Divergent responses of the diatom Thalassiosira weissflogii to ocean acidification during light and dark periods

The effects of dilution rates on the performance of a two-stage fermentation system for a recombinant Escherichia coli culture were studied. Dilution rate determines the apparent or averaged specific growth rate of a heterogeneous population of cells in the recombinant culture. The specific growth rate affects the genetic parameters involved in product formation in the second stage, such as plasmid stability, plasmid content, and specific gene expression rate. Kinetic models and correlations were developed for these parameters based on experimental data. Simulations of plasmid stability in the first stage showed that for longer fermentation periods, plasmid stability is better at higher dilution rates. However, the plasmid content is lower at these dilution rates. The optimal apparent specific growth rate for maximum productivity in the second stage was determined using two methods: (1) direct search for a constant specific growth rate, and (2) dynamic optimization using the maximum principle for a time-dependent specific growth rate profile. The results of the calculations showed that the optimum constant apparent specific growth rate for maximum over-all productivity is 0.40 h(-1). This coincides with the optimal specific growth rate for maximum plasmid content in the expressed stage. A 3.5% increase in overall productivity can be obtained by using a linear time dependent apparent specific growth rate control, micro(2)(t) = 0.0007t, in the course of the fermentation time.

In this work, metabolite and antibody production kinetics of hybridoma cultures were investigated as a function of cell density and growth rate in a homogeneous perfusion reactor. Hydrophilized hollow fiber polypropylene membranes with a pore size of 0.2 μm were used for medium perfusion. Oxygen was supplied to the cells through thin walled silicone tubing. The mouse-mouse hybridoma cells were grown in three identical bioreactors at perfusion rates of 1.1, 2.0, and 3.2/day for a period of eight days during which the viable cell concentrations reached stable values of 2.6×106, 3.5×106, and 5.2×106 cells/ml, respectively. Total cell densities reached values ranging from 8×106 to 1×106 cells/ml. Specific substrate consumption and product formation rates responded differently to changes in cell density and apparent specific growth rate, which were not varied independently. Using multiple regression analysis, the specific glucose consumption rate was found to vary with viable cell density while the specific glutamine uptake and lactate production rates varied with both viable cell density and apparent specific growth rate. These results suggest that cell density dictates the rate of glucose consumption while the cell growth rate influences how glucose is metabolized, i.e., through glycolysis or the TCA cycle. The specific antibody production rate was found to be a strong function of cell density, increasing as cell density increased, but was essentially independent of the specific growth rate for the cell line under study.

A set of fed-batch cultures feeding concentrated nutrients was carried out to find out the optimal feeding policy to give higher antibody productivity in the fed-batch culture. From the experiments, it was found that there were two different trends in the relationship between the antibody productivity and the specific growth rate. The specific antibody productivity (g/gCel/hr) was found to significantly increase (327 % over the average of other growth rates) when the apparent specific growth rate was lowered to 0.01 hr−1 This might be caused by the increased fraction of G1-arrested cells in this low specific growth rate in the fed-batch culture as proposed by Linardos et al.(1992) and Suzuki el al.(1989) in their cell cycle model. On the other hand, there was little difference in the specific antibody productivity beyond this specific growth rate. The final antibody titer was higher in the higher specific growth rates beyond 0.01 hr−1 (150% higher at 0.04 than at 0.0175 hr−1 possibly due to the higher viable cell density. Therefore, to get higher antibody productivity, it might be better to start with or grow to the higher viable cell density and then the specific growth rate should be maintained in thenear-zero (0.01 hr−1 in this study) to get highest concentration of G1-arrested cells as possible. In this paper, fed-batch data at near- zero specific growth rate are compared with data of batch culture and fed-batch culture at high growth rate.

Relationships between behavioral and physiological performance under elevated CO₂ in marine fishes

The effects of fluid-mechanical force (agitation) on the cell cycle kinetics of Chinese hamster ovary (CHO) cells cultured in suspension in 2-L bioreactors has been examined. A two-color flow cytometry method was used to determine the fraction rate of DNA synthesis. With increased agitation intensity, cell viability decreased as a result of increased cell death. However, increased agitation induced the viable cells of the culture to a higher proliferative state relative to a control culture. The fraction of viable cells of the high-agitation culture (250 rpm) in S phase was higher (up to 45%) and in G1 phase was lower (up to 50%) compared with the viable cells of the control culture (80 rpm). The DNA synthesis rate per viable S-phase cell of the high-agitation culture was confirmed by recovery experiments, which were conducted to measure the apparent specific growth rate and the cell cycle kinetics of the high-agitation culture upon reduction in the agitation rate from 250 rpm back to 80 rpm. The apparent specific growth rate of the test culture, calculated for the first 12 h of the recovery period, was greater than the apparent specific growth rate of the control culture. Furthermore, the proliferative state of the viable cells of the test culture, which had become higher relative to the control culture during the high agitation period, gradually approached the level of the control culture during recovery. Results also show that the magnitude of the agitation intensity; the culture agitated at 250 rpm attained a greater proliferative state than a parallel culture agitated at 235 rpm. The 250-rpm culture had a higher fraction of S-phase and a lower fraction of G1-phase cells than the 235-rpm culture. The DNA synthesis rate per viable S-phase cell of the 250-rpm culture was greater than of the 235-rpm culture.

Experimentally elevated pCO2 and the associated pH drop are known to differentially affect many aspects of the physiology of diatoms under different environmental conditions or in different regions. However, contrasting responses to elevated pCO2 in the dark and light periods of a diel cycle have not been documented. By growing the model diatom Phaeodactylum tricornutum under 3 light levels and 2 different CO2 concentrations, we found that the elevated pCO2/pH drop projected for future ocean acidification reduced the diatom's growth rate by 8–25% during the night period but increased it by up to 9–21% in the light period, resulting in insignificant changes in growth over the diel cycle under the three different light levels. The elevated pCO2 increased the respiration rates irrespective of growth light levels and light or dark periods and enhanced its photosynthetic performance during daytime. With prolonged exposure to complete darkness, simulating the sinking process in the dark zones of the ocean, the growth rates decreased faster under elevated pCO2, along with a faster decline in quantum yield and cell size. Our results suggest that elevated pCO2 enhances the diatom's respiratory energy supplies to cope with acidic stress during the night period but enhances its death rate when the cells sink to dark regions of the oceans below the photic zone, with implications for a possible acidification‐induced reduction in vertical transport of organic carbon.

The pulsatile activities of kisspeptin neurons, the central pacemaker activities of reproductive functions, show unexpected robustness in terms of frequency, but a tendency for the intensity to decline, during the transition to reproductive senescence in mice.

A two-stage continuous system in combination with a temperature-sensitive expression system were used as model systems to maximize the productivity of a cloned gene and minimize the problem associated with the plasmid instability for a high-expression recombinant. In order to optimize the two-stage fermentation process, the effects of such operational variables as temperature and dilution rate on productivity of cloned gene were studied using the model systems and a recombinant, Escherichia coli K12 DeltaH1 Deltatrp/pPLc23trp A1. When the expression of cloned gene is induced by raising the operating temperature above 38 degrees C, a significant decrease in the colony-forming-units (CFU) of the plasmid-harboring cell was observed, and the decrease was related to the product concentration. In order to describe this phenomenon, a new kinetic parameter related to the metabolic stress (metabolic stress factor) was introduced. It is defined as the ratio of the rate of change of pheno-type from colony-forming to non-colony-forming cells to the product accumulation per unit cell mass. At a fixed temperature of 40 degrees C, the varying dilution rate D in the range of 0.35-0.90 h(-1) did not affect the metabolic stress factor significantly. At a fixed dilution rate of D = 0.35 h(-1), this factor remained practically constant up to 41 degrees C but increased rapidly beyond 41 degrees C. The effects of temperature and dilution rate in the second stage on the specific production rate were also studied while maintaining the apparent specific growth rate (mu(2) (app)) of the second stage constant at or near mu(2) (app) = 0.26 h(-1). Under a constant dilution rate, D(2) = 0.35 h(-1), the maximum specific production rate obtained was about q(p, max) = 38 units TrpA/mg cell/h at 41 degrees C. At a constant temperature, T(2) = 40 degrees C, specific production rate increased with decreasing dilution rate with in the dilution rate range of D(2) = 0.35-0.90 h(-1). Based on the results of our study, the optimal operating conditions found were dilution rate D(2) = 0.35 h(-1) and operating temperature T(2) = 41 degrees C at the apparent specific growth rate of 0.26 h(-1). Under the optimal operating conditions, about threefold increase in productivity was achieved compared to the best batch culture result. In addition, the fermentation period could be extended for more than 100 h.

Kinetics on aggregate behaviors of human induced pluripotent stem cells in static suspension and rotating flow cultures

ANAEROBIC DIGESTION OF SWINE MANURE: INHIBITION BY AMMONIA

Photoperiods have an important impact on macroalgae living in the intertidal zone. Ocean acidification also influences the physiology of macroalgae. However, little is known about the interaction between ocean acidification and photoperiod on macroalgae. In this study, a green alga Ulva linza was cultured under three different photoperiods (L: D = 8:16, 12:12, 16:8) and two different CO2 levels (LC, 400 ppm; HC, 1,000 ppm) to investigate their responses. The results showed that relative growth rate of U. linza increased with extended light periods under LC but decreased at HC when exposed to the longest light period of 16 h compared to 12 h. Higher CO2 levels enhanced the relative growth rate at a L: D of 8:16, had no effect at 12:12 but reduced RGR at 16:8. At LC, the L: D of 16:8 significantly stimulated maximum quantum yield (Yield). Higher CO2 levels enhanced Yield at L: D of 12:12 and 8:16, had negative effect at 16:8. Non-photochemical quenching (NPQ) increased with increasing light period. High CO2 levels did not affect respiration rate during shorter light periods but enhanced it at a light period of 16 h. Longer light periods had negative effects on Chl a and Chl b content, and high CO2 level also inhibited the synthesis of these pigments. Our data demonstrate the interactive effects of CO2 and photoperiod on the physiological characteristics of the green tide macroalga Ulva linza and indicate that future ocean acidification may hinder the stimulatory effect of long light periods on growth of Ulva species.

Hepatic P450 monooxygenase activities, assessed by measurement of 7-alkoxycoumarin O-dealkylase (ACD) activities, show obvious daily fluctuations in male rats with high values during the dark period and low values during the light period. We have already confirmed that the ACD activities are controlled by the suprachiasmatic nucleus (SCN), which is well known as the oscillator of circadian rhythm. Recently, it is reported that circadian oscillators exist not only in the SCN but also in peripheral organs. To date, it is unclear which circadian oscillators predominantly drive the daily fluctuations of hepatic ACD activities. To address this question, we examined the effects of restricted feeding, which uncouples the circadian oscillators in the liver from the central pacemaker in the SCN, on the daily fluctuations in hepatic ACD activities in male rats. Here we show that restricted feeding inverts the oscillation phase of the daily fluctuations in hepatic ACD activities. Regarding the hepatic P450 content, there were no fluctuations between the light and dark periods under ad libitum and restricted feeding conditions. Therefore, it is considered that the daily fluctuations in hepatic ACD activities are predominantly driven by the circadian factors in peripheral organs rather than by the oscillator in the SCN directly.

Rates of CO2 fixation during the light period and the rates of CO2 release during the night period were measured using mature leaves from 39- to 49-d-old spinach (Spinacia oleracea L., US Hybrid 424; grown in 9 h light, 15 h darkness, daily) and mature leaves from 21-d-old barley (Hordeum vulgare L., cv. Apex; grown in 14 h light, 10 h darkness, daily). At certain times during the light and dark periods leaves were harvested for assay of their contents of soluble carbohydrates, starch, malate and the various amino acids. Evaluation of the results of these measurements shows that in spinach and barley leaves 46% and 26%, respectively, of the carbon assimilated during the light period is deposited in the leaves for export during the night period. Taking into account the carbon consumption in the source leaves by dark respiration, it is evaluated that rates of assimilate export during the light period from spinach and barley leaves [38 and 42 μatom C · (mg Chl)−1 · h−1] are reduced in the dark period to 16 μatom C · (mg Chl)−1 · h−1 in both species. The calculated C/N ratios of the photoassimilates exported during the dark period were 0.029 and 0.015 for spinach and barley leaves, respectively.

Ocean acidification (OA) caused by increased atmospheric carbon dioxide is affecting marine systems globally and is more extreme in coastal waters. A wealth of research to determine how species will be affected by OA, now and in the future, is emerging. Most studies are discrete and generally do not include the full life cycle of animals. Studies that include the potential for adaptation responses of animals from areas with different environmental conditions and the most vulnerable life stages are needed. Therefore, we conducted experiments with the widely distributed blue mussel, Mytilus edulis, from populations regularly exposed to different OA conditions. Mussels experienced experimental conditions prior to spawning, through embryonic and larval development, both highly vulnerable stages. Survivorship to metamorphosis of larvae from all populations was negatively affected by extreme OA conditions (pH 7.3, Ωar, 0.39, pCO2 2479.74), but, surprisingly, responses to mid OA (pH 7.6, Ωar 0.77, pCO21167.13) and low OA (pH 7.9, Ωar 1.53, pCO2 514.50) varied among populations. Two populations were robust and showed no effect of OA on survivorship in this range. One population displayed the expected negative effect on survivorship with increased OA. Unexpectedly, survivorship in the fourth population was highest under mid OA conditions. There were also significant differences in development time among populations that were unaffected by OA. These results suggest that adaptation to OA may already be present in some populations and emphasizes the importance of testing animals from different populations to see the potential for adaptation to OA.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 563:111-122 (2017) - DOI: https://doi.org/10.3354/meps11956 Ocean warming and acidification prevent compensatory response in a predator to reduced prey quality Ben P. Harvey1,3,*, Pippa J. Moore1,2 1Institute of Biological, Environmental, and Rural Sciences, Aberystwyth University, Aberystwyth SY23 3DA, UK 2Centre for Marine Ecosystems Research, Edith Cowan University, Perth 6027, Australia 3Present address: Shimoda Marine Research Center, University of Tsukuba, 5-10-1 Shimoda, Shizuoka 415-0025, Japan *Corresponding author: harvey.benjaminpaul@gmail.com ABSTRACT: While there is increasing evidence for the impacts of climate change at the individual level, much less is known about how species’ likely idiosyncratic responses may alter ecological interactions. Here, we demonstrate that ocean acidification and warming not only directly alter species’ (individual) physiological performance, but also their predator-prey dynamics. Our results demonstrate that tissue production (used as a proxy for prey quality) in the barnacle Semibalanus balanoides was reduced under scenarios of future climate change, and hence their ability to support energy acquisition for dogwhelk Nucella lapillus through food provision was diminished. However, rather than increasing their feeding rates as a compensatory mechanism, consumption rates of N. lapillus were reduced to the point that they exhibited starvation (a loss of somatic tissue), despite prey resources remaining abundant. The resilience of any marine organism to stressors is fundamentally linked to their ability to obtain and assimilate energy. Therefore, our findings suggest that the cost of living under future climate change may surpass the energy intake from consumption rates, which is likely exacerbated through the bottom-up effects of reduced prey quality. If, as our results suggest, changes in trophic transfer of energy are more common in a warmer, high CO2 world, such alterations to the predator-prey dynamic may have negative consequences for the acquisition of energy in the predator and result in energetic trade-offs. Given the importance of predator-prey interactions in structuring marine communities, future climate change is likely to have major consequences for community composition and the structure and function of ecosystems. KEY WORDS: Predator-prey · Climate change · Ocean warming · Ocean acidification · Trophic interactions · Ecological interactions · Compensatory Full text in pdf format Supplementary material PreviousNextCite this article as: Harvey BP, Moore PJ (2017) Ocean warming and acidification prevent compensatory response in a predator to reduced prey quality. Mar Ecol Prog Ser 563:111-122. https://doi.org/10.3354/meps11956 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 563. Online publication date: January 20, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.