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A critical challenge in developing scalable quantum systems is correcting the accumulation of errors while performing operations and measurements. It is known that systems where dominant errors can be detected and converted into erasures have relaxed requirements for quantum error correction. Recently, it has been proposed that this can be achieved using a dual-rail encoding of quantum information in the microwave photon states of two superconducting cavities. One necessary step to realize this erasure qubit is to demonstrate a measurement and to flag errors as erasures. In this work, we demonstrate a projective logical measurement of a dual-rail cavity qubit with integrated erasure detection and measure the qubit idling errors. We measure the logical state preparation and measurement errors at the 0.01% level and detect over 99% of the cavity decay events as erasures. We use the precision of this measurement protocol to distinguish different types of error in this system, finding that although decay errors occur with a probability of approximately 0.2% per microsecond, phase errors occur 6 times less frequently and bit flips occur at least 150 times less frequently. These findings represent a confirmation of the expected error hierarchy necessary to concatenate dual-rail cavity qubits into a highly efficient erasure code.

Strains of the bacteria Escherichia coli (E. coli) associated with acute, uncomplicated pyelonephritis and urinary tract infections possess specific virulence determinants such as hemolysis, or the ability to destroy red blood cells. (Pyelonephritis refers to inflammation of the kidney and pelvis. Virulence determinants affect the pathogenesis and severity of infections.) The majority of urinary tract infections (UTIs) in women are usually uncomplicated cystitis (bladder infections), but little data is available on the prevalence of virulence determinants in these cases. Three groups of age-matched, nonpregnant women were assessed: 54 with their first episode of cystitis; 33 with recurrent cystitis; and 52 with no UTI history (control group). Midstream urine specimens were obtained from the infected cases (87 women), and fecal swabs were obtained from the control group (52 women). All specimens were cultured for E. coli bacteria. First-episode and recurrent cystitis cases provided 121 isolates of E. coli, and the control group yielded 156 fecal isolates of E. coli. The presence of several virulence determinants (P fimbriae, hemolysis, aerobactin, and diffuse adhesin) was identified using DNA probes. The results are presented in detail. The findings suggest that the use of diaphragms altered the presence and concentration of E. coli virulence determinants. Hence, women who use diaphragms may develop UTIs with less virulent strains of E. coli. (Consumer Summary produced by Reliance Medical Information, Inc.)

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least 4 m. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the 6.5 m James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 yr, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.

The Near-Infrared Spectrograph (NIRSpec) is one of the four focal plane instruments on the James Webb Space Telescope. In this paper, we summarize the in-orbit performance of NIRSpec, as derived from data collected during its commissioning campaign and the first few months of nominal science operations. More specifically, we discuss the performance of some critical hardware components such as the two NIRSpec Hawaii-2RG detectors, wheel mechanisms, and the microshutter array. We also summarize the accuracy of the two target acquisition procedures used to accurately place science targets into the slit apertures, discuss the current status of the spectrophotometric and wavelength calibration of NIRSpec spectra, and provide the “as measured” sensitivity in all NIRSpec science modes. Finally, we point out a few important considerations for the preparation of NIRSpec science programs.

High-performance, integrated spectrometers operating in the far-infrared and submillimeter ranges promise to be powerful tools for the exploration of the epochs of reionization and initial galaxy formation. These devices, using high-efficiency superconducting transmission lines, can achieve the performance of a meter-scale grating spectrometer in an instrument implemented on a 4 inch silicon wafer. Such a device, when combined with a cryogenic telescope in space, provides an enabling capability for studies of the early universe. Here, the optical design process for Micro-Spec (μ-Spec) is presented, with particular attention given to its two-dimensional diffractive region, where the light of different wavelengths is focused on the different detectors. The method is based on the stigmatization and minimization of the light path function in this bounded region, which results in an optimized geometrical configuration. A point design with an efficiency of ∼90% has been developed for initial demonstration and can serve as the basis for future instruments. Design variations on this implementation are also discussed, which can lead to lower efficiencies due to diffractive losses in the multimode region.

We investigate the polarization modulation properties of a variable-delay polarization modulator (VPM). The VPM modulates polarization via a variable separation between a polarizing grid and a parallel mirror. We find that in the limit where the wavelength is much larger than the diameter of the metal wires that comprise the grid, the phase delay derived from the geometric separation between the mirror and the grid is sufficient to characterize the device. However, outside of this range, additional parameters describing the polarizing grid geometry must be included to fully characterize the modulator response. In this paper, we report test results of a VPM at wavelengths of 350 μm and 3 mm. Electromagnetic simulations of wire grid polarizers were performed and are summarized using a simple circuit model that incorporates the loss and polarization properties of the device.

The Johns Hopkins University sounding rocket group is entering the final fabrication phase of the Far-ultraviolet Off Rowland-circle Telescope for Imaging and Spectroscopy (FORTIS); a sounding rocket borne multi-object spectro-telescope designed to provide spectral coverage of 43 separate targets in the 900 - 1800 Angstrom bandpass over a 30' x 30' field-of- view. Using "on-the-fly" target acquisition and spectral multiplexing enabled by a GSFC microshutter array, FORTIS will be capable of observing the brightest regions in the far-UV of nearby low redshift (z ~ 0.002 - 0.02) star forming galaxies to search for Lyman alpha escape, and to measure the local gas-to-dust ratio. A large area (~ 45 mm x 170 mm) microchannel plate detector built by Sensor Sciences provides an imaging channel for targeting flanked by two redundant spectral outrigger channels. The grating is ruled directly onto the secondary mirror to increase efficiency. In this paper, we discuss the recent progress made in the development and fabrication of FORTIS, as well as the results of early calibration and characterization of our hardware, including mirror/grating measurements, detector performance, and early operational tests of the microshutter arrays.

The Primordial Inflation Explorer is an Explorer-class mission to measure the gravity-wave signature of primordial inflation through its distinctive imprint on the linear polarization of the cosmic microwave background. PIXIE uses an innovative optical design to achieve background-limited sensitivity in 400 spectral channels spanning 2.5 decades in frequency from 30 GHz to 6 THz (1 cm to 50 m wavelength). Multi-moded non-imaging optics feed a polarizing Fourier Transform Spectrometer to produce a set of interference fringes, proportional to the difference spectrum between orthogonal linear polarizations from the two input beams. The differential design and multiple signal modulations spanning 11 orders of magnitude in time combine to reduce the instrumental signature and confusion from unpolarized sources to negligible levels. PIXIE will map the full sky in Stokes I, Q, and U parameters with angular resolution 2.°6 and sensitivity 0.2 K per 1° square pixel. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r < 10-3at 5 standard deviations. We describe the PIXIE instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

In a previous paper,1we described a method for significantly reducing the read noise of HAWAII-2RG (H2RG) and SIDECAR application specific integrated circuit (ASIC) based detector systems by making better use of reference signals. "Improved Reference Sampling & Subtraction" (IRS2; pronounced "IRS-square") is based on: (1) making better use of the H2RG's reference output, (2) sampling reference pixels more frequently in the time domain, and (3) optimal subtraction of both the reference output and reference pixels in the Fourier domain. Here we demonstrate that IRS2works as expected using an engineering grade James Webb Space Telescope (JWST) SIDECAR ASIC and H2RG detector array. We were able to reduce the read noise per frame from 25 e- rms using traditional JWST readout to 10 e- rms per frame using IRS2. The only aspect of the system that we changed to make these impressive improvements was the SIDECAR ASIC readout software -we did not change the hardware.

Far-infrared bolometric detectors are used extensively in ground-based and space-borne astronomy, and thus it is important to understand their optical behavior precisely. We have studied the intensity and polarization response of free-space bolometers and shown that when the size of the absorber is reduced below a wavelength, the response changes from being that of a classical optical detector to that of a few-mode antenna. We have calculated the modal content of the reception patterns and found that for any volumetric detector having a side length of less than a wavelength, three magnetic and three electric dipoles characterize the behavior. The size of the absorber merely determines the relative strengths of the contributions. The same formalism can be applied to thin-film absorbers, where the induced current is forced to flow in a plane. In this case, one magnetic and two electric dipoles characterize the behavior. The ability to model easily the intensity, polarization, and straylight characteristics of electrically small detectors will be of great value when designing high-performance polarimetric imaging arrays.

We present first results of Hertz/VPM, the first submillimeter polarimeter employing the dual Variable-delay Polarization Modulator (dual-VPM). This device differs from previously used polarization modulators in that it operates in translation, rather than mechanical rotation. We discuss the basic theory behind this device and its potential advantages over the commonly used half-wave plate. The dual-VPM was tested both at the Submillimeter Telescope Observatory and in the laboratory. In each case we present a detailed description of the setup. We discovered that properties of the VPM wire grids (diameter and spacing) caused behavior that differs from theoretical predictions for ideal wire grid performance. By modifying the polarimeter settings to compensate for this behavior, we found that the dual-VPM system is robust, operating with high efficiency and low instrumental polarization. This device is well suited for air- and space-borne applications.

Filled arrays of bolometers are currently being employed for use in astronomy from the far-infrared through millimeter portion of the electromagnetic spectrum. Because of the large range of wavelengths for which such detectors are applicable, the size of a pixel (p) relative to the wavelength (?) will vary according to the specific application of a given available technology. As the pixel size becomes comparable to a wavelength of the absorbed radiation, correlations in the radiation field at the pixel can affect the imaging properties of the system independent of the correlations introduced by the front-end optics. We study the dependence of image fidelity and induced polarization on the size of the pixel by employing a formalism in which diffraction due to the pixel boundary is treated by propagating the second-order statistical correlations of the radiation field through an optical system. We construct simulated polarized images of square pixels for various ratios of p/?. For the limit in which few modes are supported by the pixel (p/? ? 1), we find that the diffraction due to the pixel edges is nonnegligible and hence must be considered along with the telescope diffraction pattern in modeling the ultimate spatial resolution of an imaging system. For the case in which the pixel is over-moded (p/??1), the geometric limit is approached as expected. This technique provides a quantitative approach to understand and optimize the imaging properties of planar detectors in the few-mode limit.

The X-Ray Spectrometer (XRS) has been designed to provide the Suzaku Observatory with non-dispersive, high-resolution X-ray spectroscopy. As designed, the instrument covers the energy range 0.3 to 12 keV, which encompasses the most diagnostically rich part of the X-ray band. The sensor consists of a 32-channel array of X-ray microcalorimeters, each with an energy resolution of about 6 eV. The very low temperature required for operation of the array (60 mK) is provided by a four-stage cooling system containing a single-stage adiabatic demagnetization refrigerator, a superfluid-helium cryostat, a solid-neon dewar, and a single-stage, Stirling-cycle cooler. The Suzaku/XRS is the first orbiting X-ray microcalorimeter spectrometer and was designed to last more than three years in orbit. The early verification phase of the mission demonstrated that the instrument worked properly and that the cryogen consumption rate was low enough to ensure a mission lifetime exceeding 3 years. However, the liquid-He cryogen was completely vaporized two weeks after opening the dewar guard vacuum vent. The problem has been traced to inadequate venting of the dewar He and Ne gases out of the spacecraft and into space. In this paper we present the design and ground testing of the XRS instrument, and then describe the in-flight performance. An energy resolution of 6 eV was achieved during pre-launch tests and a resolution of 7 eV was obtained in orbit. The slight degradation is due to the effects of cosmic rays.

We develop the Jones and Mueller matrices for structures that allow control of the path length difference between two linear orthogonal polarizations and consider the effect of placing multiple devices in series. Specifically, we find that full polarization modulation (measurement of Stokes Q, U, and V) can be achieved by placing two such modulators in series if the relative angles of the beam-splitting grids with respect to the analyzer orientation are appropriately chosen. Such a device has several potential advantages over a spinning wave plate modulator for measuring astronomical polarization in the far infrared through millimeter: (i) The use of small, linear motions eliminates the need for cryogenic rotational bearings; (ii) the phase flexibility allows measurement of circular as well as linear polarization; and (iii) this architecture allows for both multiwavelength and broadband modulation. We also present initial laboratory results.

Two-dimensional MEMS microshutter arrays (MSA) have been fabricated at the NASA Goddard Space Flight Center (GSFC) for the James Webb Space Telescope (JWST) to enable cryogenic (~35 K) spectrographic astronomy measurements at near-infrared wavelengths. Functioning as a focal plane object selection device, the MSA is a 2D programmable aperture mask with fine resolution, high efficiency and high contrast. The MSA are close-packed silicon nitride shutters (cell size of 100 µm × 200 µm) patterned with a torsion flexure to allow their opening to 90°. A layer of magnetic material is deposited onto each shutter to permit magnetic actuation. Two electrodes are deposited, one onto each shutter and another onto the support structure side-wall, permitting electrostatic latching and 2D addressing. New techniques were developed to test MSA under mission-similar conditions (8 K ? T< 300 K). The 'magnetic rotisserie' has proven to be an excellent tool for rapid characterization of MSA. Tests conducted with the magnetic rotisserie method include accelerated cryogenic lifetesting of unpackaged 128 × 64 MSA and parallel measurement of the magneto-mechanical stiffness of shutters in 'pathfinder' test samples containing multiple MSA designs. Lifetest results indicate a logarithmic failure rate out to ~106shutter actuations. These results have increased our understanding of failure mechanisms and provide a means to predict the overall reliability of MSA devices.

Studies of emission in the far-infrared and submillimeter from astrophysical sources require large arrays of detectors containing hundreds to thousands of elements. A multiplexed readout is necessary for practical implementation of such arrays, and can be developed using SQUIDS, such that, e.g., a 32 × 32 array of bolometers can be read out using ≈100 wires rather than the >2000 needed with a brute force expansion of existing arrays. These bolometer arrays are made by micromachining techniques, using superconducting transition edge sensors as the thermistors. We describe the development of this multiplexed superconducting bolometer array architecture as a step toward bringing about the first astronomically useful arrays of this design. This technology will be used in the SAFIRE instrument on SOFIA, and is a candidate for a wide variety of other spectroscopic and photometric instruments.

Diffusely adhering Escherichia coli (DAEC) strains expressing F1845 fimbrial adhesin or Dr hemagglutinin belonging to the Afa/Dr family of adhesins infect cultured polarized human intestinal cells through recognition of the brush border-associated decay-accelerating factor (DAF; CD55) as a receptor. The wild-type Afa/Dr DAEC strain C1845 has been shown to induce brush border lesions by an adhesin-dependent mechanism triggering apical F-actin rearrangements. In the present study, we undertook to further characterize cell injuries following the interaction of wild-type Afa/Dr DAEC strains C1845 and IH11128 expressing fimbrial F1845 adhesin and Dr hemagglutinin, respectively, with polarized, fully differentiated Caco-2/TC7 cells. In both cases, bacterium-cell interaction was followed by rearrangement of the major brush border-associated cytoskeletal proteins F-actin, villin, and fimbrin, proteins which play a pivotal role in brush border assembly. In contrast, distribution of G-actin, actin-depolymerizing factor, and tubulin was not modified. Using draE mutants, we found that a mutant in which cysteine replaces aspartic acid at position 54 conserved binding capacity but failed to induce F-actin disassembly. Accompanying the cytoskeleton injuries, we found that the distribution of brush border-associated functional proteins sucrase-isomaltase (SI), dipeptidylpeptidase IV (DPPIV), glucose transporter SGLT1, and fructose transporter GLUT5 was dramatically altered. In parallel, SI and DPPIV enzyme activity decreased.

Enteroaggregative Escherichia coli (EAEC) heat-stable enterotoxin 1 (EAST1) was originally discovered in EAEC but has also been associated with enterotoxigenic E. coli (ETEC). Multiple genomic restriction fragments from each of three ETEC strains of human origin showed homology with an EAST1 gene probe. A single hybridizing fragment was detected on the plasmid of ETEC strain 27D that also encodes heat-stable enterotoxin Ib and colonization factor antigen I. We isolated and characterized this fragment, showing that it (i) carries an allele of astA nearly identical to that originally reported from EAEC 17-2 and (ii) expressed enterotoxic activity. Sequence analysis of the toxin coding region revealed that astA is completely embedded within a 1,209-bp open reading frame (ORF1), whose coding sequence is on the same strand but in the -1 reading frame in reference to the toxin gene. In vitro expression of the predicted M(r)- approximately 46,000 protein product of ORF1 was demonstrated. ORF1 is highly similar to transposase genes of IS285 from Yersinia pestis, IS1356 from Burkholderia cepacia, and ISRm3 from Rhizobium meliloti. It is bounded by 30-bp imperfect inverted repeat sequences and flanked by 8-bp direct repeats. Based on these structural features, pathognomonic of a regular insertion sequence, this element was designated IS1414. Preliminary experiments to show IS1414 translocation were unsuccessful. Overlapping genes of the type suggested by the IS1414 core region have heretofore not been described in bacteria. It seems to offer a most efficient mechanism for intragenomic and horizontal dissemination of EAST1.

We discuss the utility of a low-resolution prism as a component of a multiobject spectrometer for NASA's proposed Next Generation Space Telescope(NGST). Low-resolution prism spectroscopy permits simultaneous observation of the 0.6-5 ?m wavelength regime at R?50. Such data can take advantage of modern techniques in spectral energy distribution (SED) fitting to determine source redshifts, sometimes called "photometric redshifts." We compare simulated prism observations with filter imaging for this purpose with NGST. Low-resolution prism observations of galaxy SEDs provide a significant advantage over multifilter observations for any realistic observing strategy. For an ideal prism in sky background-limited observing, the prism has a signal-to-noise ratio advantage of the square root of the resolution over serial observations by filters with similar spatial and spectral resolution in equal integration time. For a realistic case the advantage is slightly less, and we have performed extensive simulations to quantify it. We define strict criteria for the recovery of input redshifts, such that to be considered a success, redshift residuals must be ?z<0.03 + 0.1log z. The simulations suggest that in 105s, a realistic prism will recover (by our definition of success) the redshift of ?70% of measured objects (subject to multiobject spectrograph selection) at KAB<32, compared to less than 45% of the objects with serial filter observations. The advantage of the prism is larger in the regime of faint (KAB>30) objects at high redshift (z>4), where the prism recovers 80% of redshifts, while the filters recover barely 35% to similar accuracy. The primary discovery space of NGSTwill be at the faintest magnitudes and the highest redshifts. Many important objects will be too faint for follow-up at higher spectral resolution, so prism observations are the optimal technique to study them. Prism observations also reduce the contamination of high-redshift samples by lower redshift interlopers.

With high-sensitivity imaging arrays, accurate calibration is essential to achieve the limits of detection of space observatories. One can simultaneously extract information about the scene being observed and the calibration properties of the detector and imaging system from redundant dithered images of a scene. There are large differences in the effectiveness of dithering strategies for allowing the separation of detector properties from sky brightness measurements. In this paper, we quantify these differences by developing a figure of merit (FOM) for dithering procedures based on their usefulness for allowing calibration on all spatial scales. The figure of merit measures how well the gain characteristics of the detector are encoded in the measurements, and is independent of the techniques used to analyze the data. Patterns similar to the antenna arrangements of radio interferometers with good u-vplane coverage are found to have good figures of merit. We present patterns for both deep surveys of limited sky areas and for shallow surveys. By choosing a strategy that encodes the calibration in the observations in an easily extractable way, we enhance our ability to calibrate our detector systems and to reach the ultimate limits of sensitivity that are required to achieve the promise of many missions.

The Afa/Dr family of diffusely adhering Escherichia coli (Afa/Dr DAEC) includes bacteria expressing afimbrial adhesins (AFA), Dr hemagglutinin, and fimbrial F1845 adhesin. We show that infection of human intestinal Caco-2/TC7 cells by the Afa/Dr DAEC strains C1845 and IH11128 is followed by clustering of CD55 around adhering bacteria. Mapping of CD55 epitopes involved in CD55 clustering by Afa/Dr DAEC was conducted using CD55 deletion mutants expressed by stable transfection in CHO cells. Deletion in the short consensus repeat 1 (SCR1) domain abolished Afa/Dr DAEC-induced CD55 clustering. In contrast, deletion in the SCR4 domain does not modify Afa/Dr DAEC-induced CD55 clustering. We show that the brush border-associated glycosylphosphatidylinositol (GPI)-anchored protein CD66e (carcinoembryonic antigen) is recruited by the Afa/Dr DAEC strains C1845 and IH11128. This conclusion is based on the observations that (i) infection of Caco-2/TC7 cells by Afa/Dr DAEC strains is followed by clustering of CD66e around adhering bacteria and (ii) Afa/Dr DAEC strains bound efficiently to stably transfected HeLa cells expressing CD66e, accompanied by CD66e clustering around adhering bacteria. Inhibition assay using monoclonal antibodies directed against CD55 SCR domains, and polyclonal anti-CD55 and anti-CD66e antibodies demonstrate that CD55 and CD66e function as a receptors for the C1845 and IH11128 bacteria. Moreover, using structural draE gene mutants, we found that a mutant in which cysteine replaced aspartic acid at position 54 displayed conserved binding capacity but failed to induce CD55 and CD66e clustering. Taken together, these data give new insights into the mechanisms by which Afa/Dr DAEC induces adhesin-dependent cross talk in the human polarized intestinal epithelial cells by mobilizing brush border-associated GPI-anchored proteins known to function as transducing molecules.

Abstract: Following Mather et al. (1999) we describe a concept for a future space mission called SPECS, a spatial and spectral Michelson interferometer with Hubble Telescope-class angular resolution and sensitivity that operates in the far infrared and submillimeter spectral range. SPECS enables detailed studies of the physical conditions in high-redshift galaxies and has the potential to revolutionize our understanding of galaxy formation and evolution.

We isolated the genetic determinant of AF/R1 pilus production in attaching/effacing Escherichia coli RDEC-1 and identified seven genes required for pilus expression and function. DNA sequence analysis of the structural subunit gene afrA corrected an error in the published sequence and extended homology with the F18 pilus subunit of pig edema E. coli strains. AfrB and AfrC, encoded downstream from AfrA, were required for pilus expression. AfrB was related to the usher protein PefC of Salmonella typhimurium plasmid-encoded fimbriae, and AfrC was related to PefD, a chaperone protein. AfrD and AfrE, encoded downstream from AfrC, were not necessary for the expression of AF/R1 pili but were required for ileal adherence as assayed by ileal brush border aggregation. Thus, the adhesive subunit of the AF/R1 pilus is distinct from the structural subunit, as is the case for Pap pili and type 1 pili. AfrD was related to FedE of the F18 fimbrial operon of the E. coli strain that causes edema disease in pigs. AfrE was a novel protein. AfrR and AfrS are encoded upstream from AfrA, in the opposite orientation. AfrR is related to the AraC family of transcriptional regulators, and AfrR and AfrS interact to function in a novel mode of transcriptional activation of afrA. AF/R1 pili mediate the adherence to Peyer's patch M cells, ileal mucosa, and colonic mucosa in a rabbit model of diarrhea caused by enteropathogenic E. coli. Our observations will facilitate the further study of the phenomena of M-cell adherence.

We studied 10 trimethoprim-resistant (Tmpr) Haemophilus influenzae isolates for which agar dilution MICs were 10 to greater than 200 micrograms/ml. Trimethoprim resistance was transferred from two Tmpr H. influenzae isolates to a Tmps strain by conjugation or transformation. Wild-type Tmpr strains and Tmpr transcipients did not contain detectable plasmid DNA. The trimethoprim resistance gene was cloned into a cosmid vector, and recombinant plasmids were transduced into Escherichia coli. A 0.50-kilobase intragenic probe derived from a 12.9-kilobase fragment which encoded trimethoprim resistance hybridized with whole-cell DNA from Tmps and Tmpr strains. Southern blot analysis of restricted DNA from isogenic Tmps and Tmpr H. influenzae indicated that acquisition of trimethoprim resistance involved a rearrangement or change in nucleotide sequence. Hybridization was not seen with DNA derived from Tmpr E. coli containing dihydrofolate reductase I, II, and III genes or with Tmpr Neisseria meningitidis, Neisseria gonorrhoeae, and Pseudomonas cepacia. Southern hybridization with 12 multiply resistant encapsulated H. influenzae strains confirmed that the trimethoprim resistance gene was chromosomally mediated. Dihydrofolate reductase activity was significantly greater in cell sonicate supernatants of Tmpr strains in comparison with isogenic Tmps recipients. Differences were not found in the trimethoprim inhibition profile of dihydrofolate reductase activity in Tmps and Tmpr strains. We conclude that the mechanism of trimethoprim resistance in H. influenzae is overproduction of chromosomally located dihydrofolate reductase.

The trithorax group gene brahma (brm) encodes an activator of Drosophila homeotic genes that functions as the ATPase subunit of a large protein complex. To determine if BRM physically interacts with other trithorax group proteins, we purified the BRM complex from Drosophila embryos and analyzed its subunit composition. The BRM complex contains at least seven major polypeptides. Surprisingly, the majority of the subunits of the BRM complex are not encoded by trithorax group genes. Furthermore, a screen for enhancers of a dominant-negative brm mutation identified only one trithorax group gene, moira (mor), that appears to be essential for brm function in vivo. Four of the subunits of the BRM complex are related to subunits of the yeast chromatin remodeling complexes SWI/SNF and RSC. The BRM complex is even more highly related to the human BRG1 and hBRM complexes, but lacks the subunit heterogeneity characteristic of these complexes. We present biochemical evidence for the existence of two additional complexes containing trithorax group proteins: a 2 MDa ASH1 complex and a 500 kDa ASH2 complex. These findings suggest that BRM plays a role in chromatin remodeling that is distinct from the function of most other trithorax group proteins.

A genetic determinant related to that encoding the F41 fimbrial adhesin was cloned from a bovine septicemic isolate of Escherichia coli. This determinant was found to mediate expression of morphologically distinct fimbriae in E. coli HB101. The gene encoding the fimbrial subunit protein was identified, and the nucleotide sequence was determined. Homology with the amino-terminal amino acid sequence of CS31A (J. Girardeau, M. Der Vartanian, J. Ollier, and M. Contrepois, Infect. Immun. 56:2180-2188, 1988) was observed, suggesting that this determinant encodes expression of the CS31A fimbrial antigen. The CS31A subunit gene was found to share extensive homology in its signal sequence to the subunit genes encoding the F41 and K88 adhesins. No apparent homology between the mature F41 and CS31A subunits was identified. However, substantial relatedness to the K88 fimbrial subunit was observed. Analysis of the protein products encoded by the CS31A, F41, and K88 determinants in maxicells established that despite extensive genetic similarities between the determinants, each encodes a distinct profile of proteins. E. coli HB101 harboring the cloned CS31A determinant was found to adhere to epithelial cells in a tissue culture assay, suggesting a role for CS31A in adherence. A CS31A-specific DNA hybridization probe detected homologous sequences among enterotoxigenic as well as septicemic E. coli isolates from calves.

We determined the carboxylesterase B electrophoretic profiles of 74 blood isolates of Escherichia coli from patients with urosepsis. Most strains (64%) exhibited the B2 electrophoretic pattern. P fimbrial and hemolysin genetic determinants were present and expressed significantly more often among strains with the B2 than with the B1 electrophoretic pattern. In contrast, aerobactin determinants were significantly more prevalent and more commonly expressed among the B1 strains; this difference was attributable to the presence of plasmid-encoded aerobactin in one-third of the B1 strains (P = 0.02, B1 versus B2). The prevalence and extent of antimicrobial resistance was significantly greater among the B1 strains, and the B1 electrophoretic pattern was more often found in isolates from patients with urinary tract abnormalities. We conclude that the carboxylesterase B electrophoretic pattern differentiates two groups of E. coli isolates from patients with urosepsis: strains with the B1 electrophoretic pattern are associated with urologically impaired hosts, characteristically lack P fimbrial and hemolysin determinants, and often carry a plasmid-encoded aerobactin system (possibly on multiple antimicrobial resistance plasmids), whereas B2 strains more commonly invade noncompromised hosts, express P fimbriae and hemolysin, carry chromosomal aerobactin determinants, and lack antimicrobial resistance.

To assess the role of aerobactin as a virulence factor among uropathogenic Escherichia coli, we determined the prevalence, location, and phenotypic expression of aerobactin determinants among 58 E. coli strains causing bacteremic urinary tract infections. We correlated the presence of the aerobactin system with antimicrobial-agent resistance, the presence and phenotypic expression of other uropathogenic virulence factor determinants (P fimbriae, hemolysin, and type 1 fimbriae), and characteristics of patients. Colony and Southern hybridization of total and plasmid DNA with DNA probes for each virulence factor showed that aerobactin determinants were present in 78% of the strains and were plasmid associated in 21%, whereas P fimbria, hemolysin, and type 1 fimbria determinants were present in 74, 43, and 98% of the strains, respectively, and were always chromosomal. Chromosomal aerobactin, P fimbria, and hemolysin determinants occurred together on the chromosome more often in strains from patients without predisposing urological or medical conditions (P = 0.04). Strains with plasmid-encoded aerobactin lacked determinants for P fimbriae (P = 0.004) and hemolysin (P = 0.0004), were resistant to multiple antimicrobial agents (P = 0.0001), and were found only in compromised patients. Mating experiments demonstrated that some aerobactin plasmids also encoded antimicrobial-agent resistance. These findings suggest that the determinants for aerobactin, P fimbriae, and hemolysin are conserved on the chromosome of the antimicrobial-agent-susceptible uropathogenic strains of E. coli which invade noncompromised patients. In contrast, these chromosomal virulence factors are often absent from E. coli strains causing urosepsis in compromised hosts; these strains may acquire plasmid aerobactin in conjunction with antimicrobial-agent resistance genes.

Using data obtained by the DIRBE instrument on the COBEspacecraft, we present the mean 3.5-240 ?m spectrum of high-latitude dust. Combined with a spectrum obtained by the FIRAS instrument, these data represent the most comprehensive wavelength coverage of dust in the diffuse interstellar medium, spanning the 3.5-1000 ?m wavelength regime. At wavelengths shorter than ~60 ?m the spectrum shows an excess of emission over that expected from dust heated by the local interstellar radiation field and radiating at an equilibrium temperature. The DIRBE data thus extend the observations of this excess, first detected by the IRASsatellite at 25 and 12 ?m, to shorter wavelengths. The excess emission arises from very small dust particles undergoing temperature fluctuations. However, the 3.5-4.9 ?m intensity ratio cannotbe reproduced by very small silicate or graphite grains. The DIRBE data strongly suggest that the 3.5-12 ?m emission is produced by carriers of the ubiquitous 3.3, 6.2, 7.7, 8.6, and 11.3 ?m solid state emission features that have been detected in a wide variety of astrophysical objects. The carriers of these features have been widely identified with polycyclic aromatic hydrocarbons (PAHs).

The gene encoding heat-stable toxin II (STII) was cloned into an Escherichia coli K-12 strain, and its nucleotide sequence was determined. The deduced amino acid sequence indicates that STII is synthesized within the cell as a 71-amino-acid protein and that neither the DNA nor amino acid sequence bears any similarity to that of heat-stable toxin I. A DNA fragment containing the STII gene was used to probe enterotoxigenic E. coli clinical isolates with various toxin phenotypes and was shown to be useful in detecting all STII and only STII producers.