Morphogenesis of the Bacillus Anthracis Spore

With the ability to shut down metabolism, survive exposure to high degrees of heat, ultra-violet and ionizing radiation, digestive enzymes, and antimicrobials, the bacterial spore is one of the most-resistant forms of life on earth. Although most spores are harmless, several species\u27 spores cause serious diseases such as tetanus, anthrax, gas gangrene, botulism, and diarrhea. Spore-forming bacteria differentiate into spores in response to stresses (especially starvation) in a multi-stage developmental pathway involving the coordinated expression of hundreds of genes and the formation of specialized protective organelles which surround and protect the spore during dormancy. The Bacillus anthracis spore (the causative agent of anthrax) has three of these protective structures: a specialized peptidoglycan called the cortex, a proteinaceous coat and (flexible) exosporium, the latter of which is studded with collagen-like fibers made up of both proteins and glycoproteins. About 80 proteins make up the coat and exosporium. Only about nine or ten of these proteins control the deposition and assembly of all the others into these highly-organized organelles. These so-called morphogenetic proteins are highly conserved and were first identified in the model spore forming organism Bacillus subtilis where they are responsible for organizing the assembly of the coat. To better understand the role that these proteins play in forming the unique architecture of the coat and exosporium in B. anthracis my colleagues and I disrupted five homologues of morphogenetic protein genes and analyzed their role in forming spore structures. These analyses suggest that morphogenetic proteins responsible for the formation of the outer-most structures evolve to form novel surface architectures, possibly allowing each species\u27 spore to take on new functions, and may allow them to occupy novel environmental niches

BATSE Observations of Gamma-Ray Burst Spectra. IV. Time-Resolved High-Energy Spectroscopy

We report on the temporal behavior of the high-energy power law continuum component of gamma-ray burst spectra with data obtained by the Burst and Transient Source Experiment. We have selected 126 high fluence and high flux bursts from the beginning of the mission up until the present. Much of the data were obtained with the Large Area Detectors, which have nearly all-sky coverage, excellent sensitivity over two decades of energy and moderate energy resolution, ideal for continuum spectra studies of a large sample of bursts at high time resolution. At least 8 spectra from each burst were fitted with a spectral form that consisted of a low-energy power law, a spectral break at middle energies and a high-energy continuum. In most bursts (122), the high-energy continuum was consistent with a power law. The evolution of the fitted high-energy power-law index over the selected spectra for each burst is inconsistent with a constant for 34% of the total sample. The sample distribution of the average value for the index from each burst is fairly narrow, centered on -2.12. A linear trend in time is ruled out for only 20% of the bursts, with hard-to-soft evolution dominating the sample (100 events). The distribution for the total change in the power-law index over the duration of a burst peaks at the value -0.37, and is characterized by a median absolute deviation of 0.39, arguing that a single physical process is involved. We present analyses of the correlation of the power-law index with time, burst intensity and low-energy time evolution. In general, we confirm the general hard-to-soft spectral evolution observed in the low-energy component of the continuum, while presenting evidence that this evolution is different in nature from that of the rest of the continuum.Comment: 30 pages, with 2 tables and 9 figures To appear in The Astrophysical Journal, April 1, 199

Characterization of a Bacillus anthracis spore coat-surface protein that influences coat-surface morphology

Bacterial spores are encased in a multilayered proteinaceous shell, called the coat. In many Bacillus spp., the coat protects against environmental assault and facilitates germination. In Bacillus anthracis , the spore is the etiological agent of anthrax, and the functions of the coat likely contribute to virulence. Here, we characterize a B. anthracis spore protein, called CotΒ, which is encoded only in the genomes of the Bacillus cereus group. We found that CotΒ is synthesized specifically during sporulation and is assembled onto the spore coat surface. Our analysis of a cotΒ null mutant in the Sterne strain reveals that CotΒ has a role in determining coat-surface morphology but does not detectably affect germination. In the fully virulent Ames strain, a cotΒ null mutation has no effect on virulence in a murine model of B. anthracis infection.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72138/1/j.1574-6968.2008.01380.x.pd

First-year Results of Broadband Spectroscopy of the Brightest Fermi-GBM Gamma-Ray Bursts

We present here our results of the temporal and spectral analysis of a sample of 52 bright and hard gamma-ray bursts (GRBs) observed with the Fermi Gamma-ray Burst Monitor (GBM) during its first year of operation (July 2008-July 2009). Our sample was selected from a total of 253 GBM GRBs based on each event peak count rate measured between 0.2 and 40MeV. The final sample comprised 34 long and 18 short GRBs. These numbers show that the GBM sample contains a much larger fraction of short GRBs, than the CGRO/BATSE data set, which we explain as the result of our (different) selection criteria and the improved GBM trigger algorithms, which favor collection of short, bright GRBs over BATSE. A first by-product of our selection methodology is the determination of a detection threshold from the GBM data alone, above which GRBs most likely will be detected in the MeV/GeV range with the Large Area Telescope (LAT) onboard Fermi. This predictor will be very useful for future multiwavelength GRB follow ups with ground and space based observatories. Further we have estimated the burst durations up to 10MeV and for the first time expanded the duration-energy relationship in the GRB light curves to high energies. We confirm that GRB durations decline with energy as a power law with index approximately -0.4, as was found earlier with the BATSE data and we also notice evidence of a possible cutoff or break at higher energies. Finally, we performed time-integrated spectral analysis of all 52 bursts and compared their spectral parameters with those obtained with the larger data sample of the BATSE data. We find that the two parameter data sets are similar and confirm that short GRBs are in general harder than longer ones.Comment: 40 pages, 11 figures, 3 tables, Submitted to Ap

The Third BATSE Gamma-Ray Burst Catalog

The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) has triggered on 1122 cosmic gamma-ray bursts between 1991 April 19 and 1994 September 19. These events constitute the Third BATSE (3B) burst catalog. This catalog includes the events previously reported in the 2B catalog, which covered the time interval 1991 April 19 to 1993 March 9. We present tables of the burst occurrence times, locations, peak fluxes, fluences, and durations. In general, results from previous BATSE catalogs are confirmed here with greater statistical significance. The angular distribution is consistent with isotropy. The mean galactic dipole and quadrupole moments are within 0.6 a and 0.3 a, respectively, of the values expected for isotropy. The intensity distribution is not consistent with a homogeneous distribution of burst sources, with V/V(sub max) = 0.33 +/- 0.01. The duration distribution (T(sub 90)) exhibits bimodality, with peaks at approx. 0.5 and approx. 30 s. There is no compelling evidence for burst repetition, but only weak limits can be placed on the repetition rate

Here Comes Grosz

Program for the eighth annual RISD Cabaret held in Cellar at the top of the Waterman Building. Publicity, posters, cartoons and program designed by Yoon Cho, Yu-Kyung Chung,Arther Jones, Scott King, Richard Lloyd and Polly Spencer.https://digitalcommons.risd.edu/liberalarts_cabaret_programs/1007/thumbnail.jp

A New Class of Welfare Maximizing Stable Sharing Rules for Partition Function Games with Externalities

nrpages: 26status: publishe