Cell Growth Rate Research Articles

Promoted growth with dynamic cellular stoichiometry driven by utilization of in-situ dissolved organic matter: Insights from bloom-forming dinoflagellate Prorocentrum donghaiense.

Mixotrophic dinoflagellates frequently cause harmful algal blooms (HABs) in eutrophic waters that contain diverse dissolved organic matter (DOM), especially intensive mariculture areas. Compared to the extensive investigation of phagotrophy and single organic molecule uptake by causative species, we have limited knowledge about the capability of mixotrophic dinoflagellates to utilize in-situ DOM in mariculture waters and its contribution to HABs. Here we use filtered in-situ mariculture water as the sole medium to examine the physiological response of Prorocentrum donghaiense to the natural mariculture DOM. Our results showed an 87.2% increase in the cell growth rate, as well as photosynthesis (16.8%-29.2%) and cellular chlorophyll a (32.4%-70.7%) when cultured with DOM compared to those grown in the inorganic medium. Meanwhile, cellular stoichiometry varied greatly among the groups supplied with mariculture DOM of different seasons, and the ecological implications were then discussed. Additionally, parallel cultures revealed the phycosphere bacterioplankton community compete with the algae cell regarding the nutrient utilization. This study quantifies the efficient utilization of in-situ mariculture DOM by P. donghaiense and indicates its vital role in sustaining HAB events and great effects on the biogeochemical cycle.

A fractal–fractional order modeling approach to understanding stem cell-chemotherapy combinations for cancer

The main objective of this work is to study the mathematical model that combines stem cell therapy and chemotherapy for cancer cells. We study the model using the fractal fractional derivative with the Mittag-Leffler kernel. In the analytical part, we study the existence of the solution and its uniqueness, which was studied based on the fixed point theory. The equilibrium points were also studied and discussed after stem cell therapy, and the approximate solutions for the given model were obtained using the Adam Bashford method, which depends on interpolation with Lagrange polynomials. Finally, the model was simulated using the Mathematica software, and through the figures, we found that the components of the model approach the equilibrium point, which indicates the stability of the model at the equilibrium point. Also, the result of the numerical simulation and graphic for the concentration of cells over time indicate the effects of the therapies on the decay rate of tumor cells and the growth rate of effector cells to modify the cancer patient’s immune system. It is worth noting that we simulated all the model components with different fractional orders, confirming the effect of stem cell therapy and chemotherapy on the cells and the decay of cancer cells.

Multiplex genome editing eliminates lactate production without impacting growth rate in mammalian cells.

The Warburg effect, which describes the fermentation of glucose to lactate even in the presence of oxygen, is ubiquitous in proliferative mammalian cells, including cancer cells, but poses challenges for biopharmaceutical production as lactate accumulation inhibits cell growth and protein production. Previous efforts to eliminate lactate production in cells for bioprocessing have failed as lactate dehydrogenase is essential for cell growth. Here, we effectively eliminate lactate production in Chinese hamster ovary and in the human embryonic kidney cell line HEK293 by simultaneous knockout of lactate dehydrogenases and pyruvate dehydrogenase kinases, thereby removing a negative feedback loop that typically inhibits pyruvate conversion to acetyl-CoA. These cells, which we refer to as Warburg-null cells, maintain wild-type growth rates while producing negligible lactate, show a compensatory increase in oxygen consumption, near total reliance on oxidative metabolism, and higher cell densities in fed-batch cell culture. Warburg-null cells remain amenable for production of diverse biotherapeutic proteins, reaching industrially relevant titres and maintaining product glycosylation. The ability to eliminate lactate production may be useful for biotherapeutic production and provides a tool for investigating a common metabolic phenomenon.

Brassinosteroids Render Cell Walls Softer but Less Extensible in Growing Arabidopsis Hypocotyls.

Cell wall extensibility is a key biophysical characteristic that defines the rate of plant cell growth. It depends on the wall structure and is controlled by numerous proteins that cut and/or (re)form links between the wall constituents. Cell wall extensibility is currently estimated by different in vitro biomechanical tests. We used the creep method, in which isolated cell walls are extended under a constant load and their time-dependent deformation (creep) is recorded to reveal the biophysical basis of growth inhibition of Arabidopsis thaliana hypocotyls in the presence of 24-epibrassinolide (EBL), one of the most active natural brassinosteroids. We found that EBL rendered the walls of hypocotyl cells softer, i.e., more deformable under mechanical force, which was revealed using heat-inactivated cell walls to eliminate endogenous activities of cell-wall-loosening/tightening proteins. This effect was caused by the altered arrangement of cellulose microfibrils. At the same time, EBL made the walls less extensible, which was detected with native walls under conditions optimized for activities of endogenous cell-wall-loosening proteins. These apparently conflicting changes in the wall mechanics can be an adaptation by which EBL enables plant cells to grow under stress conditions.

PHA Microplastic Aging Decreases N2O Sink Capacity: Released γ-Butyrolactone Decouples Denitrifying Electron Transfer and Oxidative Phosphorylation.

Bacterial denitrification is a main pathway for soil N2O sinks, which is crucial for assessing and controlling N2O emissions. Biobased polyhydroxyalkanoate (PHA) microplastic particles (MPs) degrade slowly in conventional environments, remaining inert for extended periods. However, the impacts of PHA microplastic aging on the bacterial N2O sink capacity before degradation remain poorly understood. Here, the soil model strain Paracoccus denitrificans was exposed to 0.05-0.5% (w/w) virgin and aged PHA MPs. Although no significant changes in the molecular weights were observed, aged PHA MPs hindered cell growth and N2O reduction rates, leading to a surge in N2O emissions. 1H NMR spectroscopy and UPLC-QTOF-MS analysis identified γ-butyrolactone as the key component released from aged PHA MPs. Metabolic verifications at the cellular level confirmed its inhibition on the N2O sink and ATP synthesis. The γ-butyrolactone that protonated and hydrolyzed spontaneously in the periplasm would compete for protons with ATPase and destroy the coupling between denitrifying electron transfer and oxidative phosphorylation. Consequently, energy-deficient cells reduced the electron supply for N2O reduction, which did not contribute to energy conservation. This work unveils a novel mechanism by which PHA microplastic aging impairs the bacterial N2O sink and highlights the need to consider environmental risks posed by biobased microplastic aging.

Adiponectin facilitates the cell cycle, inhibits cell apoptosis and induces temozolomide resistance in glioblastoma via the Akt/mTOR pathway.

Adiponectin (ADN) regulates DNA synthesis, cell apoptosis and cell cycle to participate in the pathology and progression of glioblastoma. The present study aimed to further explore the effect of ADN on temozolomide (TMZ) resistance in glioblastoma and the underlying mechanism of action. Glioblastoma cell lines (U251 and U87-MG cells) were treated with ADN and TMZ at different concentrations; subsequently, 3.0 µg/ml ADN and 1.0 mM TMZ were selected as the optimal concentrations for the experimental conditions. LY294002 (a PI3K inhibitor) was added to ADN or ADN + TMZ-treated glioblastoma cell lines. Cell growth rate was determined using the Cell Counting Kit-8 assay, the apoptotic rate and cell cycle were evaluated using Annexin V/propidium iodide and cell cycle assays, and p-Akt (Thr308), p-Akt (Ser473), Akt, p-mTOR, c-caspase 3, caspase 3, Bax, cyclin B1 and cyclin D1 expression was determined by western blotting. Adiponectin receptor (ADIPOR) 1 and ADIPOR2 were expressed in glioblastoma cell lines. The glioblastoma cell line growth rate was increased by ADN in a concentration- and time-dependent manner. ADN inhibited glioblastoma cell line apoptosis and facilitated cell cycle. Of note, ADN activated the Akt/mTOR pathway and the addition of LY294002 reversed the effect of ADN, indicating that ADN activated the Akt/mTOR pathway to suppress apoptosis and promote cell cycle in glioblastoma cell lines. Notably, TMZ inhibited glioblastoma cell line growth, promoted apoptosis and increased G2 phase cell cycle arrest. However, the addition of ADN reversed the effect of TMZ in glioblastoma cell lines, disclosing that ADN induced TMZ resistance. Markedly, ADN-mediated TMZ resistance was further attenuated by LY294002, suggesting that ADN activated the Akt/mTOR pathway to induce TMZ resistance in glioblastoma cell lines. In conclusion, ADN activated the Akt/mTOR pathway to facilitate cell cycle, inhibit cell apoptosis and induce TMZ resistance in glioblastoma.

FLCCR is a fluorescent reporter system that quantifies the duration of different cell cycle phases at the single-cell level in fission yeast.

Fission yeast is an excellent model system that has been widely used to study the mechanism that control cell cycle progression. However, there is a lack of tools that allow to measure with high precision the duration of the different phases of the cell cycle in individual cells. To circumvent this problem, we have developed a fluorescent reporter that allows the quantification of the different phases of the cell cycle at the single-cell level in most genetic backgrounds. To prove the accuracy of this fluorescent reporter, we have tested the reporter in strains known to have a delay in the G1/S or G2/M transitions, confirming the strength and versatility of the system. An advantage of this reporter is that it eliminates the need for culture synchronization, avoiding stressing the cells. Using this reporter, we show that unperturbed cells lacking Sty1 have a standard cell cycle length and distribution and that the extended length of these cells is due to their increased cell growth rate but not to alterations in their cell cycle progression.

Resonance-Induced Therapeutic Technique for Skin Cancer Cells.

This study aims to evaluate the viability of a hypothesis for selective targeting of skin cancer cells by exploiting the spectral gap with healthy cells using analytical and numerical simulation. The spectral gap was first identified using a viscoelastic dynamic model, with the physical and mechanical properties of healthy and cancerous skin cells deduced from previous experimental studies conducted on cell lines. The outcome of the analytical simulation was verified numerically using modal and harmonic analysis. Finally, transient analyses were conducted analytically and numerically to evaluate the difference in vibrational response of healthy and cancerous cells when their resonant frequencies were closely matched. For analysis, we used healthy nucleus diameters of 3 µm, 5 µm and 7 µm, whereas 34 kPa was taken as the stiffness of healthy skin epithelial cells. Based on established trends, the nucleus-to-cytoplasm ratio was utilised to predict physical and mechanical properties as cells undergo neoplastic transformation. Analytical and numerical simulation revealed an approximate frequency difference of 50-100 KHz for the different nucleus diameters. The transient simulation revealed a significant difference in the growth rate of cancer cells' vibration amplitude, which was 10 times greater than that of healthy cells. This study highlights that cancer cells are more prone to resonance with tuned ultrasound frequencies, emphasising the need for detailed dynamic models incorporating the basement membrane's influence and experimental validation.

Numerical Bifurcations and Sensitivity Analysis of an SIVPC Cervical Cancer Model

We consider a mathematical model of cervical cancer based on the Natural History of Cervical Cancer. The model is a five dimensional system of the first order of ordinary differential equations that represents the interaction between the free Human Papilloma Virus (HPV) population and four cells sub-populations, i.e., the normal cells, infected cells by HPV, precancerous cells, and cancer cells. We focus our analysis to determine the existence conditions of the nontrivial equilibrium point, the bifurcations, and the sensitivity of the parameters that play important roles in metastasis. Based on the basic reproduction ratio of the system, we found that the infection rate, the new viruses production rate, the free viruses death rate, the infected cells growth rate, and the precancerous cells progression rate play important roles for the cancer spreads in the cellular level. By applying sensitivity and numerical bifurcation analysis, we found that there are some important bifurcations that trigger some irregular behaviours of the system, i.e., fold, Hopf, cusp and Bogdanov-Takens.

Establishing a Three-Dimensional Coculture Module of Epithelial Cells Using Nanofibrous Membranes.

Technical hurdles in a culture of epithelial cells include dedifferentiation and loss of function. Biomimetic three-dimensional (3D) cell culture methods can enhance cell culture efficiency. This study introduces an advanced two-layered culture system intended to cultivate epithelial cells as tissue-like layers with the culture of fibroblasts within a 3D environment. Polyvinyl alcohol (PVA) and poly(ε-caprolactone) (PCL) nanofibrous membranes (NMs) were fabricated via electrospinning and utilized as a physiologically relevant extracellular matrix for the culture of epithelial cells and fibroblasts, respectively. In the upper insert wells, lung epithelial cells were cultivated on the PVA NM, and in the lower chambers, fibroblasts were cultured on the PCL NM. This configuration eliminates direct cell-cell contact and facilitates the examination of paracrine signaling mediated by soluble factors. Confocal microscopy was employed to analyze the distribution, growth pattern, and expression of intracellular proteins, including zona occludens in epithelial cells. Z-stacking techniques enabled detailed 3D reconstructions, providing precise insights into the integrity of tight junctions and spatial organization within the epithelial layer. Scanning electron microscopy (SEM) assessed the morphological characteristics of cell types on the nanofibrous membranes. SEM imaging revealed intricate cell surface structures and interactions with the nanofibers, offering a comprehensive perspective on cellular architecture and cell interaction with nanofibrous structure. The Cell Counting Kit-8 (CCK-8) assay is a simple method for measuring epithelial cell and fibroblast growth rates over time. It provides the proliferative behaviors and potential synergistic effects of coculturing these cells. These findings highlight the effectiveness of a simple insert co-culture system for simultaneous culture of fibroblasts and epithelial cells, which is crucial in various physiological and pharmacological contexts, including epithelial tissue regeneration, tumor microenvironment with endothelial, immune, and other stroma cells, toxicity assay, and drug activity test.

Genome concentration limits cell growth and modulates proteome composition in Escherichia coli.

Defining the cellular factors that drive growth rate and proteome composition is essential for understanding and manipulating cellular systems. In bacteria, ribosome concentration is known to be a constraining factor of cell growth rate, while gene concentration is usually assumed not to be limiting. Here, using single-molecule tracking, quantitative single-cell microscopy, and modeling, we show that genome dilution in Escherichia coli cells arrested for DNA replication limits total RNA polymerase activity within physiological cell sizes across tested nutrient conditions. This rapid-onset limitation on bulk transcription results in sub-linear scaling of total active ribosomes with cell size and sub-exponential growth. Such downstream effects on bulk translation and cell growth are near-immediately detectable in a nutrient-rich medium, but delayed in nutrient-poor conditions, presumably due to cellular buffering activities. RNA sequencing and tandem-mass-tag mass spectrometry experiments further reveal that genome dilution remodels the relative abundance of mRNAs and proteins with cell size at a global level. Altogether, our findings indicate that chromosome concentration is a limiting factor of transcription and a global modulator of the transcriptome and proteome composition in E. coli. Experiments in Caulobacter crescentus and comparison with eukaryotic cell studies identify broadly conserved DNA concentration-dependent scaling principles of gene expression.

Glutathione peroxidase 4 overexpression induces anomalous subdiffusion and impairs glioblastoma cell growth

Glioblastoma tumors are the most common and aggressive adult central nervous system malignancy. Nearly all patients experience disease progression, which significantly contributes to disease mortality. Recently, it has been suggested that recurrent tumors may be characterized by a ferroptosis-prone phenotype with a significant decrease in glutathione peroxidase 4 (GPx4) expression. This led to the hypothesis that GPx4 expression negatively influences GBM cell growth. This study utilizes a doxycycline inducible GPx4 overexpression model to test this hypothesis. Consistently, the overexpression of GPx4 significantly impairs cell growth and colony formation while also causing an accumulation of cells in G1/G0 phase of the cell cycle. From a biophysical perspective, GPx4 overexpressing cells have significantly greater surface area, increased Young’s modulus, and experience anomalous sub-diffusion as opposed to normal diffusion associated with Brownian motion. Moreover, analysis of patient derived GBM cells reveal that cell growth rates, plating efficiency, and Young’s modulus are all inversely proportional to GPx4 expression. Therefore, GPx4 appears to be a biophysical regulator of GBM cell growth that warrants further mechanistic investigation in its role in GBM progression.

Practical laboratory class to assess gene silencing using CRISPR interference (CRISPRi) technology in the archaeon Haloferax volcanii.

Perturbation of gene expression using RNA interference (RNAi) or CRISPR interference (CRISPRi) is a useful strategy to explore the function of essential genes. In the archaeon Haloferax volcanii, the CRISPR-Cas system has been adapted as a CRISPRi tool to silence the expression of specific genes. We developed a laboratory class (LC) to conceptualize gene silencing through inactivation of the H. volcanii LonB protease gene, a negative regulator of carotenoid pigments biosynthesis, using CRISPRi. This LC has been successfully applied in the Biology and Biochemistry of Microorganisms course for undergraduate students of Biology in 2022 and 2023. The following objectives were proposed: (a) generate H. volcanii mutant strains with reduced expression of the lonB gene using CRISPRi; (b) examine the effect of lonB gene silencing on cell pigmentation and growth rate; (c) assess lonB gene repression by Western blotting (WB). This LC allows students to obtain and screen CRISPRi silenced-mutants by means of simple procedures using a non-pathogenic organism as well as handle basic microbiology, biochemistry and molecular biology protocols. Additionally, the LC fosters social actions through collaborative work (experimental work), the interpretation and discussion of data and the ability to communicate outcomes orally and in a written format (scientific report).

Comparison of Growth Performance of Nannochloropsis oculata Biofilm at Different Layers of Substrate Plastic

Biofilm based microalga is a structured community of microalgae attaching to substrate with a self-produced matrix of extracellular polymeric substances (EPS). One of microalgae that is potential to be improved as biofilm is Nannochloropsis oculata. Biofilm of Nannochloropsis oculata has some beneficial roles such as bioremediator of polluted waters. This study was aimed to evaluate the growth performance of Nannochloropsis oculata at different layers of substrate plastic as biofilm substrate. The experimental design used was Completely Randomized Design (CRD) with four level treatments and three replications. Several treatments tested were A: Control (without layer), B: 1 Layer of substrate, C: 2 Layers of substrate, D: 3 Layers of substrate. Several procedures were conducted in this study which were preparation of KW21 medium, cultivation of biofilm at different treatments in KW21 medium, and growth measurement. The results of this study showed that different number of substrate layers could affect the specific growth rate of free cells of Nannochloropsis oculata. The highest growth rate was found in treatment B (1 substrate layer) and the lowest one was in treatment D with their values 0.064 µ/day and 0,037 µ/day. The peak population of Nannochloropsis oculata was obtained at day 14 until 15.

The Effect of Copper Limitation on the Bioavailability of Cu-Organic Complexes.

We examined the bioavailability of synthetic organic Cu complexes (Cu-L) and inorganic Cu species (Cu') to Thalassiosira oceanica growing under Cu-limiting and Cu-inhibiting conditions. Copper bioavailability depended on the phytoplankton Cu nutritional state and whether Cu' diffusion to the cell surface was sufficient to meet the cellular demands for growth. Under Cu-limiting conditions when [Cu'] was less than the diffusion concentration threshold (DCT: 10-14.13 M), growth rate was a hyperbolic function of [Cu-L]. Increasing [Cu'] above the DCT caused growth rate to increase proportionally, but growth rate also increased with increasing [Cu-L] so that both Cu' and Cu-L were bioavailable. Short-term photosynthesis assays conducted under Cu-limiting conditions showed a similar response to Cu speciation. In contrast, the growth rate of Cu-inhibited cells at high [Cu'] varied inversely with [Cu2+] and was independent of [Cu-L], as previously reported. The change in Cu-L bioavailability correlated with expression levels of genes encoding the reduction-dependent, high-affinity Cu uptake pathway, which was regulated by [Cu']. Our analysis shows that at [Cu'] typical of the open sea, T. oceanica-like phytoplankton are diffusion limited and must rely on Cu-organic complexes to fulfill their Cu requirements for growth.

P112 An exclusive established cell model of patient-derived psoriatic keratinocyte provides a valuable in vitro tool for mechanistic studies and therapeutic testing

Abstract Chronic inflammatory skin conditions, including psoriasis, result in a wide range of distressing symptoms for affected individuals. There is a pressing need for epidermal models which can be readily utilized, enhancing our comprehension of these disorders. We report, the establishment of a novel psoriatic keratinocyte cell line that embodies essential features of psoriasis. Psoriatic keratinocytes (PSA cells), isolated from epidermal hypertrophic plaques of a 50-year-old male with psoriasis vulgaris, and a control keratinocyte (KT2) cell line, derived from an aged-matched healthy human skin sample, were immortalized with SV40-large T antigen. The transcriptomic and biological analysis of these established cellular models revealed significant phenotypic distinctions between healthy and psoriatic keratinocytes. Our findings from RNA-seq data analysis (validation by qRT-PCR) demonstrate that PSA cells from psoriatic individuals display a heightened expression profile of inflammatory cytokines and peptides (including TNF-α, IL-1β, IL-23, IL-8, LL-37, and serpin B1) compared with KT2 cells from healthy individuals, mirroring the clinical characteristics observed in psoriasis patients. Stimulation of the cells for 24 h with phorbol myristate acetate (PMA) which induces reactive oxygen species (ROS) production and protein kinase C (PKC) activation, ultimately leading to an inflammatory response further increased most of cytokine’s expression in PSA cells when compared with non-treated KT2 cells. This confirms that the psoriatic cell model is capable of launching additional inflammatory responses upon exposure to stress factors, in addition to their already innate inflammatory nature. Additional comparative analysis of PSA cells and KT2 cells in conjunction with NTERT cells, a healthy keratinocyte line conventionally used in cutaneous research, found that the PSA cells exhibited reduced expression of anti-inflammatory glucocorticoid receptor, comparable to what detected in primary keratinocytes isolated from psoriatic lesional and non-lesional skin. Further transcriptomic and morphological examination of these newly established cell models revealed enlarged nuclear and cell body size and a faster growth rate of PSA cells in comparison with either the healthy NTERT or KT2 cell lines, all trademark affiliations of psoriasis. These findings suggest that immortalized psoriatic PSA cells, the first of their kind, faithfully profile the psoriatic phenotype in vitro and may provide a novel tool for interrogating the disease's pathogenic mechanisms.

Quantitative Characterization of the Effect of Biogenic silver-based Nanoparticles on Breast Cancer Cells by High Content Analysis

Background: Among the various types of cancer, breast cancer is the most incident among women. Due to the resistance to antitumor treatments, alternative treatments have been sought, such as metallic nanoparticles. Objective: This study aimed to evaluate the antitumor potential and cytotoxicity induction mechanisms of green synthesized AgCl-NPs and Ag/AgCl-NPs. Methods: The antitumor potential of nanoparticles was evaluated in breast cancer BT-474 and MDAMB- 436 cell lines treated with 0-40 μg/mL AgCl-NPs or 0-12.5 μg/mL Ag/AgCl-NPs through imagebased high content analysis method. Normal human retinal pigment epithelial 1 (RPE-1) cells were used for comparison. Results: The growth rate of the RPE-1 cells treated with nanoparticles was insignificantly affected, and no significant changes in cell viability were observed. In these cells, the nanoparticle treatments did not induce lysosomal damage, changes in ROS production, or reduction in the mitochondrial membrane potential. The level of BT-474 and MDA-MB-436 cell proliferation was markedly decreased, and cell viability was reduced by 64.19 and 46.19% after treatment with AgCl-NPs and reduced by 98.36 and 82.29% after treatment with Ag/AgCl-NPs. The cells also showed a significant increase in ROS production and loss of mitochondrial membrane potential, which culminated in an increase in the percentage of apoptotic cells. BT-474 cells also presented lysosomal damage when treated with the highest concentrations of both nanoparticle types and actin polymerization was observed after exposure to Ag/AgCl-NPs. Conclusions: Together, the results showed overall cytotoxic effects of both AgCl-NPs and Ag/AgCl- NPs towards breast cancer cells with negligible effects against healthy cells, which suggests their promising anticancer and biomedical applications.

Interactive effects of CO2, temperature, and nitrate limitation on the growth and physiology of strain CCMP 1334 of the marine cyanobacterium Synechococcus (Cyanophyceae).

The marine cyanobacterium Synecococcus sp. (CCMP 1334) was grown in a continuous culture system on a 12:12 h light:dark cycle at all combinations of low and high pCO2 (400 and 1000 ppmv, respectively), nutrient availability (nitrate-limited and nutrient-replete conditions), and temperatures of 21, 24, 28, 32, and 35°C. The maximum nutrient-replete growth rate was ~1.15 day-1 at 32-35°C. Median nutrient-replete growth rates were higher at 1000 ppmv than at 400 ppmv pCO2 at all temperatures. Carbon:nitrogen ratios were independent of pCO2 at a fixed relative growth rate (i.e., growth rate ÷ nutrient-replete growth rate) but decreased with increasing temperature. Carbon:chlorophyll a ratios were decreased monotonically with increasing temperature and were higher under nitrate-limited than nutrient-replete conditions. Ratios of phycoerythrin to chlorophyll a were independent of growth conditions. Productivity indices were independent of temperature and nutrient limitation but were consistently higher at 1000 ppmv than 400 ppmv pCO2. Both growth rates and dark respiration rates were positively correlated with temperature, and the associated Q10 values were 2.2 and 2.3, respectively. A model of phytoplankton growth in which cellular carbon is allocated to structure, storage, or the light or dark reactions of photosynthesis accounted for the general patterns of cell composition and growth rate. This strain of Synechococcus appears well suited to changes in environmental conditions that are expected as the climate warms in response to anthropogenic emissions of CO2.

SiC nanoparticles promote CO2 fixation and biomass production of Chlorella sorokiniana via expanding the abilities of capturing and transmitting photons

Microalga-semiconductor hybrids for solar-to-biomass conversion which integrate microalgal photosynthesis with the efficient light capture of artificial semiconductors can significantly promote CO2 fixation and productivity of microalgal cells. However, such pertinent studies are poor and the promoting mechanism is unclear yet. Silicon carbide nanoparticles (SiC NPs) have remarkable biocompatibility and photocatalytic ability. Here, to get insights into the promoting mechanism the hybrids were constructed by using SiC NPs and microalga Chlorella sorokiniana, and tested the cell growth, chlorophyll fluorescence, changes in extracellular morphology and structure, absorption spectroscopy and photo-electrochemistry. The results showed that in the hybrid systems with SiC NPs in 0-20 mg/L the cell growth, CO2 fixating and biomass accumulation rate were promoted significantly, with 90 %, 49 % and 38 % increase in the maximum relative electron transport rates, maximal biomass and lipid yields, respectively, in the hybrid with 10 mg/L SiC NPs added. It suggested that SiC NPs can promote microalgal photosynthesis by transferring photogenerated electrons into the electron transport chain, expanding the capture of photoenergy and enhancing intracellular electron transport, rather than photoluminescence or photocatalytic CO2 reduction products.

Evaluating the predictive power of combined gene expression dynamics from single cells on antibiotic survival.

Heteroresistance can allow otherwise drug-susceptible bacteria to survive and resume growth after antibiotic exposure. This temporary form of antibiotic tolerance can be caused by the upregulation of stress response genes or a decrease in cell growth rate. However, it is not clear how expression of multiple genes contributes to the tolerance phenotype. By using fluorescent reporters for stress related genes, we conducted real time measurements of expression prior to, during, and after antibiotic exposure. We first identified relationships between growth rate and reporter levels based on auto and cross correlation analysis, revealing consistent patterns where changes in growth rate were anticorrelated with fluorescence following a delay. We then used pairs of stress gene reporters and time lapse fluorescence microcopy to measure the growth rate and reporter levels in cells that survived or died following antibiotic exposure. Using these data, we asked whether combined information about reporter expression and growth rate could improve our ability to predict whether a cell would survive or die following antibiotic exposure. We developed a Bayesian inference model to predict how the combination of dual reporter expression levels and growth rate impact ciprofloxacin survival in Escherichia coli . We found clear evidence of the impact of growth rate and the gadX promoter activity on survival. Unexpectedly, our results also revealed examples where additional information from multiple genes decreased prediction accuracy, highlighting an important and underappreciated effect that can occur when integrating data from multiple simultaneous measurements.