Metabolomics for the design of new metabolic engineering strategies for improving aerobic succinic acid production in Escherichia coli.

INTRODUCTION: Glycerol is a byproduct from the biodiesel industry that can be biotransformed by Escherichia coli to high added-value products such as succinate under aerobic conditions. The main genetic engineering strategies to achieve this aim involve the mutation of succinate dehydrogenase (sdhA) gene and also those responsible for acetate synthesis including acetate kinase, phosphate acetyl transferase and pyruvate oxidase encoded by ackA, pta and pox genes respectively in the ΔsdhAΔack-ptaΔpox (M4) mutant. Other genetic manipulations to rewire the metabolism toward succinate consist on the activation of the glyoxylate shunt or blockage the pentose phosphate pathway (PPP) by deletion of isocitrate lyase repressor (iclR) or gluconate dehydrogenase (gnd) genes on M4-ΔiclR and M4-Δgnd mutants respectively. OBJECTIVE: To deeply understand the effect of the blocking of the pentose phosphate pathway (PPP) or the activation of the glyoxylate shunt, metabolite profiles were analyzed on M4-Δgnd, M4-ΔiclR and M4 mutants. METHODS: Metabolomics was performed by FT-IR and GC-MS for metabolite fingerprinting and HPLC for quantification of succinate and glycerol. RESULTS: Most of the 65 identified metabolites showed lower relative levels in the M4-ΔiclR and M4-Δgnd mutants than those of the M4. However, fructose 1,6-biphosphate, trehalose, isovaleric acid and mannitol relative concentrations were increased in M4-ΔiclR and M4-Δgnd mutants. To further improve succinate production, the synthesis of mannitol was suppressed by deletion of mannitol dehydrogenase (mtlD) on M4-ΔgndΔmtlD mutant that increase ~ 20% respect to M4-Δgnd. CONCLUSION: Metabolomics can serve as a holistic tool to identify bottlenecks in metabolic pathways by a non-rational design. Genetic manipulation to release these restrictions could increase the production of succinate.

Caracterización clínica y microbiológica de niños y adolescentes con infecciones asociadas a la atención sanitaria / Clinical and microbiological characterization of children and adolescents with infections associated with health care

Se realizó un estudio descriptivo y transversal de 54 pacientes con infecciones asociadas a la asistencia sanitaria en el Hospital Infantil Sur Docente Dr Antonio María Béguez César de Santiago de Cuba, que abarcó desde enero de 2015 hasta diciembre de 2016. Las variables analizadas incluyeron edad, sexo, tipo de infección, resultado de los cultivos, microorganismo aislado y servicio de procedencia. Todas las muestras de los cultivos efectuados fueron procesadas en el Departamento de Microbiología de la mencionada institución. En la casuística predominaron el grupo etario de 5-17 años, el sexo masculino, la infección en la herida quirúrgica, la positividad de los cultivos, el aislamiento de la Escherichia coli y la Unidad de Cuidados Intensivos. Solo fallecieron 2 de los lactantes de 0-11 meses, para 3,7 por ciento.

A descriptive and cross-sectional study of 54 patients with infections associated with the health care in Dr Antonio María Béguez César Southern Teaching Pediatric Hospital was carried out in Santiago from Cuba, from January, 2015 to December, 2016. The analyzed variables included age, sex, infection type, result of the cultures, isolated organism and origin service. All the culture samples were processed in the Microbiology Department of the institution. The age group 5-17 years, male sex, infection in the surgical wound, the positivity of the cultures, isolation of Escherichia coli and the Intensive Care Unit prevailed in the case material. Only 2 of the infants with 0-11 months died, for 3,7 percent.