Integrated microbioreactors for rapid screening and analysis of bioprocesses

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005.Includes bibliographical references (leaves 131-140).(cont.) strains to characterize the bioreactor environment. The ability to reproducibly sacrifice microbioreactors mid-run is exploited to demonstrate the feasibility of linking microbioreactors to genome-wide expression studies using DNA microarrays. The potential of the microbioreactor for investigating different growth conditions is confirmed by comparing bacterial growth, as evaluated by the measured parameters, under conditions of different medium and oxygen concentration. It is shown that statistical differences can be observed, and that these differences are similar to those observed at a larger scale. The demonstrated functionality of the microbioreactor could potentially have a large impact in the numerous fields in which fermentations are used. In bioprocess development, the batch microbioreactor could be used to select strains at all stages of metabolic engineering and to explore and optimize growth conditions during scale-up. The microbioreactor could also be an effective tool in screening applications ranging from toxicology studies that use bacterial reporter strains, to studies that attempt to elucidate metabolic pathways, to intensification of genome-wide expression profiling using either direct links to DNA microarrays or screens of libraries carrying transcription reporters.This thesis presents the design, fabrication, and characterization of a batch microbioreactor with integrated, automated sensors and aeration through a permeable polymer membrane as a step towards establishing high-throughput bioprocessing platforms. In particular, the thesis demonstrates the feasibility of culturing bacterial cells in microliter volumes and obtaining reproducible results similar to those shown at larger scales. A microbioreactor designed to provide sufficient oxygen to a growing culture is fabricated out of PDMS and glass. Models are developed to understand oxygen transport and consumption as well as the kinetics of growth within the microbioreactor. Sensors are integrated to measure the growth parameters optical density (OD), dissolved oxygen (DO), and pH. Based on these measurements as well as cell morphology and total and viable cell counts, reproducibility is established and comparisons to bench-scale bioreactors are made. It is demonstrated that the behavior of bacteria at the two scales is very similar. It is further demonstrated that off-line analysis of the medium can be carried out by serial sacrifice of microbioreactors operating under identical conditions. The test case of HPLC analysis of the fermentation medium to measure glucose consumption and organic acid production is used. Additional sensing capabilities in the form of in situ measurements for luminescence and fluorescence are demonstrated, and a potential glucose sensor is modeled to explore feasibility. Once reproducibility in fabrication, experimental protocol, and experimental results is established, the microbioreactor is used for several applications. The ability to monitor luminescence and fluorescence on-line enables the use of bacterial reporterby Andrea Zanzotto.Ph.D

Human Homosexuality: A Paradigmatic Arena for Sexually Antagonistic Selection?

Sexual conflict likely plays a crucial role in the origin and maintenance of homosexuality in our species. Although environmental factors are known to affect human homosexual (HS) preference, sibling concordances and population patterns related to HS indicate that genetic components are also influencing this trait in humans. We argue that multilocus, partially X-linked genetic factors undergoing sexually antagonistic selection that promote maternal female fecundity at the cost of occasional male offspring homosexuality are the best candidates capable of explaining the frequency, familial clustering, and pedigree asymmetries observed in HS male proband families. This establishes male HS as a paradigmatic example of sexual conflict in human biology. HS in females, on the other hand, is currently a more elusive phenomenon from both the empirical and theoretical standpoints because of its fluidity and marked environmental influence. Genetic and epigenetic mechanisms, the latter involving sexually antagonistic components, have been hypothesized for the propagation and maintenance of female HS in the population. However, further data are needed to truly clarify the evolutionary dynamics of this trait

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Intorno al viaggio musicale di Andrea Zanzotto

Starting from Viaggio musicale, a small book curated by Paolo Cattelan in dialogue with Andrea Zanzotto on the theme of music and poetry, the article follows the path of formation of the poet to music: the nursery rhymes of childhood, Toti Dal Monte and the Opera arias sung by the villagers, the theatre of puppets and music by Margot Galante Garrone, Federico Fellini and Nino Rota, the musicians who met his poetry and set it to music

Sexually Antagonistic Selection in Human Male Homosexuality

Several lines of evidence indicate the existence of genetic factors influencing male homosexuality and bisexuality. In spite of its relatively low frequency, the stable permanence in all human populations of this apparently detrimental trait constitutes a puzzling ‘Darwinian paradox’. Furthermore, several studies have pointed out relevant asymmetries in the distribution of both male homosexuality and of female fecundity in the parental lines of homosexual vs. heterosexual males. A number of hypotheses have attempted to give an evolutionary explanation for the long-standing persistence of this trait, and for its asymmetric distribution in family lines; however a satisfactory understanding of the population genetics of male homosexuality is lacking at present. We perform a systematic mathematical analysis of the propagation and equilibrium of the putative genetic factors for male homosexuality in the population, based on the selection equation for one or two diallelic loci and Bayesian statistics for pedigree investigation. We show that only the two-locus genetic model with at least one locus on the X chromosome, and in which gene expression is sexually antagonistic (increasing female fitness but decreasing male fitness), accounts for all known empirical data. Our results help clarify the basic evolutionary dynamics of male homosexuality, establishing this as a clearly ascertained sexually antagonistic human trait

Gli Sguardi i Fatti e Senhal

È il 1969: l’uomo sbarca sulla luna e Zanzotto canta l’evento nei versi de «Gli Sguardi i Fatti e Senhal» come il più classico poeta civile. Meno classico è il linguaggio, che manifesta e interroga la crisi, a un tempo universale e individuale, del rapporto dell’uomo con la parola. Il commento si propone di guidare il lettore nell’esegesi con riferimenti puntuali alla produzione poetica precedente e immediatamente successiva, decifrando con parzialità programmatica quello che si potrebbe definire un primo esempio di Rorschach in poesia.It’s 1969: man lands on the moon. Andrea Zanzotto celebrates the event with his poem «Gli Sguardi i Fatti e Senhal», a complex example of the poet’s linguistic experimentalism. The comment aims at guiding the reader through this ‘poetical Rorschach’ making precise references to the previous and immediately following works