Assimilation Of Ions Research Articles

Aspectos macro e micromorfológicos e histológicos do intestino do pirarucu Arapaima gigas (SCHINZ, 1822) (Osteoglossiformes: Arapaimidae)

Currently, the fish farming with Arapaima gigas has suffered from technological obstacles in the fields of reproduction, health and nutrition, making it necessary to know the morphology of its structures, so that it can advance in more technified research in scope of production in Rondônia state, as well as in aquaculture nutrition and health. Therefore, the aimed is to characterize the macro and microscopic morphology of posterior digestive system of A. gigas. The intestine of six specimens A. gigas in ideal slaughter size was analyzed. The analyzes were performed using light-sheet microscopy (LM) and scanning electron (SEM) techniques. The intestine basically showes similar histological characteristics in three analyzed portions (proximal, middle and distal). Same type of simple columnar epithelium with goblet cells was evidenced, with subtle variations in pattern of villi in each segment, and in number of goblet cells. In the rectum, the amount of goblet cells and evident longitudinal villi was expressive. Macroscopic anatomy and histology of the intestine A. gigas analyzed showes characteristics of adaptation to cultivation, according to their diet and habitat. The intestinal mucosa can divided into three distinct portions: proximal, middle and final intestine, in addition to the rectum and anus. In the pyloric cecum, the folds are slightly higher and poorly branched. The rectum, compared to the midgut, showed a higher occurrence of goblet cells in the mucosa. This increase in goblet cells observed in the posterior portion may related to the assimilation of ions and fluids that occur at this location.

Structural Identification of Metalloproteomes in Marine Diatoms, an Efficient Algae Model in Toxic Metals Bioremediation.

The biosorption of pollutants using microbial organisms has received growing interest in the last decades. Diatoms, the most dominant group of phytoplankton in oceans, are (i) pollution tolerant species, (ii) excellent biological indicators of water quality, and (iii) efficient models in assimilation and detoxification of toxic metal ions. Published research articles connecting proteomics with the capacity of diatoms for toxic metal removal are very limited. In this work, we employed a structural based systematic approach to predict and analyze the metalloproteome of six species of marine diatoms: Thalassiosira pseudonana, Phaeodactylum tricornutum, Fragilariopsis cylindrus, Thalassiosira oceanica, Fistulifera solaris, and Pseudo-nitzschia multistriata. The results indicate that the metalloproteome constitutes a significant proportion (~13%) of the total diatom proteome for all species investigated, and the proteins binding non-essential metals (Cd, Hg, Pb, Cr, As, and Ba) are significantly more than those identified for essential metals (Zn, Cu, Fe, Ca, Mg, Mn, Co, and Ni). These findings are most likely related to the well-known toxic metal tolerance of diatoms. In this study, metalloproteomes that may be involved in metabolic processes and in the mechanisms of bioaccumulation and detoxification of toxic metals of diatoms after exposure to toxic metals were identified and described.

Biota communities influence on nutrients circulation in hyporheic zone\u2014a case study in urban spring niches in Bialystok (NE Poland)

Hyporheic zone (HZ) is an interstitial part of groundwater. Complex physical, chemical and biological processes in HZ impact water quality. We hypothesized that groundwater upwelling improves surface water with biogenic compounds in lowland spring niches, and it depends on among others biota communities. The research was conducted in two spring niches in suburbs of Białystok. Interstitial samples were collected with mini-piezometers. In the field, the physical parameters of water were examined, and the micro and macro elements were determined in the laboratory. The analysis of biota included: vascular plants and bryophytes, diatoms, macroinvertebrates and bacteria. The springs studied differed in their richness of organisms, which is associated with varying degrees of abiotic conditions and human transformation. In spring niche with high degree of naturalness were twice less nitrate ions in the surface water than in interstitial water, which indicates the assimilation of nitrate ions by plants growing on the bottom of the niche. Hydrophilic vegetation performs a stabilizing function by assimilating nitrogen compounds and contributing to a variation in nutrients concentration. Groundwater upwelling enrich surface water with DOC and TON. In spring niche No.1 with patches of vegetation, the largest number of macrozoobenthos was recorded. While, the heterogeneous bottom of spring niche No.2 affected the diversity of habitats, and greater biodiversity of benthic fauna. In interstitial waters, there were about twice as few bacteria as in spring waters. Psychrophilic bacteria were present in interstitial waters that influence natural hyporheic processes including circulation of organic matter in the microbiological loop and self-purification of water.

Assessment and mechanisms of microalgae growth inhibition by phosphonates: Effects of intrinsic toxicity and complexation

The effects of phosphonates, the heavily-used antiscalants in reverse osmosis systems, on microalgae are controversial, although they are harmless to most aquatic organisms. Herein, we assessed the inhibitory effects of etidronic acid (HEDP) and diethylenetriamine penta(methylene phosphonic acid) (DTPMP) on algal growth and revealed the mechanisms involved in both intrinsic toxicity and complexation. The phosphonates showed weak influences on Scenedesmus sp. LX1 in the first 4 d of cultivation. In contrast, a significant growth inhibition was observed subsequently with half maximal effective concentrations of 57.6 and 35.7 mg/L for HEDP and DTPMP, respectively, at 10 d. The phosphonates had little effect on cellular energy transfer and oxidative stress, quantified by adenosine triphosphate level and superoxide dismutase activity, respectively, demonstrating weak intrinsic toxicities to algal cells. Phosphonates blocked the algal assimilation of iron ions through complexation. Severe iron deficiency limited photosynthetic activity and caused chlorophyll decline, resulting in a functional loss of the photosystem followed by complete algal growth inhibition at the late cultivation stage. Our findings point to a potential ecological impact wherein harmful algal blooms are induced by the natural degradation of phosphonates due to the release of both iron and phosphate ions that stimulate algal regrowth after disinhibition.

Assimilation of water and dietary ions by the gastrointestinal tract during digestion in seawater-acclimated rainbow trout

Recent studies focusing on the consequences of feeding for ion and water balance in freshwater fish have revealed the need for similar comparative studies in seawater fish. A detailed time course sampling of gastrointestinal (GI) tract contents following the ingestion of a single meal of a commercial diet revealed the assimilation of both water and dietary ions (Na(+), Cl(-), K(+), Ca(2+), Mg(2+)) along the GI tract of seawater-acclimated rainbow trout (Oncorhynchus mykiss) which had been fasted for 1week. Consumption of the meal did not change the drinking rate. There was a large secretion of fluid into the anterior intestine and caecae (presumably bile and/or pancreatic secretions). As a result, net assimilation (63%) of the ingested water along the GI tract was lower than generally reported for fasted trout. Mg(2+) was neither secreted into nor absorbed from the GI tract on a net basis. Only K(+) (93% assimilated) and Ca(2+) (43% assimilated) were absorbed in amounts in excess of those provided by ingested seawater, suggesting that dietary sources of K(+) and Ca(2+) may be important to seawater teleosts. The oesophagus-stomach served as a major site of absorption for Na(+), Cl(-), K(+), Ca(2+), and Mg(2+), and the anterior intestine and caecae as a major site of net secretion for all of these ions, except Cl(-). Despite large absorptive fluxes of these ions, the ionic composition of the plasma was maintained during the digestion of the meal. The results of the present study were compared with previous work on freshwater-acclimated rainbow trout, highlighting some important differences, but also several similarities on the assimilation of water and ions along the gastrointestinal tract during digestion. This study highlights the complicated array of ion and water transport that occurs in the intestine during digestion while revealing the importance of dietary K(+) and Ca(2+) to seawater-acclimated rainbow trout. Additionally, this study reveals that digestion in seawater-acclimated rainbow trout appears to compromise intestinal water absorption.

Assimilation of Metal Ions Bound to Porphyrins or Porphyrin-Peptides by Vibrio vulnificus, a Human Pathogen Inhabiting Estuarine and Marine Environments

Vibrio vulnificus, a ubiquitous microorganism in aquatic environments, causes serious septicemia to the immunocompromised host. In addition to protoheme, this species can utilize Fe-TCPP [ferric tetrakis (4-carboxyphenyl) porphine] as an iron source. In the present study, heme c bound covalently to the protein in cytochrome c, as well as the Fe-TCPP complex formed with a nanopeptide with a high affinity, was found to be useful iron sources for V. vulnificus. This bacterium was also revealed to use Zn-TCPP as a single zinc source. However, other metalloporphyrins such as Mn-TCPP and Pt-TCPP delayed the bacterial growth in the broth containing Fe-TCPP, suggesting interference in the iron assimilation. These results indicate that V. vulnificus may acquire metal ions from both free and peptide-bound metalloporphyrins.

A soil bacterium regulates plant acquisition of iron via deficiency‐inducible mechanisms

Despite the abundance of iron in nature, it is the third most limiting nutrient for plants due to its minimal solubility in most soils. While certain soil microbes produce chelating agents that enhance the solubility of iron, the effectiveness of such siderophores in the assimilation of iron by plants is debated. With an increasing understanding that select soil microbes play a signaling role in activating growth and stress responses in plants, the question arises as to whether such symbionts regulate iron assimilation. Here we report a previously unidentified mechanism in which the growth-promoting bacterium Bacillus subtilis GB03 activates the plant's own iron acquisition machinery to increase assimilation of metal ions in Arabidopsis. Mechanistic studies reveal that GB03 transcriptionally up-regulates the Fe-deficiency-induced transcription factor 1 (FIT1), which is necessary for GB03-induction of ferric reductase FRO2 and the iron transporter IRT1. In addition, GB03 causes acidification of the rhizosphere by enhancing root proton release and by direct bacterial acidification, thereby facilitating iron mobility. As a result, GB03-exposed plants have elevated endogenous iron levels as well as increased photosynthetic capacity compared with water-treated controls. In contrast, loss-of-function fit1-2 mutants are compromised in terms of enhanced iron assimilation and photosynthetic efficiency triggered by GB03. In all studies reported herein, a physical partition separating roots from bacterial media precludes non-volatile microbial siderophores from contributing to GB03-stimulated iron acquisition. These results demonstrate the potential of microbes to control iron acquisition in plants and emphasize the sophisticated integration of microbial signaling in photosynthetic regulation.

A cambialistic superoxide dismutase in the thermophilic photosynthetic bacterium Chloroflexus aurantiacus.

Superoxide dismutase from the thermophilic anoxygenic photosynthetic bacterium Chloroflexus aurantiacus was cloned, purified, and characterized. This protein is in the manganese- and iron-containing family of superoxide dismutases and is able to use both manganese and iron catalytically. This appears to be the only soluble superoxide dismutase in C. aurantiacus. Iron and manganese cofactors were identified by using electron paramagnetic resonance spectroscopy and were quantified by atomic absorption spectroscopy. By metal enrichment of growth media and by performing metal fidelity studies, the enzyme was found to be most efficient with manganese incorporated, yet up to 30% of the activity was retained with iron. Assimilation of iron or manganese ions into superoxide dismutase was also found to be affected by the growth conditions. This enzyme was also found to be remarkably thermostable and was resistant to H2O2 at concentrations up to 80 mM. Reactive oxygen defense mechanisms have not been previously characterized in the organisms belonging to the phylum Chloroflexi. These systems are of interest in C. aurantiacus since this bacterium lives in a hyperoxic environment and is subject to high UV radiation fluxes.

The regulation of mineral absorption in the gastrointestinal tract.

The absorption of metal ions in the mammalian single-stomached gut is fortunately highly selective, and both luminal and tissue regulation occur. Initially, assimilation of metal ions in an available form is facilitated by the intestinal secretions, chiefly soluble mucus (mucin) that retards hydrolysis of ions such as Cu, Fe and Zn. Metal ions then bind and traverse the mucosally-adherent mucus layer with an efficiency M+ > M2+ > M3+. At the mucosa Fe3+ is probably uniquely reduced to Fe2+, and all divalent cations (including Fe2+) are transported by a membrane protein (such as divalent cation transporter 1) into the cell. This minimizes absorption of toxic trivalent metals (e.g. Al3+). Intracellular metal-binding molecules (such as mobilferrin) may be present at the intracellular side of the apical membrane, anchored to a transmembrane protein such as an integrin complex. This mobilferrin would receive the metal ion from divalent cation transporter 1 and, with part of the integrin molecule, transport the metal to the cytosol for safe sequestration in a larger complex such as ferritin or 'paraferritin'. beta 2-Microglobulin and HFE (previously termed human leucocyte antigen H) may be involved in stabilizing metal mobilferrin-integrin to form this latter complex. Finally, a systemic metal-binding protein such as transferrin may enter the antiluminal (basolateral) side of the cell for binding of the sequestered metal ion and delivery to the circulation. Regulatory proteins, such as HFE, may determine the degree of ion transport from intestinal cells to the circulation. Gradients in pH and perhaps pCa or even pNa could allow the switching of ions between the different transporters throughout this mechanism.

Reduction of Nitrate Ions by Morningglory Leaves

The reduction and assimilation of nitrate ions by 14-day old tall morningglory [Ipomoea purpurea(L.) Roth] seedlings were studied by monitoring the leaf nitrate, protein, and activity of the enzyme nitrate reductase (NADH: nitrate oxidoreductase, EC 1.6.6.1). The pH's of the grinding and assay mixtures yielding maximum nitrate reductase activity were determined to be 8.8 and 7.5 to 7.7, respectively. The maximum assay time for a linear reaction rate for nitrate reductase was estimated at 10 minutes. Decay rates of the enzyme preparations indicated a half-life of 30 min. Requirements for a cofactor to support the reaction were met with the addition of NADH (1 × 10−3M final concentration) to the assay mixture. NADPH was not effective in supporting nitrate reductase activity. Inclusion of cysteine (1 × 10−2M) in the grinding medium was necessary to insure maximum activity of the enzyme preparations. Both light and nitrate were required for nitrate reductase activity in morningglory leaves. Nitrate accumulated in leaf tissue in proportion to the concentration of nitrate in the nutrient medium. Above 7,530 lux luminescence, enzyme activity and tissue protein were related to the light intensity and the availability of nitrate in the nutrient medium on which the plants were grown.

Nitrate-reducing capacity of roots and nodules ofAlnus rubra and roots ofPseudotsuga menziesii

Nitrate-reducing capability was demonstrated for root segments of red alder and, at more than twice that rate, for alder nodules. Root segments of Douglas-fir failed to reduce nitrate despite various treatments designed to induce such activity. The reported response of Douglas-fir to nitrate fertilizer may be ascribed either to microbial assimilation of nitrate ions with subsequent liberation of ammonium in the soil or to nitrate assimilation by fungi that form mycorrhizae with Douglas-fir roots.

Metabolism of Isofloridoside (O-α-D-Galactopyranosyl-(1→1)-Glycerol) and Osmotic Balance in the Fresh Water Alga Ochromonas

So far as is known, algae tend to maintain a constant turgor with the osmotic pressure in their cells higher than the osmotic pressure of the surrounding fluid. This excess osmotic pressure seems to be held constant when the osmotic value of the water changes. Little is known about the mechanisms responsible for this regulation. The assimilation or extrusion of special inorganic ions is assumed to play the chief part in this process in marine algae; in cases of low external osmotic pressure the elimination of water by contractile vacuoles provides some regulation of osmotic balance in fresh water algae1. The experiments reported here show that the golden brown fresh water alga Ochromonas malhamensis has another mechanism for regulating turgor. Here the regulation is connected with the formation and degradation of the carbohydrate isofloridoside and further studies on the biochemistry of the osmotic balance in Ochromonas therefore seem possible.