Tandem duplication induced by an unusual ampA1-, ampC-transducing lambda phage: A probe to initiate gene amplification

Summary Secondary attachment site -lysogens were isolated in an Escherichia coli strain carrying multiple tandem 9.8 kb repeats. The repeat carried the structural gene for chromosomal -lactamase, ampC. One lysogen produced lysates with amp-transducing activity. Three types of phages with different densities were obtained from this lysogen. The one with the lowest density was found to be a helper cI857S7 phage. The other two phages showed identical restriction endonuclease fragmentation patterns. The difference in density was due to the presence or absence of phage tail. In damp the right cohesive end segment was deleted in a random fashion with the majority ending between 81.0% and 82.4% of . The chromosomal segment of damp was most likely located at the attachment site. The damp DNA was compared to that of a ColE1 hybrid carrying the chromosomal amp segment and a ColE1 hybrid carrying the same 9.8 kb amp repeat as the lysogen from which damp was isolated. It was found that the chromosomal part of damp constituted 9.8 kb, i.e. the size of one repeat. Moreover, the novel joint between adjacent repeats was present. In a attB-deleted E. coli K-12 strain, lysogenic for damp, highly ampicillin-resistant mutants occurred at an exceedingly high frequency. They were found to contain in the chromosome an amplified 9.8 kb repeat. This suggested that integration of the novel joint from damp into the amp region gives rise to an amplifiable duplication. In E. coli lysogenized for damp at attB highly ampicillin-resistant clones were also found at a high frequency. These clones carried multiple tandem repeats of damp DNA, each with an intact right end segment.     

Analyses of genetic variants of l-glycerol-3-phosphate dehydrogenase in Drosophila melanogaster by two-dimensional gel electrophoresis and immunoelectrophoresis

A protein spot corresponding to l-glycerol-3-phosphate dehydrogenase (α-GPDH, E.C. 1.1.1.8, NAD⁺ oxidoreductase) has been identified on a two-dimensional gel (isoelectric focusing-SDS gel) containing up to 150 stained protein spots from a crude Drosophila homogenate. Preliminary identification of the α-GPDH spot was made by including a suitable amount of purified Drosophila α-GPDH in crude fly homogenates prior to electrophoresis and observing an intensity enhancement of the corresponding protein spot on the gels. When three purified electrophoretic variants (slow, fast, and ultrafast) were mixed and analyzed by two-dimensional gel electrophoresis, horizontal displacements of the three protein spots were observed. Immunoprecipitation of the enzyme prior to electrophoresis and gene mapping further confirmed the identity of the α-GPDH protein spot. The α-GPDH spot can also be detected by autoradiography of a two-dimensional gel from a single fly extract, where it has been estimated to constitute 0.5–1% of the total soluble protein. Mutants which express no apparent α-GPDH activity were analyzed by two-dimensional gels and immunoelectrophoresis in an attempt to identify and characterize the inactive proteins. It is suggested that these techniques provide a powerful tool for the analysis of CRM⁺-null activity mutants of a specific gene-enzyme system.     

Structural gene sets active in embryos and adult tissues of the sea urchin

Structural gene sequences active in a variety of sea urchin adult and embryo tissues are compared. A single-copy ³H-DNA fraction, termed mDNA, was isolated, which contains sequences complementary to the messenger RNA present on gastrula stage polysomes. Gastrula message sequences are 50 fold concentrated in the mDNA compared to total single-copy DNA. mDNA reactions were carried out with excess mRNA from blastula, pluteus, exogastrula, adult ovary, tubefoot, intestine, and coelomocytes, and with excess total mature oocyte RNA. A single-copy ³H-DNA fraction totally devoid of gastrula message sequences, termed null mDNA, was also reacted with these RNAs. Large differences in the extent of both mDNA and null mDNA reaction with the various RNAs were observed, indicating that in each state of differention a distinct set of structural genes is active, generally characterized by several thousand specific sequences. The complexity of gastrula mRNA was shown in previous work to be about 17 × 10⁶ nucleotides. In units of 10⁶ nucleotides, the complexities of the RNA sequence reacting with mDNA and with null mDNA in each tissue are, respectively, as follows: intestine mRNA; 2.1 and 3.7; coelomocyte mRNA: 3.5 and ≤1.4; tubefoot mRNA: 2.7 and ≤0.4; ovary mRNA: 13 and 6.7; oocyte total RNA: 17 and 20; blastula mRNA: 12 and 15; pluteus mRNA: 14 and ≤0.6; exogastrula mRNA: 14 and ≤0.6. The total complexity of each mRNA population is the sum of these values, as verified for several cases by reactions with total single-copy DNA. A relatively small set of mRNAs, the complexity of which is about 2.1 × 10⁶ nucleotides, appears to be shared by several of the tissues studied.     

DNA sequence organization in the genomes of five marine invertebrates

The arrangement of repetitive and non-repetitive sequence was studied in the genomic DNA of the oyster (Crassostrea virginica), the surf clam (Spisula solidissima), the horseshoe crab (Limulus polyphemus), a nemertean worm (Cerebratulus lacteus) and a jelly-fish (Aurelia aurita). Except for the jellyfish these animals belong to the protostomial branch of animal evolution, for which little information regarding DNA sequence organization has previously been available. The reassociation kinetics of short (250-300 nucleotide) and long (2,000-3,000 nucleotide) DNA fragments was studied by the hydroxyapatite method. It was shown that in each case a major fraction of the DNA consists of single copy sequences less than about 3,000 nucleotides in length, interspersed with short repetitive sequences. The lengths of the repetitive sequences were estimated by optical hyperchromicity and S1 nuclease measurements made on renaturation products. All the genomes studied include a prominent fraction of interspersed repetitive sequences about 300 nucleotides in length, as well as longer repetitive sequence regions.     

Structure and synthesis of malformin A1

The structure of malformin A₁, a metabolic product of Aspergillus niger, was reexamined and the sequence of its amino acid constituents established as

The cyclopentapeptide-disulfide corresponding to this structure was prepared through stepwise synthesis of the protected pentapeptide derivative, benzyloxy-carbonyl-l-isoleucyl-S-benzyl-d-cysteinyl-S-benzyl-d-cysteinyl-l-valyl-d-leucine methylester, which in turn was converted to the hydrazide, partially deprotected, and cyclized via the azide. On removal of the S-benzyl groups and oxidation to the disulfide, a synthetic material was obtained that was indistinguishable from natural malformin A₁ and was as equally potent in causing curvatures on corn roots.     

Distribution of microtubules in prolactin cells of lactating rats

The intracellular distribution of microtubules was studied using serial sections of prolactin cells in anterior pituitary glands from lactating rats. Numerous microtubules were present in these cells following fixation with glutaraldehyde and osmium tetroxide. The greatest number of microtubules were present in the Golgi complex, situated around the perimeter and in association with the cisternae, vesicles and developing secretory granules. Microtubules were found in channels between groups of parallel cisternae of rough surfaced endoplasmic reticulum and in close proximity to small vesicles. They were also located adjacent to mitochondria, the plasmalemma, the nuclear envelope, and among mature secretory granules. Due to their orientation within the cell, it is suggested that the microtubules may act to direct the movement of organelles from one region of the cell to another and to give internal support to the cell.     

Comparison of species ordinations resulting from alternative indices of interspecific association and different numbers of included species

Summary Several measures of interspecific association are compared. Dispersion and covariance are limited in value because they respond to the commonness of the species compared. Correlation is not so limited but it responds to discrepancies in commonness among the species. The practical result of these relationships between commonness and association is that only the most common species can occupy periferal positions in a species ordination. Rare species are relegated to positions near the center not on the basis of their phytosociological pattern but simply because of their rarity. Both Cole's index of association and the tetrachoric correlation overcome the problem imposed by the relationship between ordination position and species commonness and they both produce very similar results. The effect of differing numbers of species on the ordination configuration is examined using both Pearson's correlation and Cole's index. The basic pattern of the ordination is set with the first few species when Cole's index is used, however, since rare species are given more weight in the analysis with this index, the addition of several very rare species can change the configuration of the ordination.Nomenclature of species is given in Table 1.Research supported by the Eastern Deciduous Forest Biome Project, US-IBP, funded by the National Science Foundation under Interagency Agreement AG-199, BMS69-01147 A09 with the Energy Research and Development Administration — Oak Ridge National Laboratory. Research also supported by the U.S. Energy Research and Development Administration under contract with the Union Carbide Corporation. Contribution No. 240 from the EDFB, US-IBP. Publication No. 790. Environmental Sciences Division, ORNL.     

Germination and physiological properties of Frankia spores

Spores from four Frankia strains were isolated and purified to homogeneity. The purified spores were biochemically and physiologically characterized and compared to vegetative cells. Frankia spores exhibited low levels of endogenous respiration that were at least ten-fold lower than the endogenous respiration rate of vegetative cells. The macromolecular content of purified spores and vegetative cells differed. One striking difference among the Frankia spores was their total DNA content. From DAPI staining experiments, only 9% of strain ACN1^AG spore population contained DNA. With strains DC12 and EuI1c, 92% and 67% of their spore population contained DNA. The efficiency of spore germination was correlated to the percentage of the spore population containing DNA. These results suggest that the majority of strain ACN1^AG spores were immature or nonviable. The presence of a solidifying agent inhibited the initial stages of spore germination, but had no effect once the process had been initiated. The optimal incubation temperature for spore germination was 25°C and 30°C for strains DC12 and EuI1c, respectively. A mild heat shock increased the efficiency of spore germination, while root extracts also stimulated spore germination. These results suggest that strains DC12 and EuI1c may be suitable strains for further germination and genetic studies.     

A ferrocene-perfluoroarene molecular complex

Perfluorophenanthrene and decamethylferrocene cocrystallize as a molecular adduct in monoclinic space group P2₁/c with a = 8.842(2), b = 11.262(1), c = 30.695(8) Å, β = 95.89(2)°, V = 3040.3(8) ų, Z = 4. The structure was refined to R = 0.0537 for 1567 observed reflections. The perfluoroarene is twisted and chiral; the crystal is a racemate, however.