Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures

Background: This paper presents a metabolic model describing the production of polyhydroxyalkanoate (PHA) copolymers in mixed microbial cultures, using mixtures of acetic and propionic acid as carbon source material. Material and energetic balances were established on the basis of previously elucidated metabolic pathways. Equations were derived for the theoretical yields for cell growth and PHA production on mixtures of acetic and propionic acid as functions of the oxidative phosphorylation efficiency, P/O ratio. The oxidative phosphorylation efficiency was estimated from rate measurements, which in turn allowed the estimation of the theoretical yield coefficients. Results: The model was validated with experimental data collected in a sequencing batch reactor (SBR) operated under varying feeding conditions: feeding of acetic and propionic acid separately (control experiments), and the feeding of acetic and propionic acid simultaneously. Two different feast and famine culture enrichment strategies were studied: (i) either with acetate or (ii) with propionate as carbon source material. Metabolic flux analysis (MFA) was performed for the different feeding conditions and culture enrichment strategies. Flux balance analysis (FBA) was used to calculate optimal feeding scenarios for high quality PHA polymers production, where it was found that a suitable polymer would be obtained when acetate is fed in excess and the feeding rate of propionate is limited to ∼0.17 C-mol/ (C-mol.h). The results were compared with published pure culture metabolic studies. Conclusion: Acetate was more conducive toward the enrichment of a microbial culture with higher PHA storage fluxes and yields as compared to propionate. The P/O ratio was not only influenced by the selected microbial culture, but also by the carbon substrate fed to each culture, where higher P/O ratio values were consistently observed for acetate than propionate. MFA studies suggest that when mixtures of acetate and propionate are fed to the cultures, the catabolic activity is primarily guaranteed through acetate uptake, and the characteristic P/O ratio of acetate prevails over that of propionate. This study suggests that the PHA production process by mixed microbial cultures has the potential to be comparable or even more favourable than pure cultures.publishersversionpublishe

A multibiomarker approach in the clam Ruditapes decussatus to assess the impact of pollution in the Ria Formosa lagoon, South Coast of Portugal

The Ria Formosa lagoon is an ecosystem whose water quality reflects the anthropogenic influence upon the surrounding areas. In this lagoon, the clam Ruditapes decussatus has a great economical importance and has been widely used as a biomonitor. A multibiomarker approach (d-aminolevulinic acid dehy- dratase, metallothionein, lipid peroxidation, acetylcholinesterase, alkali-labile phosphates, DNA damage) was applied to assess the environmental quality of this ecosystem and the accumulation of contaminants and their potential adverse effects on clams. Clams were sampled in different shellfish beds in the period between July 2007 and December 2008 and abiotic parameters (temperature, salinity, pH and dissolved oxygen of seawater and organic matter in the sediment), condition index, metals (Cd, Cu, Zn, Ni, Pb), TBTs and PAHs concentrations were measured in clam tissues. Data was integrated using Principal Component Analyses and biomarker indices: IBR (Integrated Biomarker Response) and HSI (Health Status Index). This multibiomarker approach enabled discrimination of a time and space trend between sites with different degrees of anthropogenic contamination, identifying one of them (site 2) as the most stressful and summer months as the most critical period for clams due to an increase of environmental stress (anthropogenic pressure along with extreme environmental conditions, e.g. temperature, dissolved oxygen, organic matter in the sediments, etc). The selected biomarkers provided an integrated response to assess the environmental quality of the system, proving to be a useful approach when complex mixtures of contaminants occur

Outcome in patients perceived as receiving excessive care across different ethical climates: a prospective study in 68 intensive care units in Europe and the USA

Purpose: Whether the quality of the ethical climate in the intensive care unit (ICU) improves the identification of patients receiving excessive care and affects patient outcomes is unknown. Methods: In this prospective observational study, perceptions of excessive care (PECs) by clinicians working in 68 ICUs in Europe and the USA were collected daily during a 28-day period. The quality of the ethical climate in the ICUs was assessed via a validated questionnaire. We compared the combined endpoint (death, not at home or poor quality of life at 1 year) of patients with PECs and the time from PECs until written treatment-limitation decisions (TLDs) and death across the four climates defined via cluster analysis. Results: Of the 4747 eligible clinicians, 2992 (63%) evaluated the ethical climate in their ICU. Of the 321 and 623 patients not admitted for monitoring only in ICUs with a good (n = 12, 18%) and poor (n = 24, 35%) climate, 36 (11%) and 74 (12%), respectively were identified with PECs by at least two clinicians. Of the 35 and 71 identified patients with an available combined endpoint, 100% (95% CI 90.0–1.00) and 85.9% (75.4–92.0) (P = 0.02) attained that endpoint. The risk of death (HR 1.88, 95% CI 1.20–2.92) or receiving a written TLD (HR 2.32, CI 1.11–4.85) in patients with PECs by at least two clinicians was higher in ICUs with a good climate than in those with a poor one. The differences between ICUs with an average climate, with (n = 12, 18%) or without (n = 20, 29%) nursing involvement at the end of life, and ICUs with a poor climate were less obvious but still in favour of the former. Conclusion: Enhancing the quality of the ethical climate in the ICU may improve both the identification of patients receiving excessive care and the decision-making process at the end of life

Presumptive germ cells derived from mouse pluripotent somatic cell hybrids

The fusion of embryonic stem (ES) cells with differentiated somatic cells is an approach that reverses a somatic cell nucleus to a state of pluripotency. the resulting ES-somatic cell hybrids (ES-SCH) retain most of the properties of ES cells: differentiate into multiple cell types and have the ability to produce embryoid bodies (EB) and chimeras. However, it is still unknown whether ES-SCH will be able to complete the differentiation into germ cells (GC) in vitro similar to ES cells. Here, we show that near diploid ES-SCH, obtained by the fusion of mouse ES and spleen cells, were able to differentiate in vitro into presumptive GC. Differentiation of ES-SCH was induced through EB formation and by the addition of retinoic acid. Presumptive GC obtained reacted positively with anti-EMA, Vasa, Fragilis and Dazl antibodies and expressed GC-specific genes, such as Vasa, Stella, Dazl, Piwii 2, Tex 14, Bmp8b, Tdrd 1 and Rnf17. Fluorescent in situ hybridization analysis indicates chromosome reduction in the GC-like cells. Expression of meiotic and postmeiotic GC-specific genes such as Haprin, Acrosin, Scyp1, Scyp3 and Stra-8 were also detected. Transmission electron microscopy confirmed ES-SCH differentiation into presumptive GC. the presence of several autosomes and the X chromosome originated from the somatic'' partner did not prevent ES-SCH differentiation towards presumptive GC. Overall our study suggests an interesting in vitro model, which allows the study GC differentiation in reprogrammed somatic cells. (C) 2009 International Society of Differentiation. Published by Elsevier B.V. All rights reserved.Clinic of Andrology of São PauloFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Butantan Inst, Genet Lab, BR-05503900 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Genet & Morphol, BR-04023900 São Paulo, BrazilRoger Abdelmassih Human Reprod Clin & Res Ctr, BR-01431000 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Genet & Morphol, BR-04023900 São Paulo, BrazilWeb of Scienc

Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures-4

Tions. Full symbols represent the experimental data and full lines the modelling results.<p><b>Copyright information:</b></p><p>Taken from "Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures"</p><p>http://www.biomedcentral.com/1752-0509/2/59</p><p>BMC Systems Biology 2008;2():59-59.</p><p>Published online 8 Jul 2008</p><p>PMCID:PMC2483998.</p><p></p

Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures-5

E feeding conditions. Full symbols represent the experimental data and full lines the modelling results.<p><b>Copyright information:</b></p><p>Taken from "Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures"</p><p>http://www.biomedcentral.com/1752-0509/2/59</p><p>BMC Systems Biology 2008;2():59-59.</p><p>Published online 8 Jul 2008</p><p>PMCID:PMC2483998.</p><p></p

Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures-3

Eeding conditions. Full symbols represent the experimental data and full lines the modelling results.<p><b>Copyright information:</b></p><p>Taken from "Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures"</p><p>http://www.biomedcentral.com/1752-0509/2/59</p><p>BMC Systems Biology 2008;2():59-59.</p><p>Published online 8 Jul 2008</p><p>PMCID:PMC2483998.</p><p></p

Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures-0

Ns. Full symbols represent parameter estimation results and open symbols the model validation results. Dashed lines are the 95% confidence limits for the parameter estimation and model validation results.<p><b>Copyright information:</b></p><p>Taken from "Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures"</p><p>http://www.biomedcentral.com/1752-0509/2/59</p><p>BMC Systems Biology 2008;2():59-59.</p><p>Published online 8 Jul 2008</p><p>PMCID:PMC2483998.</p><p></p