Absence Of Ammonium Research Articles

Modeling Free Nitrous Acid Inhibition on the Removal of Nitrogen and Atenolol during Sidestream Partial Nitritation Processes.

Sidestream serves as an important reservoir collecting pharmaceuticals from sludge. However, the knowledge on sidestream pharmaceutical removal is still insufficient. In this work, atenolol biodegradation during sidestream partial nitritation (PN) processes characterized by high free nitrous acid (FNA) accumulation was modeled. To describe the FNA inhibition on ammonia oxidation and atenolol removal, Vadivelu-type and Hellinga-type inhibition kinetics were introduced into the model framework. Four inhibitory parameters along with four biodegradation kinetic parameters were calibrated and validated separately with eight sets of batch experimental data and 60 days' PN reactor operational data. The developed model could accurately reproduce the dynamics of nitrogen and atenolol. The model prediction further revealed that atenolol biodegradation efficiencies by ammonia-oxidizing bacteria (AOB)-induced cometabolism, AOB-induced metabolism, and heterotrophic bacteria-induced biodegradation were 0, ∼ 60, and ∼35% in the absence of ammonium and FNA; ∼ 14, ∼ 29, and ∼28% at 0.03 mg-N L-1 FNA; and 7, 15, and 5% at 0.19 mg-N L-1 FNA. Model simulation showed that the nitritation efficiency of ∼99% and atenolol removal efficiency of 57.5% in the PN process could be achieved simultaneously by controlling pH at 8.5, while 89.2% total nitrogen and 57.1% atenolol were removed to the maximum at pH of 7.0 in PN coupling with the anammox process. The pH-based operational strategy to regulate FNA levels was mathematically demonstrated to be effective for achieving the simultaneous removal of nitrogen and atenolol in PN-based sidestream processes.

Unlocking the potential of elemental sulfur autotrophic denitrification through inorganic nutrient optimization

Elemental sulfur packed-bed (S0PB) bioreactors are increasingly employed to treat secondary effluents from wastewater treatment plants. Limited availability of inorganic nutrients, such as ammonium, phosphate, and inorganic carbon, significantly determines the growth of autotrophic microorganisms and the denitrification efficiency. This study investigated the constraining thresholds of inorganic nutrients on the elemental sulfur autotrophic denitrification process. In the absence of ammonium, phosphate, and bicarbonate, the denitrification rate decreased. Specifically, the ammonium assimilation process could be replaced by nitrate assimilation pathways, resulting in a 29.5 % decline in denitrification efficiency when the ammonium-N feed was reduced from 2.0 to 0 mg-N/L. However, the absence of phosphate-P and bicarbonate-C led to substantial drops in denitrification efficiency by 66.7 % and 77.5 %, respectively. This was primarily attributed to diminished biomass yield, as evidenced by reductions of 77.8–82.6 % in ATP and 35.7–44.3 % in protein content, along with a 12.4 %–14.7 % decrease in the relative abundances of dominant sulfur-oxidizing bacteria. Correlation analyses established specific thresholds for desired nitrate removal amounts: 0.131 for ammonium-N, 0.053 for phosphate-P, and 0.597 for bicarbonate-C. These thresholds provided valuable guidance for adjusting real-life wastewater through external supplementation when employing a pilot-scale S0PB bioreactor, leading to a significant enhancement of denitrification efficiency. This study emphasizes the significance of considering the concentrations of inorganic nutrients in wastewater when implementing S0PB bioreactors, which is a context that frequently neglects potential negative consequences.

Horizontally Acquired Nitrate Reductase Realized Kleptoplastic Photoautotrophy ofRapaza viridis.

While photoautotrophic organisms utilize inorganic nitrogen as the nitrogen source, heterotrophic organisms utilize organic nitrogen and thus do not generally have an inorganic nitrogen assimilation pathway. Here, we focused on the nitrogen metabolism of Rapaza viridis, a unicellular eukaryote exhibiting kleptoplasty. Although belonging to the lineage of essentially heterotrophic flagellates, R. viridis exploits the photosynthetic products of the kleptoplasts and was therefore suspected to potentially utilize inorganic nitrogen. From the transcriptome data of R. viridis, we identified gene RvNaRL, which had sequence similarity to genes encoding nitrate reductases in plants. Phylogenetic analysis revealed that RvNaRL was acquired by a horizontal gene transfer event. To verify the function of the protein product RvNaRL, we established RNAi-mediated knock-down and CRISPR-Cas9-mediated knock-out experiments for the first time in R. viridis and applied them to this gene. The RvNaRL knock-down and knock-out cells exhibited significant growth only when ammonium was supplied. However, in contrast to the wild-type cells, no substantial growth was observed when nitrate was supplied. Such arrested growth in the absence of ammonium was attributed to impaired amino acid synthesis due to the deficiency of nitrogen supply from the nitrate assimilation pathway; this in turn resulted in the accumulation of excess photosynthetic products in the form of cytosolic polysaccharide grains, as observed. These results indicate that RvNaRL is certainly involved in nitrate assimilation by R. viridis. Thus, we inferred that R. viridis achieved its advanced kleptoplasty for photoautotrophy, owing to the acquisition of nitrate assimilation via horizontal gene transfer.

Transcriptome analyses reveal the utilization of nitrogen sources and related metabolic mechanisms of Sporosarcina pasteurii.

In recent years, Sporosarcina pasteurii (S. pasteurii) has become one of the most popular bacteria in microbially induced calcium carbonate precipitation (MICP). Various applications have been developed based on the efficient urease that can induce the precipitation of calcium carbonate. However, the metabolic mechanism related to biomineralization of S. pasteurii has not been clearly elucidated. The process of bacterial culture and biomineralization consumes a large amount of urea or ammonium salts, which are usually used as agricultural fertilizers, not to mention probable environmental pollutions caused by the excessive use of these raw materials. Therefore, it is urgent to reveal the mechanism of nitrogen utilization and metabolism of S. pasteurii. In this paper, we compared the growth and gene expression of S. pasteurii under three different culture conditions through transcriptome analyses. GO and KEGG analyses revealed that both ammonium and urea were direct nitrogen sources of S. pasteurii, and the bacteria could not grow normally in the absence of ammonium or urea. To the best of our knowledge, this paper is the first one to reveal the nitrogen utilization mechanism of S. pasteurii through transcriptome methods. Furthermore, the presence of ammonium might promote the synthesis of intracellular ATP and enhance the motility of the bacteria. There should be an ATP synthesis mechanism associated with urea hydrolysis catalyzed by urease in S. pasteurii.

Does molybdenum and cobalt foliar spray mitigate nitrate starvation and ammonium deprivation stress?

Abstract Knowledge about the nutritional balance at the initial phenological stage is mandatory to overcome limitations on nutritional availabilities required by the plant species. However, little is elucidated about nitrate (NO3-) and ammonium (NH4+) deprivation stress. Our hypothesis tested is that there are benefits of the foliar application (spray) of molybdenum (Mo) and cobalt (Co) under different availabilities (ionic strength, IS) from the presence of nitric sources (CaNO32-) and absence of ammonium (NH4H2PO4) in root application (hydroponic cultivation) at the initial phenological growth stage. Nutrient supply was carried out with a nutrient solution, which is deprived of NH4+. Treatments were 25%, 50%, and 100% IS, supplied via hydroponic cultivation, combined with the absence/presence of Co/Mo spray. Plants were randomly distributed into 17 blocks (replicates) with 6 treatments conducted in a factorial scheme and data were analyzed by ANOVA and ANCOVA. We observed that Co/Mo spray diminished plant growth discrepancies between treatments at different IS’s. In addition, contents of photosynthetic pigments were higher at 25% IS without Co/Mo spray. Thus, we concluded that Mo and Co spray can alleviate NO3- starvation/NH4+ deprivation stress during the initial growth phenological stages of yellow passion fruits.

Reexamining the Role of Ammonium Ions in the Sulfidization, Xanthate-Flotation of Malachite

Ammonium ions have positive effects on the sulfidization flotation of malachite; however, the underlying mechanisms remain poorly understood. In the present work, micro-flotation tests, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and solution analysis for ammonium nitrogen were carried out. The flotation results showed positive effects of ammonium on the sulfidization flotation of malachite. Macroscopically, the sulfidized malachite produced with ammonium exhibited a darker color than that without ammonium, whereas the opposite appeared to be true for their corresponding residual liquids. FESEM images highlighted the larger particle size and higher converge density of the sulfidization product when the presence of ammonium. Furthermore, XPS results indicated a higher sulfur concentration on malachite surfaces when the presence of ammonium. XRD results showed that Cu31S16 (djurleite) and Cu7S4 (anilite) comprised the sulfidization products, regardless of the presence or absence of ammonium. However, neither EDS nor XPS analysis showed nitrogen on malachite surfaces; moreover, the residual-ratio results for ammonium nitrogen clearly demonstrated that most ammonium continued to be held in solution before and after malachite sulfidization. Based on these findings, we inferred that ammonium ions may mediate the nucleation and growth of sulfidization product during malachite sulfidization, rendering larger sulfidization product particles. The larger size of sulfidization products may result in a darker, stabler and denser sulfidization product coating layer, and then may reduce the generation of colloidal copper sulfide in the residual liquids. Ultimately, ammonium facilitates better performance of sulfidization flotation of malachite.

The Nitrate Assimilatory Pathway in Sinorhizobium meliloti: Contribution to NO Production.

The interaction between rhizobia and their legume host plants culminates in the formation of specialized root organs called nodules in which differentiated endosymbiotic bacteria (bacteroids) fix atmospheric nitrogen to the benefit of the plant. Interestingly, nitric oxide (NO) has been detected at various steps of the rhizobium-legume symbiosis where it has been shown to play multifaceted roles. It is recognized that both bacterial and plant partners of the Sinorhizobium meliloti–Medicago truncatula symbiosis are involved in NO synthesis in nodules. S. meliloti can also produce NO from nitrate when living as free cells in the soil. S. meliloti does not possess any NO synthase gene in its genome. Instead, the denitrification pathway is often described as the main driver of NO production with nitrate as substrate. This pathway includes the periplasmic nitrate reductase (Nap) which reduces nitrate into nitrite, and the nitrite reductase (Nir) which reduces nitrite into NO. However, additional genes encoding putative nitrate and nitrite reductases (called narB and nirB, respectively) have been identified in the S. meliloti genome. Here we examined the conditions where these genes are expressed, investigated their involvement in nitrate assimilation and NO synthesis in culture and their potential role in planta. We found that narB and nirB are expressed under aerobic conditions in absence of ammonium in the medium and most likely belong to the nitrate assimilatory pathway. Even though these genes are clearly expressed in the fixation zone of legume root nodule, they do not play a crucial role in symbiosis. Our results support the hypothesis that in S. meliloti, denitrification remains the main enzymatic way to produce NO while the assimilatory pathway involving NarB and NirB participates indirectly to NO synthesis by cooperating with the denitrification pathway.

Cometabolic biodegradation of cephalexin by enriched nitrifying sludge: Process characteristics, gene expression and product biotoxicity

The nitrifying systems have been reported to be able to biodegrade micropollutants, yet it is still unclear about the cometabolism of ammonia-oxidizing bacteria (AOB) towards micropollutants, in particular their enzyme and transcriptional responses under exposure of micropollutants. This study investigated cometabolic biodegradation of a selected antibiotic, cephalexin (CFX), by an enriched nitrifying culture through a series of batch experiments, together with the assessments of enzymatic activity, key gene expression, and biotoxicity of the degradation products. More than 99% CFX with an initial concentration of 50 μg/L could be removed with the presence of ammonium, while <44% of CFX removal was observed in the absence of ammonium, suggesting the cometabolic degradation of CFX by ammonia-oxidizing bacteria (AOB). After the addition of 50 μg/L CFX, the ammonia oxidizing rate (AOR) decreased from 36.6 to 11.0 mg N/(L·h·g VSS), followed by a slight recovery when CFX concentration decreased to below 8 μg/L. Ammonia monooxygenase (AMO) activity showed a similar trend with that of AOR. The quantitative reverse transcription PCR assay indicated that the expression level of amoA gene was significantly upregulated (up to 3-fold, p < 0.05) due to the addition of CFX, while decreased to the normal level once CFX was degraded, suggesting a mechanism of AOB to neutralize the toxicity of CFX by metabolizing ammonia more effectively. Meanwhile, the biotoxicity test showed the degradation products of CFX did not exhibit any antibacterial impacts in terms of cell viability, compared to the parent compounds. Our finding shed a light on AMO-mediated cometabolic biodegradation of antibiotics in nitrifying cultures.

The simultaneous removal of ammonium and manganese from surface water by MeOx: Side effect of ammonium presence on manganese removal

Manganese and ammonium pollution in surface water sources has become a serious issue. In this study, a pilot-scale filtration system was used to investigate the effect of ammonium on manganese removal during the simultaneous removal of ammonium and manganese from surface water using a manganese co-oxide filter film (MeOx). The results showed that the manganese removal efficiency of MeOx in the absence of ammonium was high and stable, and the removal efficiency could reach 70% even at 5.5 °C. When the influent ammonium concentration was lower than 0.7 mg/L, ammonium and manganese could be removed simultaneously. However, at an ammonium concentration of 1.5 mg/L, the manganese removal efficiency of the filter gradually decreased with time (from 96% to 46.20%). Nevertheless, there was no impact of manganese on ammonium removal. The mechanism by which ammonium negatively affected manganese removal was investigated, demonstrating that ammonium affected manganese removal mainly through two possible mechanisms. On one hand, the decreased pH caused by ammonium oxidation was unfavorable for the oxidation of manganese by MeOx; on the other hand, the presence of ammonium slowed the growth of new MeOx and retarded the increase in the specific surface area of the MeOx-coated sand, and induced changes in the morphology and crystal structure of MeOx. Consequently, the manganese removal efficiency of the filter decreased when ammonium was present in the inlet water.

A Future Place for Saccharomyces Mixtures and Hybrids in Wine Making

Each year, winemakers can face sluggish or stuck fermentations during wine making, especially when a spontaneous fermentation is performed, even if strains of the classical wine yeast Saccharomyces cerevisiae are applied. Problems are inevitable when low ammonium concentrations (&lt;160 mg L−1 grape must) or an excess of fructose compared to glucose are observed during grape must fermentation. S. cerevisiae strains cannot use all kinds of amino acids as the sole nitrogen source but usually need free ammonium (optimal concentration: 600 mg L−1 grape must). It preferably consumes glucose, leading often to an excess of fructose in the fermenting must, which contains glucose and fructose in an equal ratio at the beginning of fermentation. Yeast hybrids have been isolated from wines several times and different strains are already commercially available. The united properties of the parent strains can provide advantages under sophisticated fermentation conditions. However, the involvement of a hybrid yeast for the rectification of fermentation disorders in spontaneous fermentations has only been described recently in the literature. Recent investigations have provided convincing evidence that fermentation problems can be overcome when must fermentations are successively performed with Saccharomyces bayanus strain HL 77 and the triple hybrid S. cerevisiae × Saccharomyces kudriavzevii × S. bayanus strain HL 78. The triple hybrid strain HL 78 uses amino acids as a nitrogen source in the absence of ammonium and it also exhibits a fructophilic character with an enhanced uptake of fructose in comparison to glucose. The application of genetically modified yeast strains is not allowed for starter cultures in wine making, but the usage of yeast mixtures and hybrid strains could be a promising tool for winemakers to solve fermentation problems during spontaneous fermentation or for the creation of novel wine types with desired sensory characteristics under more challenging conditions, especially when the composition of the must components is not optimal because of, e.g., critical climatic or soil conditions.

Role of zeolite's exchangeable cations in phosphate adsorption onto zirconium-modified zeolite

To determine the role of zeolite's exchangeable cations such as Ca2+ and Na+ in the adsorption of phosphate on zirconium-modified zeolite (ZrMZ), the adsorption behaviors and mechanisms of phosphate on ZrMZ, NaCl-treated ZrMZ and CaCl2-treated ZrMZ in the absence and presence of ammonium were comparatively investigated in this study. Results showed that coexisting ammonium promoted the adsorption of phosphate on the raw, NaCl-treated and CaCl2-treated ZrMZs. In the absence of ammonium, the treatment of ZrMZ with NaCl inhibited the phosphate adsorption, but the treatment of ZrMZ with CaCl2 enhanced the adsorption of phosphate. In the presence of ammonium, the treatment of ZrMZ with NaCl suppressed the adsorption of phosphate, but the effect of CaCl2 treatment on the phosphate adsorption depended upon coexisting ammonium amount. In the presence of a certain amount of ammonium (5–30mg N/L), the treatment of ZrMZ with CaCl2 improved the phosphate adsorption efficiency. The mechanism for phosphate adsorption onto ZrMZ was the exchange of surface hydroxyl groups with phosphate ions and the formation of phosphate inner-sphere coordination complexes, and the enhancement of phosphate adsorption onto ZrMZ by coexisting Ca2+ could be attributed to the formation of CaHPO40 species in the calcium/phosphate solution and the formation of phosphate-bridged ternary complex (Zr)(OPO3H)Ca on the adsorbent surface. The increased phosphate adsorption induced by CaCl2 treatment could be attributed to the increase in the amount of released Ca2+ from ZrMZ, and the decreased phosphate adsorption induced by NaCl treatment could be attributed to the decrease in the amount of released Ca2+ from ZrMZ. This work suggests that the exchangeable Ca2+ in ZrMZ plays an important role in the phosphate adsorption, and its release enhances the adsorption of phosphate.

Detection of Diazotrophy in the Acetylene-Fermenting Anaerobe Pelobacter sp. Strain SFB93.

Acetylene (C2H2) is a trace constituent of the present Earth's oxidizing atmosphere, reflecting a mixture of terrestrial and marine emissions from anthropogenic, biomass-burning, and unidentified biogenic sources. Fermentation of acetylene was serendipitously discovered during C2H2 block assays of N2O reductase, and Pelobacter acetylenicus was shown to grow on C2H2 via acetylene hydratase (AH). AH is a W-containing, catabolic, low-redox-potential enzyme that, unlike nitrogenase (N2ase), is specific for acetylene. Acetylene fermentation is a rare metabolic process that is well characterized only in P. acetylenicus DSM3246 and DSM3247 and Pelobacter sp. strain SFB93. To better understand the genetic controls for AH activity, we sequenced the genomes of the three acetylene-fermenting Pelobacter strains. Genome assembly and annotation produced three novel genomes containing gene sequences for AH, with two copies being present in SFB93. In addition, gene sequences for all five compulsory genes for iron-molybdenum N2ase were also present in the three genomes, indicating the cooccurrence of two acetylene transformation pathways. Nitrogen fixation growth assays showed that DSM3426 could ferment acetylene in the absence of ammonium, but no ethylene was produced. However, SFB93 degraded acetylene and, in the absence of ammonium, produced ethylene, indicating an active N2ase. Diazotrophic growth was observed under N2 but not in experimental controls incubated under argon. SFB93 exhibits acetylene fermentation and nitrogen fixation, the only known biochemical mechanisms for acetylene transformation. Our results indicate complex interactions between N2ase and AH and suggest novel evolutionary pathways for these relic enzymes from early Earth to modern days.IMPORTANCE Here we show that a single Pelobacter strain can grow via acetylene fermentation and carry out nitrogen fixation, using the only two enzymes known to transform acetylene. These findings provide new insights into acetylene transformations and adaptations for nutrient (C and N) and energy acquisition by microorganisms. Enhanced understanding of acetylene transformations (i.e., extent, occurrence, and rates) in modern environments is important for the use of acetylene as a potential biomarker for extraterrestrial life and for degradation of anthropogenic contaminants.

Biotransformation of acyclovir by an enriched nitrifying culture

This work evaluates the biodegradation of the antiviral drug acyclovir by an enriched nitrifying culture during ammonia oxidation and without the addition of ammonium. The study on kinetics was accompanied with the structural elucidation of biotransformation products through batch biodegradation experiments at two different initial levels of acyclovir (15 mg L−1 and 15 μg L−1). The pseudo first order kinetic studies of acyclovir in the presence of ammonium indicated the higher degradation rates under higher ammonia oxidation rates than those constant degradation rates in the absence of ammonium. The positive correlation was found between acyclovir degradation rate and ammonia oxidation rate, confirming the cometabolism of acyclovir by the enriched nitrifying culture in the presence of ammonium. Formation of the product carboxy-acyclovir (P239) indicated the main biotransformation pathway was aerobic oxidation of the terminal hydroxyl group, which was independent on the metabolic type (i.e. cometabolism or metabolism). This enzyme-linked reaction might be catalyzed by monooxygenase from ammonia oxidizing bacteria or heterotrophs. The formation of carboxy-acyclovir was demonstrated to be irrelevant to the acyclovir concentrations applied, indicating the revealed biotransformation pathway might be the dominant removal pathway of acyclovir in wastewater treatment.

The Fate of Marine Bacterial Exopolysaccharide in Natural Marine Microbial Communities.

Most marine bacteria produce exopolysaccharides (EPS), and bacterial EPS represent an important source of dissolved organic carbon in marine ecosystems. It was proposed that bacterial EPS rich in uronic acid is resistant to mineralization by microbes and thus has a long residence time in global oceans. To confirm this hypothesis, bacterial EPS rich in galacturonic acid was isolated from Alteromonas sp. JL2810. The EPS was used to amend natural seawater to investigate the bioavailability of this EPS by native populations, in the presence and absence of ammonium and phosphate amendment. The data indicated that the bacterial EPS could not be completely consumed during the cultivation period and that the bioavailability of EPS was not only determined by its intrinsic properties, but was also determined by other factors such as the availability of inorganic nutrients. During the experiment, the humic-like component of fluorescent dissolved organic matter (FDOM) was freshly produced. Bacterial community structure analysis indicated that the class Flavobacteria of the phylum Bacteroidetes was the major contributor for the utilization of EPS. This report is the first to indicate that Flavobacteria are a major contributor to bacterial EPS degradation. The fraction of EPS that could not be completely utilized and the FDOM (e.g., humic acid-like substances) produced de novo may be refractory and may contribute to the carbon storage in the oceans.

Endomicrobium proavitum, the first isolate of Endomicrobia class. nov. (phylum Elusimicrobia)--an ultramicrobacterium with an unusual cell cycle that fixes nitrogen with a Group IV nitrogenase.

The bacterial tree contains many deep-rooting clades without any cultured representatives. One such clade is 'Endomicrobia', a class-level lineage in the phylum Elusimicrobia represented so far only by intracellular symbionts of termite gut flagellates. Here, we report the isolation and characterization of the first free-living member of this clade from sterile-filtered gut homogenate of defaunated (starch-fed) Reticulitermes santonensis. Strain Rsa215 is a strictly anaerobic ultramicrobacterium that grows exclusively on glucose, which is fermented to lactate, acetate, hydrogen and CO2. Ultrastructural analysis revealed a Gram-negative cell envelope and a peculiar cell cycle. The genome contains a single set of nif genes that encode homologues of Group IV nitrogenases, which were so far considered to have functions other than nitrogen fixation. We documented nitrogenase activity and diazotrophic growth by measuring acetylene reduction activity and (15)N2 incorporation into cell mass, and demonstrated that transcription of nifH and nitrogenase activity occur only in the absence of ammonium. Based on the ancestral relationship to 'Candidatus Endomicrobium trichonymphae' and other obligate endosymbionts, we propose the name 'Endomicrobium proavitum' gen. nov., sp. nov. for the first isolate of this lineage and the name 'Endomicrobia' class. nov. for the entire clade.

An Exemplary Model Study for Overcoming Stuck Fermentation during Spontaneous Fermentation with the Aid of a Saccharomyces Triple Hybrid

Sluggish or stuck fermentations cause significant financial losses for winemakers each year. In order to investigate the reasons for problems during spontaneous fermentation of Riesling must in a well-known German vineyard of the lower Moselle, yeast strains involved in must fermentation were identified during winemaking in the two years 2011 and 2012. Identification of the yeast isolates was performed by applying analyses of the ITS-1-5.8-ITS2 region and restriction fragment analyses of different gene sequences. It revealed that Saccharomyces (S.) bayanus and not Saccharomyces cerevisiae was the main fermenting yeast. Either S. bayanus finished the fermentation or led to stuck fermentation. After about four weeks of stuck, fermentation continued spontaneously S. bayanus was replaced by the triple hybrid S. cerevisiae × S. kudriavzevii × S. bayanus. The triple hybrid strain HL 78 was able to utilize fructose more efficiently than S. bayanus strain HL 77. The fructophilic character of the triple hybrid strain correlated with an enhanced uptake of radiolabeled fructose compared to glucose. In contrast to the usual starter culture S. cerevisiae, both isolates, S. bayanus strain HL 77 and the triple hybrid strain HL 78, could grow in the absence of ammonium when amino acids were present. However, the triple hybrid was able to consume glucose and especially fructose at lower amino acid concentrations. Thus, the triple hybrid strain HL 78 was a suitable strain to overcome stuck fermentation without changing the fermentation conditions and the aroma profile desired by the selected winery. It has already been successfully used to restart stuck fermentation. The procedure described here could be a useful approach for wine makers facing problems during spontaneous fermentation. Since the application of genetically modified yeast strains is not allowed for starter culture, based on these studies we suggest the generation of hybrid strains with desired phenotypical features from mother yeasts strains/species of a certain winery and their application in case that during a spontaneous fermentations a sluggish or stuck fermentation is observed.

The starvation tolerance of anammox bacteria culture at 35°C

Anammox is an environmental-friendly and cost-effective technology for nitrogen removal. This study provides the nitrogen removal profiles, physiological traits of anammox bacteria culture under the substrate deficiency conditions at the optimal cultivation temperature 35°C. The determined period of starvation tolerance was 4 weeks in the absence of nitrite, 5 weeks in the absence of ammonium, as well as 7 weeks for the absence of these two substrates at 36°C, pH 7-8 and anaerobic conditions. The physiological traits of bacteria consortium were identified through flow cytometry (FCM) analysis, and the ordinal change of increased RNA synthesizing amounts, phosphatidylserine exposure and bacteria death occurred under starvation stress. In addition, the starvation induced the increased protein content in extracellular polymeric substances and the poorer bacteria settling capacity. This study helps to develop a better understanding of anammox process in engineering environment.

Ammonium is a key determinant on the dietary restriction of yeast chronological aging in culture medium.

New evidences have recently emerged from studies in yeast and in higher eukaryotes showing the importance of nutrient balance in dietary regimes and its effects on longevity regulation.We have previously shown that manipulation of ammonium concentration in the culture and/or aging medium can drastically affect chronological lifespan (CLS)of Saccharomyces cerevisiae, especially in amino acid restricted cells. Here we describe that the CLS shortening under amino acid restriction can be completely reverted by removing ammonium from the culture medium. Furthermore, the absence of ammonium, and of any rich nitrogen source, was so effective in extending CLS that no beneficial effect could be observed by further imposing calorie restriction conditions. When present in the culture medium,ammonium impaired the consumption of the auxotrophy-complementing amino acids and caused in an improper cell cycle arrest of the culture.TOR1 deletion reverted ammonium effects both in amino acid restricted and non-restricted cultures, whereas, Ras2p and Sch9p seem to have only a milder effect in the mediation of ammonium toxicity under amino acid restriction and no effect on non-restricted cultures.Our studies highlight ammonium as a key effector in the nutritional equilibrium between rich and essential nitrogen sources and glucose required for longevity promotion.

Transcriptional profiles of Haloferax mediterranei based on nitrogen availability

The haloarchaeon Haloferax mediterranei is able to grow in the presence of different inorganic and organic nitrogen sources by means of the assimilatory pathway under aerobic conditions. In order to identify genes of potential importance in nitrogen metabolism and its regulation in the halophilic microorganism, we have analysed its global gene expression in three culture media with different nitrogen sources: (a) cells were grown stationary and exponentially in ammonium, (b) cells were grown exponentially in nitrate, and (c) cells were shifted to nitrogen starvation conditions. The main differences in the transcriptional profiles have been identified between the cultures with ammonium as nitrogen source and the cultures with nitrate or nitrogen starvation, supporting previous results which indicate the absence of ammonium as the factor responsible for the expression of genes involved in nitrate assimilation pathway. The results have also permitted the identification of transcriptional regulators and changes in metabolic pathways related to the catabolism and anabolism of amino acids or nucleotides. The microarray data was validated by real-time quantitative PCR on 4 selected genes involved in nitrogen metabolism. This work represents the first transcriptional profiles study related to nitrogen assimilation metabolism in extreme halophilic microorganisms using microarray technology.

The effects of salt stress cause a diversion of basal metabolism in barley roots: Possible different roles for glucose-6-phosphate dehydrogenase isoforms

In this study the effects of salt stress and nitrogen assimilation have been investigated in roots of hydroponically-grown barley plants exposed to 150 mM NaCl, in presence or absence of ammonium as the sole nitrogen source.Salt stress determines a diversion of root metabolism towards the synthesis of osmolytes, such as glycine betaine and proline, and increased levels of reduced glutathione. The metabolic changes triggered by salt stress result in a decrease in both activities and protein abundance of key enzymes, namely GOGAT and PEP carboxylase, and in a slight increase in HSP70. These variations would enhance the requirement for reductants supplied by the OPPP, consistently with the observed increase in total G6PDH activity.The involvement and occurrence of the different G6PDH isoforms have been investigated, and the kinetic properties of partially purified cytosolic and plastidial G6PDHs determined. Bioinformatic analyses examining co-expression profiles of G6PDHs in Arabidopsis and barley corroborate the data presented.Moreover, the gene coding for the root P2-G6PDH isoform was fully sequenced; the biochemical properties of the corresponding protein were examined experimentally.The results are discussed in the light of the possible distinct roles and regulation of the different G6PDH isoforms during salt stress in barley roots.