Map Of Strain Research Articles

The Mechanism of Strength Enhancement under Impact Loading of Cellular Materials

AbstractThis paper presents a multiscale analysis of the macroscopic rate sensitivity of metallic cellular materials. It begins with a review of likely causes responsible for the strength enhancement of cellular materials, which include the rate sensitivity of the base material, the effects of the pressure of the air entrapped in the cell, the inertia effect and the shock enhancement. A testing method using 60 mm diameter Nylon Hopkinson pressure bars with suitable signal processing is used to investigate the rate sensitivity of various metallic cellular materials, i.e. 5056, 5052 aluminium honeycombs of different cell sizes and wall thickness, IFAM and Cymat aluminium foams. In order to identify the factor responsible for the strength enhancement of those materials, a multiscale analysis is performed on a model structure which is a square tube made of rate insensitive materials. At the macroscopic level, significant enhancement is experimentally observed under impact loading, whereas the crushing mode is nearly the same under both static and impact loading. At mesoscopic level, post mortem microhardess measurement provides a map of residual plastic strain everywhere in the cell wall. Numeric simulations and theoretical models give a satisfactory explanation of the role of the lateral inertia.

Identification of genes necessary for jinggangmycin biosynthesis from Streptomyces hygroscopicus 10-22

A series of large chromosomal deletions in Streptomyces hygroscopicus 10-22 were aligned on the physical map of the wild-type strain and the mutants were assessed for their ability to produce the aminocyclitol antibiotic 5102-I (jinggangmycin). Twenty-eight mutants were blocked for jinggangmycin production and all of them were found to lack a 300 kb AseI-F fragment of the wild-type chromosome. An ordered cosmid library of the 300 kb AseI-F fragment was made and one of the cosmids conferred jinggangmycin productivity to Streptomyces lividans ZX1. Three of the overlapping cosmids (18G7, 5H3 and 9A2) also hybridized to the valA gene of the validamycin pathway from S. hygroscopicus 5008 as a probe. This gene resembles acbC from Actinoplanes sp. 50/110, which encodes a C7-cyclitol synthase that catalyses the transformation of sedoheptulose 7-phosphate into 2-5-epi-valiolone for acarbose biosynthesis. The valA/acbC-homolog (orf1) of S. hygroscopicus 10-22 was shown to be essential for jinggangmycin biosynthesis as an engineered mutant with a specific in-frame deletion removing a 609 bp sequence internal to orf1 completely abolished jinggangmycin production and the corresponding knock-out mutant (JXH4) could be complemented for jinggangmycin production by the introduction of an orf1-containing construct. Concurrently, the identities of the genes common to S. hygroscopicus strains 10-22 and 5008 prompted a comparison of the chemical structures of jinggangmycin and validamycin, which led to a clear demonstration that they are identical.

Sequence mapping of the Californian MSW strain of Myxoma virus.

Partial sequence mapping of the MSW Californian strain of Myxoma virus was performed by cloning EcoRI and SalI restriction fragments of viral DNA and sequencing the ends of these. In this way, regions of 74 MSW open reading frames were sequenced and mapped onto the complete genome sequences of the related leporipoxviruses South American Myxoma virus and Rabbit fibroma virus to form a partial map of the MSW strain. In general, gene locations and sequences were conserved between the three viruses. However the Californian Myxoma virus was more closely related to South American myxoma virus than to Rabbit fibroma virus based on sequence comparisons and the presence of three genes that have been lost from the Rabbit fibroma virus genome. Compared to the other two viruses, the main difference found in the MSW genome was that the terminal inverted repeats were extended with the duplication of 5 complete open reading frames (M151R, M152R, M153R, M154L, M156R) and partial duplication of one open reading frame (M150R). This rearrangement was associated with the loss of the majority of the M009L open reading frame. Three known virulence genes, including the serine proteinase inhibitor (SERPIN) genes M151R and M152R and leukemia associated protein (LAP) gene M153R, and the potential virulence gene M156R are now present in two copies.

Genetic linkage maps of the West African clawed frog Xenopus tropicalis.

Amphibians, and particularly the African clawed frog Xenopus laevis, have been used for more than a century as models of vertebrate embryonic development. However, in many cases, elucidation of developmental functions of specific gene sequences could be severely impeded, because X. laevis is a tetraploid species, with multiple functional copies of many genes of interest. Recent studies have shifted focus to the West African or tropical clawed frog, X. tropicalis, the only known diploid species of the genus Xenopus. Here, we present two preliminary linkage maps, constructed by analysis of joint segregation of amplified fragment length polymorphism (AFLP) markers in a X. tropicalis interstrain hybrid. A total of 53 markers, including 51 AFLP markers and 2 isozyme markers, are presently assigned to 13 multipoint linkage groups on a map of the maternal strain, whereas 9 AFLP markers from the paternal strain are assigned to 3 linkage groups on a separate map. A dense genetic linkage map is essential in mapping new developmental mutants and determining their sequences by positional cloning.

Advanced Strain Analysis by High Energy Synchrotron X-Ray Diffraction

Diffraction experiments using high energy, high intensity synchrotron X-ray beams are a powerful method of compiling two or three-dimensional orientation and phase-specific scans of the lattice parameter. This information can be converted into strain and stress maps of high accuracy and resolution, and used for the validation of numerical models of deformation. The present paper describes the use of monochromatic and white beam configurations at ESRF, Grenoble and SRS, Daresbury to study problems of fracture mechanics and plasticity. The characteristic strain variation in the vicinity of the crack front was studied in a nominally single-phase aluminium alloy and in a composite reinforced with SiC particles. Quantitatively, the experimental map of matrix strain in a composite was matched to the LEFM prediction to determine the value of the stress intensity factor. Qualitatively, the transition was clearly identified between the surface and the bulk of a specimen containing a crack. The use of an energy dispersive detector and a white beam is also described to obtain a two-dimensional map of the residual strains in a cross section of a plastically bent beam.

S. pneumoniae genome: closure beckons

More than 90% of the genome of the macrolide- and tetracycline-resistant Streptococcus pneumoniae type 19F has been sequenced, according to a report in Microbial Drug Resistance. The genetic data give a unique insight into the molecular events responsible for resistance. It is suggested that the sequenced strain participated in a previous gene transfer that changed the outer macromolecular capsule, disguising the bacterium from the host immune system. The authors also identified >47 whole or fragmented transposases, or genetic elements that can allow the bacterium to reshuffle the DNA within chromosomes. It is thought that these could explain why the genetic and physical map of this strain is so different from other studied laboratory strains. S. pneumoniae is still a major worldwide pathogen, with the estimated deaths from pneumonia totalling 3.5 million in 1998. CK http://www.mediscover.net/brknews2.cfm

Imaging longitudinal cardiac strain on short-axis images using strain-encoded MRI.

This article presents a new method for measuring longitudinal strain in a short-axis section of the heart using harmonic phase magnetic resonance imaging (HARP-MRI). The heart is tagged using 1-1 SPAMM at end-diastole with tag surfaces parallel to a short-axis imaging plane. Two or more images are acquired such that the images have different phase encodings in a direction orthogonal to the image plane. A dense map of the longitudinal strain can be computed from these images using a simple, fast computation. Simulations are conducted to study the effect of noise and the choice of out-of-plane phase encoding values. Longitudinal strains acquired from a normal human male are shown.

Genomic Map of Clostridium perfringens Strain 13

A physical and genetic map of Clostridium perfringens strain 13 was constructed. C. perfringens strain 13 was found to have a 3.1-Mb chromosome and a large 50-kb plasmid, indicating that strain 13 has a relatively small genome among C. perfringens strains. A total of 313 genetic markers were mapped on the chromosome of strain 13. Compared with the physical and genetic map of C. perfringens CPN50, strain 13 had a quite similar genome organization, but with a large deletion (approximately 400 kb) in a particular segment of the chromosome. Among several toxin genes, a beta2 toxin gene that is a novel virulence gene in C. perfringens was found to be located on the 50-kb plasmid.

A genetic linkage map of the MSM Japanese wild mouse strain with restriction landmark genomic scanning (RLGS).

A high-resolution genetic map of the Mus musculus molossinus (MSM) Japanese wild mouse strain was constructed with restriction landmark genomic scanning (RLGS) and compared with that of the laboratory strain C3H. MSM is phylogenetically 1 million years apart from common laboratory mouse strains and is distinctly resistant to chemical carcinogenesis. Since it exhibits frequent genetic polymorphisms with laboratory mice but can still be easily crossed with laboratory strains, hybrids between MSM and carcinogen-sensitive laboratory mouse strains provide excellent materials for analysis of modifier genes and genetic changes during carcinogenesis. We have generated MSM backcross progeny with the C3H strain, which is extremely sensitive to hepatocarcinogenesis, to construct the present map. RLGS profiles with two combinations of restriction enzymes (NotI-PvuII-PstI, NotI-PstI-PvuII) yielded more than 2000 spots each. The polymorphism rate was about 39.2%, and of a total of 1732 polymorphic spot loci identified, 1371 could be assigned to specific chromosomes by comparison with 79 microsatellite marker loci. Thus, 1450 loci, on all chromosomes except for Y, effectively mapped 90% of the genome (1431.7 cM length). Although some spots might be derived from the same NotI site, each NotI site potentially generating two fragments, the presence of at least 515 loci groups with different progeny distribution patterns dispersed through the genome with an average spacing of 3 cM, means that this genetic map should be useful for analysis of various biological phenomena, including carcinogenesis and ontogenesis, at the gene level.

Construction of a genomic map ofMoraxella (Branhamella) catarrhalisATCC 25238 and physical mapping of virulence-associated genes

A physical genome map of the Moraxella catarrhalis type strain (ATCC 25238) has been constructed using pulsed field gel electrophoresis. Macrorestriction analyses of the genome of M. catarrhalis were performed by digestion with the restriction enzymes SmaI, NotI, and RsrII, which cleave the single circular chromosome into 9, 10, and 6 fragments, respectively. The chromosomal fragments generated by pulsed field gel electrophoresis were converted to a linkage map utilizing a combination of partial digestions, and cross-hybridizations. Moraxella catarrhalis, like a number of other respiratory pathogens, has a relatively small genome estimated at 1750 kilobase pairs or about 40% of the size of the Escherichia coli genome. The locations of the four ribosomal RNA operons (rrnLS) were determined by Southern hybridization and by digestion with I-CeuI endonuclease. A number of genes involved in virulence have been placed onto the physical map by Southern hybridization including those encoding the predominant outer-membrane proteins and the chromosomal gene encoding beta-lactamase.Key words: Moraxella catarrhalis, physical map, genome analysis, pulsed-field gel electrophoresis, virulence.

Discussion on Diagnosis of Surface Failure of Roller Using Wavelet Transform. Observation of Dynamic Behavior due to Pitting and Spalling Failures.

In this paper, the wavelet transform was applied to diagnose the surface failures of rollers. The loading strain during a rotation of roller was analyzed using the wavelet transform. For pitting failure, the fatigue test was conducted using a two-cylinders testing machine. The occurring position of a large pit could be detected by the wavelet map of the loading strain, while it was difficult to detect the occurring position of a small pit. The roller with a groove was used to investigate the dynamic behavior due to spailing failure. The position of the groove could not be detected, but the intensity of the wavelet map was stronger after the groove contacted with the mating roller. From these results, it could be considered that the surface failure mode can be distinguished by the wavelet map, since the patterns on the wavelet maps between pitting failure and spalling failure were different from each other.

Construction of a genomic map of <i>Moraxella (Branhamella) catarrhalis</i> ATCC 25238 and physical mapping of virulence-associated genes

A physical genome map of the Moraxella catarrhalis type strain (ATCC 25238) has been constructed using pulsed field gel electrophoresis. Macrorestriction analyses of the genome of M. catarrhalis were performed by digestion with the restriction enzymes SmaI, NotI, and RsrII, which cleave the single circular chromosome into 9, 10, and 6 fragments, respectively. The chromosomal fragments generated by pulsed field gel electrophoresis were converted to a linkage map utilizing a combination of partial digestions, and cross-hybridizations. Moraxella catarrhalis, like a number of other respiratory pathogens, has a relatively small genome estimated at 1750 kilobase pairs or about 40% of the size of the Escherichia coli genome. The locations of the four ribosomal RNA operons (rrnLS) were determined by Southern hybridization and by digestion with I-CeuI endonuclease. A number of genes involved in virulence have been placed onto the physical map by Southern hybridization including those encoding the predominant outer-membrane proteins and the chromosomal gene encoding beta-lactamase.

Construction of the temperature-sensitive vectors pLUCH80 and pLUCH88 for delivery of Tn917::NotI/SmaI and use of these vectors to derive a circular map of Listeria monocytogenes Scott A, a serotype 4b isolate.

A physical map of Listeria monocytogenes Scott A was generated by the pulsed-field technique of contour-clamped-homogeneous-electric-field (CHEF) electrophoresis. The circular genome of this serotype 4b strain contains 12 AscI fragments (38 to 790 kb), 5 NotI fragments (55 to 1,400 kb), 3 SrfI fragments (110, 1,110, and 2,000 kb), and 2 SfiI fragments (1,320 and 1,920 kb). Summation of individually sized fragments derived by digestion of Scott A genomic DNA with each of these four enzymes provided an average estimated genome length of 3,210 +/- 60 kb. Efforts to assemble the macrorestriction map benefited greatly from the construction and use of pLUCH80 and pLUCH88, temperature-sensitive vectors for delivering transposon Tn917::NotI/SmaI to the chromosome of Scott A. As another component of this study, the positions of four known virulence genes (inlA, mpl, hly, and prf) and three L. monocytogenes-specific sequences (lisM44, lisM51, and lisM52) were localized on the physical map of Scott A by hybridization. Probes prepared from lisM44, lisM51, and the four virulence genes hybridized within a cluster on a 150-kb fragment of the Scott A genome that overlaps part of the NotI-B and AscI-D fragments. The lisM52 probe hybridized with the AscI-F2 (120-kb) fragment of Scott A, which is separated from the NotI-B-AscI-D region by about 300 kb. These results established the first physical and genetic map of a serotype 4b strain of L. monocytogenes and provided further insight on this important food-borne pathogen at the genome level.

Structural organization of the Streptococcus pneumoniae chromosome and relatedness of penicillin-sensitive and -resistant strains in type 9V.

Fragmentation of Streptococcus pneumoniae genomic DNA with low-frequency-cleavage restriction endonucleases and separation of the fragments by field-inversion gel electrophoresis (FIGE) provides a DNA-fingerprint of a strain. This method enables us to construct a physical and genetic map of the R6 laboratory strain what will be presented. The origin of replication containing several Dna boxes was located in the dnaA region. It was of interest to compare the profiles of subclones. Two clones of strain R36A (R6 and C13) were cultivated separately for more than 15,000 generations in two laboratories. FIGE profiles differed by only one band. Another R36A descendant, isolated in 1958 by Ravin, strain Rx was of interest since it was deficient in Dpn restriction enzymes and methylases and in the hex B function. Its origin was questionable; its profile is identical to others R6 descendants, demonstrating that Rx is derived from R36A. FIGE analysis was carried out on several penicillin-resistant strains of type 9V because penicillin-resistance in this type increased recently. The profiles of a collection of a number of these resistant isolates were very similar, showing that they result from a clone. The profiles of penicillin sensitive isolates of the same type are very similar to the resistant isolates. This suggests that the 9V type has spread recently from a clone, and the resistance genes have mutated and were selected when penicillin was extensively used.

Distribution of T1, Q, Pegasus and mariner transposable elements on the polytene chromosomes of PEST, a standard strain of Anopheles gambiae

The chromosomal locations of four families of transposable elements, T1, Q, Pegasus and mariner, have been determined by in situ hybridization to polytene chromosomes of ovarian nurse cells of the mosquito Anopheles gambiae. As part of this effort, we have developed a vigorous pink-eyed laboratory strain of A. gambiae (PEST), rendered homozygous standard for chromosomal inversions on all autosomes. Ten different individuals of this strain were studied with each transposable element probe. The average number of hybridization sites per genome was 83.9 for T1, 63.4 for Q, 31.5 for Pegasus and 64.7 for mariner, excluding pericentric and centromeric regions. However, some degree of polymorphism was observed within each family such that, considering all ten individuals, 94 different sites were detected for T1, 82 sites for Q, 45 sites for Pegasus and 71 sites for mariner. The mean occupancy per site varied from 0.70 (Pegasus) to 0.91 (mariner), which, while significantly higher than that seen for transposable elements in natural populations of Drosophila melanogaster, is comparable to that seen in established laboratory stocks. In addition, these element families were not randomly distributed. All but Pegasus were concentrated in centromeric heterochromatin and centromere-proximal euchromatin, most showed a deficit of hybridization sites in the distal section of chromosomes, and a significant proportion of sites were coincident between families. These results provide the first detailed examination of the cytogenetic location of transposable elements in a nondrosophilid insect, and, through comparison with the behavior of transposable elements in Drosophila, may provide insight into the interaction between elements and host. The mapped elements are also expected to serve as landmarks useful in integrating the developing physical map of the PEST strain with the chromosomal banding pattern.

New tools for integrated genetic and physical analyses of the Escherichia coli chromosome

Genetic and biophysical techniques have traditionally been applied to genome mapping independently of one another. We present a series of Escherichia coli mini-Tn10 insertions that contain the rare-cutting polylinker 1 (RCP1) of rare restriction sites [including BlnI/AvrlI, Spel, NheI, XbaI, NotI, PacI and Sfil; Mahillon and Kleckner, Gene 116 (1992) 69–74] which allows them to be used not just for genetic mapping, but also for rapid physical mapping and integrated physical and genetic mapping of the E. coli chromosome. Their isolation and their physical and genetic coordinates in K-12 strain MG1655 are presented. Also, their use in purifying insertion-delimited DNAs from E. coli K-12 and in macrorestriction mapping of a pathogenic strain's chromosome is demonstrated. These insertions allow integration of (i) different macrorestriction patterns of a single strain's chromosome, ( ii) the physical map of a single strain's chromosome with the genetic map of the species, and ( iii) the physical maps of different strains' chromosomes.

Comparison of the main features of polytene chromosomes in two forms of theMusca domesticacomplex

SUMMARYThe main features of the salivary gland chromosome map of Musca domestica (vicina form) collected from Cairo, Egypt, are compared with the map of a standard WHO strain of M. domestica (domestica form). Banding patterns are very similar and cannot be used for clearly defining the two forms. These results suggest that the two forms are closely related at the phylogenetic level.

Cloning, characterization and taxonomic significance of genes for the 5S ribosomal RNA of Leptonema illini strain 3055

The genes encoding the 5S ribosomal RNA (rRNA) for Leptonema illini strain 3055 were isolated and sequenced. The 5S RNA molecule encoded was 117 nucleotides long. The genome of strain 3055 contained two genes for 5S rRNA that were located close together. The nucleotide sequences of the Leptonema illini genes exhibited less similarity to the rRNA gene of Leptospira interrogans strain Moulton and also to those of typical eubacterial genes than did the rRNA genes of other leptospires. However, the overall secondary structure of the 5S rRNA encoded exhibited a strong similarity to that of typical eubacterial 5S rRNA. Southern hybridization of the 5S rRNA gene probe with the genomic DNA of strain 965, which is currently classified as Leptospira biflexa, showed the latter to have close similarity to that of strain 3055. The physical map of strain 965 was quite similar to that of strain 3055 and was greatly different from that of any other strains of L. biflexa. In the organization of 5S rRNA genes, strain 965 is sufficiently different from other members of the genus Leptospira to be regarded as a member of the genus Leptonema.

Expanded linkage map of Erwinia chrysanthemi strain 3937

In this paper we describe the chromosomal location of various loci in Erwinia chrysanthemi strain 3937. Auxotrophic markers were obtained by chemical mutagenesis, antibiotic resistances were isolated spontaneously and mutations in sugar utilization were obtained by means of Mu insertions. These markers were located on the genetic linkage map of strain 3937 by using a conjugative system mediated by RP4::mini-Mu plasmids which permitted transfer of genetic material from any point of origin. The location of these markers was compared to that of previously located mutations. Many genes involved in pectinolysis were also located on the E. chrysanthemi 3937 map. These results permitted us to present a new genetic map containing 61 markers distributed over 34 widely scattered loci on the chromosome. Some pairs of markers giving high cotransfer frequencies were tested for cotransduction mediated by the generalized transducing phage phi-EC2; nine cotransducing pairs were found. It appears that the chromosomal locations of many of these loci are quite different to those of the well-known enterobacterium Escherichia coli but seem similar to those described for other E. chrysanthemi strains.

Establishment of gene transfer systems for and construction of the genetic map of a marine Vibrio strain

Two gene transfer systems were established for a marine bacterium, Vibrio sp. strain 60. One was generalized transduction with a newly isolated bacteriophage, As3, and the other was conjugal gene transfer by the use of newly constructed transposon-facilitated recombination (Tfr) donors. As3 transduced various chromosomal markers at frequencies of 10(-4) to 10(-6). Tfr donors, which were constructed by introducing transposon Tn10 into both plasmid RP4 and the chromosome, mediated the polarized transfer of chromosomal genes from the sites of Tn10 insertion on the chromosome. By means of these gene transfer systems, a genetic map of the vibrio chromosome was constructed.