DBT (0·25 mmol l^-1 ) within 96 h. The maximum production of sulphate ions from the desulphurization of DBT (0·36 mmol l^-1 ) and crude oil (0·4 mmol l^-1 ) could be quantitatively detected after 48 h of incubation at 30°C. The high values of correlation coefficient (R² ) obtained at all studied concentrations; suggested that biodesulfurization kinetics of DBT follows the first-order reaction model. The kinetics studies showed that, DBT may have an inhibitory effect on SOB-1 when the initial concentration exceeded 0·75 mmol l^-1 . The GC-MS analysis exhibited four main metabolites rather than DBT. The most important ones are 2-hydroxybiphenyl (2-HBP) and methoxybiphenyl n(2-MBP).

CONCLUSIONS

Klebsiella oxytoca SOB-1 catalyzes the desulphurization of DBT through 4S pathway and forms four main metabolic products. The release of sulphate ion and formation of 2-HBP indicating the elimination of sulphur group without altering the carbon skeleton of DBT. The bacterial strain could also catalyzes desulphurization of crude oil. The desulphurization kinetics follows the first-order reaction model.

SIGNIFICANCE AND IMPACT OF THE STUDY

Klebsiella oxytoca SOB-1 could be used as a promising industrial and environmental biodesulfurizing agent as it is not affecting carbon skeleton of thiophenic compounds and forming less toxic metabolic product (2-MBP).

Introduction of point-of-care neonatal lung ultrasound in a developing country

Despite neonatal lung ultrasound (LU) being diffused worldwide, its introduction in limited-resource areas has not been formally investigated. We conceived a project to introduce it in a level 3 NICU of a developing country and verify if, after a short protocolized training, clinicians may efficaciously use LU. Inter-rater agreement between ultrasound trainees and trainers was analyzed within both the local test and the diffusion phases of the project. High inter-rater agreements were found between expert trainers and the two neonatologists who were trained in a skilled European center (Cohen's Kappa, 0.951; 95%CI, 0.882-0.999), as well as between the two and the second round of locally trained colleagues (Cohen's Kappa, 0.896; 95%CI, 0.797-0.996). Moreover, a high agreement was found between the clinical respiratory diagnosis (used as the "gold standard") and the LU diagnosis given by the first two trainees (intraclass correlation, 0.992; 95%CI, 0.987-0.996) and the locally trained physicians (intraclass correlation, 0.97; 95%CI, 0.95-0.98). A final survey demonstrated that the project was perceived as efficacious and that LU was going to be integrated into routine clinical practice.Conclusions: А short LU training provided sufficient proficiency and allowed the LU introduction in clinical practice in the neonatal intensive care unit in a developing country.What is Known:• Lung ultrasound is a promising technique for evaluating neonatal respiratory distress at least in high-income countries. Previous studies revealed high specificity and sensitivity in diagnosing specific neonatal disorders.• An important barrier to the more extensive use of lung ultrasound in neonatal critical care is a lack of efficient and suitable training solutions.What is New:• Descriptive LU performed by neonatologist in a developing country after a short formal training is feasible with good quality.• A short formal LU training program provided good proficiency and allowed a correct descriptive diagnosis in a neonatal unit in a developing country.

In vitro and in vivo evaluation of biologically synthesized silver nanoparticles for topical applications: effect of surface coating and loading into hydrogels

In the present study, silver nanoparticles (AgNPs) were synthesized via biological reduction of silver nitrate using extract of the fungus Fusarium verticillioides (green chemistry principle). The synthesized nanoparticles were spherical and homogenous in size. AgNPs were coated with polyethylene glycol (PEG) 6000, sodium dodecyl sulfate (SDS), and β-cyclodextrin (β-CD). The averaged diameters of AgNPs were 19.2±3.6, 13±4, 14±4.4, and 15.7±4.8 nm, for PEG-, SDS-, and β-CD-coated and uncoated AgNPs, respectively. PEG-coated AgNPs showed greater stability as indicated by a decreased sedimentation rate of particles in their water dispersions. The antibacterial activities of different AgNPs dispersions were investigated against Gram-positive bacteria (methicillin-sensitive and methicillin-resistant Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) by determination of the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). MIC and MBC values were in the range of 0.93-7.5 and 3.75-15 µg/mL, respectively, which were superior to the reported values in literature. AgNPs-loaded hydrogels were prepared from the coated-AgNPs dispersions using several gelling agents (sodium carboxymethyl cellulose [Na CMC], sodium alginate, hydroxypropylmethyl cellulose, Pluronic F-127, and chitosan). The prepared formulations were evaluated for their viscosity, spreadability, in vitro drug release, and antibacterial activity, and the combined effect of the type of surface coating and the polymers utilized to form the gel was studied. The in vivo wound-healing activity and antibacterial efficacy of Na CMC hydrogel loaded with PEG-coated AgNPs in comparison to the commercially available silver sulfadiazine cream (Dermazin®) were evaluated. Superior antibacterial activity and wound-healing capability, with normal skin appearance and hair growth, were demonstrated for the hydrogel formulations, as compared to the silver sulfadiazine cream. Histological examination of the treated skin was performed using light microscopy, whereas the location of AgNPs in the skin epidermal layers was visualized using transmission electron microscopy.

Impact of phosphorus fertilization in alleviating the adverse effects of salinity on wheat grown on different soil types

Optimum fertilization management is an important technique to alleviate the adverse effects of salinity stress on plants. A pot experiment was conducted to evaluate the ameliorative role of inorganic phosphorus (P) and organic P sources on wheat grown under salt stress in three soil types deficient in available P. Wheat (Triticum aestivum L. cv. Shakha 93) was grown on alluvial, sandy and calcareous soils at salinity levels of 4, 8 and 12 dS/m of saturated paste extract (ECe) and supplied with a constant rate of 30 mg P2O5/kg soil as superphosphate (SP), cattle manure (CM) and a 1:1 mixture of SP and CM. The results revealed that plants grown on the sandy soil were more susceptible to the adverse effects of salinity than those planted on the alluvial one, especially at zero P. Plants grown on the calcareous soil were moderately affected. The varying soil type caused significant differences in the aboveground biomass and the uptake of N, K, P and Zn. It was obvious that P ameliorated wheat growth under salt stress, and this role was greater under moderate and high salinity. The increases in N, P, K and Zn uptake driven by P application were more conspicuous in the sandy and calcareous soils. The results also indicated that the combined application of inorganic and organic P sources surpassed that of either when applied alone on all soil types and salinity levels.

Comparative analysis of idiA and isiA transcription under iron starvation and oxidative stress in Synechococcus elongatus PCC 7942 wild-type and selected mutants

In the mesophilic cyanobacterium Synechococcus elongatus PCC 7942, iron starvation induces the expression of a number of proteins, including IdiA and IsiA. Whereas IdiA protects photosystem (PS) II under mild iron limitation against oxidative stress in a yet unknown way, prolonged iron starvation leads to the formation of the PS I-IsiA supercomplex. Transcription of idiA is positively regulated by IdiB under iron starvation, and Fur represses transcription of isiAB under iron-sufficient growth conditions. In this report, data are presented suggesting a strong interrelationship between iron homeostasis and oxidative stress in S. elongatus PCC 7942, and showing that transcription of major iron-regulated genes, such as isiA, isiAB, idiA, idiB, mapA, and irpA, is induced by oxidative stress within a few minutes by treatment of cells with hydrogen peroxide or methylviologen. The overall results suggest that isiA/isiAB as well as idiB transcription in response to oxidative stress might be controlled by a transcriptional repressor possibly of the PerR-type. This fact also explains the observed cross-talk between IdiB- and Fur-mediated transcriptional regulation of gene expression and for the role of H(2)O(2) as a superior trigger coordinating expression of iron-regulated genes under iron starvation and oxidative stress. Measuring 77 K chlorophyll a fluorescence, it is shown that hydrogen peroxide treatment causes a transient short-term modification of PS II and PS I most likely leading to increased cyclic electron transport around PS I. In this context, the intriguing observation was made that idiB is transcribed as part of an operon together with a gene encoding a potential [2Fe-2S]-protein. This protein has similarity to [Fe-S]-proteins involved in the electron transport activity of the NDH I complex in eubacteria. Since the NDH I complex is involved in cyclic electron transport activity around PS I in cyanobacteria and both adaptation to iron starvation and adaptation to oxidative stress lead to an enhanced cyclic electron transport activity around PS I, this potential [Fe-S]-protein might participate in the overall adaptational response to iron starvation and/or oxidative stress in Synechococcus.

Effects of adjuvant on neuropeptide-like immunoreactivity in the temporomandibular joint and trigeminal ganglia

To study the role of the nervous system in temporomandibular joint arthritis, substance P-, calcitonin gene-related peptide-, and neuropeptide Y-like immunoreactivity in the trigeminal ganglia and temporomandibular joint of rats was examined. Arthritis was induced in female Lewis rats through bilateral injection of a suspension of heat-killed Mycobacterium butyricum in paraffin oil into the temporomandibular joint. Control rats received paraffin oil via the same route. Tissues were collected for neuropeptide extraction 28 days after injection and analyzed by radioimmunoassay and reverse-phase high-performance liquid chromatography. Calcitonin gene-related peptide was significantly increased in the arthritic trigeminal ganglia. Substance P, calcitonin gene-related peptide, and neuropeptide Y in the arthritic temporomandibular joint were significantly increased as compared to controls. The results of this study show that sensory and sympathetic neuropeptides may possibly be associated with the development of arthritis in the temporomandibular joint of rats.

Effects of capsaicin in temporomandibular joint arthritis in rats

Temporomandibular joint (TMJ) arthritis was induced in female Lewis rats by unilateral injection of a suspension of heat-killed Mycobacterium butyricum in paraffin oil into the TMJ. Control rats received paraffin oil by the same route. Arthritic and control rats were pretreated either with capsaicin or denervation of the mandibular branch of the trigeminal nerve. Tissues were collected for neuropeptide extraction and analysed by radioimmunoassay and reverse-phase high-performance liquid chromatography. In all groups, the levels of substance P-(SP), calcitonin gene-related peptide- (CGRP) and neuropeptide Y- (NPY) like immunoreactivity (LI) were higher in the trigeminal ganglia than in the TMJs. In control rats, capsaicin significantly lowered the levels of SP-LI in the trigeminal ganglia and TMJ, but not CGRP-LI and NPY-LI. In the arthritic rats, capsaicin pretreatment significantly lowered the SP-LI and CGRP-LI in the trigeminal ganglia and TMJ, but not the NPY-LI. In the trigeminal ganglia the unilateral denervation significantly lowered SP-LI in control rats, and in arthritic rats SP-LI and CGRP-LI. On the denervated side of the arthritic TMJ, NPY-LI, SP-LI and CGRP- LI were significantly lowered as compared to the arthritic control rats and to the contralateral side. In this rat model, pretreatment with capsaicin and surgical denervation decreased the neuropeptide content in the trigeminal ganglia and the TMJ. The results clearly demonstrate a close interaction between increased neuropeptide release from sensory and sympathetic neurones after induction of arthritis in the rat.