A preliminary study of the bioremediation potential of Codium fragile applied to seaweed integrated multi-trophic aquaculture (IMTA) during the summer

In integrated multi-trophic aquaculture (IMTA), seaweeds have the capacity to reduce the environmental impact of nitrogen-rich effluents in coastal ecosystems. To establish such bioremediation systems, selection of suitable seaweed species is important. The distribution and productivity of seaweeds vary seasonally based on water temperature and photoperiod. In Korea, candidate genera such as Pophyra, Laminaria, and Undaria grow from autumn to spring. In contrast, Codium grows well at relatively high water temperatures in summer. Thus, aquaculture systems potentially could capitalize on Codium’s capacity for rapid growth in the warm temperatures of late summer and early fall. In this study, we investigated ammonium uptake and removal efficiency by Codium fragile. In laboratory experiments, we grew C. fragile under various water temperatures (10, 15, 20, and 25°C), irradiances (dark, 10, and 100 μmol photons m⁻² s⁻¹), and initial ammonium concentrations (150 and 300 μM); in all cases, C. fragile exhausted the ammonium supply for 6 h. At 150 μM of , ammonium removal efficiency was greatest (99.5 ± 2.6%) when C. fragile was incubated at 20°C under 100 μmol photons m⁻² s⁻¹. At 300 μM of , removal efficiency was greatest (86.3 ± 2.1%) at 25°C under 100 μmol photons m⁻² s⁻¹. Ammonium removal efficiency was significantly greater at 20 and 25°C under irradiance of 100 μmol photons m⁻² s⁻¹ than under other conditions tested.     

Physicochemical Properties and Oxidative Inactivation of Soluble Lectin from Water Buffalo (<Emphasis Type="Italic">Bubalus bubalis</Emphasis>) Brain

Lectins are carbohydrate-binding proteins present in a wide variety of plants and animals, which serve various important physiological functions. A soluble β-galactoside binding lectin has been isolated and purified to homogeneity from buffalo brain using ammonium sulphate precipitation (40–70%) and gel permeation chromatography on Sephadex G_50–80 column. The molecular weight of buffalo brain lectin (BBL) as determined by SDS-PAGE under reducing and non-reducing conditions was 14.2 kDa, however, with gel filtration it was 28.5 kDa, revealing the dimeric form of protein. The neutral sugar content of the soluble lectin was estimated to be 3.3%. The BBL showed highest affinity for lactose and other sugar moieties in glycosidic form, suggesting it to be a β-galactoside binding lectin. The association constant for lactose binding as evidenced by Scatchard analysis was 6.6 × 10³ M⁻¹ showing two carbohydrate binding sites per lectin molecule. A total inhibition of lectin activity was observed by denaturants like guanidine HCl, thiourea and urea at 6 M concentration. The treatment of BBL with oxidizing agent destroyed its agglutination activity, abolished its fluorescence, and shifted its UV absorption maxima from 282 to 250 nm. The effect of H₂O₂ was greatly prevented by lactose indicating that BBL is more stable in the presence of its specific ligand. The purified lectin was investigated for its brain cell aggregation properties by testing its ability to agglutinate cells isolated from buffalo and goat brains. Rate of aggregation of buffalo brain cells by purified protein was more than the goat brain cells. The data from above study suggests that the isolated lectin may belong to the galectin-1 family but is glycosylated unlike those purified till date.     

Nitrogen uptake and assimilation in Enteromorpha intestinalis (L.) Link (Chlorophyta): using N to determine preference during simultaneous pulses of nitrate and ammonium

We investigated the ability of Enteromorpha intestinalis (L.) Link to take up pulses of different species of nitrogen simultaneously, as this would be an important mechanism to enhance bloom ability in estuaries. Uptake rates and preference for NH₄⁺ or NO₃⁻ following 1, 3, 6, 9, 12 or 24 h of exposure to either ¹⁵NH₄NO₃ or NH₄¹⁵NO₃ were determined by disappearance of N from the medium. Differences in assimilation rates for NH₄⁺ or NO₃⁻ were quantified by the accumulation of NH₄⁺, NO₃⁻, and atom % ¹⁵N in the algal tissue. NH₄⁺ concentration was reduced more quickly than water NO₃⁻ concentration. Water column NH₄⁺ concentration after the longest time interval was reduced from 300 to 50 μM. Water NO₃⁻ was reduced from 300 to 150 μM. The presence of ¹⁵N or ¹⁴N had no effect on uptake of either NH₄⁺ or NO₃⁻. ¹⁵N was removed from the water at an almost identical rate and magnitude as ¹⁴N. Differences in accumulation of ¹⁵NH₄⁺ and ¹⁵NO₃⁻ in the tissue reflected disappearance from the water; ¹⁵N from NH₄⁺ accumulated faster and reached an atom % twice that of ¹⁵N from NO₃⁻. This outcome suggested that when NH₄⁺ and NO₃⁻ were supplied in equal concentrations, more NH₄⁺ was taken up and assimilated. The ability to take up high concentrations of NH₄⁺, and NO₃⁻ simultaneously is important for bloom-forming species of estuarine macroalgae subject to multiple nutrient species from various sources.     

Gating Properties of Inward-Rectifier Potassium Channels: Effects of Permeant Ions

Two inward-rectifier K⁺ channels, ROMK2 (Kir1.1b) and IRK1 (Kir2.1), were expressed in Xenopus oocytes and their gating properties were studied in cell-attached membrane patches. The gating properties depended strongly on the ion being conducted (K⁺, NH₄ ⁺, Rb⁺, or Tl⁺), suggesting tight coupling between permeation and gating. Mean open times were strongly dependent on the nature of the conducted ion. For ROMK2 the order from the longest to the shortest times was K⁺ > Rb⁺ > Tl⁺ > NH₄ ⁺. For IRK1 the sequence was K⁺ > NH₄ ⁺ > Tl⁺. In both cases the open times decreased monotonically as the membrane voltage was hyperpolarized. Both the absolute values and the voltage dependence of closed times were dependent on the conducted species. ROMK2 showed a single closed state whose mean lifetimes were biphasic functions of voltage. The maxima were at various voltages for different ions. IRK1 had at least two closed states whose lifetimes decreased monotonically with K⁺, increased monotonically with Tl⁺, and were relatively constant with NH₄ ⁺ as the conducted ion. We explain the ion-dependence of gating by assuming that the ions bind to a site within the permeation pathway, resulting in a stable, ion-dependent, closed state of the channel. The patterns of voltage-dependence of closed-state lifetimes, which are specific for different ions, can be explained by variations in the rate at which the bound ions leave the pore toward the inside or the outside of the cell. Received: 18 April 2001/Revised: 28 June 2001     

Accumulation of some nitrogen compounds in response to salt stress and their relationships with salt tolerance in rice (Oryza sativa L.) seedlings

The salt-induced accumulation of some nitrogen compounds (free amino acids, ammonium and urea) in shoots of eight rice cultivars differing in salt tolerance was investigated. Salt treatment (100 mM, 6 days) significantly increased the proline content of shoots but this appeared to be a reaction to stress damage and not associated with salt tolerance, because proline contents were higher in the more sensitive cultivars. Besides proline, some other free amino acids also accumulated leading to a significant increase in the total amino acid content of the stressed seedlings. High levels of free ammonium also accumulated under conditions of stress; this was highly correlated with the accumulation of Na⁺ in the shoots and negatively correlated with salt tolerance. The accumulation of ammonium was positively correlated with the accumulation of many free amino acids, and also associated with the production of urea in the stressed seedlings. Results from the present investigations suggest that an increase in the concentration of some free amino acids including proline, may be a result of the reassimilation of the stress-induced ammonium. A high capacity to assimilate ammonium may be an important factor in alleviating the consequence of stress because ammonium can be toxic at high concentrations.     

Nitrogen Use Efficiency of Crop Plants: Physiological Constraints upon Nitrogen Absorption

Current global nitrogen fertilizer use has reached approximately one hundred billion kg per annum. In many agricultural systems, a very substantial portion of this applied nitrogen fertilizer is lost from soil to groundwaters, rivers and oceans. While soil physicochemical properties play a significant part in these losses, there are several characteristic features of plant nitrogen transporter function that facilitate N losses. Nitrate and ammonium efflux from roots result in a reduction of net nitrogen uptake. As external nitrate and ammonium concentrations, respectively, are increased, particularly into the range of concentrations that are typical of agricultural soils, elevated rates of nitrate and ammonium efflux result. The rapid down-regulation of high-affinity influx as plants become nitrogen replete further reduces the root's capacity to acquire external nitrogen; only nitrogen-starved roots absorb with both high capacity and high affinity. The results of studies using molecular biology methods demonstrate that genes encoding nitrate and ammonium transporters are rapidly down-regulated when nitrogen is resupplied to nitrogen-starved plants. Provision of ammonium to roots of plants actively absorbing nitrate imposes a block on nitrate uptake, the extent of which depends on the ammonium concentration, thus further reducing the efficient utilization of soil nitrate. During the daily variation of incoming light and during periods of low incident irradiation (i.e. heavy cloud cover) the expression levels of genes encoding nitrate and ammonium transporters, and rates of nitrate and ammonium uptake, are substantially reduced. Low temperatures reduce growth and nitrogen demand, and appear to discriminate against high-affinity nitrogen influx. In sum, these several factors conspire to limit rates of plant nitrogen uptake to values that are well below capacity. These characteristics of the plant's nitrogen uptake systems facilitate nitrogen losses from soils.     

Alternative pathway respiration is associated with ammonium ion sensitivity in spinach and pea plants

Spinach and pea plants were grown in hydroponic culture with nitrate orammonium salts as the nitrogen source. Dry matter accumulation andphotosynthetic rate declined in spinach plants fed with ammonium salts, whereasthey did not change in pea plants compared with nitrate-fed plants. Measurementof organic nitrogen and free amino acid content showed that ammonium ions wereassimilated in shoots in spinach plants and in roots in pea plants. Ammoniumionnutrition led to a decline in starch content in both species. Organic acidsincreased in roots of pea plants fed with ammonium ions whereas they declinedinspinach plants. In both species ammonium ions increased root respiration ratebut the contribution of both routes (cytochromic and alternative pathway) tothis increase was different depending on the species. In spinach plants,ammonium ions increased the cytochromic path and decreased the alternativepathway, whereas in pea plants both routes were stimulated mainly through thealternative pathway. The differences in the sensitivity to ammonium ionsbetweenboth species are discussed in terms of differences in the availability of Cskeletons and energy, which could be due in part to differences in the capacityto stimulate the alternative pathway.     

Evaluation of in vitro activity of copper gluconate against SARS-CoV-2 using confocal microscopy-based high content screening

ContextSevere Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that emerged late in 2019 is the etiologic agent of coronavirus disease 2019 (Covid-19). There is an urgent need to develop curative and preventive therapeutics to limit the current pandemic and to prevent the re-emergence of Covid-19. This study aimed to assess the in vitro activity of copper gluconate against SARS-CoV-2.MethodsVero E6 cells were cultured with or without copper gluconate 18−24 hours before infection. Cells were infected with a recombinant GFP expressing SARS-CoV-2. Cells were infected with a recombinant GFP expressing SARS-CoV-2. Infected cells were incubated in fresh medium containing varying concentration of copper gluconate (supplemented with bovine serum albumin or not) for an additional 48 -h period. The infection level was measured by the confocal microscopy-based high content screening method. The cell viability in presence of copper gluconate was assessed by XTT and propidium iodide assays.ResultsThe viability of Vero E6 cells exposed to copper gluconate up to 200 μM was found to be similar to that of unexposed cells, but it dropped below 70 % with 400 μM of this agent after 72 h of continuous exposure. The infection rate was 23.8 %, 18.9 %, 20.6 %, 6.9 %, 5.3 % and 5.2 % in cells treated prior infection with 0, 2, 10, 25, 50 and 100 μM of copper gluconate respectively. As compared to untreated cells, the number of infected cells was reduced by 71 %, 77 %, and 78 % with 25, 50, and 100 μM of copper gluconate respectively (p < 0.05). In cells treated only post-infection, the rate of infection dropped by 73 % with 100 μM of copper gluconate (p < 0.05). However, the antiviral activity of copper gluconate was abolished by the addition of bovine serum albumin.ConclusionCopper gluconate was found to mitigate SARS-CoV-2 infection in Vero E6 cells but this effect was abolished by albumin, which suggests that copper will not retain its activity in serum. Furthers studies are needed to investigate whether copper gluconate could be of benefit in mucosal administration such as mouthwash, nasal spray or aerosols.     

Bioconversion of dethiobiotin to biotin by a cell-free system of a bioYB transformant of Bacillus sphaericus

Abstract Potassium-limited cultures of Candida utilis grown with ammonium chloride as the sole nitrogen source attained a higher dry weight than similar cultures grown with sodium nitrate as the sole nitrogen source. This increase depended on the extracellular ammonia concentration and was not due to accumulation of storage polymers. We conclude that in this yeast ammonium ions can fulfill to some extent the physiological role of potassium ions and that the intracellular concentration of ammonium ions is predominantly determined by the ammonia concentration in the culture medium.