The Effect of Gibberellic Acid on the Production Characteristics and Biochemical Parameters of Tetraselmis Suecica in an Enrichment Culture

The use of gibberellic acid as a stimulator of microalgae growth has beensubstantiatedexperimentally.This research aimed to assess the effect of exposure to a wide range of gibberellic acid concentrations on the growth dynamics ofthe microalgaTetraselmissuecicain an enrichment culture. The duration of the experiments was 14 days. It has been shown that gibberellic acid,atconcentrations of 0.39–3.20× 10−8M, stimulates algaegrowth. In this research, the exposure to gibberellic acid at concentrations of 0.39–3.20 × 10−8M was accompanied by a variation in the pattern of growth curves: the maximum number of cells was recorded on day seven of the experiment. A higher concentration of the phytohormone (3.84 × 10−8М) inhibited the increase inculture density. The growth of theT. suecicaculture in the control group was 332%;the growth of the culture exposed to gibberellic acid at a concentration of 0.39 × 10−8M was1136%. The values of the specific growth rate ofT. suecicawere estimated for different periods of cultivation. On day14 of the experiment, the biochemical composition of microalgae biomass was analyzed.According to the results, gibberellic acid stimulated the accumulation of carbohydrates, proteins, and chlorophyll. Nevertheless, the phytohormone had no effect on lipidaccumulation. An assumption was made thatexposure to low concentrations of phytohormone stimulates the growth of microalgae by reducing the lag phase of growth. Keywords: gibberellic acid, microalga, cultivation, lipids, carbohydrates, proteins

Guidelines for model adaptation: a study of the transferability of a general seagrass ecosystem DBN model

Ecological models are extensively and increasingly used in support of environmental policy and decision making. Dynamic Bayesian Networks (DBN) as a tool for conservation have been demonstrated to be a valuable tool for providing a systematic and intuitive approach to integrating data and other critical information to help guide the decision-making process. However, data for a new ecosystem are often sparse. In this case, a general DBN developed for similar ecosystems could be applicable, but this may require the adaptation of key elements of the network. The research presented in this paper focused on a case study to identify and implement guidelines for model adaptation. We adapted a general DBN of a seagrass ecosystem to a new location where nodes were similar, but the conditional probability tables varied. We focused on two species of seagrass (Zostera noltei and Z. marina) located in Arcachon Bay, France. Expert knowledge was used to complement peer-reviewed literature to identify which components needed adjustment including parameterisation and quantification of the model and desired outcomes. We adopted both linguistic labels and scenario-based elicitation to elicit from experts the conditional probabilities used to quantify the DBN. Following the proposed guidelines, the model structure of the DBN was retained, but the conditional probability tables were adapted for nodes that characterised the growth dynamics in Zostera spp. population located in Arcachon Bay, as well as the seasonal variation on their reproduction. Particular attention was paid to the light variable as it is a crucial driver of growth and physiology for seagrasses. Our guidelines provide a way to adapt a general DBN to specific ecosystems to maximise model reuse and minimise re-development effort. Especially important from a transferability perspective are guidelines for ecosystems with limited data, and how simulation and prior predictive approaches can be used in these contexts.

The centrality of organisational factors in the growth of new technology-based firms

PurposeNew technology-based firms (NTBFs) are a great potential source of job creation and economic growth. In France, strong heterogeneity of their growth trajectories is observed yet many of them remain small. A better understanding of these trajectories is thus necessary. The purpose of this paper is to explore the influence of individual and organisational factors on 253 growth trajectories of NTBFs.Design/methodology/approachThe authors use a Heckman ordered probit model to study explanatory factors of growth trajectories in NTBFs created between 1999 and 2012. This method allows them to study the determinants of the presence of a growth dynamics at the same time as the determinants of growth intensity.FindingsThe model shows that entrepreneurs play a weak role in understanding the growth trajectories of their company. Rather, it is organisational factors – such as the level of innovation and the governance structure – that explain initiation of a growth trajectory and the intensity of the growth.Originality/valueBy using an original methodology, the authors highlight the importance of organisational factors and encourage entrepreneurs to develop a governance structure focused on internal stakeholders to support growth.

Membrane tension propagation couples axon growth and collateral branching

Neuronal axons must navigate a mechanically heterogeneous environment to reach their targets, but the biophysical mechanisms coupling mechanosensation, growth, and branching are not fully understood. Here, we show that local changes in membrane tension propagate along axons at approximately 20 μm/s, more than 1000-fold faster than in other non-motile cells. This rapid and long-range mechanical signaling mediates bidirectional competition between axonal branch initiation and growth cone extension. Our data suggest a mechanism by which mechanical cues at one part of a growing axon can affect growth dynamics remotely.

Method for the estimation of antibacterial activity of the polyfunctional protein from transferrin family in the experimental model of the kinetics of Staphylococcus aureus development

Introduction. Lactoferrin is a cationic monomeric glycoprotein produced by acinar cells and glands, present in different places of the mucous membrane in different concentrations. In connection with the development of various variants of hygienic and medicinal products for the treatment of inflammatory diseases of the oral cavity based on lactoferrin, there was a need for an objective assessment of its antibacterial and antibiofilms properties, followed by an analysis of the preservation of activity in various variants of the isolation of this protein from the substrate and storage.Aim - to improve the effectiveness of evaluating the antibacterial activity of lactoferrin and the duration of its preservation in various biological substrates containing the active substance and individual experimental batches of the manufactured drug using automatic cultivation.Materials and methods. As part of the experiment, a microbiological diagnostic technique employing a system for the automatic cultivation of microbial populations was used. A pre-prepared bacterial suspension was inoculated into the nutrient broth and the studied lactoferrin samples were added, followed by cultivation and analysis of the possible antibacterial effects of transferrin protein. To determine the sensitivity of the isolated strains, we used our own modification of the serial dilution method developed at the Department of microbiology, virology, immunology of the A.I. Yevdokimov Moscow State University of Medicine and Dentistry. The experiment was based on the programmed automatic cultivation using the RTS-1 bioreactor. The interpretation of the results was carried out by changing the optical density at a wavelength of λ = 850 nm. The study of the growth dynamics of microorganisms was carried out in several repetitions, which was reflected in the graphs of the development of bacterial populations. The assessment of the growth control of the corresponding bacterial species was reflected in the change in the optical density values, on the basis of which the curve was built. Results and discussion. According to the results of an experimental study of the growth curves of bacterial populations, statistically significant differences in the number of viable cells in different phases of the growth curves were noted, when using different lactoferrin samples. Higher activity of human recombinant lactoferrin samples was established. An analysis of growth dynamics revealed differences in the onset of the maximum reproduction and its inhibition under the influence of various aggravating factors during cultivation. The bacteriostatic effect of lactoferrin is realized through the binding of iron ions, depriving the bacteria of this microelement, causing inhibition of their development. Along with this, lactoferrin is active against certain virulence factors of microorganisms, splitting them like serine proteases, and thus prevents their penetration into human cells.Conclusion. The method used for automatic cultivation of microorganisms in the bioreactor used allows one to obtain reproducible results, is available for wide use, and can be recommended for obtaining objective, comparable, reliable information about the antimicrobial properties of various samples of the bactericidal protein lactoferrin produced by the domestic pharmaceutical industry. The studied substrate containing recombinant human lactoferrin of Russian production is characterized by high antibacterial activity that persists for 3 years as minimum.

Elimination of [PSI+] Prion and Influence on Yeast Cell Growth

Background Prions are proteinaceous infectious particles that act as pathogens and cause the development of lethal neurodegenerative diseases in humans and other animals. Yeast Saccharomyces cerevisiae is a widespread model system in which mechanisms of prion induction and elimination have been identified. New and safe substances and methods are being sought to cure cells of prion proteins. It is particularly important that by treating cells from prions and restoring them from the [PSI+] to the [psi−] form, the primary growth of the cells is restored. One of the main objectives of this study was to determine the growth dynamics of S. cerevisiae cells with different [PSI+] prion variants, cells that have lost [PSI+] prion variants, and cells that never had [PSI+] prion variants. Results In this research, we applied GuHCl and combined GuHCl and PEF treatment against [PSI+] prion. We evaluated cells culture growth dynamics – optical density and doubling time and determined that method of [PSI+] prion elimination does not affect cell doubling time. Also, we found that both elimination methods affect the optical density reached by [psi−] cells. However, the cells in which the [PSI+] prion has been eliminated by GuHCl alone are able to reach the same optical density as unaffected [psi−] cells and higher optical density than the affected [psi−] cells by GuHCl alone. Conclusions These findings indicate the potential long-term positive effect of [PSI+] prion on cell growth, which persists after [PSI+] removal.

Accurate and robust inference of microbial growth dynamics from metagenomic sequencing reveals personalized growth rates

Patterns of sequencing coverage along a bacterial genome---summarized by a peak-to-trough ratio (PTR)---have been shown to accurately reflect microbial growth rates, revealing a new facet of microbial dynamics and host-microbe interactions. Here, we introduce CoPTR (Compute PTR): a tool for computing PTRs from complete reference genomes and assemblies. Using simulations and data from growth experiments in simple and complex communities, we show that CoPTR is more accurate than the current state-of-the-art, while also providing more PTR estimates overall. We further develop theory formalizing a biological interpretation for PTRs. Using a reference database of 2935 species, we applied CoPTR to a case-control study of 1304 metagenomic samples from 106 individuals with inflammatory bowel disease. We show that growth rates are personalized, are only loosely correlated with relative abundances, and are associated with disease status. We conclude by demonstrating how PTRs can be combined with relative abundances and metabolomics to investigate their effect on the microbiome.