Exploiting the Anaerobic Expression of Pyruvate Dehydrogenase for the Production of Biofuels

The Pyruvate dehydrogense complex (PDH) is a primarily aerobic enzyme which catalyses pyruvate to acetyl-CoA and carbon dioxide. Its counterpart in anaerobic metabolism is pyruvate formate lyase (Pfl) which converts pyruvate to acetyl-CoA and formate. A novel fermentation pathway involving PDH rather than Pfl (or equivalent), which retains the reducing equivalents from pyruvate oxidation, could provide a novel route for ethanol production, as well as changes in redox balance opening up opportunities for the production of higher alcohols such as butanol. Utilising PDH for the production of biofuels has been investigated in three microorganisms: Geobacillus thermodenitrificans, Bacillus subtilis, and E. coli. Geobacillus thermodenitrificans does express Pfl, thus PDH is always active in the G. thermodenitrificans regardless of whether the bacterium is growing in aerobic or anaerobic conditions. To utilise this PDH in the production of ethanol a bi-functional alcohol dehydrogenase (AdhE) was introduced to G. thermodenitrificans K1041. Further optimisation of ethanol production was achieved by knocking-out lactate dehydrogenase (Ldh), which would otherwise compete with ethanol for flux from acetyl-CoA, and activity of the PDH promoter verses potential alternative promoters to increase the expression of the native PDH was investigated. Like G. thermodenitrificans, Bacillus subtilis also does not have a PFL pathway, but does have a native Adh so can undergo fermentation, albeit poorly. To increase ethanol production competing fermentation pathways were knocked-out, however this resulted in strains which were unable to grow anaerobically. The activity of the native PDH promoter was investigated, and PDH subsequently upregulated. The production of 1-butanol from B. subtilis was also achieved using expression of Clostridial genes encoding a butanol synthetic pathway from a plasmid and from chromosomal integrations. PDH in Gram-negative bacteria such as E. coli are not active during anerobic growth due to fermentation resulting in elevated levels of intracellular NADH; which in turn triggers negative feedback inhibition of PDH. A consequence of this is E. coli strains which are engineered to produce increased titres of ethanol by knocking-out pfl are unable to grow anaerobically. To alleviate this problem a PDH from gram-positive bacteria was expressed in E. coli. The effect of these PDH was also used to assess their potential benefits on 1-butanol in E. coli, by introducing Clostridial genes encoding a butanol synthetic pathway via plasmids

I think I might be gay

For young people struggling with issues around their sexuality, 'coming out' to their families, schools and communities can be traumatic. The alarming statistics for youth suicide, risk-taking behaviours and mental health concerns reflect the alienation and harassment felt by gay, lesbian, bisexual and transgendered young people as they wrestle in isolation with the difficulties of 'being different'. They need families, schools and communities to provide support, understanding and affirmation; and to be their allies against homophobia. Maria Pallotta-Chiarolli has compiled a valuable guide for all those whose lives are affected by a young person coming out. In this work she includes first-hand accounts from families, schools and communities across different socioeconomic levels, diverse regions and many cultural backgrounds. She also provides vital suggestions and advice for those at the coalface of this issue - parents of young people who need to come out, high-school teachers and community leaders - as well as effective responses and strategies for dealing with homophobia in any environment

Intimate citizenship and gendered well-being: the claims and interventions of women’s movements in Europe

European social movements improve the well-being of men and women but need further analysis through a gender-sensitive lens. Taking an international and cross-disciplinary perspective, this book examines the impact of European social movements on gendered political and material well-being. Insights from history, politics, sociology and gender studies help identify how social movements have been instrumental in changing individual well-being through participation and empowerment. These movements have contributed to collective well-being thanks to victories in health, sexualities, political recognition and access to material goods. The contributions pay particular attention to the role of women activists in social movements varying from unions and religious movements to the women's movement itself. The settings range from 19th century Catalonia to Switzerland and Poland, including studies on European transnational movements today and their impact on global gendered well-being. The authors consider how gender has been important in defining the goals, strategies and outcomes of social movements. Thanks to the international spread of contributions a comparative record can be examined. Together the authors provide unique and concrete illustrations of the role of collective action and the participatory process on transforming women and well-being in European societies. The book provides essential insights for students and scholars working on social and women's movements, European well-being and welfare, and transnational action

High-Pressure Synthesis of a Pentazolate Salt

The pentazolates, the last all-nitrogen members of the azole series, have been notoriously elusive for the last hundred years despite enormous efforts to make these compounds in either gas or condensed phases. Here we report a successful synthesis of a solid state compound consisting of isolated pentazolate anions N5-, which is achieved by compressing and laser heating cesium azide (CsN3) mixed with N2 cryogenic liquid in a diamond anvil cell. The experiment was guided by theory, which predicted the transformation of the mixture at high pressures to a new compound, cesium pentazolate salt (CsN5). Electron transfer from Cs atoms to N5 rings enables both aromaticity in the pentazolates as well as ionic bonding in the CsN5 crystal. This work provides a critical insight into the role of extreme conditions in exploring unusual bonding routes that ultimately lead to the formation of novel high nitrogen content species

Sedimentary record of Early Permian deglaciation in southern Gondwana from the Falkland Islands

The deglaciation of southern Gondwana during the Early Permian was preceded by waxing and waning of the south polar ice sheet. The fluctuations in ice extent are recorded in the sedimentary record by strata separating thick deposits of glacial diamictite from post-glacial mudrock. These deposits span across all of the major Gondwana fragments, now recognized as South Africa, South America, India, Antarctica and Australia, and also occur on the Falklands and Ellsworth Mountains microplates created during break-up of the supercontinent in the Mesozoic. We present sedimentary evidence for the progression of deglaciation from the Falkland Islands microplate using a series of borehole core runs acquired during onshore mineral exploration. Glacial advance and retreat phases are inferred from the Hells Kitchen Member of the Port Sussex Formation; the rock succession that conformably overlies the main body of glacial diamictite known locally as the Fitzroy Tillite Formation. The pulsated nature of the transition to fully post-glacial conditions was accompanied by an intricate interplay of sedimentary processes, including soft sediment deformation, meltwater pulses and turbidity currents. The Falkland Islands core data lend insight into the evolving Early Permian environment and offer an unusually complete view of continental margin deglaciation preserved in the ancient sedimentary record. Supplementary material: Borehole core photographs from the Fitzroy Tillite Formation, Hells Kitchen Member and Black Rock Member for cores DD029 and DD090 are available at https://doi.org/10.6084/m9.figshare.c.4031119.v

Pressure-induced phase transition in the electronic structure of palladium nitride

We present a combined theoretical and experimental study of the electronic structure and equation of state (EOS) of crystalline PdN2. The compound forms above 58 GPa in the pyrite structure and is metastable down to 11 GPa. We show that the EOS cannot be accurately described within either the local density or generalized gradient approximations. The Heyd-Scuseria-Ernzerhof exchange-correlation functional (HSE06), however, provides very good agreement with experimental data. We explain the strong pressure dependence of the Raman intensities in terms of a similar dependence of the calculated band gap, which closes just below 11 GPa. At this pressure, the HSE06 functional predicts a first-order isostructural transition accompanied by a pronounced elastic instability of the longitudinal-acoustic branches that provides the mechanism for the experimentally observed decomposition. Using an extensive Wannier function analysis, we show that the structural transformation is driven by a phase transition of the electronic structure, which is manifested by a discontinuous change in the hybridization between Pd-d and N-p electrons as well as a conversion from single to triple bonded nitrogen dimers. We argue for the possible existence of a critical point for the isostructural transition, at which massive fluctuations in both the electronic as well as the structural degrees of freedom are expected.Comment: 9 pages, 12 figures. Revised version corrects minor typographical error

North Atlantic millennial-scale climate variability 910 to 790 ka and the role of the equatorial insolation forcing

The Mid-Pleistocene transition (MPT) was the time when quasi-periodic (not, vert, similar 100 kyr), high-amplitude glacial variability developed in the absence of any significant change in the character of orbital forcing, leading to the establishment of the characteristic pattern of late Pleistocene climate variability. It has long been known that the interval around 900 ka stands out as a critical point of the MPT, when major glaciations started occurring most notably in the northern hemisphere. Here we examine the record of climatic conditions during this significant interval, using high-resolution stable isotope records from benthic and planktonic foraminifera from a sediment core in the North Atlantic (Integrated Ocean Drilling Program Expedition 306, Site U1313). We have considered the time interval from late in Marine Isotope Stage (MIS) 23 to MIS 20 (910 to 790 ka). Our data indicate that interglacial MIS 21 was a climatically unstable period and was broken into four interstadial periods, which have been identified and correlated across the North Atlantic region. These extra peaks tend to contradict previous studies that interpreted the MIS 21 variability as consisting essentially of a linear response to cyclical changes in orbital parameters. Cooling events in the surface record during MIS 21 were associated with low benthic carbon isotope excursions, suggesting a coupling between surface temperature changes and the strength of the Atlantic meridional overturning circulation. Time series analysis performed on the whole interval indicates that benthic and planktonic oxygen isotopes have significant concentrations of spectral power centered on periods of 10.7 kyr and 6 kyr, which is in agreement with the second and forth harmonic of precession. The excellent correspondence between the foraminifera δ18O records and insolation variations at the Equator in March and September suggests that a mechanism related to low-latitude precession variations, advected to the high latitudes by tropical convective processes, might have generated such a response. This scenario accounts for the presence of oscillations at frequencies equal to precession harmonics at Site U1313, as well as the occurrence of higher amplitude oscillations between the MIS22/21 transition and most of MIS 21, times of enhanced insolation variability