Pseudomonas aeruginosa LptE is crucial for LptD assembly, cell envelope integrity, antibiotic resistance and virulence

Lipopolysaccharide (LPS) is an essential structural component of the outer membrane (OM) of most Gram-negative bacteria. In the model organism Escherichia coli, LPS transport to the OM requires seven essential proteins (LptABCDEFG) that form a continuous bridge across the cell envelope. In Pseudomonas aeruginosa the recently-demonstrated essentiality of LptD and LptH, the P. aeruginosa LptA homologue, confirmed the crucial role of the Lpt system and, thus, of LPS in OM biogenesis in this species. Surprisingly, independent high-throughput transposon mutagenesis studies identified viable P. aeruginosa insertion mutants in the lptE gene, suggesting that it might be dispensable for bacterial growth. To test this hypothesis, we generated an lptE conditional mutant in P. aeruginosa PAO1. LptE depletion only slightly impairs P. aeruginosa growth in vitro. Conversely, LptE is important for cell envelope stability, antibiotic resistance and virulence in an insect model. Interestingly, the maturation and OM localization of LPS is only marginally affected in LptE-depleted cells, while the levels of the OM component LptD are strongly reduced. This suggests that P. aeruginosa LptE might not be directly involved in LPS transport, although it is clearly essential for the maturation and/or stability of LptD. While poor functionality of LptD caused by LptE depletion is somehow tolerated by P. aeruginosa, this has a high cost in terms of cell integrity, drug resistance and virulence, highlighting LptE function(s) as an interesting target to weaken P. aeruginosa defenses and reduce its infectivity

End-to-end algorithm for hierarchical area searches for long-duration GW sources for GEO 600

We describe a hierarchical, highly parallel computer algorithm to perform searches for unknown sources of continuous gravitational waves -- spinning neutron stars in the Galaxy -- over wide areas of the sky and wide frequency bandwidths. We optimize the algorithm for an observing period of 4 months and an available computing power of 20 Gflops, in a search for neutron stars resembling millisecond pulsars. We show that, if we restrict the search to the galactic plane, the method will detect any star whose signal is stronger than 15 times the $1\sigma$ noise level of a detector over that search period. Since on grounds of confidence the minimum identifiable signal should be about 10 times noise, our algorithm does only 50% worse than this and runs on a computer with achievable processing speed.Comment: 7 pages, for proceedings of Jan 1999 Moriond meeting "Gravitational Waves and Experimental Gravity

Discourses on family time: the cultural interpretation of family togetherness in Los Angeles and Rome

In this article, we examine U.S. and Italian parents' discourses on family time in parent-filled weekly activity charts and interviews with parents. Analysis indicates that in Los Angeles, California, parents talk about sheltering and isolating their nuclear family from the outside world and from everyday routine by creating special times and special activities for the nuclear family. In contrast, Roman parents' discourse allows for spontaneous times with the family that are diffused within routines and merged with other community members, institutions, and social spaces. We argue that differences displayed in parents' discourses are shaped by culturally specific orientations toward time, family, and individual versus shared responsibility. Through this cross-cultural comparison we contribute to the understanding of how local cultural models shape different ways in which parents interpret time spent in family and influence individuals' perceptions of their everyday lives

Scalar radiation from Chameleon-shielded regions

I study the profile of the Chameleon field around a radially pulsating mass. Focusing on the case in which the background (static) Chameleon profile exhibits a thin-shell, I add small perturbations to the source in the form of time-dependent radial pulsations. It is found that the Chameleon field inherits a time-dependence, there is a resultant scalar radiation from the region of the source and the metric outside the spherically symmetric mass is not static. This has several interesting and potentially testable consequences.Comment: 4 pages, 4 figures, slightly edited version matching the journal versio

Skilled and Unskilled Wage Dynamics in Italy in the ‘90s: Changes in the individual characteristics, institutions, trade and technology.

In this paper we use individual micro data on workers combined with industry and regional data to study the wage dynamics of skilled and unskilled workers in Italy in the period 1991-1998. Being different to previous empirical studies, our data allow us to explore in a unique framework the role of many of the factors indicated in the literature as possible causes of the widening of the wage gap between skilled and unskilled workers: changes in the individual characteristics of workers, changes in the institutions of the labour market, increasing international integration and skill-biased technological progress. Our results show that international integration, both in terms of trade in goods and in terms of international labour mobility, plays a role in determining the wage dynamics of skilled (white collar) and of unskilled (blue collar) workers. In addition, in line with the research in labour economics, our findings show that the individual characteristics of workers, and the institutional variables matter more in explaining skilled and unskilled wage dynamics than differential wage one.Skilled and unskilled wages, individual characteristics, labour market institutions, international trade.