bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced Thermal Resistance of Salmonella in Whole Muscle Compared to Ground Beef
Authors: Orta‐Ramirez Alicia , Marks Bradley P. , Warsow Christopher R. , Booren Alden M. , Ryser Elliot T. 
Published: October 2006

ABSTRACTIrradiated beef (whole ‐muscle and ground product with identical fat, protein, and moisture composition) was exposed to a Salmonella‐ inoculated marinade and heated in brass tubes in a water bath at 55 °C, 60 °C, and 62.5 °C. The bacterial load and thermal lag time were similar (α= 0.05) for both whole and ground muscle; therefore, all samples had equivalent composition, inoculation levels, and thermal histories. Assuming 1st‐order kinetics, the inactivation rate constants (k values) in whole muscle were 50% lower than those in ground product at each temperature (P = 0.0001), and Arrhenius‐type models described the temperature dependency of k (R2 > 0.95). Because thermal processing regulations are generally based on ground product studies, thermal process validations for meat and poultry products may need to consider the physical state (whole ‐muscle versus ground) of the product being manufactured.
Heat shock 70 gene is differentially expressed in Histoplasma capsulatum strains with different levels of thermotolerance and pathogenicity
Authors: Caruso M. , Sacco M. , Medoff G. , Maresca B. 
Published: October 2006

SummaryThe response to heat shock has been examined In two strains of the dimorphic pathogenic fungus Histoplasma capsulatum, which differ considerably in thermotolerance and pathogenicity. The gene for the 70 kD heat shock protein (hsp70) was isolated using a Drosophila hsp70 gene to screen a cosmid library of the DNA from the temperature‐sensitive Downs strain (low level of thermotolerance for mice). Using the cloned gene as a probe, we have measured the transcription of the endogenous hsp70 gene at 25°C and in response to temperature shift to 34°, 37° and 40°C, temperatures that trigger the mycelial to yeast phase transition in this fungus. The gene is constitutively transcribed at low levels, both in the yeast and the mycelial stages. Synthesis of hsp70 mRNA was transiently increased 1 to 3 h after the temperature shifts. By Northern analysis, peak levels of transcription were shown to occur at 34°C in the Downs strain and at 37°C in the more pathogenic G222B strain. Our results are consistent with reports in which it has been shown that heat shock gene expression is part of temperature adaptation and probably developmental processes. The low levels of transcription of the hsp70 gene in the Downs strain at 37°C correlate with its greater temperature sensitivity and low level of virulence.
Nucleotide sequence, regulation and functional analysis of the papC gene required for cell surface localization of Pap pili of uropathogenic Escherichia coli
Authors: Norgren. M. , Bága. M. , Tennent J.M. , Normark S. 
Published: October 2006

SummaryThe papC gene of uropathogenic Escherichia coli is required for the formation of digalactoside‐binding Pap pili. papC forms part of an operon wherein the regulatory gene papS, the major pilin gene papA, a minor pilin‐like gene papH, and papC are co‐transcribed. Furthermore, the extent of PapC synthesis was found to affect the number of pili expressed on the cell surface. The DNA sequence of the papC gene is presented and its deduced amino acid sequence is compared to that of the FaeD protein encoded by the K88 pili gene cluster. The PapC protein was localized to the E. coli outer membrane where it may form a trans‐membrane channel through which pilin subunits are surface localized.
An E. coli promoter induced by the cessation of growth
Authors: Connell N. , Han Z. , Moreno F. , Kolter R. 
Published: October 2006

SummaryThe production of the bacterial DNA replication inhibitor Microcin B17 is induced as cultures enter stationary phase. Using SI nuclease protection assays we have shown that this induction is the result of increased levels of transcription initiation from a promoter located upstream from mcbA, the structural gene for Microcin B17. Upstream from the start site of transcription there is a rather typical ‐35 region. However, there is no good homology to the consensus –10 region. While most of the cell's transcription is shut off as a result of the cessation of growth, transcription from the mcbA promoter continues for several hours in stationary phase. A single‐copy gene fusion between mcbA and lacZ was used to monitor the response of the promoter to different nutritional conditions and in different host backgrounds altered in metabolic regulatory loci. Starvation for nitrogen, phosphate or carbon sources all induced transcription from the promoter. Levels of transcription were reduced in ompR backgrounds, in contrast, mutations in other global regulatory loci, fnr, relA and cya had little or no effect.
pWW174: A large plasmid from Acinetobacter calcoaceticus encoding benzene catabolism by the β‐ketoadipate pathway
Authors: Winstanley C. , Taylor S. C. , Williams P. A. 
Published: October 2006

Summary Acinetobacter calcoaceticus RJE74 contains a large transmissible catabolic plasmid, pWW174, of about 200 kb, which encodes its ability to grow on benzene (Bzn+). pWW174 was unstable in Acinetobacter hosts and was lost at high frequency in the absence of selection for Bzn*. The catabolic pathway appeared to be via benzene cis‐glycol, catechol and the β‐ketoadipate (ortho) pathway. pWW174 encodes a catechol 1,2‐oxygenase which is significantly more thermolabile than the chromosomally determined enzyme. pWW174 was able to complement all cat mutants (catechol to central metabolites) of A. calcoaceticus ADP1 (BD413) tested. Two regions of the plasmid were cloned, one carrying catA, the gene for catechol 1,2‐oxygenase, and another carrying catBCDE, the subsequent four enzymes of the β‐ketoadipate pathway: these two regions appeared to be separated by at least 10 kbp. Hybridization indicated homology between the plasmid cat genes and the corresponding chromosomal genes of ADPL.
Utilization of a mini‐mu transposon to construct defined mutants in Streptococcus mutans
Authors: Kuramltsu H. K. 
Published: October 2006

SummaryThe gtfB gene coding for glucosyltransferase‐l (GTF‐I) activity previously isolated from Streptococcus mutans GS–5 was insertionally inactivated with the newly constructed transposon MudE in an Escherichia coli background, insertion of MudE into various regions of the gtfB gene led to inactivation of GTF‐I activity. The altered gene was introduced back into S. mutans GS–5 by transformation and produced mutants defective in insoluble glucan synthesis as well as the ability to colonize smooth surfaces in the presence of sucrose. Therefore, the MudE transposon can be utilized to produce specific mutants in oral streptococci as well as in other transformable Gram‐positive bacteria expressing an erythromycin‐resistance marker.
Sensitivity of Escherichia coli to various β‐lactams is determined by the interplay of outer membrane permeability and degradation by periplasmic β‐lactamases: a quantitative predictive treatment
Authors: Nikaido H. , Normark S. 
Published: October 2006

SummaryIn Gram‐negative bacteria, β‐lactam antibiotics must overcome two barriers, the outer membrane and the periplasmic β‐lactamase, before they reach the targets of their action, penicillin‐binding proteins. Although the barrier property of the outer membrane and catalytic property of the β‐lactamases have been studied and their significance in creating β‐lactam resistance emphasized, the interaction between these two barriers has not been treated quantitatively. Such treatment shows that the sensitivity, to a variety of β‐lactams, of the Escherichia coli K‐12 cells containing very different levels of chromosomally coded AmpC β‐lactamase, or a plasmid‐coded TEM‐type β‐lactamase, can be predicted rather accurately from the penetration rate through the outer membrane and the hydrolysis rate in the periplasm. We further propose a new parameter,‘target access Index', which is a quantitative expression of the result of interaction between the two barriers, and reflects the probability of success for the antibiotic to reach the targets.
Activation of the lac Operon of Escherichia coli by a mutant FNR protein
Authors: Spiro S. , Guest J. R. 
Published: October 2006

SummaryThe FNR protein of E. coli is a transcriptional activator required for the expression of genes involved in anaerobic respiratory pathways. Site‐directed mutagenesis was used to alter three amino acids in the recognition helix of the putative DNA‐binding domain of FNR, with the aim of changing its specificity to that of the cyclic AMP receptor protein (CRP). in the presence of the mutant protein (FNR‐215) expression of the lac Operon was activated during anaerobiosis and unaffected by glucose. FNR‐215 did not have a uniform effect on the expression of other cAMP‐CRP‐dependent genes, but the results demonstrate the fundamental similarity between FNR‐ and CRP‐mediated transcriptional activation.
ParD: a new gene coding for a protein required for chromosome partitioning and septum localization in Escherichia coli
Authors: Hussain K. , Begg K. J. , Salmond G. P. C. , Donachie W. D. 
Published: October 2006

SummaryA new gene, parD, has been located at 88.5 min on the genetic map of E. coli. Cells carrying an amber mutation in this gene, together with a temperature‐sensitive suppressor tRNA, are able to grow, synthesize DNA and divide at both 30°C and 42°C. At 42°C, however, they are defective both in the separation of replicated chromosomes and in the placement of septa. Both the amount of DNA and the number of septa per cell mass are normal in cells growing at 42°C: only the localization of the chromosomes and septa are altered. As a result, cells of random sizes are produced at 42°C and the smallest of these contain no DNA.
Molecular cloning and characterization of the beta‐amylase gene from Bacillus circulans
Authors: Siggens K. W. 
Published: October 2006

SummaryA gene encoding the β‐amylase of Bacillus circulans was isolated from a lambda library and sequenced. The structural gene consists of a 1725 bp open reading frame encoding a polypeptide with a predicted molecular wt of 62830 Daltons. Two active forms of the enzyme were found when the gene was expressed In E. coli. The larger 60 kD form was approximately 3 kD larger than the mature β‐amylase secreted from B. circulans, suggesting that processing of this protein is different between the two species. The smaller 49 kD form is also present at a low level in B. circulans and may result from proteolytic cleavage. The enzyme has a temperature optimum of 50°C. Two other genes, one encoding an α‐amylase and one a pullulanase, were also isolated from the lambda library.
Isolation and sequence of the spoOE gene: its role in initiation of sporulation in Bacillus subtills
Authors: Perego M. , Hoch J. A. 
Published: October 2006

SummaryThe pleiotropic stage 0 sporulation focus spoOE was isolated and sequenced. The spo0E gene was found to code for a protein of 9791 molecular weight. Two Spo0E mutations were identified by sequence analysis and were found to give rise to nonsense codons within the gene. The results indicated that it is the lack of the spo0E gene product that is responsible for the sporulation‐defective phenotype. The DNA fragment containing the spo0E locus was inhibitory to sporulation when present on a multicopy plasmid. Since DNA fragments containing only the upstream region of the gene were also inhibitory, this effect was not due to over‐production of the spoOE gene product. Coupling the transcription of the spoOE gene to 3‐galactosidase in an integrative plasmid vector revealed that active transcription of this gene begins at the end of exponential growth and continues through the early part of sporulation. Studies of the regulation of this gene have allowed the generation of a hypothesis to explain the interactions of those five stage 0 genes involved in the activation of sporulation‐specific transcription.
The ParD‐ mutant of Escherichia coli also carries Aam mutation. The complete sequence of gyrA
Authors: Hussain K. , Elliott E. J. , Salmond G. P. C. 
Published: October 2006

SummaryThe phenotype of a recently‐described mutant (OVG), conditionally defective in chromosome partitioning and septal positioning, was originally thought to be due to a new gene (parD) mapping at 88.4 min. We have now shown that, in addition to the parD mutation, OV6 carries a gyrAam mutation and that this mutation is probably responsible for the gross phenotype of the mutant. We have cloned the gyrA gene, identified the GyrA protein, sequenced the gyrA gene and flanking genes, cloned and sequenced the gyrAam, mutation, and identified its truncated product, in addition, we have identified the transcriptional start point of the gyrA gene. The E. coli GyrA protein has extensive homologies with Gyrase proteins of other organisms and weak sequence homologies with some eukaryotic cytoskeletal proteins.
Regulatory circuits controlling transcription of TOL plasmid operon encoding meta‐cleavage pathway for degradation of alkylbenzoates by Pseudomonas
Authors: Ramos J. L. , Mermod N. , Timmis K. N. 
Published: October 2006

SummaryTOL plasmid PWWO of Pseudomonas putida contains two operons that specify a pathway for the degradation of aromatic hydrocarbons. The ‘upper’ operon encodes enzymes for the oxidation of toluene to benzoate and xylenes to toluates, whereas the meta‐cleavage operon specifies the further oxidation of benzoate and toluates. Transcription of the upper pathway operon (s positively regulated by the XylR protein, which is activated by toluene/xylenes and their alcohol catabolic products, in combination with the NtrA protein, a sigma factor. Expression of the meta‐operon is positively controlled by the XylS protein which is activated by meta‐pathway substrates, and is Independent of NtrA protein. Expression of the meta pathway is also Induced by toluene/xylene‐activated XylR protein via a cascade regulatory system in which this protein in combination with NtrA protein stimulates transcription from the xylS gene promoter. Hyper‐production of XylS protein in turn provokes high level expression of the meta‐operon, which is independent of meta‐pathway substrates. The two promoters, which are activated by the XylR and NtrA proteins, the upper pathway promoter and the xylS gene promoter, exhibit three regions of homology centred at –12(5′–TTGCTÃG–3′), –24(5′ ‐TGGCPuT –3) and –45(5′‐TTAAATÃGPuPuGCGPuTc‐3′), with respect to their principal transcription initiation points. The possible physiological significance of activated XylR‐protein‐induced expression of the meta‐operon through amplification of XylS protein levels is considered.
Nucleotide sequencing of the structural gene for colicin N reveals homology between the catalytic, C‐terminal domains of colicins A and N
Authors: Pugsley A. P. 
Published: October 2006

SummaryAn 1800 bp fragment of DNA from a natural ColN plasmid (pCHAP4) encompassing the colicin N structural gene (cna) and its regulatory region was subjected to nucleotide sequencing and deletion analysis. The region of DNA immediately upstream from cna contains two tandemly‐arranged and overlapping potential LexA binding sites (SOS boxes), in line with the previous demonstration that cna expression is repressed by LexA protein. Deletion of the LexA binding site allowed efficient transcription of cna from an upstream lacZ promoter, whereas its presence reduced lacZ‐promoted cna expression to varying extents depending on the proximity of lacZp and the SOS boxes. The molecular weight of colicin N, as deduced from the nucleotide sequence, is 41696, which is ciose to the experimentally determined molecular weight of 39000. Colicin N has a glycine‐rich amino terminus similar to that found in many other colicins. Part of the glycine‐rich domain of colicin N could be replaced by an unrelated sequence devoid of glycine residues without affecting either colicin release or activity. The carboxy‐terminal half of colicin N exhibits significant homology to the C‐terminus of colicin A. The latter colicin forms pores In the cyto‐plasmic membrane of Escherichia coli, thereby depolarizing the membrane and causing cell death. The C‐terminus of colicin A is endowed with this catalytic activity. Although colicin N was previously found to cause lysis of Escherichia coli cells, a more detailed Investigation revealed that it too depolarizes the Escherichia coli cytopiasmic membrane and that lysis is a secondary effect.
Defective Escherichia coli signal peptides function in yeast
Authors: Pines O. , Lunn C. A. , Inouye M. 
Published: October 2006

SummaryTo investigate structural characteristics important for eukaryotic signal peptide function In vivo, a hybrid gene with interchangeable signal peptides was cloned into yeast. The hybrid gene encoded nine residues from the amino terminus of the major Escherichia coli lipoprotein, attached to the amino terminus of the entire mature B. coli β‐lactamase sequence. To this sequence were attached sequences encoding the non‐mutant E. coli lipoprotein signal peptide, or lipoprotein signal peptide mutants lacking an amino‐terminal cationic charge, with shortened hydrophobic core, with altered potential helicity, or with an altered signal‐peptide cleavage site. These signal‐peptide mutants exhibited altered processing and secretion in E. coli. Using the GAL10 promoter, production of all hybrid proteins was induced to constitute 4–5% of the total yeast protein. Hybrid proteins with mutant signal peptides that show altered processing and secretion in E. coli, were processed and translocated to a similar degree as the non‐mutant hybrid protein in yeast (approximately 36% of the total hybrid protein). Both non‐mutant and mutant signal peptides appeared to be removed at the same unique site between cysteine 21 and serine 22. one residue from the E. coli signal peptidase II processing site. The mature lipo‐β‐lactamase was translocated across the cytoplasmic membrane into the yeast periplasm. Thus the protein secretion apparatus in yeast recognizes the lipoprotein signal sequence in vivo but displays a specificity towards altered signal sequences which differs from that of E. coli.
A replication region of the IncHI plasmid, R27, is highly homologous with the RepFIA replicon of F
Authors: Saul D. , Lane D. , Bergquist P. L. 
Published: October 2006

SummaryA region of the IncHl plasmid R27 has been found to share very close nucleotide sequence homology with the RepFIA replicon of F. This region has been located on a 1.6 kb segment of R27 plasmid DNA, and corresponds to ori‐2 and the E gene of F. The IncC repeat sequence region shows reduced homology, with the F repeats being an imperfect subset of a larger repeated sequence found in R27. The E gene homologue of R27 is able to initiate replication from the F ori‐2 sequence and to repress the E gene promoter of F. The results are consistent with the observed incompatibility behaviour of R27, and have a bearing on the specificity of interaction of E protein with its DNA‐binding sites.
Cloned structural genes for the osmotically regulated binding‐protein‐dependent glycine betaine transport system (ProU) of Escherichia coli K‐12
Authors: Faatz E. , Middendorf A. , Bremer E. 
Published: October 2006

SummaryThe proU locus of Escherichia coli encodes a high‐affinity, binding‐protein‐dependent transport system (ProU) for the osmoprotectant glycine betaine. We cloned this locus into both low‐copy‐number lambda vectors and multicopy plasmids and demonstrated that these clones restore osmotically controlled synthesis of the periplasmic glycine betaine binding protein (GBBP) and the transport of glycine betaine in a δ(proU) strain. These clones allowed us to investigate the influence of osmolarity on ProU transport activity independent of the osmotically controlled expression of proU. ProU activity was strongly stimulated by a moderate increase in osmolarity and was partially inhibited by high osmolarity. This activity profile differs from the profile of the osmotically regulated proU expression. The proU locus is organized in an operon and the position of the structural gene (proV) for GBBP is defined using a minicell system. We determined that at least three proteins (in addition to GBBP) are encoded by the proU locus. We also investigated the permeation of glycine betaine across the outer membrane. At low substrate concentration (0.7 μM), permeation of glycine betaine was entirely dependent on the OmpF and OmpC porins.
Amino acid sequence homology between the enzymic domains of diphtheria toxin and Pseudomonas aeruginosa exotoxin A
Authors: Carroll S. F. , Collier R. J. 
Published: October 2006

SummaryDespite similarities In their enzymic properties, diphtheria toxin (DT) and exotoxin A (ETA) of Pseudomonas aeruginosa have major differences in structure and action: consequently, the question of possible evolutionary relatedness of these two proteins remains unanswered. Here we report the existence of significant amino acid sequence homology between the enzymic domain of DT and that of ETA. Iajor segments of sequence may be aligned with high percentages of identity and of conservative substitutions. The homologous stretches in ETA form much of the active‐site cleft in the X‐ray crystallographic structure. This evidence implies that these domains, at least, have diverged from a common ancestral protein and that active‐site residues have been strongly conserved.
Regulation of components of the Pseudomonas aeruginosa phosphate‐starvation‐inducible regulon in Escherichia coli
Authors: Siehnel R. J. , Worobec E. A. , Hancock R. E. W. 
Published: October 2006

SummaryPlasmids pPBP and pRS‐XP containing the cloned genes for the Pseudomonas aeruginosa phosphate‐starvation‐ inducible periplasmic phosphate‐binding protein and outer membrane porin P (oprP), respectively, were introduced into various Escherichia coli Pho‐regulon regulatory mutants. Using Western immunoblots and specific antisera, the production of both gene products was observed to be under the control of regulatory elements of the E. coli Pho regulon. Sequencing of the region upstream of the translational start site of the oprP gene revealed a ‘Pho box’ with strong homology to the E. coli consensus ‘Pho box’, the putative binding site of the PhoB activator. Since P. aeruginosa and E. coli belong to different families and have quite different GC contents, these data suggest strong evolutionary conservation of regulatory elements of the Pho regulon.
Covalent modification of ribulose 1,5‐bisphosphate carboxylase/oxygenase in Rhodomicrobium vannielii
Authors: Mann N. H. , Turner A. M. 
Published: October 2006

SummaryThe most abundant phosphorus‐containing polypeptide in the purple non‐sulphur bacterium Rhodomicrobium vannielli has been identified by a combination of immunoprecipitation and sucrose density gradient centrifugation as the large subunit of ribulose 1,5 bisphosphate carboxylase/oxygenase. The covalent modification of the large subunit involves the phosphorylation of one or more tyrosine residues and appears to occur prior to assembly of the large subunit into the mature enzyme. In addition, the phosphorylated form of the large subunit was found to exist in at least two distinct protein complexes of M, 410000 and 440000.
Inactivation of the FNR protein of Escherichia coli by targeted mutagenesis in the N‐terminal region
Authors: Spiro S. , Guest J. R. 
Published: October 2006

SummaryThe FNR protein of Escherichia coli is a regulatory protein that activates the transcription of its target genes in response to oxygen limitation. Site‐directed mutagenesis was used to show that a 28‐residue N‐terminal segment containing three cysteines is essential for normal FNR function. The cysteine residue which is centrally located in the three‐cysteine cluster (Cys‐Ala‐Ile‐His‐Cys‐Gln‐Asp‐Cys) was also shown to be essential for FNR activity. Possible mechanisms by which this cysteine residue might function in the response of FNR to anaerobiosis are discussed.