EfeUOB (YcdNOB) is a tripartite, acid-induced and CpxAR-regulated, low-pH Fe2+ transporter that is cryptic in Escherichia coli K-12 but functional in E-coli O157 : H7

Escherichia coli possesses iron transporters specific for either Fe2+ or Fe3+. Although Fe2+ is far more soluble than Fe3+, it rapidly oxidizes aerobically at pH >= 7. Thus, FeoAB, the major Fe2+ transporter of E. coli, operates anaerobically. However, Fe2+ remains stable aerobically under acidic conditions, although a low-pH Fe2+ importer has not been previously identified. Here we show that ycdNOB (efeUOB) specifies the first such transporter. efeUOB is repressed at high pH by CpxAR, and is Fe2+-Fur repressed. EfeU is homologous to the high-affinity iron permease, Ftr1p, of Saccharomyces cerevisiae and other fungi. EfeO is periplasmic with a cupredoxin N-terminal domain; EfeB is also periplasmic and is haem peroxidase-like. All three Efe proteins are required for Efe function. The efeU gene of E. coli K-12 is cryptic due to a frameshift mutation - repair of the single-base-pair deletion generates a functional EfeUOB system. In contrast, the efeUOB operon of the enterohaemorrhagic strain, O157:1147, lacks any frameshift and is functional. A 'wild-type' K-12 strain bearing a functional EfeUOB displays a major growth advantage under aerobic, low-pH, low-iron conditions when a competing metal is provided. Fe-55 transport assays confirm the ferrous iron specificity of EfeUOB.

Intraspecific heritable variation in life-history traits can alter the outcome of interspecific competition among insect herbivores

Competition is one of the most important biotic factors determining the structure of ecological communities. In this study, we show that there is variation in competitive ability between two clones of the pea aphid, Acyrthosiphon pisum, both of which out-compete a clone of the vetch aphid, Megoura viciae, in the laboratory. We tested whether this variation in competitive ability would alter the outcome of interspecific competition in the field. White one pea aphid clone followed the pattern set in the laboratory, out-competing the Megoura viciae clone, another showed the reverse effect with Megoura viciae dominating. These differences appear to be the result of variation in early population growth rate between the pea aphid clones, rather than predation, although predation did lead to the eventual extinction of colonies. We also questioned whether intra- and interspecific differences in predator escape behaviour could affect the outcome of competition in the field. All three clones responded similarly to the presence of foraging hoverfly larvae (Episyrphus balteatus), but the Megoura viciae clone dropped from the plant significantly less often in response to the presence of a foraging two-spot ladybird (Adalia bipunctata). This work provides evidence that intraspecific variation in competitive ability can alter the outcome of interspecific competitive interactions in nature and suggests that species-specific behavioural. traits may have the potential to modify the outcome of these interactions. (c) 2005 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

Global iron-dependent gene regulation in Escherichia coli - A new mechanism for iron homeostasis

Organisms generally respond to iron deficiency by increasing their capacity to take up iron and by consuming intracellular iron stores. Escherichia coli, in which iron metabolism is particularly well understood, contains at least 7 iron-acquisition systems encoded by 35 iron-repressed genes. This Fe-dependent repression is mediated by a transcriptional repressor, Fur ( ferric uptake regulation), which also controls genes involved in other processes such as iron storage, the Tricarboxylic Acid Cycle, pathogenicity, and redox-stress resistance. Our macroarray-based global analysis of iron- and Fur-dependent gene expression in E. coli has revealed several novel Fur-repressed genes likely to specify at least three additional iron- transport pathways. Interestingly, a large group of energy metabolism genes was found to be iron and Fur induced. Many of these genes encode iron- rich respiratory complexes. This iron- and Fur-dependent regulation appears to represent a novel iron-homeostatic mechanism whereby the synthesis of many iron- containing proteins is repressed under iron- restricted conditions. This mechanism thus accounts for the low iron contents of fur mutants and explains how E. coli can modulate its iron requirements. Analysis of Fe-55-labeled E. coli proteins revealed a marked decrease in iron- protein composition for the fur mutant, and visible and EPR spectroscopy showed major reductions in cytochrome b and d levels, and in iron- sulfur cluster contents for the chelator-treated wild-type and/or fur mutant, correlating well with the array and quantitative RT-PCR data. In combination, the results provide compelling evidence for the regulation of intracellular iron consumption by the Fe2+-Fur complex.

A naked ape would have fewer parasites

Unusually among the mammals, humans lack an outer layer of protective fur or hair. We propose the hypothesis that humans evolved hairlessness to reduce parasite loads, especially ectoparasites that may carry disease. We suggest that hairlessness is maintained by these naturally selected benefits and by sexual selection operating on both sexes. Hairlessness is made possible in humans owing to their unique abilities to regulate their environment via fire, shelter and clothing. Clothes and shelters allow a more flexible response to the external environment than a permanent layer of fur and can be changed or cleaned if infested with parasites. Naked mole-rats, another hairless and non-aquatic mammal species, also inhabit environments in which ectoparasite transmission is expected to be high, but in which temperatures are closely regulated. Our hypothesis explains features of human hairlessness-such as the marked sex difference in body hair, and its retention in the pubic regions-that are not explained by other theories.

Crystal structure of (isothiocyanato)(2-pyridinecarboxaldehydebenzoylhydrazonato)copper(I),Cu(C13H10N3O)(NCS)

C14H10CuN4OS, monoclinic, P12(1)/nl (no. 14), a = 8.837(1) angstrom, b = 15.625(2) angstrom, c = 10.366(1) angstrom, beta = 103.36(1)degrees, V = 1392.6 angstrom(3), Z = 4, R-gt(F) = 0.029, WRref(F-2) = 0.076, T = 150 K.

The threading of [(CuCN)(2)(mu-4,4 '-bpy)] sheets by CuCN chains

Yellow (CuCN)(2)[(CuCN)(2)(mu-4,4'-bpy)], formed in the hydrothermal reaction of CuCN with 4,4'-bipyridine at 453 K, contains two types of infinite CuCN chains. One set of CuCN chains is linked by 4,4'-bpy ligands to form almost flat sheets of composition [(CuCN)(2)(mu-4,4'-bpy)]. Holes in these sheets are aligned to allow pairs of approximately linear, infinite -(CuCN)- chains to thread through them. The closest interatomic approach between copper atoms in the threading chains and host sheets (similar to2.74 Angstrom) does not appear to represent a significant covalent bond as it leads to only a small distortion of the -(CuCN)- chains from linearity The relationship of this material to the previously determined structures of the host [(CuCN)(2)(mu-4,4'-bpy)] sheets and (CuCN)(3)[(CuCN)(2)(mu-4,4'-bPY)](2), in which these sheets are threaded by single -(CuCN)- chains, is discussed.

Crystal structure of (2-pyridinecarboxaldehydeisonicotinoyl-hydrazonato)copper(I) thiocyanate, [Cu(C12H9N4O)]NCS

C13H9CuN5OS, monoclinic, P12(1)/c1 (no. 14), a = 9.900(2) angstrom, b = 11.018(1) angstrom, c = 12.861(2) angstrom, beta = 103.55(1)degrees, V = 1363.8 angstrom(3), Z = 4, R-gt(F) = 0.029, wR(ref)(F-2) = 0.088, T = 150 K.

The surface geometry of carbon monoxide and oxygen co-adsorbed on Ni{111}

Low energy electron diffraction (LEED) structure determinations have been performed for the p(2 x 2) structures of pure oxygen and oxygen co-adsorbed with CO on Ni{111}. Optimisation of the non-geometric parameters led to very good agreement between experimental and theoretical IV-curves and hence to a high accuracy in the structural parameters. In agreement with earlier work atomic oxygen is found to adsorb on fee sites in both structures. In the co-adsorbed phase CO occupies atop sites. The positions of the substrate atoms are almost identical, within 0.02 Angstrom, in both structures, implying that the interaction with oxygen dominates the arrangement of Ni atoms at the surface.