Diaminopimelic Acid Synthesis in Cultures of an Escherichia coli Double Auxotroph: Effects of Cultural Conditions

The metabolic response to L-lysine of Escherichia coli ATCC 13002, a lysine-histidine double auxotroph, has been examined in a synthetic medium containing sucrose. In shaken cultures largest amounts of extracellular DAP were produced with an initial lysine concentration of 7·5 mg/1 and in static cultures of 2·5 mg/1. Considerably smaller amounts of DAP accumulated under stationary conditions. In cultures shaken for 20 and 43 h there was an overall decrease in the yields of DAP, expressed in terms of cell biomass and of sucrose consumed, as the initial concentration of lysine was increased from 0·75 mg/1 in steps up to 25 mg/1. The regulatory effect of lysine on DAP production was also observed when lysine was supplied to cultures at a constant rate employing diffusion capsules.     

Phagocytosis of degenerating myelin in transected feline optic nerve: an immunohistochemical study

The phagocytic activity of neuroglial cells in adult feline degenerating optic nerve was investigated by immunocytochemistry at both light and electron microscopy levels. Degeneration was initiated by unilateral eye enucleation and the segment distal to the transection showing true Wallerian degeneration was examined. Following enucleation, twelve adult domestic cats were examined over a period of seven to 215 days. All cases showed slow clearance of myelin debris and absence of proliferating monocytes throughout the post-enucleation period. All phagocytic cells present were neuroglial cells, and many of these cells expressed oligodendroglial antigens. These findings demonstrate the persistence of an active population of oligodendrocytes that might play an additional functional role during Wallerian degeneration of feline optic nerve.     

EDTA reduces heavy metal impacts on Tribulus terrestris photosynthesis and antioxidants

The effects of EDTA application to heavy metal-polluted soil on phytoextraction of heavy metals, leaf anatomy, gas exchange parameters, enzyme activities of C₄ carbon cycle, antioxidant defense, and active compounds of Tribulus terrestris L. were evaluated. The addition of EDTA to the soil polluted with Cd and Pb markedly increased dry weight and Pb, Zn, and Cd contents in shoots. Plants responded to the action of EDTA by an increased stomatal conductance, photosynthetic and transpiration rates, water use efficiency, chlorophyll and carotenoid contents. The activities of C₄ carbon cycle enzymes simultaneously increased, thus concentrating CO₂ for enhanced CO₂ assimilation and providing NADPH for the antioxidant system. Antioxidants, such as ascorbate, reduced glutathione, and flavonoids, increased more in the shoots of T. terrestris after the addition of EDTA. The activities of guaiacol peroxidase, catalase, and the enzymes of the ascorbate-glutathione cycle enhanced significantly in the presence of EDTA. Increased activities of antioxidant enzymes suggest that they have some additive functions in the mechanism of metal tolerance. EDTA application lowered the activity of phenylalanine ammonia-lyase and the content of total phenols, MDA, hydrogen peroxide, dehydroascorbate, and lipid-soluble antioxidant capacity expressed as α-tocopherol. Increased levels of total radical-scavenging activity are in correspondence with the activity of water-soluble antioxidant compounds in T. terrestris tissues. The content of furostanol saponins protodioscin, prototribestin, and rutin increased as a result of EDTA addition. The results obtained allowed us to assume that applied EDTA reduced a negative heavy metal impact on puncture vine photosynthesis and antioxidant potential.     

Identity and phylogenetic placement of Spirogyra species (Zygnematophyceae,Charophyta) from California streams and elsewhere1

Diversity of the filamentous green algae in the genus Spirogyra (Zygnematophyceae) was investigated from more than 1,200 stream samples from California. We identified 12 species of Spirogyra not previously known for California (CA), including two species new to science, Spirogyra californica sp. nov. and Spirogyra juliana sp. nov. Environmental preferences of the Californian species are discussed in the light of their restricted distribution to stream habitats with contrasting nutrient levels. We also investigated the systematic relationships of Spirogyra species from several continents using the chloroplast‐encoded genes ribulose‐1,5‐bisphosphate carboxylase/hydrogenase large subunit (rbcL) and the beta subunit of the ATP synthase (atpB). Californian species were positioned in most major clades of Spirogyra. The phylogeny of Spirogyra and its taxonomic implications are discussed, such as the benefits of combining structural and molecular data for more accurate and consistent species identification. Considerable infraspecific genetic variation of globally distributed Spirogyra species was observed across continental scales. This finding suggests that structurally similar species from distant regions may be genetically dissimilar and that Spirogyra may contain a large number of cryptic species. Correlating the morphological and genetic variation within the genus will be a major challenge for future researchers.     

Production, recovery and immunogenicity of the protective antigen from a recombinant strain of Bacillus anthracis

The protective antigen (PA) is one of the three components of the anthrax toxin. It is a secreted nontoxic protein with a molecular weight of 83 kDa and is the major component of the currently licensed human vaccine for anthrax. Due to limitations found in the existing vaccine formulation, it has been proposed that genetically modified PA may be more effective as a vaccine. The expression and the stability of two recombinant PA (rPA) variants, PA-SNKE-ΔFF-E308D and PA-N657A, were studied. These proteins were expressed in the nonsporogenic avirulent strain BH445. Initial results indicated that PA-SNKE-ΔFF-E308D, which lacks two proteolysis-sensitive sites, is more stable than PA-N657A. Process development was conducted to establish an efficient production and purification process for PA-SNKE-ΔFF-E308D. pH, media composition, growth strategy and protease inhibitors composition were analyzed. The production process chosen was based on batch growth of B. anthracis using tryptone and yeast extract as the only source of carbon, pH control at 7.5, and antifoam 289. Optimal harvest time was 14–18 h after inoculation, and EDTA (5 mM) was added upon harvest for proteolysis control. Recovery of the rPA was performed by expanded-bed adsorption (EBA) on a hydrophobic interaction chromatography (HIC) resin, eliminating the need for centrifugation, microfiltration and diafiltration. The EBA step was followed by ion exchange and gel filtration. rPA yields before and after purification were 130 and 90 mg/l, respectively. The purified rPA, without further treatment, treated with small amounts of formalin or adsorbed on alum, induced, high levels of IgG anti-PA with neutralization activities. Journal of Industrial Microbiology & Biotechnology (2002) 28, 232–238 DOI: 10.1038/sj/jim/7000239 Received 28 August 2001/ Accepted in revised form 20 December 2001     

Second‐derivative synchronous spectrofluorimetric determination of nebivolol hydrochloride and amlodipine besylate in their combined dosage form

A rapid, simple, accurate and highly sensitive spectrofluorimetric method was developed for the simultaneous analysis of nebivolol hydrochloride (NEB) and amlodipine besylate (AML). The method was based on measuring the synchronous fluorescence intensity of the drugs at Δλ = 40 nm in methanol. Various experimental parameters affecting the synchronous fluorescence of the studied drugs were carefully studied and optimized. The calibration plots were rectilinear over concentration ranges of 0.05–1.5 µg/mL and 0.5–10 µg/mL for NEB and AML with limits of detection (LOD) of 0.010 and 0.051 µg/mL and limits of quantitation (LOQ) of 0.031 and 0.156, respectively. The peak amplitudes (²D) of the second derivative synchronous fluorimetry (SDSF) were estimated at 282 nm for NEB and at 393 nm for AML. Good linearity was obtained over the concentration ranges. The proposed method was successfully applied to the determination of the studied compounds in laboratory‐prepared mixtures, commercial single and laboratory‐prepared tablets. The results were in good agreement with those obtained using the comparison method. The mean percent recoveries were found to be 100.12 ± 0.77 and 99.91 ± 0.77 for NEB and AML, respectively. Copyright © 2015 John Wiley & Sons, Ltd.