Computational analysis of fluorescence induction curves in intact spinach leaves treated at different pH

Effects of change in pH have been investigated on spinach leaf discs by measuring fluorescence induction kinetics using plant efficiency analyzer (PEA). On the basis of computational analysis of the results, we have reported that acidic pH causes a significant inhibition of the donor and the acceptor side of PS II. Energy flux models have been presented using the software Biolyzer HP 3. Effects of pH were investigated on the antenna size heterogeneity of PS II and a relative change in the proportions of α, β, and γ centers was observed.     

Radiation dose measurements in a dental orthopantogram unit using indigenously developed optically stimulated luminescence dosimeters

Dental orthopantogram (OPG)/cone beam computed tomography (CBCT) scanners are gaining popularity due to their 3D imaging with multiplanar view that provides clinical benefits over conventional dental radiography systems. Dental OPG/CBCT provides optimal visualization of adjacent overlaying anatomical structures that will be superpositioned in any single projection. The characteristics of indigenously developed optically stimulated luminescence dosimeters, namely, aluminium oxide doped with carbon (Al₂O₃:C), lithium magnesium phosphate doped with terbium and boron (LiMgPO₄:Tb,B) and lithium calcium aluminium fluoride doped with europium and yttrium (LiCaAlF₆:Eu,Y) were evaluated for their use in dental dosimetry. The dose?response of these dosimeters was studied at X‐ray energies 60 kV, 70 kV and 81 kV. Radiation doses were also measured using Gafchromic film for comparison. Radiation dose was measured at eight different locations of a polymethyl methacrylate (PMMA) head phantom including eyes. The optically stimulated luminescence (OSL) sensitivity of LiMgPO₄:Tb,B is about 1.5 times and LiCaAlF₆:Eu, is about 20 times higher than the sensitivity of Al₂O₃:C. It was found that measured radiation doses by the three optically stimulated luminescence dosimeters (OSLDs) and Gafchromic film in the occipital region (back side) of a PMMA phantom, were consistent but variations in dose at other locations were significantly higher. The three OSLDs used in this study were found to be suitable for radiation dose measurement in dental units.     

Overexpression of citrate operon in Herbaspirillum seropedicae Z67 enhances organic acid secretion,mineral phosphate solubilization and growth promotion of Oryza sativa

Background and aims

Herbaspirillum seropedicae Z67, nitrogen fixing endophyte, significantly promotes the growth of cereals. Organic acid secreting nitrogen fixing rhizobacteria have better plant growth promotion abilities due to mineral phosphate solubilization.

Method

Plasmids pAB7, pJNK3 and pJNK4 containing Escherichia coli cs (gltA), NADH insensitive cs (gltA1), and citrate operon consisting of gltA1 gene along with Salmonella typhimurium Na⁺ dependent citrate transporter (citC) gene under constitutive lac promoter were constructed in broad host range plasmid pUCPM18-Km^r. The plasmid transformants of H. seropedicae Z67 were obtained by electroporation.

Results

Hs (pAB7) and Hs (pJNK3) had increased CS activity but citric acid secretion was not significant. Hs (pJNK3) secreted 45 mM acetic acid while Hs (pJNK4) secreted 2.7 mM citric and 51 mM acetic acids. Hs (pJNK3) and Hs (pJNK4) released 80 μM and 110 μM amount of P from rock phosphate, respectively, in buffered medium under both aerobic and micro aerobic conditions. These transformants showed better plant growth promoting factors. Upon inoculation to rice plants (Gujarat – 17), increase of Fresh weight, Dry weight N, P and K content was observed.

Conclusion

Thus the study demonstrates that artificial citrate operon in H. seropedicae Z67 enhances phosphate solubilization and plant growth promotion abilities.     

An evaluation of phycoremediation potential of cyanobacterium Nostoc muscorum: characterization of heavy metal removal efficiency

The present study relates to the use of cyanobacterium Nostoc muscorum as a model system for removal of heavy metals such as Pb and Cd from aquatic systems. The effects of various physicochemical factors on the surface binding and intracellular uptake of Pb and Cd were studied to optimize the metal removal efficiency of the living cells of N. muscorum. Results demonstrated that a significant proportion of Pb and Cd removal was mediated by surface binding of metals (85 % Pb and 79 % Cd), rather than by intracellular accumulation (5 % Pb and 4 % Cd) at the optimum level of cyanobacterial biomass (2.8 g L^?1), metal concentration (80 μg mL^?1), pH (pH 5.0–6.0), time (15–30 min), and temperature (30–40 °C). N. muscorum has maximum amounts of metal removal (q _max) capacity of 833 and 666.7 mg g^?1 protein for Pb and Cd, respectively. The kinetic parameters of metal binding revealed that adsorption of Pb and Cd by N. muscorum followed pseudo-second-order kinetics, and the adsorption behavior was better explained by both Langmuir and Freundlich isotherm models. The surface binding of both the metals was apparently facilitated by the carboxylic, hydroxyl, and amino groups as evident from Fourier transform infrared spectra.     

Characterization of M. tuberculosis SerB2, an Essential HAD-Family Phosphatase,Reveals Novel Properties

M. tuberculosis harbors an essential phosphoserine phosphatase (MtSerB2, Rv3042c) that contains two small- molecule binding ACT-domains (Pfam 01842) at the N-terminus followed by the phosphoserine phosphatase (PSP) domain. We found that exogenously added MtSerB2 elicits microtubule rearrangements in THP-1 cells. Mutational analysis demonstrates that phosphatase activity is co-related to the elicited rearrangements, while addition of the ACT-domains alone elicits no rearrangements. The enzyme is dimeric, exhibits divalent metal- ion dependency, and is more specific for l- phosphoserine unlike other classical PSPases. Binding of a variety of amino acids to the ACT-domains influences MtSerB2 activity by either acting as activators/inhibitors/have no effects. Additionally, reduced activity of the PSP domain can be enhanced by equimolar addition of the ACT domains. Further, we identified that G18 and G108 of the respective ACT-domains are necessary for ligand-binding and their mutations to G18A and G108A abolish the binding of ligands like l- serine. A specific transition to higher order oligomers is observed upon the addition of l- serine at ∼0.8 molar ratio as supported by Isothermal calorimetry and Size exclusion chromatography experiments. Mutational analysis shows that the transition is dependent on binding of l- serine to the ACT-domains. Furthermore, the higher-order oligomeric form of MtSerB2 is inactive, suggesting that its formation is a mechanism for feedback control of enzyme activity. Inhibition studies involving over eight inhibitors, MtSerB2, and the PSP domain respectively, suggests that targeting the ACT-domains can be an effective strategy for the development of inhibitors.     

The effect of antiapoptosis genes on clarification performance

Optimal bioreactor harvest time is typically determined based on maximizing product titer without compromising product quality. We suggest that ease of downstream purification should also be considered during harvest. In this view, we studied the effect of antiapoptosis genes on downstream performance. Our hypothesis was that more robust cells would exhibit less cell lysis and thus generate lower levels of cell debris and host‐cell contaminants. We focused on the clarification unit operation, measuring postclarification turbidity and host‐cell protein (HCP) concentration as a function of bioreactor harvest time/cell viability. In order to mimic primary clarification using disk‐stack centrifugation, a scale‐down model consisting of a rotating disk (to simulate shear in the inlet feed zone of the centrifuge) and a swinging‐bucket lab centrifuge was used. Our data suggest that in the absence of shear during primary clarification (typical of depth filters), a 20–50% reduction in HCP levels and 50–65% lower postcentrifugation turbidity was observed for cells with antiapoptosis genes compared to control cells. However, on exposing the cells to shear levels typical in a disk‐stack centrifuge, the reduction in HCP was 10–15% while no difference in postcentrifugation turbidity was observed. The maximum benefit of antiapoptosis genes is, therefore, realized using clarification options that involve low shear, <1 × 10⁶ W/m³ and minimal damage to the cells. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 30:100–107, 2014     

Hidden reservoirs of pathogens in dental settings

Nosocomial infections are a major concern to both clinicians and health care seekers. Investigations have suggested that laptops & mobile phones may contribute to cross-contamination and can serve as vehicles for infection transmission. Therefore, it is of interest to document the data on hidden reservoirs such as mobile phones and laptops of pathogens in dental settings at the Hazaribag College of dental sciences and Hospital, Jharkhand. The samples were collected from 25 laptops and 25 mobile phones from dentists working in a dental college in Hazaribag city. The samples were collected aseptically using sterile cotton swabs dipped in sterile saline by rotating the swabs on the keyboard surfaces of laptops and mobile phones, inoculated into Brain Heart Infusion broth, vortexed for 1 minute in Fischer Vortex Genie 2 on highest setting & streaked immediately on 5% sheep blood agar plates and were incubated at 37°C for 24 hours aerobically. The isolates were identified based on the colony morphology, colony characteristics and biochemical reactions. The bacterial species isolated were Staphylococcus aureus, Coagulase negative Staphylococcus, Bacillus species, Enterococci, Micrococci, and Pseudomonas etc. Predominant species isolated was Staphylococcus aureus and least was Micrococci. Higher percentage of organisms was found at the Department of Periodontics, Endodontics and least was found in Department of Public Health Dentistry. The percentage and type of organism isolated from keyboards of laptops and mobile phones were similar. Thus, laptops and mobile phones act as vehicles for transfer of potential pathogens associated with dental hospitals. Disinfecting the hands prior to examination of patients and disinfection of laptops and mobiles with alcohol wipes should be done to prevent nosocomial infections.