bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards a molecular definition of worker sterility: differential gene expression and reproductive plasticity in honey bees
Authors: Thompson G. J. , Kucharski R. , Maleszka R. , Oldroyd B. P. 
Published: October 2006

AbstractWe show that differences in the reproductive development of honey bee workers are associated with locus‐specific changes to abundance of messenger RNA. Using a cross‐fostering field experiment to control for differences related to age and environment, we compared the gene expression profiles of functionally sterile workers (wild‐type) and those from a mutant strain in which workers are reproductively active (anarchist). Among the set of three genes that are significantly differentially expressed are two major royal jelly proteins that are up‐regulated in wild‐type heads. This discovery is consistent with sterile workers synthesizing royal jelly as food for developing brood. Likewise, the relative underexpression of these two royal jellies in anarchist workers is consistent with these workers’ characteristic avoidance of alloparental behaviour, in favour of selfish egg‐laying. Overall, there is a trend for the most differentially expressed genes to be up‐regulated in wild‐type workers. This pattern suggests that functional sterility in honey bee workers may generally involve the expression of a suite of genes that effectively ‘switch’ ovaries off, and that selfish reproduction in honey bee workers, though rare, is the default developmental pathway that results when ovary activation is not suppressed.
Rheological and Morphological Comparison of Thermal and Hydrostatic Pressure‐Induced Filamentous Myosin Gels
Authors: Iwasaki Tomohito , Washio Masahiro , Yamamoto Katsuhiro , Nakamura Kunio 
Published: October 2006

ABSTRACTThe structure and rheological properties of heat‐ and pressure‐induced myosin filament gels were investigated. The apparent elasticity of heat‐induced gel peaked at 55 °C (4.35 ± 0.57 kPa), whereas that of pressure‐induced gel increased with elevating pressure, and the gel formed at 500 MPa had a value of 4.79 ± 0.25 kPa. All pressure‐ and heat‐induced gels showed similar internal structure, namely, the gels were composed of a fine‐strand network. The detailed structures of the strands induced by pressure‐ and heat‐treatment of myosin filaments were observed using an atomic force microscope. The structural differences among the strands were not observed, whereas the elasticity of the strands measured by atomic force microscope revealed differences among the strands formed with varying heating temperature and pressure. The elasticities of the heat‐induced strands were 1.19 ± 0.09 MPa, 10.24 ± 1.16 MPa, and 3.09 ± 0.25 MPa at 40 °C, 55 °C, and 70 °C, respectively. On the other hand, the elasticity of the pressure‐induced strand increased with elevating pressure. The elasticity values were 1.24 ± 0.09 MPa, 2.32 ± 0.17 MPa, and 9.80 ± 0.84 MPa at pressures of 150, 300, and 500 MPa, respectively. Because the changes in the elasticity of the whole gel corresponded to those of the strand, it is concluded that the rheological properties of the constituting strands determine that of myosin filamentous gel.
A Novel Technique for Ice Crystal Visualization in Frozen Solids Using X‐Ray Micro‐Computed Tomography
Authors: Mousavi Reza , Miri Taghi , Cox P.W. , Fryer Peter J. 
Published: October 2006

ABSTRACTA novel technique, using an X‐ray micro‐computed tomography system (X‐ray micro‐CT system) has been developed for visualization of the two‐ (2‐D) and three‐dimensional (3‐D) ice crystal structures formed during freezing. The system reconstructs all 3‐D images based on a set of 2‐D images obtained by multiple slicing of an X‐ray shadow image. This study demonstrates the capability of the technique to characterize the ice crystal microstructure of mycoprotein products after freezing. Results are presented for the 2‐D ice crystals formed within mycoprotein frozen at different rates. The method requires freeze‐drying of the sample to remove frozen water before scanning to indicate ice crystal and internal structure of the material at a depth of 1 cm. The dendrite spacing of ice crystals has been related to the freezing conditions of the material.
Effects of Calcium Ascorbate and Ionizing Radiation on the Survival of Listeria monocytogenes and Product Quality of Fresh‐cut ‘Gala’ Apples
Authors: Fan Xuetong , Sokorai Kimberly J. B. , Sommers Christopher H. , Niemira Brendan A. , Mattheis James P. 
Published: October 2006

ABSTRACT:The interactive effects of calcium ascorbate (CaA) and ionizing radiation on viability of Listeria monocytogenes inoculated in solutions and on ‘Gala’ apple slices were investigated. The D10 values (radiation doses that inactivate 90% of bacterial population) for L. monocytogenes inoculated in water, 3.5%, and 7.0% CaA solutions were 0.32, 0.61, and 0.58 kGy, respectively. The D10 values of the pathogen on the surface of apple slices treated with water, 3.5%, and 7.0% CaA were 0.24, 0.32, and 0.32 kGy, respectively. To determine the impact of CaA and irradiation on quality of apple slices, apple slices treated with 0%, 3.5%, and 7.0% CaA were exposed to 1.6 kGy gamma radiation (a dose that produced a 5‐log reduction of L. monocytogenes) and stored under modified atmosphere at 4 °C for 14 d. CaA at levels of both 3.5% and 7.0% prevented the browning of the apple slices. The apple aroma intensity, however, decreased as the concentration of CaA increased. Irradiation at 1.6 kGy did not significantly affect color, soluble solid content, titratable acidity, or apple aroma intensity. The only negative effect of irradiation on apple slices appeared to be a loss of firmness. Our results suggest that CaA, used as an antibrowning agent, protected L. monocytogenes from radiation both in solution and on apple slices, but radiation at doses sufficient to inactivate 5‐log of the bacterium did not significantly influence product quality attributes except for the loss in firmness.
Survival Analysis Applied to Sensory Shelf Life of Yogurts–I: Argentine Formulations
Authors: Curia Ana , Aguerrido Martin , Langohr Klaus , HOUGH GUILLERMO 
Published: October 2006

ABSTRACT::Sensory shelf lives of Argentine commercial stirred yogurts of different compositions stored at 10 °C were studied. Variations were as follows: fat‐free and whole‐fat, and vanilla and strawberry flavors. Yogurts were tested between 0 and 84 d of storage by consumers who expressed their acceptance or rejection of each sample; yogurts also were measured overall, as well as their attribute acceptability, with a hedonic scale. Survival analysis statistics were used to estimate shelf lives. Considering 25% of consumers rejecting the product, shelf lives were between 28 and 41 d; thus, a unique shelf life for this product does not seem reasonable. A log‐linear model and a direct quantile comparison formula were introduced to analyze the effect of formulation on rejection time distributions and shelf life values, respectively. Overall, fat‐free yogurts had lower shelf lives than whole‐fat yogurts.
Consumer Acceptability of Muffins with Flaxseed (Linum usitatissimum)
Authors: Ramcharitar Anisa , Badrie Neela , Mattfeldt‐Beman Mildred , Matsuo Hisako , Ridley Charlotte 
Published: October 2006

ABSTRACTFlaxseed has recently gained attention as a functional food. The effect of adding flaxseed (7.3%, 11.6%, and 15.5%) to muffins on consumer acceptability was evaluated by a focus group, hedonic scoring, and food action rating scale (FACT). The majority of consumers (82.6%, P < 0.001) rated the control muffin (0 % flaxseed) higher than the flax muffin for appearance, color, flavor, texture, overall acceptability, and food acceptance. Flaxseed muffin (11.6%) was “neither liked nor disliked” to “liked slightly” in overall acceptability. This may have been accounted for by the observation that many persons aged 18 to 25 y did not think they needed to consume “health foods”. This “indifferent” and in some cases “negative” attitude toward the flax muffins, which they considered a “health food”, may have influenced the ratings the flax muffins received. Texture and flavor were strongly and positively correlated (P < 0.01) to overall acceptability. A flaxseed muffin provided at least 16% fiber of the daily recommended value.
Primary structure and subcellular localization of two fimbrial subunit‐like proteins involved in the biosynthesis of K99 fibrillae
Authors: Roosendaal E. , Jacobs A. A. C. , Rathman P. , Sondermeyer C. , Stegehuis F. , Oudega B. , de Graaf F. K. 
Published: October 2006

SummaryAnalysis of the nucleotide sequence of the distal part of the fan gene cluster encoding the proteins involved In the biosynthesis of the fibrillar adhesin, K99, revealed the presence of two structural genes, fanG and fanH. The amino acid sequence of the gene products (FanG and FanH) showed significant homology to the amino acid sequence of the fibrillar subunit protein (FanC). Introduction of a site‐specific frame‐shift mutation in lanG or fanH resulted in a simultaneous decrease in fibrillae production and adhesive capacity. Analysis of subcellular fractions showed that, in contrast to the K99 fibrillar subunit (FanC), both the FanH and the FanG protein were loosely associated with the outer membrane, possibly on the periplasmic side, but were not components of the fimbriae themselves.
Sequence of nifL from Klebsiella pneumoniae: mode of action and relationship to two families of regulatory proteins
Authors: Drummond1 M. H. , Wootton J. C. 
Published: October 2006

SummaryWe present the nucleotide sequence of K. pneumoniae nifL, which negatively regulates nif transcription in response to oxygen and fixed nitrogen. It shows partial sequence homology to the general nitrogen regulatory proteins NtrB of K. pneumoniae and Bradyrhizobium parasponiae. This homology is weaker than that shown between the NifA and NtrC activator components of the nif and general nitrogen control systems. The N‐terminal section of the NifL protein includes a structural duplication sharing sequence homology with part of NtrB, and a region containing a cysteine pair which might be implicated in redox control. Unlike NtrB, NifL appears to lack a DNA‐binding motif, consistent with evidence that NifL represses by interacting directiy with NifA. The C‐terminal section of NifL shows clear homology to NtrB and to a family of proteins involved in transcriptional control or chemotaxis, each of which probably interacts with a member of the family of regulatory proteins showing homology to NtrC.
Characterization of the toxicity and cytopathic specificity of a cloned Bacillus thuringiensis crystal protein using insect cell culture
Authors: Haider M. Z. , Ellar D. J. 
Published: October 2006

SummaryAn insecticidal protein gene from Bacillus thuringiensis var. aizawal was cloned in Escherichia coli. The cloned gene expressed at a high level and the synthesized protein appeared as an insoluble, phase‐bright inclusion in the cytoplasm. These inclusions were isolated by density gradient centrifugation, the isolated protein was activated in vitro by different proteloytic regimes and the toxicity of the resulting preparations was studied using insect cells grown in tissue culture. The inclusions consisted of a 130 kDa polypeptide which was processed to a protease‐resist‐ant 55 kDa protein by tryptic digestion. This preparation lysed lepidopteran (Choristoneura fumiferana) CFI ceils but not dipteran (Aedes albopictus) calls. When the crystal protein was activated by sequential treatment, first with trypsin and then with Aedes aegypti gut proteases, the resulting 53 kDa polypeptide was now toxic only to the dipteran cells and not to the lepidopteran cells. Thus the dual specificity of this var. aizawal toxin results from differential proteolytic processing of a single protoxin. The trypsin‐activated preparation was weakly active against Spodoptera frugiperda cells. Membrane binding studies of the trypsin‐activated toxin revealed a 68 kDa protein in the lepidopteran ceil membranes, which may be the receptor for this toxin.
Requirements for transcriptional activation in vitro of the nitrogen‐regulated gInA and nifLA promoters from Klebsiella pneumoniae: dependence on activator concentration
Authors: Austin S. , Henderson N. , Dixon R. 
Published: October 2006

SummaryThree proteins involved in nitrogen regulation In Klebsiella pneumoniae, NTRA, NTRB and NTRC, have been purified. In a defined in vitro system all three NTR proteins are required for initiation of transcription at the ntr activatable glnA and nifLA promoters. However, in crude S‐30 extracts, transcription from the glnA promoter, but not the nifLA promoter, can be activated in the absence of NTRB. A higher concentration of NTRC is required for activation of nifLA transcription than for glnA transcription. Sequences located between ‐227 and ‐158 with respect to the nifL transcription start site are required for efficient activation of the nifLA promoter in vitro.
The frequency of expression of pyelonephritis‐associated pili is under regulatory control
Authors: Low D. , Robinson E. N. , McGee Z. A. , Falkow S. 
Published: October 2006

SummaryThe Bscherfchia coli urinary tract Isolate C1212 contains two pyelonephritis‐associated pili (pap) DNA sequences designated here as pap‐17 and pap‐21. Each of these pap sequences encodes antigenically‐distinct pilin monomers, pllin‐17 and pilin‐21, respectively. Most individual strain C1212 cells isolated from a single bacterial colony expressed pilin‐21. Only a small fraction (5%) of strain C1212 cells expressed pilin‐17. Most of the latter population simultaneously expressed pilin‐21, but a low percentage of cells expressed pill composed of pilin‐17 alone. In contrast, almost every E. coli K‐12 cell containing multicopy pap‐17 expressed pilin‐17 at the ceil surface. These results Indicated that the regulation of pilin‐17 expression observed for strain C1212 was lost when pap‐17 was in the multicopy state. Transfer of pap‐17 to a single copy vector resulted in a pilin‐17 expression frequency lower than strain C1212 (1%). Using E. coli K‐12 containing single copy pap‐17, we found that the frequency of piiin‐17 expression increased about 15‐foid when pap‐21 was present in multiple copies in trans. Subcloning of pap‐21 showed that a 2.2 kilobase‐pair DNA sequence adjacent to, but not including, the pilin‐21 structural gene was sufficient for activation of pilin‐17 expression.
Plasmid‐mediated sucrose metabolism in Escherichia coli K12: mapping of the scr genes of pUR400
Authors: Schmid K. , Ebner R. , Altenbuchner J. , Schmitt R. , Lengeler J. W. 
Published: October 2006

SummaryThe scr genes located on plasmid pUR400 and responsible for sAucrose (Scr) metabolism of Escherichia coli K12 and other enteric bacteria have been cloned on a 9.3 kb DNA fragment. The different genes were mapped by transposon insertion mutagenesis, by restriction endonuclease and deletion mapping, and the corresponding gene products were identified. Besides the known structural genes scrA, coding for an EnzymellScr (45 kD) of the phosphoenolypyruvate‐dependent phosphotransferase system (PTS), and scrB, coding for a sucrose 6‐phosphate hydrolase (invertase) (55 kD), two new structural genes were discovered. Gene scrK apparently codes for an intracellular and ATP‐dependent fructokinase (39 kD), while scry seems to code for a sucrose porin (58 kD) in the outer cell membrane. No genes for an Enzyme IIIScr of the PTS or for (a) glycosyltransferase(s) were detected. The four genes form an scr operon (gene order, scrK scrY scrA scrB, transcription from K to B), regulated by a repressor (gene scrR, 37 kD) and inducible by sucrose, fructose and fructose‐containing oligosaccharides
Divergent effects of a dnaK mutation on abnormal protein degradation in Escherichia coli
Authors: Keller J. A. , Simon L. D. 
Published: October 2006

Summary Escherichia coli bacteria produce at least one 70 kD stress protein, the product of the dnaK gene. We have compared the rates of degradation of different types of abnormal proteins in null Ion E. coli with a partial deletion of the dnaK gene with the rates observed in null Ion dnaK+ cells. We have found that both canavanyl proteins and puromycyl polypeptides are degraded more slowly in the null dnaK mutants than in the dnaK+ strain. However, a temperature‐sensitive mutant Lacl protein is degraded more rapidly in the null dnaK strain. The stability of this temperature‐sensitive Lad protein was also examined in detail under various other conditions.
Organization and regulation of the Corynebacterium glutamicum hom‐thrB and thrC loci
Authors: Follettie M. T. , Shin H. K. , Sinskey A. J. 
Published: October 2006

SummaryThe genes encoding the three terminal enzymes in the threonine biosynthetic pathway, homoserine dehydrogenasa (hom), homoserine kinase (thrB) and threonine synthase (thrC) have been isolated from Corynebacterium glutamicum. The C. glutamicum hom and thrB genes were subcloned on a 3.6 kb Sal l‐generated chromosomal fragment. The C. glutamicum thrC gene was shown not to be linked to the hom‐thrB locus. L‐methionine represses the cloned homoserine dehydrogenase and homoserine kinase similar to that of the chromosomally encoded hom and thrB gene products. Northern hybridization analysis demonstrates that this repression is mediated at the level of transcription and that hom‐thrB represents an operon in C. glutamicum.
The plasmid‐encoded Yop2b protein of Yersinia pseudotuberculosis is a virulence determinant regulated by calcium and temperature at the level of transcription
Authors: Bölin I. , Wolf‐Watz H. 
Published: October 2006

SummaryThe basic Yop2b protein, encoded by the virulence plasmid pIBI of Yersinia pseudotuberculosis, is produced under Ca2+‐deficient conditions. A mutant deleted for the entire yopH gene, which encodes the Yop2b protein, was found to be avirulent. Virulence could be restored by trans‐complementation. The DNA‐Sequence of yopH predicted a 50 737 D polypeptide lacking a typical signal peptide. Transcription of yopH is regulated by both temperature and Ca2+‐concentration. Mutations within the region of the virulence plasmid known to be involved in regulating gene expression in response to Ca2+ abolished transcription of yopH. Other temperature‐sensitive mutations in the Ca2+‐regulatory locus showed a high level of transcription regardless of Ca2+‐concentration. These responses were similar to those of the yopE gene. The promoter region of the yopE and yopH genes were compared and four conserved motifs identified.
Nucleotide sequencing and expression of the fadL gene involved in long‐chain fatty acid transport in Escherichia coli
Authors: Said B. , Ghosn C. R. , Vu L. , Nunn W. D. 
Published: October 2006

SummaryThe fadL gene of Escherichia coli codes for an outer membrane protein involved in long‐chain fatty acid transport. Its product was purified from outer membrane proteins. We determined the nucleotide sequence of a 2.8‐kb chromosomal DNA segment that contains the fadL gene. The fadL gene consists of a 1149‐nucEeottde coding region and contains a highly hydrophobic polypeptide of 383 amino acids with a calculated molecular weight of 42 380. We have used S1‐mapping analysis to identify the transcription initiation site. A region exhibiting extensive dyad symmetry and perfect homology to the catabolite activator protein binding site was detected.
Repression of the aroF promoter by the TyrR repressor in Escherichia coli K‐12: role of the ‘upstream’ operator site
Authors: Cobbett C. S. 
Published: October 2006

SummaryThree sequences are required for complete repression of the aroF promoter by the TyrR repressor protein. Two of these operator sites lie adjacent to each other and overlap the −35 region of the aroF promoter while the third lies about 70 base pairs upstream of the promoter. An aroF‐cat (chloramphenicol acetyltransferase) gene fusion has been used to assay the effect of DNA insertions that alter the distance between the two promoter‐proximal and the third, distal, operator sites on the repression of the aroF promoter in vivo. The distal site contributes to the repression of the promoter up to a distance of about 400 base pairs and its effect is not dependent on its separation from the first and second sites by an integral number of turns of the DNA helix.
Nucleotide sequence of the mannitol (mtl) operon in Escherichia coli
Authors: Davis T. , Yamada M. , Elgort M. , Saier M. H. 
Published: October 2006

SummaryThe nucleotide sequence of the known portions of the mannitol operon in Escherichia coli (mtlOPAD) has been determined. Both the operator‐promoter region and the intercistronic region between the mtlA and mtID genes (encoding the mannitol‐specific Enzyme II of the phosphotransferase system and mannitol–1‐ phosphate dehydrogenase, respectively) show parallels with corresponding regions of the glucitol (gut) operon, but neither the mtlA nor the mtlD gene products show obvious homology with the corresponding gene products of the glucitol operon. Five potential cyclic AMP receptor protein binding sites were identified in the mtlOP region, all showing near identity with the consensus sequence. Four regions of dyad symmetry (four to seven bases in length), serving as potential repressor binding sites, overlap with the potential cyclic AMP receptor protein binding sites. Repetitive extragenic pallndromic (REP) sequences, forming stem‐loop structures in the intercistronic region between mtlA and mtlD and following the mtlD gene were identified. Probable terminator sequences were not found in any of these three regulatory regions. Mannitol–1‐phosphate dehydrogenase exhibits two overlapping, potential NAD+ binding sites near the W‐terminus of the protein. Computer techniques were used to analyse the mtlD gene and its product.
The role of activator binding sites in transcriptional control of the divergently transcribed nifF and nif LA promoters from Klebsiella pneumoniae
Authors: Minchin S. D. , Austin S. , Dixon R. A. 
Published: October 2006

SummaryThe regulatory region spanning the divergently transcribed nif F and nifLA promoters contains a NIFA‐specific upstream activator sequence (UAS) located around +59, and two NTRC binding sites centred at −142 and −163 with respect to the nifLA transcription start site. We have constructed mutations in each of these binding sites and examined their role in transcriptional activation of the divergently transcribed promoters. Analysis of a mutation at +60 confirms that the UAS is required for efficient NIFA‐mediated activation of nifF transcription. This sequence is also required for maximal activation of the nifLA promoter. Mutations at −169 and −148, within the two NTRC binding sites, reduce activation of the nifLA promoter by NTRC in vivo and lower the affinity of the activator for these sites in vitro. Phosphorylation of NTRC by NTRB is required for efficient binding of NTRC to these sites.
Alterations in the carboxy‐termianl half of cloacin destabilize the protein and prevent its export by Escherichia coli
Authors: van Putten A. J. , Stegehuis F. , van Bergen Henegouwen P. M. P. , De Graaf F. K. , Oudega B. 
Published: October 2006

SummarySeveral overlapping carboxy‐terminal and internal deletions were constructed in the cloacin structural gene. The expression, the binding of the cloacin DF13 immunity protein and the release into the culture medium of the mutant cloacin polypeptides were studied by immunoblotting and ELISAs. Minor alterations at the carboxy‐terminal end of the cloacin did not affect protein expression, stability or release to a large extent, but larger carboxy‐terminal deletions strongly destabilized the protein and no release was observed. The removal of a particular region within the carboxy‐terminal portion of cloacin strongly destabilize the polypeptide and made it a target for proteolytic degradation. Binding of immunity protein did not affect stability and release of the mutant polypeptides. By using immunoelectron microscopy, the polypeptides that were not exported were located in the cytoplasm of producing cells. Large aggregates of these mutant polypeptides were not observed in the cytoplasm: the polypeptides were present in a soluble form.