scholarly journals New Insights into Methyl Bromide Cooxidation byNitrosomonas europaea Obtained by Experimenting with Moderately Low Density Cell Suspensions

2000 ◽  
Vol 66 (7) ◽  
pp. 2726-2731 ◽  
Author(s):  
Khrystyne N. Duddleston ◽  
Peter J. Bottomley ◽  
Angela J. Porter ◽  
Daniel J. Arp
Keyword(s):  
Cell Division ◽  
Methyl Bromide ◽  
Cell Activity ◽  
Dry Weight ◽  
Cell Suspensions ◽  
Low Density ◽  
Level Of Activity ◽  
End Products ◽  
Uptake Activity ◽  
Fresh Growth Medium

ABSTRACT We examined the rates and sustainability of methyl bromide (MeBr) oxidation in moderately low density cell suspensions (∼6 � 107 cells ml−1) of the NH3-oxidizing bacterium Nitrosomonas europaea. In the presence of 10 mM NH4 + and 0.44, 0.22, and 0.11 mM MeBr, the initial rates of MeBr oxidation were sustained for 12, 12, and 24 h, respectively, despite the fact that only 10% of the NH4 +, 18% of the NH4 +, and 35% of the NH4 +, respectively, were consumed. Although the duration of active MeBr oxidation generally decreased as the MeBr concentration increased, similar amounts of MeBr were oxidized with a large number of the NH4 +-MeBr combinations examined (10 to 20 μmol mg [dry weight] of cells−1). Approximately 90% of the NH3-dependent O2uptake activity and the NO2 −-producing activity were lost after N. europaea was exposed to 0.44 mM MeBr for 24 h. After MeBr was removed and the cells were resuspended in fresh growth medium, NO2 −production increased exponentially, and 48 to 60 h was required to reach the level of activity observed initially in control cells that were not exposed to MeBr. It is not clear what percentage of the cells were capable of cell division after MeBr oxidation because NO2 − accumulated more slowly in the exposed cells than in the unexposed cells despite the fact that the latter were diluted 10-fold to create inocula which exhibited equal initial activities. The decreases in NO2 −-producing and MeBr-oxidizing activities could not be attributed directly to NH4 + or NH3 limitation, to a decrease in the pH, to the composition of the incubation medium, or to toxic effects caused by accumulation of the end products of oxidation (NO2 − and formaldehyde) in the medium. Additional cooxidation-related studies of N. europaea are needed to identify the mechanism(s) responsible for the MeBr-induced loss of cell activity and/or viability, to determine what percentages of cells damaged by cooxidative activities are culturable, and to determine if cooxidative activity interferes with the regulation of NH3-oxidizing activity.

scholarly journals Accessory and stimulating properties of dendritic cells and macrophages isolated from various rat tissues

1982 ◽  
Vol 156 (1) ◽  
pp. 1-19 ◽  
Author(s):  
WEF Klinkert ◽  
JH LaBadie ◽  
WE Bowers
Keyword(s):  
T Cells ◽  
Dendritic Cells ◽  
Cell Activity ◽  
Accessory Cell ◽  
Nonspecific Esterase ◽  
Rat Tissues ◽  
Low Density ◽  
Γ Irradiation ◽  
Accessory Cells ◽  
Ia Antigens

Single cell suspensions of rat lymphoid and nonlymphoid tissues were fractionated on discontinuous gradients of bovine serum albumin into high density and low density subfractions. In general, accessory activity required for responses of periodate-treated T lymphocytes was recovered only in a low density population containing a small percent of the total fractionated cells from lymph nodes, spleen, liver, skin, and peritoneal exudates. Further purification always led to an increase of both accessory activity and number of dendritic cells present in nonrosetting and nonadherent populations. After purification, a high recovery of the total accessory activity was found in fractions that contained a high percentage of dendritic cells resulting in a more than 1,000-fold enrichment in accessory activity per cell. No other fraction obtained during the purification contained significant accessory activity. In all cases, macrophage-enriched populations lacked accessory cell activity. With the exception of peritoneal exudate cell preparations, which contained an inhibitory cell, the level of accessory activity in a given population was always found to be a function of the number of dendritic cells present. Dendritic cells from all sources were nonadherent, nonphagocytic, radio- resistant, and nonspecific esterase negative. They expressed Ia antigens and lacked Fc receptors. Both epidermal and lymph node dendritic cells contain Birbeck granules, subcellular structures previously described only for Langerhans cells. Accessory activity requires viable dendritic cells but is unaffected by 1,000 rad of γ-irradiation. However, ultraviolet irradiation abolished the activity of accessory cells. The cells that responded to periodate were IgG-negative T cells, whereas IgG-positive B cells could not be stimulated under the same conditions. Only periodate-treated T cells and dendritic cells were needed for responses to occur; removal of virtually all macrophages from these purified preparations had no effect. Dendritic cells were also required as stimulators in mixed leukocyte cultures, whereas macrophages, even though Ia positive, were inert.

Interferon inhibition of DNA synthesis and cell division

1972 ◽  
Vol 18 (2) ◽  
pp. 145-151 ◽  
Author(s):  
M. V. O'Shaughnessy ◽  
S. H. S. Lee ◽  
K. R. Rozee
Keyword(s):  
Cell Division ◽  
Antiviral Activity ◽  
Dna Synthesis ◽  
S Phase ◽  
Cell Suspensions ◽  
Depression Effect ◽  
Growth Depression ◽  
Synchronized Cells ◽  
Inhibition Of Dna Synthesis ◽  
New Protein

Using monodispersed cell suspensions, interferon preparations were shown to have both a lethal and a growth-depression effect in the same concentration range as that required for antiviral activity. In addition, synchronized cells treated with interferon respond by delaying their normal uptake of thymidine during S phase until after a period during which new protein is synthesized. Puromycin added during this period prevents both the synthesis of this protein and the subsequent synthesis of DNA.

Tests by Tissue Culture Methods on the Nature of Immunity Transplanted Skin

1948 ◽  
Vol s3-89 (7) ◽  
pp. 239-252
Author(s):  
P. B. MEDAWAR
Keyword(s):  
Tissue Culture ◽  
Cell Division ◽  
Epidermal Cell ◽  
Cell Suspensions ◽  
Acquired Immunity ◽  
Culture Methods ◽  
Division Frequency

The transplantation of skin from one rabbit to another elicits a reaction that conforms in main outline with that of an actively acquired immunity. The experiments described in this paper were designed to test the hypothesis that the regression of such grafts is secured by the action of antibodies demonstrable in vitro. Skin from adult rabbits has therefore been cultivated in the presence of serum and growing mesenchymal tissues derived solely from rabbits heavily and specifically immunized against it. Immune sera and tissues are without effect on the survival, cell-division frequency and migratory activities of explanted skin, and agglutinins for epidermal cell suspensions are not demonstrable in immune sera. With certain stated qualifications, it has therefore been concluded that the occurrence of free antibodies is not a sufficient explanation of the regression of skin homografts in vivo.

Tissue Factor Activity of Cultured Macrophages. Enhancement by Specific Antigenic Stimulation

1975 ◽  
Author(s):  
S. Beguin ◽  
A. Goutner ◽  
F. Josso
Keyword(s):  
Human Serum ◽  
Tissue Factor ◽  
Cell Activity ◽  
Cell Suspensions ◽  
Rabbit Serum ◽  
Factor Activity ◽  
Clotting System ◽  
Subsequent Increase ◽  
Macrophage Activity ◽  
Tissue Factor Activity

Peritoneal macrophage suspensions (95 p. cent pure) were obtained in rabbits either intact or previously immunized against human serum. Cell suspensions exhibited a clear tissue factor activity, closely related to the cell concentration.Macrophages (10000/mm3) were cultured in the presence of PO4)2 Ca3 adsorbed and decomplemented serum of either rabbit or human origin. Clotting activity of the supernatant medium was tested after 24 hour culture. In immunized animals, tissue factor activity was much higher when the cells were cultured in the presence of the antigens (human serum) instead of rabbit serum; no difference was observed in intact rabbits.Contamination of the cell suspensions by lymphocytes seems too low to play a role in this stimulation of macrophage activity. The reported data suggest that antibodies bound to macrophage membrane react with the medium antigens with subsequent increase of the cell activity.Such a phenomenon could initiate the activation of the clotting system observed in some immune reactions.

scholarly journals Visualization is crucial for understanding microbial processes in the ocean

2019 ◽  
Vol 374 (1786) ◽  
pp. 20190083 ◽  
Author(s):  
Marta Sebastián ◽  
Josep M. Gasol
Keyword(s):  
Single Cell ◽  
Metabolic Activity ◽  
Cell Activity ◽  
Level Of Activity ◽  
Single Cell Activity ◽  
Recent Developments ◽  
Insight Into ◽  
Do So

Recent developments in community and single-cell genomic approaches have provided an unprecedented amount of information on the ecology of microbes in the aquatic environment. However, linkages between each specific microbe's identity and their in situ level of activity (be it growth, division or just metabolic activity) are much more scarce. The ultimate goal of marine microbial ecology is to understand how the environment determines the types of different microbes in nature, their function, morphology and cell-to-cell interactions and to do so we should gather three levels of information, the genomic (including identity), the functional (activity or growth), and the morphological, and for as many individual cells as possible. We present a brief overview of methodologies applied to address single-cell activity in marine prokaryotes, together with a discussion of the difficulties in identifying and categorizing activity and growth. We then provide and discuss some examples showing how visualization has been pivotal for challenging established paradigms and for understanding the role of microbes in the environment, unveiling processes and interactions that otherwise would have been overlooked. We conclude by stating that more effort should be directed towards integrating visualization in future approaches if we want to gain a comprehensive insight into how microbes contribute to the functioning of ecosystems. This article is part of a discussion meeting issue ‘Single cell ecology’.

Purple Nutsedge Control with Allyl Isothiocyanate under Virtually Impermeable Film Mulch

2014 ◽  
Vol 28 (1) ◽  
pp. 200-205 ◽  
Author(s):  
Sanjeev K. Bangarwa ◽  
Jason K. Norsworthy
Keyword(s):  
Methyl Bromide ◽  
Field Experiments ◽  
Standard Treatment ◽  
Allyl Isothiocyanate ◽  
Low Density Polyethylene ◽  
Vegetable Production ◽  
Low Density ◽  
Purple Nutsedge ◽  
Treated Soil ◽  
Polyethylene Mulch

Nutsedge control is challenging in commercial vegetable production in the absence of methyl bromide, and therefore, an effective alternative is needed. This study investigated allyl isothiocyanate (ITC) as a methyl bromide alternative for purple nutsedge control under polyethylene-mulch. Greenhouse experiments were conducted to compare the retention of allyl ITC in treated soil (3,000 nmol g−1) under low-density polyethylene (LDPE) and virtually impermeable film (VIF) mulches. Field experiments were conducted to evaluate the effectiveness of allyl ITC (6 rates: 0, 15, 75, 150, 750, 1500 kg ai ha−1) under VIF mulch against purple nutsedge. Additionally, a standard treatment of methyl bromide+chloropicrin (67 : 33%) at 390 kg ai ha−1under LDPE mulch was included for comparison. In the greenhouse experiment, the predicted half-life of allyl ITC under LDPE and VIF mulch was 0.15 and 0.59 d, respectively. In the field experiment, it was predicted that allyl ITC at 1,240 and 1,097 kg ha−1under VIF mulch is required to control purple nutsedge shoot and tubers equivalent to methyl bromide + chloropicrin at 4 wk after treatment (WAT). It is concluded that allyl ITC under VIF mulch would need to be applied at 2.8 to 3.2 times the standard treatment of methyl bromide + chloropicrin under LDPE mulch for commercially acceptable purple nutsedge control.

scholarly journals Cellulose Catabolism by Clostridium cellulolyticum Growing in Batch Culture on Defined Medium

2000 ◽  
Vol 66 (6) ◽  
pp. 2461-2470 ◽  
Author(s):  
Mickaël Desvaux ◽  
Emmanuel Guedon ◽  
Henri Petitdemange
Keyword(s):  
Batch Culture ◽  
Cellulose Degradation ◽  
Growth Arrest ◽  
Dry Weight ◽  
Defined Medium ◽  
Carbon Flow ◽  
Natural Ecosystem ◽  
Clostridium Cellulolyticum ◽  
End Products ◽  
Cellulose Concentration

ABSTRACT A reinvestigation of cellulose degradation by Clostridium cellulolyticum in a bioreactor with pH control of the batch culture and using a defined medium was performed. Depending on cellulose concentration, the carbon flow distribution was affected, showing the high flexibility of the metabolism. With less than 6.7 g of cellulose liter−1, acetate, ethanol, H2, and CO2 were the main end products of the fermentation and cellulose degradation reached more than 85% in 5 days. The electron flow from the glycolysis was balanced by the production of H2 and ethanol, the latter increasing with increasing initial cellulose concentration. From 6.7 to 29.1 g of cellulose liter−1, the percentage of cellulose degradation declined; most of the cellulase activity remained on the cellulose fibers, the maximum cell density leveled off, and the carbon flow was reoriented from ethanol to acetate. In addition to that of previously indicated end products, lactate production rose, and, surprisingly enough, pyruvate overflow occurred. Concomitantly the molar growth yield and the energetic yield of the biomass decreased. Growth arrest may be linked to sufficiently high carbon flow, leading to the accumulation of an intracellular inhibitory compound(s), as observed on cellobiose (E. Guedon, M. Desvaux, S. Payot, and H. Petitdemange, Microbiology 145:1831–1838, 1999). These results indicated that bacterial metabolism exhibited on cellobiose was distorted compared to that exhibited on a substrate more closely related to the natural ecosystem of C. cellulolyticum. To overcome growth arrest and to improve degradation at high cellulose concentrations (29.1 g liter−1), a reinoculation mode was evaluated. This procedure resulted in an increase in the maximum dry weight of cells (2,175 mg liter−1), cellulose solubilization (95%), and end product concentrations compared to a classical batch fermentation with a final dry weight of cells of 580 mg liter−1 and 45% cellulose degradation within 18 days.

Soil physical environment affecting root growth of upland rice

1979 ◽  
Vol 93 (3) ◽  
pp. 719-726 ◽  
Author(s):  
S. Kar ◽  
S. B. Varade ◽  
B. P. Ghildyal
Keyword(s):  
Root Growth ◽  
Bulk Density ◽  
Physical Environment ◽  
Oxygen Diffusion ◽  
Dry Weight ◽  
Moisture Stress ◽  
Rice Root ◽  
Soil Types ◽  
Low Density ◽  
Depth Of Penetration

SUMMARYRoot growth of rice (Oryza saliva L.) is frequentlyinhibited by an adverse physical environment resulting from high moisture stress and strength of soilunder upland conditions, and the effects are often reflected in poor performance of the crop. This necessitates a critical understanding of rice root growth under varying soil physical conditions.The growth responses of the rice root system to the interaction between moisture regime and bulk density of soil as well as to the induced soil physical characteristics were assessed under controlled glasshouse conditions. Four moisture regimes: 0 (M1), 0–20 (M2), 0–350(M3), and 350–10000 (M4) mb, were superimposed on low, medium and high bulk density treatments in clay, loam and sandy loam soils. The soil physical environment was characterized by measurements of moisture distribution, penetrationenergy and oxygen diffusion rate in soils as functions of depth.A low moisture stress of 20 mb in low density soils favoured rice root growth. In low density soils, even though the number of roots at the base (proximal end) was maximum under M1, the depth of penetration, volume and dry weight of root were significantly more underM2 than under M1; M3 and M4. Irrespective of bulk density, even though oxygen diffusion rates in soils under M3 and M4 were greater than those under M1 and M2, the number of roots at the base, volume and dry weight of the root system decreased under M3 and M4 owing to low moisture content and high penetration energy in the surface layer (0–5 cm) of all the soil types. Lower moisture content and higher penetration energy at higher bulk densities of the soil types significantly reduced the root growth and especially the depth of penetration.

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