We present a new optical spectroscopic survey of 1777 'star-forming' ('SF') and 366 'non-starforming' ('non-SF') galaxies at redshifts z ∼ 0−1 (2143 in total), 22 AGN and 423 stars, observed by instruments such as the Deep Imaging Multi-Object Spectrograph, the Visible Multi-Object Spectrograph and the Gemini Multi-Object Spectrograph, in three fields containing five quasi-stellar objects (QSOs) with Hubble Space Telescope (HST) ultraviolet spectroscopy. We also present a new spectroscopic survey of 173 'strong' (10 14 ≤ N H I 10 17 cm −2 ) and 496 'weak' (10 13 N H I < 10 14 cm −2 ) intervening H I (Lyα) absorption-line systems at z 1 (669 in total), observed in the spectra of eight QSOs at z ∼ 1 by the Cosmic Origins Spectrograph and the Faint Object Spectrograph on the HST. Combining these new data with previously published galaxy catalogues such as the Very Large Telescope Visible Multi-Object Spectrograph Deep Survey and the Gemini Deep Deep Survey, we have gathered a sample of 654 H I absorption systems and 17 509 galaxies at transverse scales 50 Mpc, suitable for a two-point correlation function analysis. We present observational results on the H I-galaxy (ξ ag ) and galaxy-galaxy (ξ gg ) correlations at transverse scales r ⊥ 10 Mpc, and the H I-H I autocorrelation (ξ aa ) at transverse scales r ⊥ 2 Mpc. The two-point correlation functions are measured both along and transverse to the line of sight, ξ (r ⊥ , r ). We also infer the shape of their corresponding 'real-space' correlation functions, ξ (r), from the projected along the line-of-sight correlations, assuming power laws of the form ξ (r) = (r/r 0 ) −γ . Comparing the results from ξ ag , ξ gg and ξ aa , we constrain the H I-galaxy statistical connection, as a function of both H I column density and galaxy star formation activity. Our results are consistent with the following conclusions: (i) the bulk of H I systems on ∼ Mpc scales have little velocity dispersion ( 120 km s −1 ) with respect to the bulk of galaxies (i.e. no strong galaxy outflow/inflow signal is detected); (ii) the vast majority (∼100 per cent) of 'strong' H I systems and 'SF' galaxies are distributed in the same locations, together with 75 ± 15 per cent of 'non-SF' galaxies, all of which Based partly on observations made with the NASA/ESA Hubble Space Telescope, under programmes GO 12264 and GO 11585, and on observations collected at the European Southern Observatory, Chile, under programmes 070.

Modern analyses of structure formation predict a universe tangled in a 'cosmic web' of dark matter and diffuse baryons. These theories further predict that at low-z, a significant fraction of the baryons will be shock-heated to T ∼ 10 5 − 10 7 K yielding a warm-hot intergalactic medium (WHIM), but whose actual existence has eluded a firm observational confirmation. We present a novel experiment to detect the WHIM, by targeting the putative filaments connecting galaxy clusters. We use HST/COS to observe a remarkable QSO sightline that passes within ∆d = 3 Mpc from the 7 inter-cluster axes connecting 7 independent cluster-pairs at redshifts 0.1 z 0.5. We find tentative excesses of total H I, narrow H I (NLA; Doppler parameters b < 50 km s −1 ), broad H I (BLA; b 50 km s −1 ) and O VI absorption lines within rest-frame velocities of ∆v 1000 km s −1 from the cluster-pairs redshifts, corresponding to ∼ 2, ∼ 1.7, ∼ 6 and ∼ 4 times their field expectations, respectively. Although the excess of O VI likely comes from gas close to individual galaxies, we conclude that most of the excesses of NLAs and BLAs are truly intergalactic. We find the covering fractions, f c , of BLAs close to cluster-pairs are ∼ 4 − 7 times higher than the random expectation (at the ∼ 2σ c.l.), whereas the f c of NLAs and O VI are not significantly enhanced. We argue that a larger relative excess of BLAs compared to those of NLAs close to cluster-pairs may be a signature of the WHIM in inter-cluster filaments. By extending the present analysis to tens of sightlines our experiment offers a promising route to detect the WHIM.

We have cloned and expressed in Escherichia coli a gene encoding a 15,000-apparent-molecular-weight peptidoglycan-associated outer membrane lipoprotein (PAL) of Haemophilus influenzae. The nucleotide sequence of this gene encodes an open reading frame of 153 codons with a predicted mature protein of 134 amino acids. The amino acid composition and sequence of the predicted mature protein agree with the chemically determined composition and partial amino acid sequence of PAL purified from H. influenzae outer membranes. We have also identified a second gene from H. influenzae that encodes a second 15,000-apparent-molecular-weight protein which is recognized by antiserum against PAL. This protein has been shown to be a lipoprotein. The nucleotide sequence of this gene encodes an open reading frame of 154 codons with a predicted mature protein of 136 amino acids and has limited sequence homology with that of the gene encoding PAL. Southern hybridization analysis indicates that both genes exist as single copies in H. influenzae chromosomal DNA. Both genes encode polypeptides which have amino-terminal sequences similar to those of reported membrane signal peptides and are associated primarily with the outer membrane when expressed in E. coli.

Epidemiological and immunological evidence indicates that the K1 capsular polysaccharide confers the property of virulence on Escherichia coli. E coli K1 is associated with invasive diseases in humans and in laboratory and domesticated animals. K1 isolates account for 80% of E. coli neonatal meningitis and comprise the majority of capsular types in neonatal septicaemia without meningitis and in childhood pyelonephritis. Passive administration of K1 antibodies prevented bacteraemia and meningitis in infant rats fed E. coli K1. Nonencapsulated derivatives of these invasive K1 strains did not cause bacteraemia in infant rats, although intestinal colonization was similar to that of the parent strains (M. Achtman and R.P.S., unpublished results). Several reports propose that the E. coli K1 capsular polysaccharide exerts an anti-phagocytic effect similar to that observed with other pathogenic encapsulated bacteria. One approach to studying whether the K1 antigen is sufficient to confer virulence of if other E. coli structures are necessary is to isolate the K1 genes for genetic and biochemical analysis. Recombinant DNA methodology provides a powerful tool for such an approach. Here, we report the molecular cloning of the E. coli K1 antigen genes. The cloned K1 genes synthesize a capsule in E. coli K12 indistinguishable chemically and immunologically from that of wild-type K1 strains.

We investigate the properties of the H i Lyα absorption systems (Lyα forest) within and around galaxy voids at z ≲ 0.1. We find a significant excess (>99 per cent confidence level, c.l.) of Lyα systems at the edges of galaxy voids with respect to a random distribution, on ∼5 h−1 Mpc scales. We find no significant difference in the number of systems inside voids with respect to the random expectation. We report differences between both column density (NnormalH0.16emnormali) and Doppler parameter (bnormalH0.16emnormali) distributions of Lyα systems found inside and at the edge of galaxy voids at the ≳98 and ≳90 per cent c.l., respectively. Low‐density environments (voids) have smaller values for both NnormalH0.16emnormali and bnormalH0.16emnormali than higher density ones (edges of voids). These trends are theoretically expected and also found in Galaxies‐Intergalactic Medium Interaction Calculation (GIMIC), a state‐of‐the‐art hydrodynamical simulation. Our findings are consistent with a scenario of at least three types of Lyα systems: (1) containing embedded galaxies and so directly correlated with galaxies (referred to as ‘halo‐like’), (2) correlated with galaxies only because they lie in the same overdense large‐scale structure (LSS) and (3) associated with underdense LSS with a very low autocorrelation amplitude (≈random) that are not correlated with luminous galaxies. We argue that the latter arise in structures still growing linearly from the primordial density fluctuations inside galaxy voids that have not formed galaxies because of their low densities. We estimate that these underdense LSS absorbers account for 25–30 ± 6 per cent of the current Lyα population (NHi≳1012.5 cm−2), while the other two types account for the remaining 70–75 ± 12 per cent. Assuming that only NHi≥1014 cm−2 systems have embedded galaxies nearby, we have estimated the contribution of the ‘halo‐like’ Lyα population to be ≈12–15 ± 4 per cent and consequently ≈55–60 ± 13 per cent of the Lyα systems to be associated with the overdense LSS.