The growth rate of single bacterial cells is continuously disturbed by random fluctuations in biosynthesis rates and by deterministic cell-cycle events, such as division, genome duplication, and septum formation. It is not understood whether, and how, bacteria reject these growth-rate disturbances. Here, we quantified growth and constitutive protein expression dynamics of single Bacillus subtilis cells as a function of cell-cycle progression. We found that, even though growth at the population level is exponential, close inspection of the cell cycle of thousands of single Bacillus subtilis cells reveals systematic deviations from exponential growth. Newborn cells display varying growth rates that depend on their size. When they divide, growth-rate variation has decreased, and growth rates have become birth size independent. Thus, cells indeed compensate for growth-rate disturbances and achieve growth-rate homeostasis. Protein synthesis and growth of single cells displayed correlated, biphasic dynamics from cell birth to division. During a first phase of variable duration, the absolute rates were approximately constant and cells behaved as sizers. In the second phase, rates increased, and growth behavior exhibited characteristics of a timer strategy. These findings demonstrate that, just like size homeostasis, growth-rate homeostasis is an inherent property of single cells that is achieved by cell-cycle-dependent rate adjustments of biosynthesis and growth.
Jurgen Haanstra and Bas Teusink collaborated with several research groups on interdisciplinary research combining wetlab experiments with computational models.
Haanstra and Teusink collaborated with research groups in Gothenburg (Sweden), Groningen and Heidelberg (Germany). Their work on a quantitative analysis of amino acid metabolism in liver cancer, with Jurgen as co-first author, was just published in PNAS.
Metabolic changes are a well-known hallmark of cancer, but an integrative view on how metabolic fluxes sustain (high) growth rates is often lacking. In this study the authors used a combination of experimental measurements and computational modelling to understand metabolism of HepG2 liver cancer cells during in vitro growth at different glucose levels. The measured fluxes of glucose, pyruvate, lactate and amino acids during growth were integrated with a genome-scale reconstruction of liver cancer metabolism to estimate the intracellular metabolic fluxes that should be operational to sustain this growth.
The analysis published in PNAS shows that many amino acids are consumed at rates exceeding the need for biomass formation. The intracellular fluxes indicate that a large part of the glutamine that is consumed is metabolised in the cytosol to support biosynthetic processes. A large part of the glutamate that results from these processes is excreted. This led to the hypothesis that inhibition of glutamate export would decrease growth and this was validated in an experiment where glutamate export was inhibited.
The work shows that genome-scale metabolic models constrained with measured fluxes can be used to estimate the effects of inhibitors of metabolic reactions.
Systeembioinformaticus Daan de Groot met Self-organising adaptation: a universal mechanism for microbial protein expression regulation Cellen kunnen zich aanpassen aan, en groeien in, een verbluffende hoeveelheid omgevingen. Dit lijkt, gezien de eenvoud van individuele cellen, een onmogelijke prestatie. Maar hoe zit dit als een populatie cellen gaat samenwerken? De onderzoekers stellen een universeel mechanisme voor dat een populatie cellen in staat stelt te overleven, maar waar individuele cellen zouden falen.
Vijf VU-projecten ontvangen uit het NWA-programma (Nationale Wetenschapsagenda) Ideeëngenerator ieder een financiering van 50.000 euro voor de looptijd van één jaar om hun idee verder te onderzoeken.
Journal of Biology, Agriculture and Healthcare www.iiste.org Vol.9, No.10, 2019
From Functional Potential of Soil Bacterial Communities Towards Petroleum Hydrocarbons Bioremediation
Molecular ecology researches are rapidly advancing the knowledge of microorganisms associated with
petroleum hydrocarbon degradation, one of the major large-scale pollutants in terrestrial ecosystems. The design
and monitoring of bioremediation techniques for hydrocarbons rely on a thorough understanding of the diversity
of enzymes involved in the processes of hydrocarbon degradation and the microbes that harbor their allocated
genes. This review describes the impact of hydrocarbon pollution on soil microbial communities, the state of the
art of detecting functional genes, and functional groups. We will focus on i) the structure, function and
succession behavior of microbial communities exposed to hydrocarbons, ii) key genes and pathways, iii) future
prospect into bioremediation of petroleum hydrocarbons in aerobic environments. The aim is to get a
fundamental insight in these issues to ultimately improve petroleum hydrocarbons bioremediation.
Although the weather still gives the idea that summer didn’t end yet, we had end-of-summer drinks last week. It was a nice get-together and many people joined for a drink and a chat.. The drinks were accompanied by a photo competition with 21 entries. During the drinks the photos were hanging on the wall for the participants to judge which photo stood out most and should win a prize. Ten pictures got at least one vote, but there was a clear winner: Julia’s picture of a duck in Leiden got 7 votes and made her the winner of our competition. She won a 500-piece puzzle of an image of of O|2. Congratulations!
After the voting, lively discussions arose on who had sent in which picture. As the pictures were a clear added value to the first-floor balcony, they were still there by the end of the week – and remained a talking point.