Multidrug Efflux Pumps at the Crossroad between Antibiotic Resistance and Bacterial Virulence

Multidrug efflux pumps can be involved in bacterial resistance to antibiotics at different levels. Some efflux pumps are constitutively expressed at low levels and contribute to intrinsic resistance. In addition, their overexpression may allow higher levels of resistance. This overexpression can be transient, in the presence of an effector (phenotypic resistance), or constitutive when mutants in the regulatory elements of the expression of efflux pumps are selected (acquired resistance). Efflux pumps are present in all cells, from human to bacteria and are highly conserved, which indicates that they are ancient elements in the evolution of different organisms. Consequently, it has been suggested that, besides antibiotic resistance, bacterial multidrug efflux pumps would likely contribute to other relevant processes of the microbial physiology. In the current article, we discuss some specific examples of the role that efflux pumps may have in the bacterial virulence of animals’ and plants’ pathogens, including the processes of intercellular communication. Based in these evidences, we propose that efflux pumps are at the crossroad between resistance and virulence of bacterial pathogens. Consequently, the comprehensive study of multidrug efflux pumps requires addressing these functions, which are of relevance for the bacterial–host interactions during infection.Work in our laboratory is supported by grants from the Spanish Ministry of Economy and Competitiveness (BIO2014-54507-R and JPI Water StARE JPIW2013-089-C02-01); from Madrid Autonomous Community [S2010/BMD2414 (PROMPT)]; and from the Instituto de Salud Carlos III [Spanish Network for Research on Infectious Diseases (REIPI RD12/0015)]. MA-R and PB are recipients of FPI fellowships from MINECO.Peer reviewedPeer Reviewe

Genetic differentiation for size at first reproduction through male versus female functions in the widespread Mediterranean tree Pinus pinaster

Background and Aims The study of local adaptation in plant reproductive traits has received substantial attention in short-lived species, but studies conducted on forest trees are scarce. This lack of research on long-lived species represents an important gap in our knowledge, because inferences about selection on the reproduction and life history of short-lived species cannot necessarily be extrapolated to trees. This study considers whether the size for first reproduction is locally adapted across a broad geographical range of the Mediterranean conifer species Pinus pinaster. In particular, the study investigates whether this monoecious species varies genetically among populations in terms of whether individuals start to reproduce through their male function, their female function or both sexual functions simultaneously. Whether differences among populations could be attributed to local adaptation across a climatic gradient is then considered. Methods Male and female reproduction and growth were measured during early stages of sexual maturity of a P. pinaster common garden comprising 23 populations sampled across the species range. Generalized linear mixed models were used to assess genetic variability of early reproductive life-history traits. Environmental correlations with reproductive life-history traits were tested after controlling for neutral genetic structure provided by 12 nuclear simple sequence repeat markers. Key Results Trees tended to reproduce first through their male function, at a size (height) that varied little among source populations. The transition to female reproduction was slower, showed higher levels of variability and was negatively correlated with vegetative growth traits. Several female reproductive traits were correlated with a gradient of growth conditions, even after accounting for neutral genetic structure, with populations from more unfavourable sites tending to commence female reproduction at a lower individual size. Conclusions The study represents the first report of genetic variability among populations for differences in the threshold size for first reproduction between male and female sexual functions in a tree species. The relatively uniform size at which individuals begin reproducing through their male function probably represents the fact that pollen dispersal is also relatively invariant among sites. However, the genetic variability in the timing of female reproduction probably reflects environment-dependent costs of cone production. The results also suggest that early sex allocation in this species might evolve under constraints that do not apply to other conifer

Lattice-Energy Calculations on Organometallic Compounds

Lattice-energy calculations in the atom-atom approach have been performed for five organometallic com­ pounds of previously determined crystal structure. Minimization of energy in terms of positional, orienta­ tional, torsional and cell parameters gave satisfactory results. Computation of energy as a function of torsion angle gave two-dimensional cross sections which o108-7681/88/030259-04$03.00 present minimum-energy conformations at maximum deviations of 10° from the experimental conforma­ tions

High-temperature anti-Invar behavior of gamma-Fe precipitates in Fe_xCu_(100-x) solid solutions: Ferromagnetic phases

High-temperature magnetization and neutron diffraction measurements on metastable Fe_xCu_(100-x) solid solutions have recently shown to imply that γ-Fe precipitates present ferromagnetic anti-Invar behavior. For this reason, we have studied the ferromagnetic phases of γ-Fe in moment-volume parameter space, using the general potential linearized-augmented plane-wave method and the fixed spin moment procedure in order to calculate the corresponding total energy. We find that only two ferromagnetic phases (one related to a low- spin state and the other to a high-spin state) can exist and even coexist in limited volume ranges (3.55-3.59 Å). Hence, our results provide a "revisited" version of the local spin density calculations used in the early article by Moruzzi [Phys. Rev. B 34, 1784 (1986)]. In addition, the fixed spin moment method-using an energy-moment-volume space representation-allows us to conclude that the high-spin state is the ground state of the gamma-Fe precipitates, as the anti-Invar behavior is an intrinsic property of these states. This simple scenario seems to adequately describe the perplexing phenomenology recently observed on Fe_xCu_(100-x) solid solutions

Formación e identificación de carbamato de etilo en bebidas alcohólicas y alimentos fermentados

The formation and identification of ethyl carbamate have led to numerous studies in order to better understand its formation and its further identification and quantification. In this review the contributions accumulated over the last decades to this field, are summarized. Particular emphasis is placed on ethyl carbamate formation, its precursors and the analytical methods used for its identification and quantification.La formación e identificación del carbamato de etilo ha conducido a numerosos estudios para entender mejor su formación y su posterior identificación y cuantificación. En esta revisión sintetizamos lo que ha sido aportado en la literatura que se ha publicado en este tema en las últimas décadas. Se realiza un especial interés en la formación, los precursores y los métodos analíticos de identificación y cuantificación del carbamato de etilo