Ordinary stoichiometry of extraordinary microorganisms

All life on Earth seems to be made of the same chemical elements in relatively conserved proportions (stoichiometry). Whether this stoichiometry is conserved in settings that differ radically in physicochemical conditions (extreme environments) from those commonly encountered elsewhere on the planet provides insight into possible stoichiometries for putative life beyond Earth. Here, we report measurements of elemental stoichiometry for extremophile microbes from hot springs of Yellowstone National Park (YNP). Phototrophic and chemotrophic microbes were collected in locations spanning large ranges of temperature (24 °C to boiling), pH (1.6–9.6), redox (0.1–7.2 mg L^?1 dissolved oxygen), and nutrient concentrations (0.01–0.25 mg L^?1 , 0.7–12.9 mg L^?1 , 0.01–42 mg L^?1 NH₄⁺, 0.003–1.1 mg L^?1 P mostly as phosphate). Despite these extreme conditions, the microbial cells sampled had a major and trace element stoichiometry within the ranges commonly encountered for microbes living in the more moderate environments of lakes and surface oceans. The cells did have somewhat high C:P and N:P ratios that are consistent with phosphorus (P) limitation. Furthermore, chemotrophs and phototrophs had similar compositions with the exception of Mo content, which was enriched in cells derived from chemotrophic sites. Thus, despite the extraordinary physicochemical and biological diversity of YNP environments, life in these settings, in a stoichiometric sense, remains much the same as we know it elsewhere.     

Ontogeny of the antennal glands in the crayfish Astacus leptodactylus (Crustacea, Decapoda): immunolocalization of Na+,K+-ATPase

The involvement of the antennal urinary glands in the ontogeny of osmoregulatory functions was investigated during the development of Astacus leptodactylus by measurements of hemolymph and urine osmolality in juvenile and adult crayfish and by the immunodetection of the enzyme Na⁺,K⁺-ATPase. In stage II juveniles, 1-year-old juveniles, and adults, all of which were maintained in freshwater, urine was significantly hypotonic to hemolymph. In adults, chloride and sodium concentrations were much lower in urine than in hemolymph. During embryonic development, Na⁺,K⁺-ATPase was detected by immunocytochemistry in ionocytes lining the tubule and the bladder, at an eye index (EI) of 220–250 m, and in the labyrinth, at EI 350 m. In all regions, immunofluorescence was mainly located at the basolateral side of the cells. No immunofluorescence was detected at any stage in the coelomosac. In late embryonic stages (EI 410–440 m), in stage I juveniles, and in adults, strong positive immunofluorescence was found from the labyrinth up to and including the bladder. These results show that, as early as hatching, juvenile crayfish are able to produce dilute urine hypotonic to hemolymph. This ability originates from the presence of Na⁺,K⁺-ATPase in ion-transporting cells located in the labyrinth, the tubule, and the bladder of the antennal glands and constitutes one of the main adaptations of crayfish to freshwater.We thank the University of Tarbiat Modarres and Ministry of Science, Research and Technology, Islamic Republic of Iran for financial aid and support. Special thanks are also due to the Société Française dExportation des Ressources Educatives (SFERE) for the scholarship to S.K.     

A late methanogen origin for molybdenum-dependent nitrogenase

Mounting evidence indicates the presence of a near complete biological nitrogen cycle in redox-stratified oceans during the late Archean to early Proterozoic (c. 2.5-2.0 Ga). It has been suggested that the iron (Fe)- or vanadium (V)-dependent nitrogenase rather than molybdenum (Mo)-dependent form was responsible for dinitrogen fixation during this time because oceans were depleted in Mo and rich in Fe. We evaluated this hypothesis by examining the phylogenetic relationships of proteins that are required for the biosynthesis of the active site cofactor of Mo-nitrogenase in relation to structural proteins required for Fe-, V- and Mo-nitrogenase. The results are highly suggestive that among extant nitrogen-fixing organisms for which genomic information exists, Mo-nitrogenase is unlikely to have been associated with the Last Universal Common Ancestor. Rather, the origin of Mo-nitrogenase can be traced to an ancestor of the anaerobic and hydrogenotrophic methanogens with acquisition in the bacterial domain via lateral gene transfer involving an anaerobic member of the Firmicutes. A comparison of substitution rates estimated for proteins required for the biosynthesis of the nitrogenase active site cofactor and for a set of paralogous proteins required for the biosynthesis of bacteriochlorophyll suggests that Nif emerged from a nitrogenase-like ancestor approximately 1.5-2.2 Ga. An origin and ensuing proliferation of Mo-nitrogenase under anoxic conditions would likely have occurred in an environment where anaerobic methanogens and Firmicutes coexisted and where Mo was at least episodically available, such as in a redox-stratified Proterozoic ocean basin.     

Effects of sodium chloride, formalin and iodine on the hatching success of common carp, Cyprinus carpio, eggs

Saprolegniales are ubiquitous in natural water supplies of fish hatcheries, and often cause serious disease problems. Sodium chloride, formalin and iodine, administered twice a day as a flush at different concentrations, were tested on infected eggs of common carp, Cyprinus carpio, to evaluate their antifungal activity and effect on hatching rates. Sodium chloride at 35 000 mg L^?1 and formalin at 400 mg L^?1 were found to be most effective in controlling Saprolegnia sp., with 85.4 and 91.8% hatching rates, respectively. Iodine increased the hatching rate by 27% at 200 mg L^?1 (P < 0.05). There were infections on eggs exposed to all levels of iodine, but not on eggs treated with sodium chloride and formalin. Sodium chloride and formalin were more effective than iodine in controlling Saprolegnia. Sodium chloride is a safe, efficacious and economical treatment of Saprolegniosis and is therefore recommended for treating common carp eggs.     

Ontogeny and osmoregulatory function of the urinary system in the Persian sturgeon,Acipenser persicus (Borodin, 1897)

The structure of the kidney and the localization of Na⁺, K⁺-ATPase (NKA) immunopositive cells were examined throughout the postembryonic development of the Persian sturgeon, Acipenser persicus, from newly hatched prelarvae (10 mm) to 20 days post hatch (20 DPH) larvae (31 mm). Investigations were conducted through histology and immunohistochemistry by using the light and immunofluorescence microscopy. The pronephros was observed in newly hatched prelarvae. The cells lining the distal pronephric tubules and their collecting ducts showed laterally expressed NKA immunofluorescence that later extended throughout the whole cytoplasm. Mesonephrogenous placodes and pre-glomeruli were distinguished at 2 DPH along the collecting ducts posteriorly. Their tubules were formed and present in kidney mesenchyma, differentiated into neck, proximal, distal and collecting segments at 7 DPH when NKA immunopositive cells were observed. Their distal and collecting tubules showed an increasing immunofluorescence throughout their cytoplasm while the glomeruli remained unstained. From D 9 to D 17, the epithelial layer of pronephric collecting duct changed along the mesonephros to form ureters. Ureters, possessing isolated strong NKA immunopositive cells, appeared as two sac-like structures hanging under the trunk kidney. Since NKA immunopositive cells were not observed on the tegument or along the digestive tract of newly hatched prelarva, and also the gills are not formed yet, the pronephros is the only osmoregulatory organ until 4 DPH. At the larval stage, the pronephros and mesonephros are functional osmoregulatory organs and actively reabsorb necessary ions from the filtrate.     

Global marine redox changes drove the rise and fall of the Ediacara biota

The role of O₂ in the evolution of early animals, as represented by some members of the Ediacara biota, has been heavily debated because current geochemical evidence paints a conflicting picture regarding global marine O₂ levels during key intervals of the rise and fall of the Ediacara biota. Fossil evidence indicates that the diversification the Ediacara biota occurred during or shortly after the Ediacaran Shuram negative C‐isotope Excursion (SE), which is often interpreted to reflect ocean oxygenation. However, there is conflicting evidence regarding ocean oxygen levels during the SE and the middle Ediacaran Period. To help resolve this debate, we examined U isotope variations (δ²³⁸U) in three carbonate sections from South China, Siberia, and USA that record the SE. The δ²³⁸U data from all three sections are in excellent agreement and reveal the largest positive shift in δ²³⁸U ever reported in the geologic record (from ~ ?0.74‰ to ~ ?0.26‰). Quantitative modeling of these data suggests that the global ocean switched from a largely anoxic state (26%–100% of the seafloor overlain by anoxic waters) to near‐modern levels of ocean oxygenation during the SE. This episode of ocean oxygenation is broadly coincident with the rise of the Ediacara biota. Following this initial radiation, the Ediacara biota persisted until the terminal Ediacaran period, when recently published U isotope data indicate a return to more widespread ocean anoxia. Taken together, it appears that global marine redox changes drove the rise and fall of the Ediacara biota.     

Lecithin soybean phospholipid nano-transfersomes as potential carriers for transdermal delivery of the human growth hormone

Pharmaceutical molecules such as peptides and proteins are usually injected into the body. Numerous efforts have been made to find new noninvasive ways to administer these peptides. In this study, highly flexible vesicles (transfersomes [TFs]) were designed as a new modern transdermal drug delivery system for systemic drug administration through the skin, which had also been evaluated in vitro. In this study, two growth hormone-loaded TF formulations were prepared, using soybean lecithin and two different surfactants; F₁_sodium deoxycholate and F ₂_sodium lauryl sulfate. Thereafter, the amount of skin penetration by the two formulas was assessed using the Franz diffusion cell system. TF formulations were evaluated for size, zeta potential and in vitro skin penetration across the rat skin. Results indicated that vesicle formulations were stable for 4 weeks and their mean sizes were 241.33 ± 17 and 171 ± 12.12 nm in the F ₁ and F ₂ formulation, respectively. After application to rat skin, transport of the human growth hormone (hGH) released from the TF formulations was found to be higher than that of the hGH alone. Maximum amounts of transdermal hormone delivery were estimated to be 489.54 ± 8.301 and 248.46 ± 4.019 ng·cm−2 , for F ₁ and F ₂, respectively. The results demonstrate the capability of the TF-containing growth hormone in transdermal delivery and superiority of the F ₁ to F ₂ TFs.     

Heat-Induced Production of Human Growth Hormone by High Cell Density Cultivation of Recombinant Escherichia Coli

The temperature-induced, over-expression of the human growth hormone gene in a recombinant E. coli during high cell density cultivation is reported. Human growth hormone (hGH) production and stability were tested under different heat shock conditions. Cell densities were 25 and 60 g l(-1) in a pH-stat fed-batch mode in defined and complex medium, respectively, and the fermentation time was decreased from 41 to 32 h. hGH was produced at 2 g l(-1) in complex medium. By using glycerol as main carbon source in the complex medium with exponential feeding, cell density and hGH production were increased to 100 g l(-1) and 2.7 g l(-1), respectively.