The effect of acetate on population heterogeneity in different cellular characteristics of Escherichia coli in aerobic batch cultures

Acetate as the major by-product in industrial-scale bioprocesses with Escherichia coli is found to decrease process efficiency as well as to be toxic to cells, which has several effects like a significant induction of cellular stress responses. However, the underlying phenomena are poorly explored. Therefore, we studied time-resolved population heterogeneity of the E. coli growth reporter strain MG1655/pGS20PrrnBGFPAAV expressing destabilized green fluorescent protein during batch growth on acetate and glucose as sole carbon sources. Additionally, we applied five fluorescent stains targeting different cellular properties (viability as well as metabolic and respiratory activity). Quantitative analysis of flow cytometry data verified that bacterial populations in the bioreactor are more heterogeneous in growth as well as stronger metabolically challenged during growth on acetate as sole carbon source, compared to growth on glucose or acetate after diauxic shift. Interestingly, with acetate as sole carbon source, significant subpopulations were found with some cells that seem to be more robust than the rest of the population. In conclusion, following batch cultures population heterogeneity was evident in all measured parameters. Our approach enabled a deeper study of heterogeneity during growth on the favored substrate glucose as well as on the toxic by-product acetate. Using a combination of activity fluorescent dyes proved to be an accurate and fast alternative as well as a supplement to the use of a reporter strain. However, the choice of combination of stains should be well considered depending on which population traits to aim for.     

Che‐1 is targeted by c‐Myc to sustain proliferation in pre‐B‐cell acute lymphoblastic leukemia

Despite progress in treating B‐cell precursor acute lymphoblastic leukemia (BCP‐ALL), disease recurrence remains the main cause of treatment failure. New strategies to improve therapeutic outcomes are needed, particularly in high‐risk relapsed patients. Che‐1/AATF (Che‐1) is an RNA polymerase II‐binding protein involved in proliferation and tumor survival, but its role in hematological malignancies has not been clarified. Here, we show that Che‐1 is overexpressed in pediatric BCP‐ALL during disease onset and at relapse, and that its depletion inhibits the proliferation of BCP‐ALL cells. Furthermore, we report that c‐Myc regulates Che‐1 expression by direct binding to its promoter and describe a strict correlation between Che‐1 expression and c‐Myc expression. RNA‐seq analyses upon Che‐1 or c‐Myc depletion reveal a strong overlap of the respective controlled pathways. Genomewide ChIP‐seq experiments suggest that Che‐1 acts as a downstream effector of c‐Myc. These results identify the pivotal role of Che‐1 in the control of BCP‐ALL proliferation and present the protein as a possible therapeutic target in children with relapsed BCP‐ALL.     

The capacity to remove 8-oxoG is enhanced in newborn neural stem/progenitor cells and decreases in juvenile mice and upon cell differentiation

In mammalian cells, 8-oxoguanine DNA glycosylase-1 (OGG1) is the main DNA glycosylase for the removal of 8-oxoguanine (8-oxoG). 8-oxoG, one of the most common products of the oxidative attack of DNA, is a premutagenic lesion that accumulates spontaneously at high frequencies in the genome. In this study, Ogg1 mRNA expression was detected throughout embryonic development in mice. In situ hybridization showed that in the neonatal brain, Ogg1 expression was detected in a distinct layer of cells in the medial wall of the lateral ventricle, which may correspond to ependymal cells, and in some scattered cells in the subventricular zone (SVZ), a brain region rich in neural stem/progenitor cells. Using neurospheres as a model for the study of neural stem/progenitor cells, we found that both the expression and activity of Ogg1 were high in neurospheres derived from newborn mice and decreased in adults and upon induction of cell differentiation. Furthermore, Ogg1 was shown to be the major DNA glycosylase initiating 8-oxoG repair in neurospheres. Our results strongly indicate that enhanced DNA repair capacity is an important mechanism by which neural stem/progenitor cells maintain their genome.     

Genetic diversity of different apricot geographical groups determined by SSR markers.

Forty apricot cultivars with different geographic origins belonging to the germplasm collections of St. Istvan University (Budapest, Hungary) and the Instituto Valenciano de Investigaciones Agrarias (IVIA) (Valencia, Spain) were studied by means of SSR markers. The aim of the study was to determine the genetic relationships among genotypes from different eco-geographical groups. Sixteen primer pairs flanking microsatellite sequences in the peach genome were assayed. Eleven of them were polymorphic in the set of cultivars studied and allowed every genotype to be unambiguously distinguished. Genetic diversity in the population studied was analyzed using several variability parameters. A total of 34 alleles were detected with a mean value of 3.1 alleles/locus. The expected heterozygosity mean was 0.46 and the observed heterozygosity was 32% on an average leading to a high value of the Wright's fixation index (0.32). Additionally, UPGMA cluster analysis based on Nei's genetic distance grouped genotypes according to their geographic origins and pedigrees. SSR markers have proved to be an efficient tool for fingerprinting cultivars and conducting genetic-diversity studies in apricot.     

The synthetic purine reversine selectively induces cell death of cancer cells

The synthetic purine reversine has been shown to possess a dual activity as it promotes the de‐differentiation of adult cells, including fibroblasts, into stem‐cell‐like progenitors, but it also induces cell growth arrest and ultimately cell death of cancer cells, suggesting its possible application as an anti‐cancer agent. Aim of this study was to investigate the mechanism underneath reversine selectivity in inducing cell death of cancer cells by a comparative analysis of its effects on several tumor cells and normal dermal fibroblasts. We found that reversine is lethal for all cancer cells studied as it induces cell endoreplication, a process that malignant cells cannot effectively oppose due to aberrations in cell cycle checkpoints. On the other hand, normal cells, like dermal fibroblasts, can control reversine activity by blocking the cell cycle, entering a reversible quiescent state. However, they can be induced to become sensitive to the molecule when key cell cycle proteins, e.g., p53, are silenced. J. Cell. Biochem. 113: 3207–3217, 2012. © 2012 Wiley Periodicals, Inc.     

Molecular and cellular characterization of the age-related neuroinflammatory processes occurring in normal rat hippocampus: potential relation with the loss of somatostatin GABAergic neurons

Increased neuroinflammatory reaction is frequently observed during normal brain aging. However, a direct link between neuroinflammation and neurodegeneration during aging has not yet been clearly shown. Here, we have characterized the age-related hippocampal inflammatory processes and the potential relation with hippocampal neurodegeneration. The mRNA expression of the pro-inflammatory cytokines IL-1beta and tumor necrosis factor-alpha (TNF-alpha), and the iNOs enzyme was significantly increased in aged hippocampus. Accordingly, numerous activated microglial cells were observed in aged rats. These cells were differentially distributed along the hippocampus, being more frequently located in the hilus and the CA3 area. The mRNA expression of somatostatin, a neuropeptide expressed by some GABAergic interneurons, and the number of somatostatin-immunopositive cells decreased in aged rats. However, the number of hippocampal parvalbumin-containing GABAergic interneurons was preserved. Interestingly, in aged rats, the mRNA expression of somatostatin and IL-1beta was inversely correlated and, the decrease in the number of somatostatin-immunopositive cells was higher in the hilus of dentate gyrus than in the CA1 region. Finally, intraperitoneal chronic lipopolysaccharide (LPS) injection in young animals mimicked the age-related hippocampal inflammation as well as the decrease of somatostatin mRNA expression. Present results strongly support the neuroinflammation as a potential factor involved in the age-related degeneration of somatostatin GABAergic cells.     

Characterization of cellulases of fungal endophytes isolated from Espeletia spp.

Endophytes are microorganisms that asymptomatically invade plant tissues. They can stimulate plant growth and/or provide defense against pathogen attacks through the production of secondary metabolites. Most endophyte species are still unknown, and because they may have several applications, the study of their metabolic capabilities is essential. We characterized 100 endophytes isolated from Espeletia spp., a genus unique to the paramo ecosystem, an extreme environment in the Andean mountain range. We evaluated the cellulolytic potential of these endophytes on the saccharification of the oil palm empty fruit bunch (OPEFB). The total cellulolytic activity was measured for each endophyte on filter paper (FPA). In addition, the specific carboxymethyl cellulase (CMCase), exoglucanase, and β-glucosidase activities were determined. We found four fungi positive for cellulases. Of these fungi, Penicillium glabrum had the highest cellulolytic activity after partial purification, with maximal CMCase, exoglucanase and β-glucosidase enzyme activities of 44.5, 48.3, and 0.45 U/ml, respectively. Our data showed that the bioprospection of fungi and the characterization of their enzymes may facilitate the process of biofuel production.