scholarly journals The instability of gyrotactically trapped cell layers

2019 ◽  
Vol 868 ◽  
Author(s):  
Smitha Maretvadakethope ◽  
Eric E. Keaveny ◽  
Yongyun Hwang
Keyword(s):  
Cell Layer ◽  
Cell Concentration ◽  
Gravitational Instability ◽  
Plane Channel ◽  
Thin Layers ◽  
Relevant Parameter ◽  
Potential Mechanism ◽  
Cell Layers ◽  
Maximum Cell ◽  
Maximum Cell Concentration

Several metres below the coastal ocean surface there are areas of high ecological activity that contain thin layers of concentrated motile phytoplankton. Gyrotactic trapping has been proposed as a potential mechanism for layer formation of bottom-heavy swimming algae cells, especially in flows where the vorticity varies linearly with depth (Durham et al., Science, vol. 323(5917), 2009, pp. 1067–1070). Using a continuum model for dilute microswimmer suspensions, we report that an instability of a gyrotactically trapped cell layer can arise in a pressure-driven plane channel flow. The linear stability analysis reveals that the equilibrium cell-layer solution is hydrodynamically unstable due to negative microswimmer buoyancy (i.e. a gravitational instability) over a range of biologically relevant parameter values. The critical cell concentration for this instability is found to be $N_{c}\simeq 10^{4}~\text{cells}~\text{cm}^{-3}$, a value comparable to the typical maximum cell concentration observed in thin layers. This result indicates that the instability may be a potential mechanism for limiting the layer’s maximum cell concentration, especially in regions where turbulence is weak, and motivates the study of its nonlinear evolution, perhaps, in the presence of turbulence.

scholarly journals PRODUCTION OF DOCOSAHEXAENOIC ACID (DHA) FROM Thraustochytrium sp. ATCC 26185 USING DIFFERENTS NITROGEN CONCENTRATIONS

2014 ◽  
Vol 32 (1) ◽  
Author(s):  
VALCENIR JUNIOR MENDES FURLAN ◽  
MARIA DO CASTELO PAULO ◽  
VICTOR WEGNER MAUS ◽  
JULIA FERREIRA ◽  
IRINEU BATISTA ◽  
...  
Keyword(s):  
Cell Concentration ◽  
Batch Process ◽  
Fed Batch ◽  
The Third ◽  
Culture Time ◽  
Cell Biomass ◽  
Oleaginous Microorganism ◽  
Nitrogen Concentrations ◽  
Maximum Cell ◽  
Maximum Cell Concentration

In this work it was studied the polyunsaturated fatty acids (PUFAs) production, especially DHA, from Thraustochytrium sp. ATCC 26185, under different total nitrogen (TN) availability. Three different TN conditions were evaluated: two with initial concentrations of 2.4 g/L and 0.8 g/L, and the third in a fed-batch process with a rate of 0.009 g/L.h. For each experiment the biomass, glucose, TN and PUFAs were determined. The major composition of the PUFAs in Thraustochytrium sp. ATCC 26185 cell biomass were DPA ω6 (21-25 %) and DHA (69-73 %), regardless of the type and time of culture. The maximum cell concentration (30.2 g/L) was obtained using 2.4 g/L TN in 168 h of culture. With this same concentration of TN it was possible to produce the highest concentration of DHA (1.16 g/L) in 120 h of culture, demonstrating that the growth of Thraustochytrium sp. ATCC 26185 and yield of PUFAs are dependent on the source concentration of TN available for consumption of this oleaginous microorganism, as well as culture time.

Oxygen supply in disposable shake-flasks: prediction of oxygen transfer rate, oxygen saturation and maximum cell concentration during aerobic growth

2013 ◽  
Vol 35 (8) ◽  
pp. 1223-1230 ◽  
Author(s):  
Sarah Schiefelbein ◽  
Alexander Fröhlich ◽  
Gernot T. John ◽  
Falco Beutler ◽  
Christoph Wittmann ◽  
...  
Keyword(s):  
Oxygen Saturation ◽  
Oxygen Transfer ◽  
Transfer Rate ◽  
Oxygen Supply ◽  
Cell Concentration ◽  
Oxygen Transfer Rate ◽  
Aerobic Growth ◽  
Shake Flasks ◽  
Maximum Cell ◽  
Maximum Cell Concentration

PRODUCTION OF DOCOSAHEXAENOIC ACID (DHA) FROM Thraustochytrium sp. ATCC 26185 USING DIFFERENTS NITROGEN CONCENTRATIONS

2015 ◽  
Vol 32 (1) ◽  
Author(s):  
Valcenir Júnior Mendes Furlan ◽  
MARIA DO CASTELO PAULO ◽  
Victor Wegner Maus ◽  
Júlia Ferreira ◽  
Irineu Batista ◽  
...  
Keyword(s):  
Cell Concentration ◽  
Glucose Consumption ◽  
Batch Process ◽  
Human Organism ◽  
Fed Batch ◽  
Cell Biomass ◽  
Oleaginous Microorganism ◽  
Nitrogen Concentrations ◽  
Maximum Cell ◽  
Maximum Cell Concentration

Polyunsaturated fatty acids (PUFAs) of the type ω3 and ω6 play important physiological functions in human organism, since they are components of cell membranes and brain cells; they decrease the levels of triglycerides and can prevent the incidence of coronary heart disease. Various parameters, including concentration of the nitrogen source in the cultivation of oleaginous microorganisms have been reported to be essential in the biosynthesis and accumulation of PUFAs. The objective of this work is to study the effect of different concentrations of total nitrogen (TN) in the production of PUFAs, especially DHA, from Thraustochytrium sp. ATCC 26185. The concentrations of TN evaluated were 2.4 and 0.8 g/L (batch) and 0.009 g/L (hourly) under fed-batch process. The content of cell biomass, glucose consumption, TN and production of PUFAs was determined. The major composition of the PUFAs in Thraustochytrium sp. ATCC 26185 cell biomass were DPA ω6 (21-25%) and DHA (69-73%), regardless of the type and time of culture. The maximum cell concentration obtained (30.2 g/L) was using 2.4 g/L TN in 168 h of culture. With this same concentration of TN it was possible to produce the highest concentration of DHA (1.16 g/L) in 120 h of culture, demonstrating that the growth of Thraustochytrium sp. ATCC 26185 and yield of PUFAs are dependent on the concentration TN source available for consumption of this oleaginous microorganism, as well as culture time.

scholarly journals 3-D Wire Cloth Electrode for Higher Throughput DielectrophoreticSeparation of Bacterial Cell

2019 ◽  
Vol 8 (6S4) ◽  
pp. 381-385
Keyword(s):  
Flow Rate ◽  
Cell Separation ◽  
Cell Concentration ◽  
Surface Areas ◽  
Total Percentage ◽  
Textile Technology ◽  
Percentage Yield ◽  
Maximum Cell ◽  
Wire Cloth ◽  
Maximum Cell Concentration

Dielectrophoresis (DEP) is one of an alternative way for cell separation. It has mainly been limited to processing small volumes due to constrain in fabrication of microelectrode over large surface areas. This work incorporated the wire cloth electrode fabricated using textile technology into a high throughput chamber experiment. The plain-weave wire cloth consists of 71µm stainless steel wires as the microelectrode arrays hold together by polyester yarn warp. This work determines the cell separation yield with parameters on applied voltage, flow rate and cell concentration as well as its optimized variables on the chamber width of 1.2cm and 2.5cm. The optimum voltage achieved was 30Vpk-pk, with flow rate of 3.5 ml/min and maximum cell concentration of 2.08x107 cells/ml. In chamber width comparison, 1.2cm width chamber gives better total percentage yield of 96% than the 2.5cm width chamber of 85% total percentage yield.

scholarly journals FEATURES OF SPIRULINA PLATENSIS CULTIVATED UNDER AUTOTROPHIC AND MIXOTROPHIC CONDITIONS

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
Zahra Rasouli ◽  
Mahdi Parsa ◽  
Hossein Ahmadzadeh
Keyword(s):  
Spirulina Platensis ◽  
Cell Concentration ◽  
Biomass Productivity ◽  
Stability Index ◽  
Cell Number ◽  
Membrane Stability ◽  
Tolerance Index ◽  
Chlorophyll Protein ◽  
Maximum Cell ◽  
Maximum Cell Concentration

Cultivation of Spirulina platensis in Zarrouk media containing 0–20 g l-1 glucose was studied in a photobioreactor for 30 days using a light intensity of 3 klux. Various parameters were measured to evaluate the enhancement of cell performance with glucose such as cell number, osmolarity, membrane stability, biomass productivity, doubling time, stress intensity, stress tolerance, chlorophyll, protein, carbohydrates, and lipid contents. Based on the results, we concluded that S. platensis is able to grow and produce some ingredients in Zarrouk media containing up to 20 g l-1 of glucose which is the first to be reported. The cell concentration of the mixotrophic cultures (80 cells per mm2) corresponded well to the sum of the autotrophic cell concentrations (50 cells per mm2), showing that the addition of carbohydrate positively effects on the microalgae growth. The continuous operation supplemented with 0.5 g l-1 of glucose (G0.5) led to the maximum cell concentration about 9.06 g l-1 wet and 1.32 g l-1 dry weights. The highest tolerance index, specific growth rate, biomass productivity, cell division, osmolarity and membrane stability index were respectively 102.5%, 0.15 d-1, 0.04 g l-1d-1, 0.26 div d-1, 0.87 osmol kg-1 and 93.8%, obtained in the same treatment. Chlorophyll (6.7 % in G0; 0.046 g l-1 in G0.5), protein (79.9 % and 0.884 g l-1 in G0.5), carbohydrates (55.5% in G20; 0.492 g l-1 in G6) and lipid (53.3% in G10; 0.636 g l-1 in G0) percentages and yields were mostly enhanced in the mixotrophic condition. This study indicated that mixotrophic growth of S. platensis is useful for commercial biomass production.

Regulation of cell proliferation patterns by homeotic genes during Arabidopsis floral development

Development ◽  
2000 ◽  
Vol 127 (6) ◽  
pp. 1267-1276 ◽  
Author(s):  
P.D. Jenik ◽  
V.F. Irish
Keyword(s):  
Cell Proliferation ◽  
Apical Meristem ◽  
Floral Development ◽  
Developmental Process ◽  
Cell Layer ◽  
Homeotic Genes ◽  
Transmitting Tract ◽  
Organ Identity ◽  
Element System ◽  
Cell Layers

The shoot apical meristem of Arabidopsis thaliana consists of three cell layers that proliferate to give rise to the aerial organs of the plant. By labeling cells in each layer using an Ac-based transposable element system, we mapped their contributions to the floral organs, as well as determined the degree of plasticity in this developmental process. We found that each cell layer proliferates to give rise to predictable derivatives: the L1 contributes to the epidermis, the stigma, part of the transmitting tract and the integument of the ovules, while the L2 and L3 contribute, to different degrees, to the mesophyll and other internal tissues. In order to test the roles of the floral homeotic genes in regulating these patterns of cell proliferation, we carried out similar clonal analyses in apetala3-3 and agamous-1 mutant plants. Our results suggest that cell division patterns are regulated differently at different stages of floral development. In early floral stages, the pattern of cell divisions is dependent on position in the floral meristem, and not on future organ identity. Later, during organogenesis, the layer contributions to the organs are controlled by the homeotic genes. We also show that AGAMOUS is required to maintain the layered structure of the meristem prior to organ initiation, as well as having a non-autonomous role in the regulation of the layer contributions to the petals.

Non-cell-autonomous function of the Antirrhinum floral homeotic proteins DEFICIENS and GLOBOSA is exerted by their polar cell-to-cell trafficking

Development ◽  
1996 ◽  
Vol 122 (11) ◽  
pp. 3433-3441 ◽  
Author(s):  
M.C. Perbal ◽  
G. Haughn ◽  
H. Saedler ◽  
Z. Schwarz-Sommer
Keyword(s):  
Cell Layer ◽  
Epidermal Cells ◽  
Molecular Techniques ◽  
Cell Trafficking ◽  
Mads Box ◽  
Organ Identity ◽  
Cell Layers ◽  
Periclinal Chimeras ◽  
The Difference ◽  
Cell Autonomy

In Antirrhinum majus, petal and stamen organ identity is controlled by two MADS-box transcription factors, DEFICIENS and GLOBOSA. Mutations in either of these genes result in the replacement of petals by sepaloid organs and stamens by carpelloid organs. Somatically stable def and glo periclinal chimeras, generated by transposon excision events, were used to study the non-cell-autonomous functions of these two MADS-box proteins. Two morphologically distinct types of chimeras were analysed using genetic, morphological and molecular techniques. Restoration of DEF expression in the L1 cell layer results in the reestablishment of DEF and GLO functions in L1-derived cells only; inner layer cells retain their mutant sepaloid features. Nevertheless, this activity is sufficient to allow the expansion of petal lobes, highlighting the role of DEF in the stimulation of cell proliferation and/or cell shape and elongation when expressed in the L1 layer. Establishment of DEF or GLO expression in L2 and L3 cell layers is accompanied by the recovery of petaloid identity of the epidermal cells but it is insufficient to allow petal lobe expansion. We show by in situ immunolocalisation that the non-cell-autonomy is due to direct trafficking of DEF and GLO proteins from the inner layer to the epidermal cells. At least for DEF, this movement appears to be polar since DEF acts cell-autonomously when expressed in the L1 cell layer. Furthermore, the petaloid revertant sectors observed on second whorl mutant organs and the mutant margins of petals of L2L3 chimeras suggest that DEF and GLO intradermal movement is limited. This restriction may reflect the difference in the regulation of primary plasmodesmata connecting cells from the same layer and secondary plasmodesmata connecting cells from different layers. We propose that control of intradermal trafficking of DEF and GLO could play a role in maintaining of the boundaries of their expression domains.

Sign in / Sign up

Export Citation Format

Share Document