Nitrogen-deficient Medium Research Articles

STUDIES ON THE NUTRITION AND GROWTH OF DROSERA SPECIES WITH REFERENCE TO THE CARNIVOROUS HABIT

SUMMARY Drosera whittakeri was grown in sand cultures supplemented with inorganic salt solutions lacking either nitrogen, sulphur, phosphorus or the microelements. Application of the insect Drosophila melanogaster to the tentacles of plants raised on nitrogen or sulphur deficient medium, enhanced growth, which on nitrogen deficient medium was accompanied by decreased nitrogen content per unit weight although the total nitrogen per plant was unaffected. Application of insects to plants on media deficient in phosphorus or the microelements had no effect on growth but significantly increased the phosphorus content of plants grown on a complete nutrient solution or media deficient in phosphorus or nitrogen. Insects would not serve as a heterotrophic carbon source for the realization of maximum growth of plants grown at very low light intensities.Optimum growth of Drosera binata (and usually D. whittakeri) was attained by applying insects to plants raised on nitrogen‐free medium; addition of inorganic nitrogen (as nitrate) to the nutrient solution to plants raised under these conditions inhibited growth. Optimum growth was not achieved by growing plants on a complete nutrient solution in the absence of insects.Up to 50% of the phosphorus in the tubers of D. whittakeri occurred as inositol hexaphos‐phate. Phosphorus was rapidly transferred to the growing parts of the plant on emergence. During the growing season, plants with higher than average phosphorus content developed new rhizomes on which new tubers formed. The indigenous distribution of Drosera species in southeastern Australia is not restricted to soils of very low phosphorus, nitrogen and sulphur status.

SEXUAL REPRODUCTION OF PERIDINUM CINCTUM F. OVOPLANUM (DINOPHYCEAE)1,2

SUMMARYSexual reproduction is induced in the dinoflagelate Peridinium cinctum f. ovoplanum Lindemann when exponentially growing cells are inoculated into nitrogen deficient medium. Small, naked vegetative cells, produced by division of the thecate cells, then act as gametes. The zygote remains motile for 12–13 days during which time it enlarges and the theca which it forms becomes warty. Thirteen to 14 day s following plasmogamy the zygote is nonmotile, the protoplast contracts, a large red oil droplet appears, the wall thickens and becomes chitinized. This hypnozygote germinates within 7–8 weeks at 20 c producing 1 post‐zygotic cell retaining the large red oil droplet. The presence of 4 nuclei in these post‐zygotic cells may be demonstrated by staining them with acetocarmine. Two of these nuclei are smaller than the other two and probably abort. One may infer that meiosis occurs immediately prior to or at the germinartion of the hypnozygote. This post‐zygotic cell divides within 24 h into 2 daughter cells each with a promment red oil droplet. These daughter cells divide after 2–3 days into ordinary vegetative cells.Attempts to induce sexual reproduction by changes in temperature or light and by inoculation of cells into media deficient in a number of basic elements were unsuccessful.

Influence of the type of growth medium on steroid reduction in Actinomycetales

Nocardia corallina hydrogenates progesterone to 5 α-pregnane-3,20-dione in growth medium containing excess glucose. The Δ4 steroid reductase appears in such conditions, in the acellular extracts. Likewise in nonproliferating cells incubated in nitrogen-deficient medium containing different carbon sources, glucidic sources stimulate hydrogenation of the Δ4. The significance of oxydations and reductions of steroids among Actinomycetales are discussed in relation to the metabolic characteristics of these organisms.

Elektronenmikroskopische Untersuchungen zur reversiblen Veränderung der Chloroplastenfeinstruktur von Rhodella violacea bei Stickstoffmangel )

The structure of the unicellular marine red alga, Rhodella violacea, was investigated by electron microscopy after growth in a complete medium, nitrogen deficient medium, and after 8 and 48 h regeneration in complete medium after switching from N-deficient medium. Changes in cell composition after N-deficiency are described. These changes are a considerable reduction of the peripheral parts of the plastid and also a reduction of the nucleus, while floridean starch and vacuoles become dominating features in the cell. After being in nitrogen deficient medium for 6 days, most of the phycobilisomes disappeared, the main part of the thylakoids is collapsed and shows a contorted form in the stroma of the plastid. The contrast of the thylakoid limiting membranes is increased. A small part of phycobilisomebearing thylakoids, with distances of 29–40 nm between them, as found in plastids of cells cultured normally, remains visible. After transfer of N-deficient cells to complete medium, the regeneration of the plastid occurs in two distinct phases. In the first phase, the equidistant arrangement of the thylakoids is restored without the presence of phycobilisomes. Simultaneously, the stroma substance is increased. In the second phase, the regeneration of the phycobilisomes on the thylakoid surface is completed within 48 h.

Studies on Fat Accumulation in Nitzschia palea Kütz

Fat accumulation in Nitzschia palea Kutz. starts perceptibly at the end of the exponential phase of growth and reaches a maximum during the stationary phase of growth when the whole cell is filled with fat. Filtrates from old cultures enhanced fat synthesis probably by the production of an autotoxin which inhibits cell growth but at the same time favours fat synthesis. The presence of an inhibitory autotoxin has not been proved but indirect evidence suggests its presence. The nitrogen content of the culture medium also influences the amount of fat formed, more fat being accumulated in nitrogen-deficient media than in media provided with adequate nitrate supply. The optimum temperature for the growth of N. palea was found to be about 30 °C while that for fat synthesis was around 35 °C. Below 15 °C and above 40 °C, fat synthesis was drastically reduced. Blue and red light independently favoured fat synthesis whereas a combination of both did not. This is probably due to the selective influence of these wavelengths on the production of fat precursors or

Potential pathogens in the environment: Klebsiella pneumoniae, a taxonomic and ecological enigma.

A nitrogen-deficient medium and m-Endo agar were employed in the isolation of members of the tribe Klebsielleae from surfaces of vegetables and seeds. With m-Endo agar at an incubation temperature of 37 C, nearly 50% of the vegetables and seven out of seven seed samples yielded organisms which biochemically and serologically were identified as Klebsiella pneumoniae, Viable counts were generally in the range of 10(3) cells per g of vegetable peel or seed. Organisms classified as K. pneumoniae exhibited seven different IMViC patterns, with the --++, ++++, and -+++ patterns most common. Seven of the eleven K. pneumoniae serotypes encountered have previously been isolated from human urinary tract and other infections. Fifty percent of the 40 K. pneumoniae examined exhibited positive acetylene-reducing activity, i.e., they possessed the capability for fixing N(2). Vegetables containing K. pneumoniae may constitute a potential reservoir for human nosocomial genitourinary or other infections.

Potential Pathogens in the Environment: Klebsiella pneumoniae, a Taxonomic and Ecological Enigma1

A nitrogen-deficient medium and m-Endo agar were employed in the isolation of members of the tribe Klebsielleae from surfaces of vegetables and seeds. With m-Endo agar at an incubation temperature of 37 C, nearly 50% of the vegetables and seven out of seven seed samples yielded organisms which biochemically and serologically were identified as Klebsiella pneumoniae, Viable counts were generally in the range of 10(3) cells per g of vegetable peel or seed. Organisms classified as K. pneumoniae exhibited seven different IMViC patterns, with the --++, ++++, and -+++ patterns most common. Seven of the eleven K. pneumoniae serotypes encountered have previously been isolated from human urinary tract and other infections. Fifty percent of the 40 K. pneumoniae examined exhibited positive acetylene-reducing activity, i.e., they possessed the capability for fixing N(2). Vegetables containing K. pneumoniae may constitute a potential reservoir for human nosocomial genitourinary or other infections.

The isolation of mutants not accumulating poly-?-hydroxybutyric acid

Five mutant strains of Hydrogenomonas H 16 which synthesize poly-β-hydroxybutyric acid either slowly or not at all have been isolated following nitrite and NMG treatment of wild type cells. When grown on a nitrogen deficient agar medium, the colonies of PHB-free cells can be recognized by their diminished retention of the dye sudanblack B. Enrichment procedures for such mutants have been devised employing the 32P-phosphate inactivation technique and sucrose gradient centrifugation. The mutants have been characterized with respect to their growth properties, respiratory control and other properties.

Nitrogen Fixation and Availability

D escribed here is an experiment in symbiotic plant growth which can be set up and maintained with a minimum of equipment. The experiment is designed to show that wheat plants grown in a nitrogen deficient medium can obtain an adequate nitrogen supply from soybean plants whose roots were infected with the bacterium Rhizobium, a symbiotic nitrogen fixing bacteria. The plants can be grown from seed and within 26 days the results are striking. Wheat plants grown in a nitrogen deficient medium do not survive whereas wheat plants grown with soybean plants innoculated with Rhizobium look healthy and vigor-

Nutritional value of lipids in Hydrogenomonas eutropha as measured in the rat.

Hydrogenomonas eutropha is known to accumulate lipid, comprised largely of polymerized beta-hydroxybutyric acid, when maintained in nitrogen-deficient medium. This lipid was very poorly absorbed by mice from bacteria-containing diets, even though nitrogen absorption was adequate. The monomer, free beta-hydroxybutyric acid, was well absorbed from purified diet. Rats fed the monomer or butyric acid ate less food and grew more slowly than rats fed corn oil.

Nutritional Value of Lipids in Hydrogenomonas eutropha as Measured in the Rat1

Hydrogenomonas eutropha is known to accumulate lipid, comprised largely of polymerized beta-hydroxybutyric acid, when maintained in nitrogen-deficient medium. This lipid was very poorly absorbed by mice from bacteria-containing diets, even though nitrogen absorption was adequate. The monomer, free beta-hydroxybutyric acid, was well absorbed from purified diet. Rats fed the monomer or butyric acid ate less food and grew more slowly than rats fed corn oil.

Starvation and encystment of a soil amoeba Hartmannella castellanii.

SYNOPSIS. The behavior of the amoeba H. castellanii was investigated in various carbon and nitrogen deficient media with a view to developing a satisfactory replacement medium for the study of encystment and excystment. Media which had been devised for other soil amoebae did not cause H. castellanii to encyst. In these media there was an efflux of material from the cells which was independent of osmolarity but which was minimized by the addition of magnesium. Maximal encystment occurred in a medium containing magnesium chloride alone.The cysts produced in the magnesium chloride replacement medium are viable and readily excyst when resuspended in the growth medium. The cysts contain cellulose, which is not present in the vegetative amoebae, and differ from the amoebae in their greater resistance to induced lysis and mechanical injury.

Ultraviolet microscopy of purines and amino acids in the vacuole of Candida albicans.

Ultraviolet (UV) microscopy was used to study the capacity of yeast (ATCC 10231 and 10261) and filamentous (ATCC 10259) strains of Candida albicans to accumulate UV-absorbing materials from a medium supplemented with purines, pyrimidines, amino acids, or related compounds as the main nitrogen source. All strains accumulated UV-absorbing compounds when adenine, adenosine, isoguanine, xanthine, or uric acid was supplied as a nitrogen source, but they did not accumulate UV-absorbing compounds when pyrimidines were supplied. The filamentous strain accumulated UV-absorbing material from medium supplemented with hypoxanthine, but the yeast strains did not. In contrast, the yeast strains accumulated more UV-absorbing material than did the filamentous strain when guanine was the nitrogen source. Yeast strain 10231 not only accumulated UV-absorbing material from tyrosine-supplemented medium, but it became filamentous in form as well. Yeast strain 10261 and filamentous strain 10259 did not accumulate detectable amounts of UV-absorbing material, nor was their morphology noticeably affected by the supplement. The two yeast strains accumulated more lipid than the filamentous strain when they were incubated in a nitrogen-deficient medium.

Nitrogen-deficient medium in the differential isolation of Klebsiella and Enterobacter from feces.

On a nitrogen-deficient agar medium, the tribe Klebsielleae formed large, glistening, mucoid colonies which were easily distinguished from other colony types. Of 113 Klebsielleae isolates from human feces which were characterized, Klebsiella accounted for 88% of the total; 75% were K. pneumoniae; K. ozaenae (13%) was isolated from one individual only. The remaining strains (12%) were identified as Enterobacter cloacae. Counts (for the tribe) ranged from 10(2) to 10(6), with a median of 10(4); 9 of 53 stool specimens were negative. K. pneumoniae was also isolated from 6 of 41 frozen foil-pack foods. Anaerobic studies at room temperature and 37 C revealed no appreciable differences from aerobic plates. The nitrogen-deficient medium appeared better than E M B for isolation of Klebsielleae when they were present in low numbers relative to other coliforms; slime production by Klebsielleae concomitant with minimal growth of other bacteria is involved.

Nitrogen-deficient Medium in the Differential Isolation of Klebsiella and Enterobacter from Feces

On a nitrogen-deficient agar medium, the tribe Klebsielleae formed large, glistening, mucoid colonies which were easily distinguished from other colony types. Of 113 Klebsielleae isolates from human feces which were characterized, Klebsiella accounted for 88% of the total; 75% were K. pneumoniae; K. ozaenae (13%) was isolated from one individual only. The remaining strains (12%) were identified as Enterobacter cloacae. Counts (for the tribe) ranged from 10(2) to 10(6), with a median of 10(4); 9 of 53 stool specimens were negative. K. pneumoniae was also isolated from 6 of 41 frozen foil-pack foods. Anaerobic studies at room temperature and 37 C revealed no appreciable differences from aerobic plates. The nitrogen-deficient medium appeared better than E M B for isolation of Klebsielleae when they were present in low numbers relative to other coliforms; slime production by Klebsielleae concomitant with minimal growth of other bacteria is involved.

Biosynthesis of 3-ethylthiopropionic acid and degradation of ethionine by Escherichia coli

3-Ethylthiopropionic acid has been isolated from a nitrogen-deficient medium of Escherichia coli, the first demonstration of its natural occurrence. It was identified by a combination of chemical, electrophoretic, paper chromatographic, synthetic, gas chromatographic, and mass spectrometric studies. A chemically related material recovered from chromatograms was an artifact formed by oxidation during the chromatography. Biosynthesis of 3-ethylthiopropionic acid utilized the sulfur of either 35SO 4 2− or ethionine- 35S. With exogenous nitrogen E. coli grew linearly using the sulfur of ethionine. Even without exogenous nitrogen, except for that from ethionine, a slight increase in turbidity occurred. While endogenous reserves may have been utilized to some extent, 35S was incorporated into cells even under these conditions. 3-Ethylthiopropionic acid also supplied 35S to cells when added to a nitrogen-sulfur deficient medium and was utilized more readily from a sulfur-deficient medium than was ethionine.

Substrate-accelerated death' of nitrogen-limited bacteria.

SUMMARY: ‘Substrate-accelerated death’ ( Postgate & Hunter, 1963a ; 1964) occurred when a nitrogen-limited variant of Aerobacter aerogenes NCTC 418 ( Postgate & Hunter, 1962 ) was starved at growth temperature (37° or 40°) in aerated saline buffers containing ammonium ion; it was not observed when the parent strain of A. aerogenes or Escherichia coli (MRE 162) was grown and starved under similar conditions. Sulphate ion increased the lethal effect of ammonium ion on the variant and magnesium did not abolish either the effect of ammonium or ammonium + sulphate ions. The A. aerogenes variant differed from the parent strain in morphology, colonial appearance on nutrient agar, biochemical and immunological reactions and ability to synthesize polysaccharide. In ammonium-limited medium at 37° or 40° at a dilution rate near 0·25 hr−1 the variant contained 3-5% and the parent strain 12-16% of dry weight as polysacharide; in spent medium or phosphate buffer at 37° with added glycerol the rate of polysaccharide synthesis by the variant was about 25% that of the parent strain. When grown in nitrogen-deficient medium with excess glycerol in batch culture, populations of the variant containing 25% polysaccharide were obtained; the survival of the polysaccharide-rich variant was not affected by ammonium ion.

Photoreactivation of ultraviolet-induced suppression of division in Chilomonas paramecium

The two phases of division-suppression found after UV-irradiation of Chilomonas paramecium populations were examined for photoreactivability. The second, or delayed, phase was readily photoreactivated whether the tests were run on cultures growing in complete medium, on nitrogen-depleted cells in nitrogen-deficient medium, or nitrogen-depleted cells returned to complete medium. Photoreactivability declined as cells progressed toward division, and could not be demonstrated if PR exposure was performed later than a few hours before the first post-UV division. Photoreactivability was prolonged when division was prevented by nitrogen deprivation. The initial, or immediate, phase of division-suppression was also photoreactivable, but this, for unknown reasons, could only be demonstrated if lag was prolonged by nitrogen-deprivation. These results may be interpreted as indicating that both phases of the division-suppression are the result of UV-damage to DNA, and that there is retention of photoreactivating enzyme complement even under conditions of nitrogen depletion. It is noted, however, that UV may produce photoreactivable lesions in cell constituents other than DNA, and that these may also account for either or both of the two phases of division-suppression.

Antibiotic Production by Actinomycete Species on Nitrogen‐Deficient Media

Summary: Actinomycetes isolated from nitrogen deficient Azotobacter plating medium were checked for antibiotic production on nitrogen deficient media and on these media with yeast extract or ammonium sulphate as nitrogen sources. In nitrogen deficient liquid media cobalt, molybdenum and citrate were required for growth and antibiotic formation. Evidence is presented that the antibiotics resulting from growth under these conditions are different from those produced when combined nitrogen is included in the medium, and it is suggested that this is an area for exploration for new antibiotics.

Production of Protein and Lipid by Chlorella vulgaris and Chlorella pyrenoidosa

Cultures of <i>Chlorella vulgaris</i> reach the stationary phase of their growth cycle more slowly than cultures of <i>C. pyrenoidosa</i> when both are provided with conditions favorable for their growth. But after 3weeks of incubation, the yields from the two organisms are nearly identical in terms of packed volume, dry weight, and cell population. There is only a relatively small difference in protein content—about 8 per cent in favor of C <i>vulgaris.</i> There is a somewhat larger difference in lipid content, C. <i>pyrenoidosa</i> yielding about 11 to 12 per cent more lipid than C. <i>vulgaris.</i> Both species produce more lipid and relatively less protein with increasing age. Accumulation of lipid in excess of about 25 per cent of total dry weight is indicative of waning vigor in cultures of <i>Chlorella,</i> and a lipid content that equals or exceeds the protein content is indicative of extreme senescence. Both organisms grow poorly in a nitrogen-deficient medium but differ in their response to it. The yield from <i>C. vulgaris</i> is about 80 to 86 per cent of the yield from <i>C. pyrenoidosa</i> with respect to packed volume, dry weight, and per cent lipid. Only with respect to per cent protein are the two organisms the same. However, in absolute terms (mg./ml. of culture) <i>C. vulgaris</i> yields about 14 per cent less protein and nearly 30 per cent less lipid than <i>C. pyrenoidosa</i> in such a medium.