Experimental evidence for kin-biased helping in a cooperatively breeding vertebrate

The widespread belief that kin selection is necessary for the evolution of cooperative breeding in vertebrates has recently been questioned. These doubts have primarily arisen because of the paucity of unequivocal evidence for kin preferences in cooperative behaviour. Using the cooperative breeding system of long-tailed tits (Aegithalos caudatus) in which kin and non-kin breed within each social unit and helpers are failed breeders, we investigated whether helpers preferentially direct their care towards kin following breeding failure. First, using observational data, we show that not all failed breeders actually become helpers, but that those that do help usually do so at the nest of a close relative. Second, we confirm the importance of kinship for helping in this species by conducting a choice experiment. We show that potential helpers do not become helpers in the absence of close kin and, when given a choice between helping equidistant broods belonging to kin and non-kin within the same social unit, virtually all helped at the nest of kin. This study provides strong evidence that kinship plays an essential role in the maintenance of cooperative breeding in this species

Sculpture new and old from the Antonine basilica at Utica

Over the last two hundred years various pieces of sculpture have been found in what is left of the ruins of the centre of the Roman city of Utica (modern Tunisia). This material is now mostly spread between museum collections in Tunis, Copenhagen, Leiden and London, though some of it remains at Utica, and at least one piece is lost. To judge from what little documentation survives, many of these sculptural elements were found in the same area of Utica and indeed can with reasonable confidence be associated with a single structure, an Antonine-era civil basilica, first identified in the 19th century and recently excavated by a team from the Institut National du Patrimoine and the University of Oxford. This paper presents the new sculptural material unearthed by these excavations for the first time and compares them to the sporadic finds made from the early 19th century onwards. In reconstituting this sculptural assemblage new insights into the decorative programme of the Utican basilica and the aspirations of its commissioners and their community can be gained.Over the last two hundred years various pieces of sculpture have been found in what is left of the ruins of the centre of the Roman city of Utica (modern Tunisia). This material is now mostly spread between museum collections in Tunis, Copenhagen, Leiden and London, though some of it remains at Utica, and at least one piece is lost. To judge from what little documentation survives, many of these sculptural elements were found in the same area of Utica and indeed can with reasonable confidence be associated with a single structure, an Antonine-era civil basilica, first identified in the 19th century and recently excavated by a team from the Institut National du Patrimoine and the University of Oxford. This paper presents the new sculptural material unearthed by these excavations for the first time and compares them to the sporadic finds made from the early 19th century onwards. In reconstituting this sculptural assemblage new insights into the decorative programme of the Utican basilica and the aspirations of its commissioners and their community can be gained

Warped Axions

We study a number of realizations of axions existing in a multi-`throat' generalization of the warped throat geometry of a Randall-Sundrum slice of $AdS_5$. As argued by previous authors, the problem of generating a suitable, phenomenologically allowed Peccei-Quinn scale is simply and elegantly solved by the warping. In compactifications with two or more throats it is possible to simultaneously solve the Standard Model hierarchy problem by the Randall-Sundrum mechanism while implementing interesting warped axion models. The constructions discussed are related to holographic duals of previously studied models of composite axions arising from strongly coupled four-dimensional dynamics.Comment: 14 pages, 1 figure, references adde

Examining the role of structural dynamics in the assembly and function of the multidrug efflux pump AcrAB-TolC

Membrane efflux pumps are a leading cause of increasing multidrug resistant bacterial infections, which pose a significant threat to global human health. Understanding the mechanisms that underpin their function is critical for the development of inhibitors targeting these systems, with the aim being to ‘revive’ the activities of pre-existing antibiotics known to suffer bacterial resistance. AcrAB-TolC is a membrane spanning, tripartite multidrug efflux pump native to Escherichia coli and prototypical of homologous systems across other ESKAPE bacteria. The work in this thesis investigates the role of structural dynamics in the function, assembly, and inhibition of AcrAB-TolC, with a focus on the membrane fusion protein (MFP) AcrA, to reveal critical information on how these efflux systems work, which could be essential for developing novel methods of inhibition to combat multidrug resistance. Throughout this work, structural mass spectrometry (MS) techniques such as hydrogen deuterium exchange mass spectrometry (HDX-MS) and native MS were used alongside a range of complementary biophysical/biochemical techniques to investigate AcrAB-TolC.This work reveals that AcrA lipidation promotes the propensity of AcrA to form oligomers, whereas a non-lipidated, water soluble AcrA construct (AcrAS) is still monomeric. Moreover, HDX-MS showed AcrAS exhibits increased backbone structural dynamics at pH 6.0 compared to pH 7.4, yet this was largely tempered by the presence of magnesium. In the periplasm, the pH can often be ∼1.7 pH units lower than in the cytosol, and there is a significantly higher concentration of magnesium ions (7.56 times). This suggests a regulatory role of magnesium to help AcrA function within the periplasmic environment. To expand the investigations on AcrAS further, a soluble pseudo-dimer construct (AcrASD) was used to infer biological information on the AcrA functional dimer. It was found the pseudo-dimer has unique structural dynamics compared to AcrA, with extensive protection in the α-helices and in regions of the αβ-barrel and MP domains. Furthermore, whilst AcrAS and AcrASD appeared to bind peptidoglycan similarly, AcrASD had a higher propensity to form higher order complexes with AcrB. This suggests dimerization may help prime the AcrA protomers for interactions with its binding partners.Traditionally, efflux pumps inhibitors (EPIs) have been targeted against AcrB, but none have made it past clinical trials, often due to toxicity issues. This has led to a switch in focus for the next generation of EPIs, with AcrA becoming a promising target. In this work, HDX-MS and native MS were used in combination with molecular dynamics (MD) simulations, to investigate the effect of a recently identified EPI, NSC 60339, on the structural dynamics of AcrAS. The data showed NSC 60339 likely binds to AcrA in a cleft bridging the lipoyl and αβ-barrel domains, stabilising these areas as well as the MP domain which usually exhibits intrinsic disorder; NSC 60339 inhibition of AcrASD presented the same. This work proposes the first mechanism of action regarding an AcrA inhibitor and reveals a promising new way to target the AcrAB-TolC complex.Due to the hydrophobic nature of membrane proteins, a suitable membrane mimetic is required for in vitro investigations. As the AcrAB-TolC multidrug efflux pump spans the entire Gram-negative cell envelope and are therefore membrane proteins, studying them in lipid environments rather than detergents is essential as they provide a more representative environment. In this work, HDX-MS was used to show MBX-3756 stabilises the hydrophobic trap of AcrB in membrane scaffold protein (MSP) nanodiscs. Furthermore, a novel SMALP-liposome-SMALP assay was utilised to show that previously designed AcrB antimicrobial peptides did not make the AcrB trimer, purified in styrene maleic acid lipid particles (SMALPs), dissociate into monomers. Lastly, assembly of the AcrAB-TolC complex was probed using two different pull-down assays and native polyacrylamide gel electrophoresis (PAGE), however the heterogeneity and hydrophobicity of SMALPs complicated these investigations, combined with the slow energetics of this assembly in vitro.<br/

Sheep Updates2003 - Keynotes

This session covers two papers from different authors: 1. Economic outlook for sheep and wool Dale Ashton, Australian Bureau of Agricultural and Resource Economics 2. Why is the future so bright? Dr Ben Russell, Manager, Southern Australia, Meat and Livestock Australi