A global view of antibiotic resistance

Antibiotic resistance is one of the few examples of evolution that can be addressed experimentally. The present review analyses this resistance, focusing on the networks that regulate its acquisition and its effect on bacterial physiology. It is widely accepted that antibiotics and antibiotic resistance genes play fundamental ecological roles – as weapons and shields, respectively – in shaping the structures of microbial communities. Although this Darwinian view of the role of antibiotics is still valid, recent work indicates that antibiotics and resistance mechanisms may play other ecological roles and strongly influence bacterial physiology. The expression of antibiotic resistance determinants must therefore be tightly regulated and their activity forms part of global metabolic networks. In addition, certain bacterial modes of life can trigger transient phenotypic antibiotic resistance under some circumstances. Understanding resistance thus requires the analysis of the regulatory networks controlling bacterial evolvability, the physiological webs affected and the metabolic rewiring it incurs.     

Fractal dimension of birds population sizes time series

Information about fractal dimension is collected so that it can be applied to time series interpreting Hurst coefficient. The population size of a species is modelled as a dynamic system. The Hurst coefficient is calculated for these times series. A computer programme has been elaborated to compute the Hurst exponent of time series using the algorithms of range increment, second order moment increment and local second order moment increment. It has been applied to time series of birds' populations.     

Klebsiella pneumoniae subverts the activation of inflammatory responses in a NOD1‐dependent manner

Klebsiella pneumoniae is an important cause of community‐acquired and nosocomial pneumonia. Subversion of inflammation is essential for pathogen survival during infection. Evidence indicates that K. pneumoniae infections are characterized by lacking an early inflammatory response although the molecular bases are currently unknown. Here we unveil a novel strategy employed by a pathogen to counteract the activation of inflammatory responses. K. pneumoniae attenuates pro‐inflammatory mediators‐induced IL‐8 secretion. Klebsiella antagonizes the activation of NF‐κB via the deubiquitinase CYLD and blocks the phosphorylation of mitogen‐activated protein kinases (MAPKs) via the MAPK phosphatase MKP‐1. Our studies demonstrate that K. pneumoniae has evolved the capacity to manipulate host systems dedicated to control the immune balance. To exert this anti‐inflammatory effect, Klebsiella engages NOD1. In NOD1 knock‐down cells, Klebsiella neither induces the expression of CYLD and MKP‐1 nor blocks the activation of NF‐κB and MAPKs. Klebsiella inhibits Rac1 activation; and inhibition of Rac1 activity triggers a NOD1‐mediated CYLD and MKP‐1 expression which in turn attenuates IL‐1β‐induced IL‐8 secretion. A capsule (CPS) mutant does not attenuate the inflammatory response. However, purified CPS neither reduces IL‐1β‐induced IL‐8 secretion nor induces the expression of CYLD and MKP‐1 thereby indicating that CPS is necessary but not sufficient to attenuate inflammation.     

Characterization of TccP-mediated N-WASP activation during enterohaemorrhagic Escherichia coli infection

Subversion of the host cell cytoskeleton is the hallmark of enterohaemorrhagic Escherichia coli (EHEC) infection. EHEC translocates the trans -membrane receptor protein Tir (translocated intimin receptor), which links the extracellular bacterium to the eukaryotic cell actin cytoskeleton, triggering formation of actin-rich pedestals beneath adherent bacteria. Tir-mediated actin accretion by EHEC requires TccP (Tir cytoskeleton coupling protein), a recently discovered type III secretion system effector protein which, following translocation, binds and activates Wiskott–Aldrich syndrome protein (N-WASP), which in turn activates the actin-related protein 2/3 complex leading to localized polymerization of actin. In this study, truncated N-WASP and TccP derivatives were generated and tested in in vitro actin polymerization and epithelial cell infection assays. The C-terminal amino acids 253–276 of the GTPase binding domain (GBD) of N-WASP were identified as essential, although not sufficient, for TccP:N-WASP protein:protein interaction, TccP-mediated N-WASP activation and induction of actin polymerization. TccP from EHEC O157:H7 strain EDL933 consists of a unique N-terminal domain and six proline-rich repeats. Progressive deletions within the N-terminus of TccP revealed that residues 1–21 are necessary and sufficient for its translocation, while amino acids 1–181, encompassing the N-terminal translocation signal and two proline-rich repeats, are sufficient for triggering actin polymerization in EHEC-infected epithelial cells and in in vitro actin polymerization assays. This study defines the modular domain structure of TccP and the molecular basis of TccP-mediated N-WASP activation and EHEC-induced remodelling of the host actin cytoskeleton.     

Acetato, formato and chloride copper(II) complexes with 2-(aminomethyl)pyridine: Synthesis, crystal structure, magnetic properties and EPR results

By the reactions of Cu(OAc)₂ · H₂O and Cu(HCOO)₂ · 4H₂O with 2-(aminomethyl)pyridine in different proportions, the compounds Cu(OAc)₂(2-amp) (1), Cu(HCOO)₂(2-amp) (2), Cu(HCOO)₂(2-amp)_1/2 (5), Cu(OAc)₂(2-amp)₂ · H₂O (6) and Cu(HCOO)₂(2-amp)₂ · H₂O (7) were obtained. In 1 the copper shows an elongated rhombic octahedral stereochemistry determined by a 2-amp molecule and two asymmetrical bidentate acetate groups. The hydrogen bonds between the NH₂ groups and O atoms yield to the formation of a double chain. Compound 2 instead consists in monodimensional chains of Cu(2-amp)(HCOO) units, with monodentate formate groups, linked by syn-anti bridging formate groups. Sheets are formed by hydrogen bonds between the chains. By crystallization of a solution of 6 in chloroform, CuCl₂(2-amp)₂ (3) was obtained. It presents a highly distorted square pyramidal geometry around the copper atom. The sheets, formed by the hydrogen bonds between NH₂ and Cl, are interpenetrated and shows π stacking. Magnetic properties and EPR spectra for these new compounds have been studied. Also the magnetic behaviour of Cu(OAc)₂(2-amp)_1/2 (4) is described.     

Molecular characterization of the myxosporean associated with parasitic encephalitis of farmed Atlantic salmon Salmo salar in Ireland

During seasonal epizootics of neurologic disease and mass mortality in the summers of 1992, 1993 and 1994 on a sea-farm in Ireland, Atlantic salmon Salmo salar smolts suffered from encephalitis associated with infection by a neurotropic parasite. Based on ultrastructural studies, this neurotropic parasite was identified as an intercellular presporogonic multicellular developmental stage of a histozoic myxosporean, possibly a Myxobolus species. In order to generate sequence data for phylogenetic comparisons to substantiate the present morphological identification of this myxosporean in the absence of detectable sporogony, polymerase chain reaction (PCR), Southern blot hybridization, dideoxynucleotide chain-termination DNA sequencing, and in situ hybridization (ISH) were used in concert to characterize segments of the small subunit ribosomal RNA (SSU rRNA) gene. Oligonucleotide primers were created from sequences of the SSU rRNA gene of M. cerebralis and were employed in PCR experiments using DNA extracted from formalin-fixed paraffin-embedded tissue sections of brains from Atlantic salmon smolts in which the myxosporean had been detected by light microscopy. Five segments of the SSU rRNA gene of the myxosporean, ranging in length from 187 to 287 base pairs, were amplified, detected by hybridization with sequence-specific probes, and sequenced. Consensus sequences from these segments were aligned to create a partial sequence of the SSU rRNA gene of the myxosporean. Assessments of sequence identity were made between this partial sequence and sequences of SSU rRNA genes from 7 myxosporeans, including Ceratomyxa shasta, Henneguya doori, M. arcticus, M. cerebralis, M. insidiosus, M. neurobius, and M. squamalis. The partial SSU rRNA gene sequence from the myxosporean had more sequence identity with SSU rRNA gene sequences from neurotropic and myotropic species of Myxobolus than to those from epitheliotropic species of Myxobolus or Henneguya, or the enterotropic species of Ceratomyxa, and was identical to regions of the SSU rRNA gene of M. cerebralis. Digoxigenin-labeled oligonucleotide DNA probes complementary to multiple segments of the SSU rRNA gene of M. cerebralis hybridized with DNA of the parasite in histologic sections of brain in ISH experiments, demonstrating definitively that the segments of genome amplified were from the organisms identified by histology and ultrastructural analysis. Based on sequence data derived entirely from genetic material of extrasporogonic stages, the SSU rDNA sequence identity discovered in this study supports the hypothesis that the myxosporean associated with encephalitis of farmed Atlantic salmon smolts is a neurotropic species of the genus Myxobolus, with sequences identical to those of M. cerebralis.     

Effectiveness of three Glomus species in protecting pepper (Capsicum annuum L.) against verticillium wilt

The objective of this work was to study the influence of three Glomus species—Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe, Glomus intraradices (Schenck and Smith) and Glomus deserticola (Trappe, Bloss, and Menge)—on the development of Verticillium-induced wilt in Capsicum annuum cv. Piquillo. Results showed that the effectiveness of arbuscular mycorrhizal fungi (AMF) as biocontrol agents varied among different Glomus species. In pepper colonized by G. intraradices the severity of the disease was even higher than that observed in non-mycorrhizal plants in terms of plant growth and pepper yield. On the other hand, the high effectiveness exhibited by G. mosseae in improving plant growth and the early beginning of the reproductive stage in these plants was not associated with great plant protection and high pepper yield in diseased plants. Only plants associated with G. deserticola had greater yield than non-mycorrhizal ones despite the lower P fertilization applied to the mycorrhizal treatment and this fact was observed in both healthy and diseased plants. It is suggested that the higher specific phosphorus uptake in Verticillium-inoculated plants associated with G. deserticola could contribute to diminish the deleterious effect of pathogen on yield. On the other hand, the possible influence of endogenous phenolics in roots on the tolerance or resistance of pepper against wilt induced by Verticillium dahliae remains unclear.