"Gastrospirillum hominis" is an uncultured gastric spiral bacterium that has recently been shown by 16S rDNA sequence analysis to be a newly recognized species of Helicobacter that infects humans, and it has been provisionally designated "Helicobacter heilmannii." We used PCR to directly amplify the urease structural genes of "H. heilmannii" from infected gastric tissue. DNA sequence analysis identified two open reading frames, ureA and ureB, which code for polypeptides with predicted molecular weights of 25,729 and 61,831, respectively. The urease subunit genes from "H. heilmannii" were cloned and expressed in Escherichia coli. Western blot (immunoblot) analysis showed that antiserum directed against the ureA and ureB gene products from H. pylori was cross-reactive with the corresponding polypeptides from "H. heilmannii." Analysis of the derived amino acid sequences of "H. heilmannii" UreA and UreB demonstrated that "H. heilmannii" urease is more highly related to the urease from H. felis (found in the stomachs of cats and dogs) than to the urease from H. pylori. These data are consistent with 16S rDNA sequence analysis and suggest that "H. heilmannii" is phylogenetically most closely related to H. felis.

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When an incident particle collides with an electron or nucleus in an insulating crystal, the recoil kinetic energy is converted rapidly into a burst of low-energy phonons. If the crystal is very pure and free of defects, and if it is very cold (T-O.IK), the phonons will propagate ballistically for distances of several centimeters. We report on experiments with two types of superconducting phonon sensors being considered for use on a new kind of particle detector, called a Silicon Crystal Acoustic Detector (SiCAD), which reads out phonons generated by particle scattering events. Jn~dUCtiOrlOne of the most fascinating mysteries confronting modern physics is the nature of "dark matter", which originally was postulated to explain the formation, distribution, and motion of the galaxies. The extent to which it is present ultimately will decide the fate of the cosmos, for it determines whether or not the universe is open, closed, or flat. A possible explanation for the invisible matter is that the various neutrinos have minute masses (-10 eV). Alternative but more exotic theories from elementary particle physics suggest that space is permeated by weakl interacting massive the particles --neutrinos or WIMPS --interact so weakly that they virtually elude detection by conventional techniques. Thus identification of dark matter candidates depends upon the development of improved particle detectors having lower thresholds of sensitivity and significantly larger cross sections. Crvstal Acoustic DetectorsTo meet this challenge, B. Cabrera, C.J. Martoff, and B. Neuhauser have proposed a novel particle detector, called a Silicon Crystal Acoustic Detector (SiCAD), consisting of a 1 kg cube of single crystal silicon covered with arrays of phonon sensors [l]. About 70% of the energy deposited in the crystal during a particle scattering event is converted to very short wavelength phonons generated when electron-hole excitations quickly decay to the band edge. In approximately 10 nanoseconds these phonons relax to low frequency phonons roughly characterized by a 10 Kelvin thermal distribution [ 2 ] . This spectrum is relatively stable because the phonon decay rate varies nearly as the fifth power of the frequency and because the wavelengths are long enough to be in the dispersionless regime. If the crystal is very pure and defect-free, and if it is cooled to a temperature on the order of 0.1 Kelvin so that there are few thermally generated phonons, then scattering is negligible. This so-called "ballistic" mode of propagation allows the burst of phonons from the scattering event to travel to the faces of the crystal without degradation. We are seeking a sensor which responds rapidly and efficiently to these low energy phonons.Because of crystal anisotropies, the phonon group velocity vector vg in general is not parallel to the wave vector k. As a result, the phonon wavefronts emanating from a pointlike energy deposition are not spherical but are in fact distorted as shown in Figure 1. This causes the acoustic energy to be directed int...