Optimal management of nutrient reserves in microorganisms under time-varying environmental conditions

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Intracellular reserves are a conspicuous feature of many bacteria; such internal stores are often present in the form of inclusions in which polymeric storage compounds are accumulated. Such reserves tend to increase in times of plenty and be used up in times of scarcity. Mathematical models that describe the dynamical nature of reserve build-up and use are known as “cell quota,” “dynamic energy/nutrient budget,” or “variable-internal-stores” models. Here we present a stoichiometrically consistent macro-chemical model that accounts for variable stores as well as adaptive allocation of building blocks to various types of catalytic machinery. The model posits feedback loops linking expression of assimilatory machinery to reserve density. The precise form of the “regulatory law” at the heart of such a loop expresses how the cell manages internal stores. We demonstrate how this “regulatory law” can be recovered from experimental data using several empirical data sets. We find that stores should be expected to be negligibly small in stable growth-sustaining environments, but prominent in environments characterised by marked fluctuations on time scales commensurate with the inherent dynamic time scale of the organismal system.OAN was funded through EU Research Framework programme 7 Marie Curie Actions, grant 316630 Centre for Analytical Science – Innovative Doctoral Programme (CAS-IDP)

Optical monitoring system

Instrument can measure optical transmission, reflectance, and scattering. This information can be used to identify changes in optical properties or deviations from required optical standards. Device consists of monochromatic source, photo detector, transfer mirror, and hemiellipsoid. System might be used to measure optical properties of thin film

Political Business Cycle and Fiscal Discipline in Sub-Saharan Africa

[Abstract] We tested the Political Business Cycle theory in Sub-Sahara Africa. To provide an empirical explanation for this nexus, this paper used unbalanced panel data from thirty-six (36) Sub-Saharan African countries between 1990 and 2018. The system Generalized Method of Moment (GMM) developed by Arrelano-Bover/Blundell-Bond was employed to analyze the collected data. The results of the system GMM revealed that the fiscal deficit is significantly large in election years and the deficit spending spills into the year after the election, though not as high as in the election year. We could not, however, find a significant effect in the pre-election year. In addition, we found evidence suggesting that though democracy significantly lowers the fiscal deficit, it promotes higher deficit spending in the election year and the year after the election. Hence, the study established the existence of a political business cycle in Sub-Saharan African countries. The study thus recommends that sound economic policies should be put in place to reduce the persistent deficit in SSA so as to maintain sustainable fiscal health, as well as the sustainability of macroeconomics, particularly enhanced industrialization, as the study found that countries' fiscal deficits are lower in more industrialized countries in the region

Mathematical models of microbial growth and metabolism: A whole-organism perspective

This is the author accepted manuscript. The final version is available from Science Reviews 2000 via the DOI in this record.We review the principles underpinning the development of mathematical models of the metabolic activities of micro-organisms. Such models are important to understand and chart the substantial contributions made by micro-organisms to geochemical cycles, and also to optimise the performance of bioreactors that exploit the biochemical capabilities of these organisms. We advocate an approach based on the principle of dynamic allocation. We survey the biological background that motivates this approach, including nutrient assimilation, the regulation of gene expression, and the principles of microbial growth. In addition, we discuss the classic models of microbial growth as well as contemporary approaches. The dynamic allocation theory generalises these classic models in a natural manner and is readily amenable to the additional information provided by transcriptomics and proteomics approaches. Finally, we touch upon these organising principles in the context of the transition from the free-living unicellular mode of life to multicellularity.Olga Nev was funded through EU Research Framework programme 7 Marie Curie Actions, grant 316630 Centre for Analytical Science – Innovative Doctoral Programme (CAS-IDP)

Variable-Internal-Stores models of microbial growth and metabolism with dynamic allocation of cellular resources.

This is the final version of the article. Available from Springer via the DOI in this record.An erratum to this article is available at http://dx.doi.org/10.1007/s00285-016-1044-y and in ORE at http://hdl.handle.net/10871/31444Variable-Internal-Stores models of microbial metabolism and growth have proven to be invaluable in accounting for changes in cellular composition as microbial cells adapt to varying conditions of nutrient availability. Here, such a model is extended with explicit allocation of molecular building blocks among various types of catalytic machinery. Such an extension allows a reconstruction of the regulatory rules employed by the cell as it adapts its physiology to changing environmental conditions. Moreover, the extension proposed here creates a link between classic models of microbial growth and analyses based on detailed transcriptomics and proteomics data sets. We ascertain the compatibility between the extended Variable-Internal-Stores model and the classic models, demonstrate its behaviour by means of simulations, and provide a detailed treatment of the uniqueness and the stability of its equilibrium point as a function of the availabilities of the various nutrients.OAN was funded through EU Research Framework programme 7 Marie Curie Actions, grant 316630 Centre for Analytical Science – Innovative Doctoral Programme (CAS-IDP)

Erratum to: Variable-Internal-Stores models of microbial growth and metabolism with dynamic allocation of cellular resources

This is the final version of the article. Available from Springer via the DOI in this record. The online version of the original article can be found under doi: 10.1007/s00285-016-1030-4In the original publication of the article the symbol Phi ‘φ’ should be changed to symbol Psi ‘φ’in Table 1 under the section “Unscaled stoichiometric coefficients”,line 2, column 1.The original article has been updated to reflect the above change

Investigation of anatomical landmarks for paravertebral anaesthesia in West African Dwarf goats (Capra hircus)

West African dwarf goats play important roles in providing meat, milk and generate income in farmers. Information on the techniques and morphometric dimensions on performing paravertebral regional anaesthesia in our local breeds of goats is scanty. The proximal and distal paravertebral nerve block postulated by Farquharson and Magda are used in caprine and ovine species by extrapolation. This study was carried out to quantitatively determine the anatomical site of the spinal nerves (T13, L1. L2, L3 and L4) for the standardized administration of paravertebral regional anaesthesia in West African dwarf goats. Ten adult WAD goats of either sex weighing 10-15kg were used for the study. The animals were euthanized then used for dissection to expose the spinal nerves and subsequently morphometry was carried out. The result of this study showed that the spinal nerve emerges from the intervertebral foramina and bifurcates into dorsal and ventral branches with the dorsal nerve branch passing cranially to the body of the succeeding lumbar transverse process in a caudolateral manner. While the ventral branches of the lumbar nerves each run obliquely, just below the intertransverse ligament, across the space between the transverse processes. The means of (T13, L1, L2 , L3 and L4 ) were considered for the right and left sides of the WAD goats. The mean depth was 3.00±0.38cm while the mean length of nerve was 2.65±0.47cm. This study established reference anatomical landmarks of the spinal nerves 2-3cm away from the spine dorsolateral for proximal approach and 1-1.5cm for the distance of needle placement medially from the tip of the transverse process dorsal and ventral.Keywords: Land marks, Morphometry, Paravertebral anaesthesia, Spinal nerve, WAD goa

Holling Type I versus Holling Type II functional responses in Gram-negative bacteria

We consider how the double-membrane structure of the cell envelope of Gram-negative bacteria affects its functional response, which is the mathematical relationship that expresses how the nutrient uptake flux depends on environmental conditions. We show that, under suitable conditions, the Holling Type I functional response is a plausible model, as opposed to the Holling Type II (rectangular hyperbolic, ‘Michaelis–Menten’) response that is the default model in much of the literature. We investigate both diffusion-limited and capacity-limited regimes. Furthermore, we reconcile our findings with the preponderance in the established literature of hyperbolic models for the growth response, which are generally assumed to be valid, for both Gram-negative and Gram-positive bacteria. Finally, we consider the phenomenon of dynamic adjustment of investment of molecular building blocks in cellular components, and show how this will affect the functional response as observed by the experimenter

Predicting community dynamics of antibiotic-sensitive and -resistant species in fluctuating environments (article)

This is the author accepted manuscript. The final version is available from the Royal Society via the DOI in this recordThe dataset associated with this article is available in ORE: https://doi.org/10.24378/exe.2323Microbes occupy almost every niche within and on their human hosts. Whether colonizing the gut, mouth or bloodstream, microorganisms face temporal fluctuations in resources and stressors within their niche but we still know little of how environmental fluctuations mediate certain microbial phenotypes, notably antimicrobial-resistant ones. For instance, do rapid or slow fluctuations in nutrient and antimicrobial concentrations select for, or against, resistance? We tackle this question using an ecological approach by studying the dynamics of a synthetic and pathogenic microbial community containing two species, one sensitive and the other resistant to an antibiotic drug where the community is exposed to different rates of environmental fluctuation. We provide mathematical models, supported by experimental data, to demonstrate that simple community outcomes, such as competitive exclusion, can shift to coexistence and ecosystem bistability as fluctuation rates vary. Theory gives mechanistic insight into how these dynamical regimes are related. Importantly, our approach highlights a fundamental difference between resistance in single-species populations, the context in which it is usually assayed, and that in communities. While fast environmental changes are known to select against resistance in single-species populations, here we show that they can promote the resistant species in mixed-species communities. Our theoretical observations are verified empirically using a two-species Candida community.European Research Council (ERC)Engineering and Physical Sciences Research Council (EPSRC