Acetate and carbon dioxide assimilation by Desulfovibrio vulgaris (Marburg), growing on hydrogen and sulfate as sole energy source

Desulfovibrio vulgaris (Marburg) was grown on hydrogen plus sulfate as sole energy source and acetate plus CO₂ as the sole carbon sources. The incorporation of U-¹⁴C acetate into alanine, aspartate, glutamate, and ribose was studied. The labelling data show that alanine is synthesized from one acetate (C-2 + C-3) and one CO₂ (C-1), aspartate from one acetate (C-2 + C-3) and two CO₂ (C-1 + C-4), glutamate from two acetate (C-1–C-4) and one CO₂ (C-5), and ribose from 1.8 acetate and 1.4 CO₂. These findings indicate that in Desulfovibrio vulgaris (Marburg) pyruvate is formed via reductive carboxylation of acetyl-CoA, oxaloacetate via carboxylation of pyruvate or phosphoenol pyruvate, and -ketoglutarate from oxaloacetate plus acetyl-CoA via citrate and isocitrate. Since C-5 of glutamate is derived from CO₂, citrate must have been formed via a (R)-citrate synthase rather than a(S)-citrate synthase. The synthesis of ribose from 1.8 mol of acetate and 1.4 mol of CO₂ excludes the operation of the Calvin cycle in this chemolithotrophically growing bacterium.     

Nitrite utilization by Chaetoceros muelleri under elevated CO2 concentration

Chaetoceros muelleri (Lemn.) was cultured with nitrite (NO₂⁻) or nitrate (NO₃⁻) as the sole nitrogen source and aerated with air or with CO₂-enriched air. Cells of C. muelleri excreted into the medium nitrite produced by reduction of nitrate when grown with 100 μM NaNO₃ as nitrogen source. Accordingly, NO₂⁻ concentration reached 10.4 μM after 95 h at the low CO₂ condition (aerated with air); while the maximum NO₂⁻ concentration was only around 2.0 μM at the high CO₂ condition (aerated with 5% CO₂ in air), furthermore, after 30 h it decreased to no more than 1.0 μM. NO₂⁻ was almost assimilated in 80 h when C. muelleri was cultured at the high CO₂ condition with 100 μM NaNO₂ as sole nitrogen source. At the high CO₂ condition, after 3 h the activity of nitrite reductase was as much as 50% higher than that at the low CO₂ condition. It was indicated that enriched CO₂ concentration could inhibit nitrite excretion and enhance nitrite assimilation by cells. Therefore, aeration with enriched CO₂ might be an effective way to control nitrite content in aquaculture systems.     

Arginine catabolism in Aphanocapsa 6308

The catabolic products of arginine metabolism were observed in Aphanocapsa 6308, a unicellular cyanobacterium, by thin layer chromatography of growth media, by limiting growth conditions, and by enzymatic analysis. Of the organic, nitrogenous compounds examined, only arginine supported growth in CO₂-free media. The excretion of ornithine at a concentration level greater than citrulline suggested the existence in Aphanocapsa 6308 of the arginine dihydrolase pathway which produced ornithine, CO₂, NH₄, + adenosine 5-triphosphate. Its existence was confirmed by enzymatic analysis. Although cells could not grow on urea as a sole carbon source a very active urease and subsequently an arginase were also demonstrated, indicating that Aphanocapsa can metabolize arginine via the arginase pathway. The level of enzymes for both pathways indicates a lack of genetic control. It is suggested that the arginase pathway provides only nitrogen for the cells whereas the arginine dihydrolase pathway provides not only nitrogen, but also CO₂ and adenosine 5-triphosphate.Nonstandard Abbreviations CCCP carbonylcyanide mchlorophenyl hydrazone - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethyl urea - CGP cyanophycin granule protein - PS II photosystem II - PSI photosystem I - TLC thin layer chromatography - TCA trichloroacetic acid - DPM disintegrations per min     

镍离子对尖叶莴苣氮素吸收和生长生理的影响

以‘全年油麦菜’尖叶莴苣为试验材料,采用水培方式,研究3个浓度(0 mg·L^-1、0.1 mg·L^-1、1 mg·L^-1)Ni²⁺在22.4 mg·L^-1 N处理下对尖叶莴苣氮素吸收的生长及生理影响。结果显示：(1)尖叶莴苣根系和地上部生物量随处理时间的增加呈上升趋势。与对照T₁(0 mg·L^-1 Ni²⁺、112 mg·L^-1 N)相比,T₂处理(0 mg·L^-1 Ni²⁺、22.4 mg·L^-1 N)对尖叶莴苣根系及叶片生长具有一定抑制作用,植株鲜重、干重、根冠比、根系长度、平均直径、表面积、体积、根尖数、分根数、叶片表面积和体积在T3处理(0.1 mg·L^-1 Ni²⁺、22.4 mg·L^-1 N)下显著高于对照,T₄处理(1 mg·L^-1 Ni²⁺、22.4 mg·L^-1 N)对尖叶莴苣根系及其叶片生长具有一定促进作用,但对其根尖数和分根数表现出一定抑制性。(2)随着Ni²⁺浓度的增加,尖叶莴苣叶片叶绿素a、叶绿素b和总叶绿素含量呈先升后降的变化规律,且均在T₃处理下显著提高。(3)随着处理时间的增加,尖叶莴苣叶片的净光合速率(P_n)、气孔导度(G_s)和蒸腾速率(T_r)逐渐上升,胞间CO₂浓度(C_i)逐渐下降,且T₃处理叶片的G_s显著高于对照,其C_i最低,P_n最大。(4)施加Ni²⁺对尖叶莴苣有机酸、可溶性蛋白和可溶性糖含量以及SOD和POD活性有显著影响,在T₃处理下有机酸含量降低,可溶性糖和可溶性蛋白含量显著增加,SOD和POD活性显著提高。(5)T₃处理尖叶莴苣根系中N及叶片中B和Ca含量较高;根系中Ni含量高于叶片,T₃处理叶片中的Ni含量较低,Mg含量较高;植株体内Cu含量随Ni²⁺浓度增加而下降。研究表明,外源Ni²⁺处理能影响低氮条件下(22.4 mg·L^-1 N)尖叶莴苣幼苗生长及生理状况,适宜浓度(0.1 mg·L^-1)Ni²⁺可有效提高尖叶莴苣根系对氮素的吸收利用效率,减少氮素施用量,促进尖叶莴苣根系和地上部叶片生长,增加光合色素含量,并提高净光合速率,进而改善植株的产量和营养品质。     

Ammonium and urea as nitrogen sources for bromeliads

Epiphytic bromeliads have no contact with the pedosphere, so they need to draw their nutrients from the atmosphere as well as from the host tree and animal debris. Terrestrial bromeliads, like Ananas comosus, generally depend on the soil as their main nutrient source. The aim of this study was to investigate and compare some aspects of the nitrogen metabolism of two bromeliads with different growth habits: Ananas comosus, a terrestrial bromeliad, and Vriesea gigantea, an epiphytic tank bromeliad. Nitrogen-starved plants were grown in vitro for 3, 7, 15, 30, and 60 days, either with 5 mmol L⁻¹ ammonium [(NH₄)₂SO₄] or urea as the sole nitrogen source. When NH₄⁺ was supplied to the plants, it stimulated a faster increase of chlorophyll content in A. comosus than in V. gigantea. In the presence of urea, after 15 days of the plants in culture, there was a significant increase in tissue free-NH₄⁺ and total amino acids for V. gigantea only. V. gigantea presented a higher level of total free amino acids than A. comosus when nitrogen was supplied to the plants. Asparagine was the main amino acid accumulated in both bromeliads when plants were transferred to the medium with nitrogen. When the ratio of the main individual free amino acids between the bromeliads grown in NH₄⁺ and urea was compared, values such as 7.2 for asparagine, 5.3 for glutamate, and 1.8 for aspartate in A. comosus, and values such as 2.3 for asparagine, 1.1 for glutamate and 0.7 for aspartate in V. gigantea were observed, demonstrating that the last is more efficient in assimilating urea. The results prompted us to support the idea that V. gigantea, an epiphytic tank bromeliad, is better adapted to absorb and assimilate organic nitrogen, such as urea, while A. comosus, a terrestrial plant, is better adapted to inorganic nitrogen forms, such as ammonium. The natural exposure of tank bromeliads to urea is discussed in the paper.     

On-line estimation of O<Subscript>2</Subscript> production,CO<Subscript>2</Subscript> uptake,and growth kinetics of microalgal cultures in a gas-tight photobioreactor

Growth of the green algae Chlamydomonas reinhardtii and Chlorella sp. in batch cultures was investigated in a novel gas-tight photobioreactor, in which CO₂, H₂, and N₂ were titrated into the gas phase to control medium pH, dissolved oxygen partial pressure, and headspace pressure, respectively. The exit gas from the reactor was circulated through a loop of tubing and re-introduced into the culture. CO₂ uptake was estimated from the addition of CO₂ as acidic titrant and O₂ evolution was estimated from titration by H₂, which was used to reduce O₂ over a Pd catalyst. The photosynthetic quotient, PQ, was estimated as the ratio between O₂ evolution and CO₂ up-take rates. NH₄ ⁺, NO₂ ⁻, or NO₃ ⁻ was the final cell density limiting nutrient. Cultures of both algae were, in general, characterised by a nitrogen sufficient growth phase followed by a nitrogen depleted phase in which starch was the major product. The estimated PQ values were dependent on the level of oxidation of the nitrogen source. The PQ was 1 with NH₄ ⁺ as the nitrogen source and 1.3 when NO₃ ⁻ was the nitrogen source. In cultures grown on all nitrogen sources, the PQ value approached 1 when the nitrogen source was depleted and starch synthesis became dominant, to further increase towards 1.3 over a period of 3–4 days. This latter increase in PQ, which was indicative of production of reduced compounds like lipids, correlated with a simultaneous increase in the degree of reduction of the biomass. When using the titrations of CO₂ and H₂ into the reactor headspace to estimate the up-take of CO₂, the production of O₂, and the PQ, the rate of biomass production could be followed, the stoichiometrical composition of the produced algal biomass could be estimated, and different growth phases could be identified.     

Role of nitrogen sources and metal ions in urease synthesis byMicrococcus varians

Urease (urea amidohydrolase E.C.3.5.1.5) synthesis inMicrococcus varians U-9 was not affected by nitrogen source (peptone or glutamic acid) or its concentration: but depended on the ratio of peptone and urea in culture medium. WhenM. varians grew in culture medium with peptone at or above 0.48g/l and NH₄Cl as an additional nitrogen source, two maxima of urease synthesis occurred; one in the exponential growth phase and the second in the stationary growth phase. Though this bacterium could not utilize either urea or ammonia as the sole nitrogen source, urea caused only one maximum of urease synthesis to occur and shifted the maximum into late exponential phase, suggesting that urea acts as a regulatory factor in urease synthesis. Synthesis of urease was not induced either by urea or by nitrogen starvation and was not repressed by ammonia or by excess of complex nitrogen source. NI²⁺ (up to 0.1 mM) stimulated urease synthesis but decreased bacterial growth, while Co²⁺ only affected bacterial growth and at 0.1 mM Inhibited the growth.

---

Résumé La synthèse d'uréase (urée-amidohydrolase E.C.3.5.1.5) chezMicrococcus varians n'est pas affectée par la source d'azote (peptone ou acide glutamique), ni par leurs concentrations, mais dépend du rapport de la peptone à l'urée dans le milieu de culture. QuandM. varians croît dans un milieu de culture contenant la peptone à la concentration égale ou supérieure à 0.48 g/l et le NH₄Cl comme source additionnelle d'azote, on observe deux maximum de synthèse d'uréase: la première dans la phase exponentielle de croissance, et la seconde dans la phase stationnaire de croissance. Blen que cette bactérie ne puisse utilliser ni l'urée ni l'ammoniac comme seule source d'azote, l'urée provoque un seul des maximum de synthèse d'uréase et déplace ce maximum vers la partie ultime de la phase exponentielle, suggérant que l'urée agit comme facteur de régulation dans la synthèse d'uréase. La synthèse d'uréase n'est induite ni par l'urée ni par la starvation d'azote et n'est réprimée ni par l'ammoniac ni par un excès de la source d'azote complexe. Le Ni²⁺ (jusqu'à 0.1 mM) stimule la synthèse d'uréase, mais diminue la croissance bactérienne, tandis que le Co²⁺ n'affecte que la croissance bactérienne et à 0.1 mM inhibe la croissance.

---

---

This work was carried out at the Faculty of Food Technology and Biotechnology, University of Zagreb. Department of Biochemical Engineering, 41000 Zagreb, Pierottijeva 6/IV, Croatia, Yugoslavia.     

Cosubstrate independent mineralization of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by a <Emphasis Type="Italic">Desulfovibrio</Emphasis> species under anaerobic conditions

Past handling practices associated with the manufacturing and processing of the high explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has resulted in extensive environmental contamination. In-situ biodegradation is a promising technology for remediating RDX contaminated sites but often relies on the addition of a cosubstrate. A sulfate-reducing bacterium isolated from an RDX-degrading enrichment culture was studied for its ability to grow on RDX as a sole source of carbon and nitrogen and for its ability to mineralize RDX in the absence of a cosubstrate. The results showed the isolate degraded 140 μM RDX in 63 days when grown on RDX as a carbon source. Biomass within the carbon limited culture increased 9-fold compared to the RDX unamended controls. When the isolate was incubated with RDX as sole source of nitrogen it degraded 160 μM RDX in 41 days and exhibited a 4-fold increase in biomass compared to RDX unamended controls. Radiolabeled studies under carbon limiting conditions with ¹⁴C-hexahydro-1,3,5-trinitro-1,3,5-triazine confirmed mineralization of the cyclic nitramine. After 60 days incubation 26% of the radiolabel was recovered as ¹⁴CO₂, while in the control bottles less than 1% of the radiolabel was recovered as ¹⁴CO₂. Additionally, ~2% of the radiolabeled carbon was found to be associated with the biomass. The 16S rDNA gene was sequenced and identified the isolate as a novel species of Desulfovibrio, having a 95.1% sequence similarity to Desulfovibrio desulfuricans. This is the first known anaerobic bacterium capable of mineralizing RDX when using it as a carbon and energy source for growth.     

Carbon assimilation pathways in sulfate reducing bacteria. Formate,carbon dioxide,carbon monoxide,and acetate assimilation by Desulfovibrio baarsii

Desulfovibrio baarsii is a sulfate reducing bacterium, which can grown on formate plus sulfate as sole energy source and formate and CO₂ as sole carbon sources. It is shown by ¹⁴C labelling studies that more than 60% of the cell carbon is derived from CO₂ and the rest from formate. The cells thus grow autotrophically. Labelling studies with [¹⁴C]acetate, ¹⁴CO and [¹⁴C]formate indicate that CO₂ fixation does not proceed via the Calvin cycle. The labelling patterns of alanine, aspartate, glutamate, and glucosamine indicate that acetate (or activated acetic acid) is an early intermediate in formate and CO₂ assimilation; the methyl group of acetate is derived from formate, and the carboxyl group from CO₂ via CO; pyruvate is formed from acetyl-CoA by reductive carboxylation. The capacity to synthesize an acetate unit from two C₁-compounds obviously distinguishes D. baarsii from those Desulfovibrio species, which require acetate as a carbon source in addition to CO₂.     

The negligible role of carbon dioxide and ethylene in ajmalicine production by Catharanthus roseus cell suspensions

Summary Removal of gaseous metabolites in an aerated fermenter affects ajmalicine production by Catharanthus roseus negatively. Therefore, the role of CO₂ and ethylene in ajmalicine production by C. roseus was investigated in 3 l fermenters (working volume 1.8 l) with recirculation of a large part of the exhaust air. Removal of CO₂, ethylene or both from the recirculation stream did not have an effect on ajmalicine production. Inhibition of ethylene biosynthesis in shake flasks with Co²⁺, Ni²⁺ or aminooxyacetic acid did not affect ajmalicine production. However, the removal of CO₂ did enhance the amount of extracellular ajmalicine.     

CO2 Dynamics and Growth in Photoautotrophic and Photomixotrophic Apple Cultures

The daily dynamics of CO₂ concentration in the culture vessels and the photoautotrophic or photomixotrophic growth capacity of apple (Malus pumila hybrid MM 106 paradisiaca× Northern Spy) cultures were studied. The photoautotrophic cultures were grown on a sugar-free growth medium and submitted (0S+CO₂) or not (0S-CO₂) to periodic injections of exogenous CO₂. The photomixotrophic cultures were grown in the presence of 30 g dm⁻³ sucrose, with (30S+CO₂) or without (30S-CO₂) CO₂ enrichment. The photosynthetic photon flux density applied was of 210 ± 5 μmol m⁻²s⁻¹. In the 0S-CO₂ treatment, CO₂ showed rather uniform and narrow light-dark fluctuations throughout the culturing cycle. In the 30S-CO₂ treatment, the daily ratio between CO₂ produced during the dark period and that uptaken during the following light period, was almost always above 1 with the only exception of a few days (from the 5^th to the 9^th day) when the amount of photosynthesised CO₂ was equal to or higher than that produced during dark respiration. The 0S+CO₂ cultures needed to be enriched all days with exogenous CO₂ to avoid periods of gas deficiency while in 30S+CO₂ the CO₂ injected the first culturing day was uptaken over 5 d; thereafter, daily injections were necessary. Culture fresh and dry mass, number of newly formed shoots and number of nodes per shoot in 0S+CO₂ treatment did not statistically differ from the values obtained with 30S−CO₂. The highest growth was observed in 30S+CO₂ treatment. The increase in culture fresh mass due to 1 μmol of CO₂ added to the culture vessels was 1.54 and 1.36 mg for 30S and 0S respectively, while in terms of dry mass the increase was about 2.5 times higher in the sugar-enriched treatment. CO₂ enrichment accounted for 77.3 % and 21.2 % of the final fresh mass in 0S+CO₂ and 30S+CO₂, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of low and high levels of magnesium on the response of sunflower plants grown with ammonium and nitrate

The effect of the nitrogen source (ammonium and nitrate) and its interaction with magnesium on various physiological processes was studied in sunflower plants (Helianthus annuusL.). Plants were grown in hydroponic culture with nitrate (5 mM) or ammonium (5 mM) and four concentrations of magnesium (0.1, 0.8, 5 and 10 mM). After 2 weeks, growth, gas exchange and fluorescence parameters, soluble carbohydrates, free amino acids, soluble protein and mineral elements were determined. Ammonium nutrition resulted in a reduction of dry matter accumulation, as well as in a decrease in the CO₂ assimilation. Moreover, ammonium-fed plants showed a greater content of free amino acids, soluble protein, Rubisco and anions, and a lower cation content, mostly Mg²⁺. The presence of high levels of Mg²⁺ in the nutrient solution containing NH₄ ⁺ resulted in a stimulation of growth and CO₂ assimilation to the levels observed in nitrate-fed plants. The lower photosynthetic rate of ammonium-fed plants grown with low level of magnesium does not seem to be due to a lower photosynthetic pigment content, or a deficiency in Photosystem II activity, or to lower Rubisco content. Hence, Rubisco activity or other enzymes involved in CO₂ fixation could have been affected in ammonium-fed plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Atrazine degradation by a simple consortium of <Emphasis Type="Italic">Klebsiella</Emphasis> sp. A1 and <Emphasis Type="Italic">Comamonas</Emphasis> sp. A2 in nitrogen enriched medium

A simple consortium consisted of two members of Klebsiella sp. A1 and Comamonas sp. A2 was isolated from the sewage of a pesticide mill in China. One member of Klebsiella sp. A1 is a novel strain that could use atrazine as the sole carbon and nitrogen source. The consortium showed high atrazine-mineralizing efficiency and about 83.3% of 5 g l⁻¹ atrazine could be mineralized after 24 h degradation. Contrary to many other reported microorganisms, the consortium was insensitive to some nitrogenous fertilizers commonly used, not only in presence of 200 mg l⁻¹ atrazine but also in 5 g l⁻¹ atrazine mediums. After 24 h incubation, 200 mg l⁻¹ atrazine was completely mineralized despite of the presence of urea, (NH₄)₂CO₃ and (NH₄)₂HPO₄ in the medium. Very minor influence was observed when NH₄Cl was added as additional nitrogen source. Advantages of the simple consortium, high mineralizing efficiency and insensitivity to most of exogenous nitrogen sources, all suggested application potential of the consortium for the bioremediation of atrazine-contaminated soils and waters.     

Submerged culture conidial germination and conidiation of the bioherbicideColletotrichum truncatum are influenced by the amino acid composition of the medium

Summary Submerged culture experiments were conducted to determine the optimal nitrogen source for rapidly producing conidia of the bioherbicide,Colletotrichum truncatum. Germination ofC. truncatum conidial inocula in submerged culture occurred most rapidly (>95% in 6 h) in media provided with a complete complement of amino acids. When (NH₄)₂SO₄, urea, or individual amino acids were provided as the sole nitrogen source, conidial germination was less than 20% after 6 h incubation. Conidia production was delayed inC. truncatum cultures grown in media with urea or individual amino acids as nitrogen sources compared to cultures supplied with Casamino acids or complete synthetic amino acid nitrogen sources. The use of methionine, lysine, tryptophan, isoleucine, leucine or cysteine as a sole nitrogen source severely inhibitedC. truncatum conidia production. Media with synthetic amino acid mixtures less these inhibitory amino acids produced significantly higher conidia yields compared to media with amino acid mixtures containing these amino acids. When various amounts of each individual inhibitory amino acid were added to media which contained amino acid mixtures, cysteine and methionine were shown to be most effective in reducing conidiation. An optimal nitrogen source forC. truncatum conidiation in submerged culture should contain a complete mixture of amino acids with low levels of cysteine, methionine, leucine, isoleucine, lysine and tryptophan for rapid conidiation and optimal conidia yield.The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned.     

Conversion of sodium cyanide to carbon dioxide and ammonia by immobilized cells ofPseudomonas putida

Summary Pseudomonas putida, isolated from contaminated industrial wastewaters and soil sites, was found to utilize sodium cyanide (NaCN) as a sole source of carbon and nitrogen. Cells, immobilized in calcium alginate beads (1–2 mm diameter) were aerated in air-uplift-type fluidized batch bioreactor containing 100–400 ppm of NaCN. Degradation of NaCN was monitored for 168 h by analyzing gaseous and dissolved ammonia (NH₃), CO₂, pH and optical density. The results indicated that the alginate-immobilized cells ofP. putida were able to degrade NaCN into NH₃ and CO₂ in a time-dependent manner.     

Effects of combined nitrogen on anapleurotic carbon assimilation and bleeding sap composition in Phaseolus vulgaris L.

Dwarf french beans, Phaseolus vulgaris L., were grown with or without inoculation with rhizobia (strain 3644), and with or without a combined nitrogen source (nitrate or ammonium ions). The distribution of radioactivity into products of dark ¹⁴CO₂ assimilation was studied in roots or nodules from these plants. A detailed study was also made of the distribution and rates of excretion of nitrogen in xylem bleeding sap in 28 day old plants grown on the various sources of nitrogen. Whereas detached nodules accumulated radioactive glycine, serine and glutamate when incubated with ¹⁴CO₂, bleeding sap from plants root fed ¹⁴CO₂ contained low levels of radioactivity in these compounds but higher levels in allantoin. Chemical analysis showed allantoin to be the major compound transported in the xylem of nodulated plants, whether or not they were fed on combined nitrogen. In contrast uninoculated plants accumulated mainly amino acids in the bleeding sap, the amount and chemical composition of which depended on the combined nitrogen source.Abbreviations PEP phosphoenol pyruvate - OAA oxaloacetate     

Regulation of nitrogen-fixation by different nitrogen sources in the marine non-heterocystous cyanobacterium Trichodesmium sp. NIBB1067

The effect of various nitrogen sources on the synthesis and activity of nitrogenase was studied in the marine, non-heterocystous cyanobacterium Trichodesmium sp. NIBB1067 grown under defined culture conditions. Cells grown with N₂ as the sole inorganic nitrogen source showed light-dependent nitrogenase activity (acetylene reduction). Nitrogenase activity in cells grown on N₂ was not suppressed after 7 h incubation with 2 mM NaNO₃ or 0.02 mM NH₄Cl. However, after 3 h of exposure to 0.5 mM of urea, nitrogenase was inactivated. Cells grown in medium containing 2 mM NaNO₃, 0.5 mM urea or 0.02 mM NH₄Cl completely lacked the ability to reduce acetylene. Western immunoblots tested with polyclonal antisera against the Fe-protein and the Mo–Fe protein, revealed the following: (1) both the Fe-protein and the Mo–Fe protein were synthesized in cells grown with N₂ as well as in cells grown with NaNO₃ or low concentration of NH₄Cl; (2) two bands (apparent molecular mass of 38 000 and 40 000) which cross-reacted with the antiserum to the Fe-protein, were found in nitrogen-fixing cells; (3) only one protein band, corresponding to the high molecular mass form of the Fe-protein, was found in cells grown with NaNO₃ or low concentration of NH₄Cl; (4) neither the Fe-protein nor the Mo–Fe protein was found in cells grown with urea; (5) the apparent molecular mass of the Fe-protein of Trichodesmium sp. NIBB1067 was about 5000 dalton higher than that of the heterocystous cyanobacterium, Anabaena cylindrica IAM-M1.     

Isolation and Characterization of a Pseudomonas putida Strain able to Grow with Trimethyl-1,2-dihydroxy-propyl-ammonium as Sole Source of Carbon, Energy and Nitrogen

Trimethyl-1,2-dihydroxypropyl-ammonium (TM) originates from the hydrolysis of the parent esterquat surfactant, which is widely used as softener in fabric care. Based on test procedures mimicking complex biological systems, TM is supposed to degrade completely when reaching the environment. However, no organisms able to degrade TM were isolated nor has the degradation pathway been elucidated so far. We isolated a Gram-negative rod able to grow with TM as sole source of carbon, energy and nitrogen. The strain reached a maximum specific growth rate of 0.4 h^–1 when growing with TM as the sole source of carbon, energy and nitrogen. TM was degraded to completion and surplus nitrogen was excreted as ammonium into the growth medium. A high percentage of the carbon in TM (68% in continuous culture and 60% in batch culture) was combusted to CO₂ resulting in a low yield of 0.54 mg cell dry weight per mg carbon during continuous cultivation and 0.73 mg cell dry weight per mg carbon in batch cultures. Choline, a natural structurally related compound, served as a growth substrate, whereas a couple of similar other quaternary aminoalcohols also used in softeners did not. The isolated bacterium was identified by 16S-rDNA sequencing as a strain of Pseudomonas putida with a difference of only one base pair to P. putida DSM 291^T. Despite their high identity, the reference strain P. putida DSM 291^T was not able to grow with TM and the two strains differed even in shape when growing on the same medium. This is the first microbial isolate able to degrade a quaternary ammonium softener head group to completion. Previously described strains growing on quaternary ammonium surfactants (decyltrimethylammonium, hexadecyltrimethylammonium and didecyldimethylammonium) either excreted metabolites or a consortium of bacteria was required for complete degradation.     

Stimulation of heterotrophic and autotrophic growth ofSphaerotilus discophorus by manganous ions

Growth ofS. discophorus in a casamino acids-mineral salts medium was stimulated 3-fold on addition of 0.05% MnSO₄·H₂O to the medium. Growth was measured by determinations of total nitrogen, protein and DNA on the washed cellular material.Autotrophic growth ofS. discophorus strain 43-R was obtained in an inorganic mineral salts medium supplemented with trace amounts of the essential vitamins, thiamin, biotin and cyanocobalamin and with Mn⁺⁺ as the sole available source of energy. A gas mixture of 5% CO₂-95% air was bubbled continuously through the cultures during incubation. Concomitant with growth, Mn⁺⁺ disappeared from the cultures and MnO₂ was formed.     

Nitrogen assimilation in Rhodopseudomonas acidophila

Rhodopseudomonas acidophila strain 7050 assimilated ammonia via a constitutive glutamine synthetase/glutamate synthase enzyme system.Glutamine synthetase had a K _m for NH ₄ ⁺ of 0.38 mM whilst the nicotinamide adenine dinucleotide linked glutamate synthase had a K _m for glutamine of 0.55 mM. R. acidophila utilized only a limited range of amino acids as sole nitrogen sources: l-alanine, glutamine and asparagine. The bacterium did not grow on glutamate as sole nitrogen source and lacked glutamate dehydrogenase. When R. acidophila was grown on l-alanine as the sole nitrogen source in the absence of N₂ low levels of a nicotinamide adenine dinucleotide linked l-alanine dehydrogenase were produced. It is concluded, therefore, that this reaction was not a significant route of ammonia assimilation in this bacterium except when glutamine synthetase was inhibited by methionine sulphoximine. In l-alanine grown cells the presence of an active alanine-glyoxylate aminotransferase and, on occasions, low levels of an alanine-oxaloacetate aminotransferase were detected. Alanine-2-oxo-glutarate aminotransferase could not be demonstrated in this bacterium.Abreviations ADH alanine dehydrogenase - GDH glutamate dehydrogenase - GS glutamine synthetase - GOGAT glutamate synthase - MSO methionine sulphoximine