Yersinia enterocolitica is a heterogeneous group of organisms with more than 50 serotypes and several biotypes. Only a few of these serotypes cause gastrointestinal disease in otherwise healthy hosts; these serotypes are the pathogenic serotypes. Although Y. enterocolitica requires a high-molecular-weight plasmid to cause disease, chromosome-encoded determinants are required for the full expression of virulence. The ability of Yersinia spp. to invade eucaryotic cells is thought to be a virulence factor, because nonpathogenic serotypes are noninvasive in animals and in tissue culture cell models. Current evidence indicates that invasion ability is chromosome encoded. We recently reported cloning two loci, inv and ail, from Y. enterocolitica 08 strain 8081c that allow Escherichia coli to invade tissue culture cells. We investigated the link between invasion in an in vitro tissue culture invasion (TCI) model and hybridization to probes derived from the two invasion loci, inv and ail. We examined 177 Yersinia strains. Strains of serotypes and species associated with disease were TCI+, whereas strains of serotypes and species not associated with disease were TCI-. Only TCI+ strains had DNA homologous to probes derived from all. All strains (TCI+ and TCI-) had DNA homologous to probes derived from inv, but there were certain restriction fragment-linked polymorphisms that were associated primarily with TCI+ strains. These observations held true for strains epidemiologically associated with disease. Both the inv and ail loci were found to be clearly located on the chromosome. No other genera, including other invasive organisms, had DNA homologous to inv or ail. These data support the hypothesis that the all locus encodes a Y. enterocolitica invasion factor that may be involved in pathogenesis.

Translation initiation factor IF3 is an essential bacterial protein, consisting of two domains (IF3C and IF3N) separated by a linker, which interferes with ribosomal subunit association, promotes codon-anticodon interaction in the P site, and ensures translation initiation fidelity. Using time-resolved chemical probing, we followed the dynamic binding path of IF3 on the 30S subunit and its release upon 30S-50S association. During binding, IF3 first contacts the platform (near G700) of the 30S subunit with the C domain and then the P-decoding region (near A790) with its N domain. At equilibrium, attained within less than a second, both sites are protected, but before reaching binding equilibrium, IF3 causes additional transient perturbations of both the platform edge and the solvent side of the subunit. Upon 30S-50S association, IF3 dissociates concomitantly with the establishment of the 30S-50S bridges, following the reverse path of its binding with the IF3N-A790 interaction being lost before the IF3C-G700 interaction.

The use of a DNA-based identification system (DNA barcoding) founded on the mitochondrial gene cytochrome c oxidase subunit I (COI) was investigated for updating the U.S. Food and Drug Administration Regulatory Fish Encyclopedia (RFE; http://www.cfsan.fda.gov/-frf/rfe0.html). The RFE is a compilation of data used to identify fish species. It was compiled to help regulators identify species substitution that could result in potential adverse health consequences or could be a source of economic fraud. For each of many aquatic species commonly sold in the United States, the RFE includes high-resolution photographs of whole fish and their marketed product forms and species-specific biochemical patterns for authenticated fish species. These patterns currently include data from isoelectric focusing studies. In this article, we describe the generation of DNA barcodes for 172 individual authenticated fish representing 72 species from 27 families contained in the RFE. These barcode sequences can be used as an additional identification resource. In a blind study, 60 unknown fish muscle samples were barcoded, and the results were compared with the RFE barcode reference library. All 60 samples were correctly identified to species based on the barcoding data. Our study indicates that DNA barcoding can be a powerful tool for species identification and has broad potential applications.

Monomer chromatin nu bodies (nu1) from chicken erythrocyte nuclei were exposed to 0-10 M urea plus 0.2 mM EDTA (PH 7). Alterations in nu1 conformation were examined using hydrodynamic methods (i.e., S, eta, and (formula: see text)), thermal denaturation, circular dichroism, reactivity of histone thiol groups to N-ethyl maleimide, and electron microscopy. The two domains of a nu body (i.e., the DNA-rich shell and the protein-rich core) aeared to respond differently to the destabilizing effects of increasing urea; DNA conformation and stability exhibited noncooperative changes; the core protein structure revealed cooperative destabilization between 4 and 7 M urea. Companion studies on the conformation of the inner histone "heterotypic tetramer" also revealed cooperative destabilization with increasing urea concentration.

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The Food Safety and Inspection Service (FSIS) conducted microbiological testing programs for ready-to-eat (RTE) meat and poultry products produced at approximately 1,800 federally inspected establishments. All samples were collected at production facilities and not at retail. We report results here for the years 1990 through 1999. Prevalence data for Salmonella, Listeria monocytogenes, Escherichia coli O157:H7, or staphylococcal enterotoxins in nine different categories of RTE meat and poultry products are presented and discussed. The prevalence data have certain limitations that restrict statistical inferences, because these RTE product-testing programs are strictly regulatory in nature and not statistically designed. The cumulative 10-year Salmonella prevalences were as follows: jerky, 0.31%; cooked, uncured poultry products, 0.10%; large-diameter cooked sausages, 0.07%; small-diameter cooked sausages, 0.20%; cooked beef, roast beef, and cooked corned beef, 0.22%; salads, spreads, and pâtés, 0.05%; and sliced ham and luncheon meat, 0.22%. The cumulative 3-year Salmonella prevalence for dry and semidry fermented sausages was 1.43%. The cumulative 10-year L. monocytogenes prevalences were as follows: jerky, 0.52%; cooked, uncured poultry products, 2.12%; large-diameter cooked sausages, 1.31%; small-diameter cooked sausages, 3.56%; cooked beef, roast beef, and cooked corned beef, 3.09%; salads, spreads, and pâtés, 3.03%; and sliced ham and luncheon meat, 5.16%. The cumulative 3-year L. monocytogenes prevalence for dry and semidry fermented sausages was 3.25%. None of the RTE products tested for E. coli O157:H7 or staphylococcal enterotoxins was positive. Although FSIS and the industry have made progress in reducing pathogens in these products, additional efforts are ongoing to continually improve the safety of all RTE meat and poultry products manufactured in federally inspected establishments in the United States.

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DNAs extracted from Vibrio vulnificus seeded into oyster homogenates were evaluated as templates for the polymerase chain reaction. Several extraction procedures were examined, and it was determined that DNA recovered from cells lysed by guanidine isothiocyanate, extracted with chloroform, and precipitated with ethanol was most suitable for use as a polymerase chain reaction template. The region targeted was a 519-bp portion of the cytotoxin-hemolysin gene of V. vulnificus. This region was amplified only when DNA from this species was present in the homogenate. V. vulnificus seeded into oyster homogenates at an initial level of 102 CFU/g of oyster meat was consistently observed after 24 h of incubation in alkaline peptone water.