Croissance de la biomasse azotée du Phaeodactylum tricornutum (Bacillariophyceae) en cultures discontinues dialysante et non dialysante

1992 ◽  
Vol 38 (9) ◽  
pp. 945-952 ◽  
Author(s):  
Pierre Marsot ◽  
Allan D. Cembella ◽  
Khadija Mouhri
Keyword(s):  
Phaeodactylum Tricornutum ◽  
Inorganic Nitrogen ◽  
Biomass Concentration ◽  
Diffusion Limit ◽  
Active Growth ◽  
Culture Techniques ◽  
Uptake Activity ◽  
Nitrogen Nutrients ◽  
Menten Constant ◽  
Dialysis Culture

The unique conditions associated with discontinuous (batch) dialysis culture of the diatom Phaeodactylum tricornutum elicit different nutritional responses from those observed in nondialysis culture. Simultaneous determinations of the nitrogen biomass concentration and of the nitrogen nutrients (NO3− + NO2−) in the culture chamber, as well as in the seawater nutrient medium at the entrance and exit of the dialyzer, revealed that nitrogen-biomass production in dialysis cultures is achieved mainly (>90%) during postexponential growth, when the concentration of nutrients is limiting (smaller than Michaelis-Menten constant). Almost half of this biomass is produced at the diffusion limit of the apparatus, i.e., when the mass transfer of nutrient substrates, which determines the total uptake activity of the culture, reaches a maximum. In contrast, in nondialysis discontinuous cultures, in which the postexponential growth phase is short, most of the total cellular nitrogen is accumulated during active growth. Certain physiological indices relating to the active uptake and assimilation of inorganic nitrogen are consistent with the different nutritional responses elicited by these two types of culture techniques and explain the high biomass levels obtained in dialysis culture. Key words: dialysis culture, diatom, nitrogen metabolism.

scholarly journals Construction of a Ginseng Root-Meristem Sensor and a Sensing Kinetics Study on the Main Nitrogen Nutrients

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 681
Author(s):  
Shiang Wang ◽  
Dingqiang Lu ◽  
Guangchang Pang
Keyword(s):  
Limit Of Detection ◽  
Inorganic Nitrogen ◽  
Equilibrium Analysis ◽  
Ginseng Root ◽  
Continuous Cropping ◽  
Sodium Glutamate ◽  
Sensor Sensitivity ◽  
Group A ◽  
Hardy Weinberg Equilibrium ◽  
Nitrogen Nutrients

Severe continuous cropping obstacles exist in ginseng cultivation. In order to assess these obstacles, a “sandwich” ginseng root tissue sensor was developed for the kinetic determination of five nitrogen nutrients. The results showed that the sensing parameters of the sensor reached an ultrasensitive level (limit of detection up to 5.451 × 10−24 mol/L) for the five nitrogen nutrients, and exhibited good stability and reproducibility. In the order of two-, four-, and six-year-old ginseng plants, the sensitivity to inorganic nitrogen nutrients (sodium nitrate and urea) showed an upward trend following an initial decline (the interconnected allosteric constant Ka values acted as the parameter). The fluctuations in sensor sensitivity to organic nitrogen nutrients, specifically nucleotides (disodium inosinate and disodium guanylate), were relatively small. The sensor sensitivity of two-, four-, and six-year-old ginseng plants to sodium glutamate was 9.277 × 10−19 mol/L, 6.980 × 10−21 mol/L, and 5.451 × 10−24 mol/L, respectively. Based on the survival rate of the seedlings and mortality rate of the ginseng in each age group, a Hardy–Weinberg equilibrium analysis was carried out. The results showed that the sensing ability of the root system to sodium glutamate may be an important factor affecting its survival under continuous cropping obstacles with increasing age.

scholarly journals Spatial-temporal dynamics of N-cycle functional genes in a temperate Atlantic estuary (Douro, Portugal)

2020 ◽  
Vol 84 ◽  
pp. 205-216
Author(s):  
P Salgado ◽  
A Machado ◽  
AA Bordalo
Keyword(s):  
Microbial Communities ◽  
Temporal Dynamics ◽  
Inorganic Nitrogen ◽  
Functional Genes ◽  
Estuarine Ecosystem ◽  
Monthly Basis ◽  
N Cycle ◽  
Low Salinity ◽  
Key Factor ◽  
Nitrogen Nutrients

Understanding the spatial and seasonal dynamics of nitrogen (N)-cycle microbial communities is pivotal for the knowledge of N biogeochemistry. The present study addressed the spatial-temporal variability of nitrification (bacterial and archaeal amoA) and denitrification (nirS, nirK, and nosZI) key genes, as well as of non-denitrifying nitrous oxide (N2O) reducers (nosZII), coupled with key environmental variables, in an estuarine ecosystem (Douro, NW Portugal). Samples were collected on a monthly basis over 1 yr, key physical-chemical parameters were measured, and specific functional gene abundances were assayed. The results revealed a clear seasonality for nirS, nosZII, and bacterial and archaeal amoA abundance, with an increase during the winter/spring seasons. This period was especially characterized by high levels of dissolved oxygen, low temperature, low salinity, and increased turbidity. Indeed, turbidity emerged as the key factor controlling the distribution of nirS, nosZII bacterial, and archaeal amoA abundance. In contrast, the abundance of nosZI increased during the summer, while nirK abundance was enhanced from the fall to late spring. Additionally, the availability of dissolved inorganic nitrogen nutrients had no commensurable effect on N-cycle functional genes. This study of the annual variation of N-cycle functional genes in a temperate Atlantic estuary provides a major contribution to the understanding of how environmental factors potentially influence the distribution and abundance of N-cycle microbial communities.

scholarly journals Consistency of thresholds for eutrophication assessments, examples and recommendations

2021 ◽  
Vol 193 (10) ◽  
Author(s):  
D. Topcu ◽  
U. Brockmann
Keyword(s):  
Chlorophyll A ◽  
North Sea ◽  
Coastal Waters ◽  
Inorganic Nitrogen ◽  
Mixing Processes ◽  
The North ◽  
The North Sea ◽  
International Harmonisation ◽  
Nitrogen Nutrients ◽  
Mixing Diagrams

AbstractInternational harmonisation of management goals for eutrophication processes in coastal waters, requiring reduction of discharges and depositions of nutrients and organic matter, needs coordinated assessments and measures. This is especially necessary in open areas, connected by currents and mixing processes with trans-boundary exchanges. Management goals, defined nationally as local thresholds for nutrients and chlorophyll-a, had been applied recently (2006–2014) within international eutrophication assessments in the North Sea (OSPAR) and Baltic Sea (HELCOM). Consistency of thresholds for nitrogen nutrients and chlorophyll-a concentrations is tested by mixing diagrams and correlations between nitrogen nutrients (total and inorganic nitrogen) and chlorophyll-a. Results indicate mean consistent relations, but single deviations as in the continental coastal water of the North Sea surpassed means by a factor up to 5 for chlorophyll-a in relation to inorganic nitrogen. Thresholds differed across national borders significantly. Correlations of thresholds and assed data reflect the degree of regional deviations by comparison. Consistency of regionally applied thresholds can be achieved stepwise, by application of regionally correlated means, by adaptation to mixing and parameter relations, and finally by relations of thresholds to natural background concentrations. By this, consistency of international assessments can be improved generally, allowing coordinated management of open coastal waters.

STEROL PRODUCTION BY SOME WOOD-ROTTING BASIDIOMYCETES

1965 ◽  
Vol 43 (11) ◽  
pp. 1347-1353 ◽  
Author(s):  
Francis H. Milazzo
Keyword(s):  
Growth Medium ◽  
Organic Nitrogen ◽  
Inorganic Nitrogen ◽  
Defined Medium ◽  
Chemically Defined Medium ◽  
Active Growth

Fourteen species (six genera) of wood-rotting basidiomycetes cultured in a chemically defined medium were examined for the presence of sterol material. These fungi were found to contain ergosterol in amounts that ranged in value from 0.017 to 0.42% of their mycelial dry weights. Such values are, in general, comparable to sterol values reported for other fungi.The synthesis of sterol by Fomes meliae was found to accompany active growth of the fungus and was quantitatively influenced by the composition of the growth medium. Hexose supported greater production of sterol than did pentose, and organic nitrogen was superior to inorganic nitrogen in respect to this synthesis. The combination of hexose and organic nitrogen supported the greatest synthesis of sterol.

Production of antibacterial activities by two Bacillariophyceae grown in dialysis culture

1983 ◽  
Vol 29 (3) ◽  
pp. 338-341 ◽  
Author(s):  
Sam Cooper ◽  
Aviva Battat ◽  
Pierre Marsot ◽  
Michel Sylvestre
Keyword(s):  
Phaeodactylum Tricornutum ◽  
Marine Algae ◽  
Skeletonema Costatum ◽  
Antibacterial Activities ◽  
Gram Negative Bacteria ◽  
High Cell ◽  
Direct Relation ◽  
Algal Extracts ◽  
Time Of Harvest ◽  
Dialysis Culture

Using a dialysis culture system for marine algae which allows for the recovery of high cell yield, we detected in the aqueous phase of the algal extracts an active component which inhibited gram-negative bacteria. Results show a direct relation between cell growth phase at time of harvest and the activity observed. It was possible to confirm previous results whereby Bacillariophyceae produce lipophilic substances inhibiting gram-positive terrestrial and marine bacteria. These findings corroborate the observation that Skeletonema costatum is more active man Phaeodactylum tricornutum against Staphyloccoci.

scholarly journals The Inorganic Nutrient Regime and the mre Genes Regulate Cell and Filament Size and Morphology in the Phototrophic Multicellular Bacterium Anabaena

mSphere ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Cristina Velázquez-Suárez ◽  
Ignacio Luque ◽  
Antonia Herrero
Keyword(s):  
Cell Size ◽  
Inorganic Nitrogen ◽  
Oxygenic Photosynthesis ◽  
Filament Length ◽  
Wild Type ◽  
Active Growth ◽  
Lower Growth ◽  
Combined Nitrogen ◽  
Size And Morphology ◽  
Diazotrophic Growth

ABSTRACT The model cyanobacterium Anabaena sp. PCC 7120 exhibits a phototrophic metabolism relying on oxygenic photosynthesis and a complex morphology. The organismic unit is a filament of communicated cells that may include cells specialized in different nutritional tasks, thus representing a paradigm of multicellular bacteria. In Anabaena, the inorganic carbon and nitrogen regime influenced not only growth, but also cell size, cell shape, and filament length, which also varied through the growth cycle. When using combined nitrogen, especially with abundant carbon, cells enlarged and elongated during active growth. When fixing N2, which imposed lower growth rates, shorter and smaller cells were maintained. In Anabaena, gene homologs to mreB, mreC, and mreD form an operon that was expressed at higher levels during the phase of fastest growth. In an ntcA mutant, mre transcript levels were higher than in the wild type and, consistently, cells were longer. Negative regulation by NtcA can explain that Anabaena cells were longer in the presence of combined nitrogen than in diazotrophic cultures, in which the levels of NtcA are higher. mreB, mreC, and mreD mutants could grow with combined nitrogen, but only the latter mutant could grow diazotrophically. Cells were always larger and shorter than wild-type cells, and their orientation in the filament was inverted. Consistent with increased peptidoglycan width and incorporation in the intercellular septa, filaments were longer in the mutants, suggesting a role for MreB, MreC, and MreD in the construction of septal peptidoglycan that could affect intercellular communication required for diazotrophic growth. IMPORTANCE Most studies on the determination of bacterial cell morphology have been conducted in heterotrophic organisms. Here, we present a study of how the availability of inorganic nitrogen and carbon sources influence cell size and morphology in the context of a phototrophic metabolism, as found in the multicellular cyanobacterium Anabaena. In Anabaena, the expression of the MreB, MreC, and MreD proteins, which influence cell size and length, are regulated by NtcA, a transcription factor that globally coordinates cellular responses to the C-to-N balance of the cells. Moreover, MreB, MreC, and MreD also influence septal peptidoglycan construction, thus affecting filament length and, possibly, intercellular molecular exchange that is required for diazotrophic growth. Thus, here we identified new roles for Mre proteins in relation to the phototrophic and multicellular character of a cyanobacterium, Anabaena.

scholarly journals A Panax notoginseng Root Tip Meristem Biosensor and Its Sensing Kinetics for Five Important Nitrogen Nutrients

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zi Qing Zheng ◽  
Bo Niu ◽  
Ding Qiang Lu ◽  
Guang Chang Pang
Keyword(s):  
Sodium Nitrate ◽  
Inorganic Nitrogen ◽  
Low Cost ◽  
Panax Notoginseng ◽  
Interaction Constant ◽  
Electrode System ◽  
Plant Age ◽  
Root Tip ◽  
Sodium Glutamate ◽  
Nitrogen Nutrients

Plants absorb nitrogen mainly through their roots. Nitrogen sensing is required for the absorption and transport of different nitrogen nutrients. In this study, we constructed biosensors with immobilized Panax notoginseng root tip meristems based on a three-electrode system and successfully determined the kinetics of the interactions between the P. notoginseng root tip meristems and five important nitrogen nutrients, namely, urea, sodium nitrate, sodium glutamate, disodium inosinate, and disodium guanylate. We discovered that the biosensor’s sensing kinetics was similar to the enzyme–substrate kinetics, and the receptor–ligand interconnected allosteric interaction constant Ka (mol/L), analogous to the Michaelis constant, was calculated. The result showed that the root tip meristems of two- to four-year-old P. notoginseng plants had a higher capacity to sense inorganic nitrogen nutrients (sodium nitrate and urea) than the three organic nitrogen nutrients. The ability of the plants to sense inorganic nitrogen nutrients decreased with an increase in plant age. The sensing sensitivity of four-year-old P. notoginseng plants to disodium inosinate and disodium guanylate was 100- to 10,000-fold lower than that of the two- and three-year-old plants. Additionally, the capability to sense sodium glutamate decreased initially and then increased with an increase in plant age. The biosensors reached an ultra-sensitive level ( 1 × 10 − 22  mol/L) in sensing the five nitrogen nutrients and exhibited advantages such as good stability and reproducibility, low cost, a simple structure, and a rapid response, providing a new approach for quantitative determination of the capability of plants to sense different nitrogen nutrients.

A T.E.M. study of mouse mammary epithelial cell secretory differentiation cultured on collagen and Matrigel

1991 ◽  
Vol 49 ◽  
pp. 188-189
Author(s):  
W.N. Bentham ◽  
V. Rocha
Keyword(s):  
Cell Culture ◽  
Mammary Epithelial ◽  
Secretory Process ◽  
Cell Culture System ◽  
Protein Maturation ◽  
Cell Culture Techniques ◽  
Culture Techniques ◽  
Mouse Mammary Epithelial Cell ◽  
Secretory Differentiation

It has been an interest of our lab to develop a mammary epethelial cell culture system that faithfully duplicates the in vivo condition of the lactating gland. Since the introduction of collagen as a matrix on which cells are cultivated other E.C.M. type matrices have been made available and are used in many cell culture techniques. We have previously demonstrated that cells cultured on collagen and Matrigel do not differentiate as they do in vivo. It seems that these cultures often produce cells that show a disruption in the secretory process. The appearance of large ribosomal studded vesicles, that specifically label with antibody to casein, suggest an interruption of both protein maturation and secretion at the E.R. to golgi transition. In this report we have examined cultures on collagen and Matrigel at relative high and low seeding densities and compared them to cells from the in vivo condition.

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