bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of Neuraminidase andN-Acetylneuraminate Lyase Activities Among Corynebacteria, Mycobacteria, and Nocardias
Authors: Arden Sheldon B. , Chang Woo-Hyun , Barksdale Lane
Published: January 2020

InCorynebacterium diphtheriaeand closely related neuraminidase-producing corynebacteria, we have found anN-acetylneuraminate (NAN) lyase activity which cleaves NAN intoN-acetyl-d-mannosamine and, presumably, pyruvate. In vitro, these lyases can be shown to synthesize NAN. A survey of representative corynebacteria, “plant pathogenic corynebacteria,” mycobacteria, and nocardias revealed that only those corynebacteria closely related toC. diphtheriaeexhibited both neuraminidase and NAN lyase activities.
Inhibition of Cell-Free Protein Synthesis by Hydrostatic Pressure
Authors: Schwarz J. R. , Landau J. V.
Published: January 2020

Pressure inhibition of cell-free polypeptide synthesis is manifested in the same manner as that observed in the intact cell: (i) starting at approximately 200 atm, there is a progressive inhibition with increasing pressures; (ii) there is complete inhibition at 680 atm; (iii) incorporation into polypeptide is instantaneously reversible after pressure release and proceeds at a rate parallel to an atmospheric control; and (iv) the volume change of activation (Δ
V
*) is 100 cm
3
/mole. Peptide bond formation per se can occur at a pressure level which is totally inhibitory to polypeptide synthesis. The one investigated step in translation that is inhibited in an identical manner is the binding of aminoacyl-transfer ribonucleic acid (AA-tRNA) to the ribosome-messenger RNA (mRNA) complex. The volume change of activation (Δ
V
*) calculated for the binding reaction is also 100 cm
3
/mole. Thus, the inability of AA-tRNA to bind to ribosomes and mRNA under pressure, possibly in conjunction with translocation, appears to be responsible for the observed inhibition of the translational mechanism.
Comparative Effect of Oxygen and Nitrate on Protoporphyrin and Heme Synthesis from Δ-Amino Levulinic Acid in Bacterial Cultures
Authors: Jacobs N. J. , Jacobs J. M. , Morgan H. E.
Published: January 2020

Pseudomonas aeruginosa
and
P. denitrificans
accumulate more protoheme and considerably more protoporphyrin during anaerobic growth under denitrifying conditions than during aerobic growth. In
Escherichia coli
, the small accumulation of protoporphyrin and protoheme which occurs during anaerobic growth is slightly stimulated by nitrate and markedly stimulated by oxygen.
Porphyrin-Accumulating Mutants of
Escherichia coli
Authors: Cox Roger , Charles H. P.
Published: January 2020

Four mutants (
pop-1, pop-6, pop-10
, and
pop-14
) which accumulate a red water-insoluble pigment were obtained in
Escherichia coli
K-12 AB1621. For each mutant, the red pigment was shown to be protoporphyrin IX, a late precursor of heme. Mutagenic treatment of mutant
pop-1
yielded a secondary mutant,
pop-1 sec-20
, which accumulated a brown water-soluble pigment. The brown pigment was shown to be coproporphyrin III. Mutant
pop-1
resembled the parental strain in its cytochrome absorption spectrum, catalase activity, and ability to grow on nonfermentable carbon and energy sources; therefore, its ability to produce and utilize heme was unimpaired. Judged on the same criteria, the secondary mutant,
pop-1 sec-20
, was partially heme and respiratory deficient. Growth in anaerobic conditions decreased by 25% the accumulation of protoporphyrin by
pop-1;
under the same conditions,
pop-1 sec-20
did not accumulate coproporphyrin or coproporphyrinogen. The mutations causing protoporphyrin accumulation in all four
pop
mutants were found to map in the
lac
to
purE
(10–13 min) region of the
E. coli
chromosome. In the case of mutant
pop-1
, the mutation was shown to be strongly linked to the
tsx
locus (12 min). In mutant
pop-1 sec-20
, the second mutation causing coproporphyrin accumulation was co-transducible with the
gal
locus at a frequency of 88 to 96%. The mechanism of porphyrin accumulation by the mutants is discussed.
α-Mannosidase and Microcyst Differentiation in the Cellular Slime Mold
Polysphondylium pallidum
Authors: O'day Danton H.
Published: January 2020

The intracellular and extracellular pattern of α-mannosidase (EC 3.2.1.24) activity was studied during microcyst differentiation in the cellular slime mold,
Polysphondylium pallidum
. The evidence suggests that microcyst differentiation requires continuous protein synthesis. α-Mannosidase activity is present in amoebae and increases with differentiation, and the data indicate that this increase in activity requires concurrent protein synthesis. The enzyme is excreted during the differentiation process, and the release of the enzyme is not stopped by cycloheximide. A cystless mutant does not show the normal intracellular pattern of α-mannosidase but does excrete the enzyme. Microcyst differentiation is proposed as an alternative system to multicellular slime mold development for the biochemical analysis of certain aspects of cellular differentiation.
Effect of Growth Rate on the Macromolecular Composition of
Prototheca zopfii
, a Colorless Alga Which Divides by Multiple Fission
Authors: Poyton Robert O.
Published: January 2020

Prototheca zopfii
, a eukaryote that divides by multiple fission, was investigated to determine how growth rate controls daughter cell number. The macromolecular composition, cell size, and number of nuclei per cell were determined in cultures during balanced growth in various media. Cellular mass, ribonucleic acid (RNA), deoxyribonucleic acid (DNA), carbohydrate, and nuclear number increased as positive linear functions of growth rate, whereas nuclear ploidy remained constant with a value of 0.098 pg of DNA/nucleus. The ratios of RNA to protein, protein to mass, and carbohydrate to mass were unaffected by growth rate, whereas the ratios of DNA to protein and RNA to DNA could be expressed as curvilinear functions of growth rate, the former negative and the latter positive. The dependency of normalized gene dosage (DNA/protein) on growth rate appeared as a distinguishing feature of multiple fission. Determination of the normalized rates of protein and RNA synthesis revealed that both increase linearly with growth rate. It is concluded that
Prototheca zopfii
may exist in a number of physiological states which are characterized by a unique size and macromolecular composition and which are dictated by growth rate.
Channel-Shuttle Mechanism for the Regulation of Phenylalanine and Tyrosine Synthesis at a Metabolic Branch Point in
Pseudomonas aeruginosa
Authors: Calhoun David H. , Pierson Duane L. , Jensen Roy A.
Published: January 2020

A bifunctional protein complex was partially purified from
Pseudomonas aeruginosa
. Catalytic activities for chorismate mutase and prephenate dehydratase coeluted from gel filtration and DEAE-cellulose chromatography columns. The protein complex had a molecular weight of approximately 134,000, as determined by gel filtration. In crude extracts or in partially purified preparations about one-half of the chorismate utilized by the complex is converted to phenylpyruvate, and the other half accumulates as prephenate. The chorismate mutase activity is strongly product-inhibited by prephenate, competitively with chorismate. Accordingly, the first reaction of the complex can be sufficiently retarded by prephenate so that all of the reaction product is phenylpyruvate. Chorismate mutase activity is also competitively inhibited by phenylalanine. Although phenylalanine is effective at low concentrations, maximal inhibition is only 50 to 60%. Inhibition of chorismate mutase by phenylalanine was completely lost after gel filtration. The prephenate dehydratase activity of the protein complex is nearly completely inhibited by 0.1 m
m
phenylalanine in either crude extracts or partially purified preparations. A second species of prephenate dehydratase was separated from the prephenate dehydratase-chorismate mutase aggregate by gel filtration or anion exchange chromatography. The second prephenate dehydratase had an estimated molecular weight of 76,000, a high affinity for prephenate, and was insensitive to feedback inhibition by phenylalanine. The physiological role of the latter enzyme is uncertain. The other regulatory enzymes of tyrosine and phenylalanine biosynthesis, prephenate mutase aggregate by gel filtration or anion exchange chromatography. The other regulatory enzymes of tyrosine and phenylalanine biosynthesis, prephenate dehydrogenase (molecular weight of 120,000) and 3-deoxy-
d
-
arabino
-heptulosonate-7-phosphate synthetase (molecular weight of 52,000), elute from Sephadex G-100 columns as fractions which are distinct from both the chorismate mutase-prephenate dehydratase complex and from the low-molecular-weight species of prephenate dehydratase. A shuttle mechanism governing the metabolic fate of prephenate (to phenylalanine or to tyrosine) is proposed in the context of a model which also accommodates several previously puzzling findings: (i) the dominating role of tyrosine in the control of 3-deoxy-
d
-
arabino
-heptulosonate-7-phosphate synthetase and (ii) the lack of feedback control of prephenate dehydrogenase by tyrosine.
Homogeneity of Envelope Proteins of
Escherichia coli
Separated by Gel Electrophoresis in Sodium Dodecyl Sulfate
Authors: Inouye Masayori , Yee Mei-Lan
Published: January 2020

Some envelope proteins of
Escherichia coli
show variable behavior in acrylamide gel electrophoresis in 1% sodium dodecyl sulfate, depending upon the conditions of the solubilization. When solubilized in 1% sodium dodecyl sulfate at 70 C for 20 min, three distinct peaks (peaks 4, 6, and 7) are seen at molecular weights of 57,800, 44,300, and 38,400, respectively. However, when the envelope fractions are solubilized in 1% sodium dodecyl sulfate at 100 C for 5 min, or when they are treated with
N, N
-dimethylformamide at acidic
p
H before solubilization by our method, only a single peak at 48,000 molecular weight is observed in the molecular weight range mentioned above. That is, peaks 4 and 7 disappear and a new peak appears at the position overlapping with peak 6. Proteins isolated from peaks 4 and 7 show the similar molecular weight shifts to the new peak by the treatment at 100 C. No other peaks show any change by the heat treatment. The increase at the new peak is completely accounted for by the decrease at peaks 4 and 7, indicating that the new peak is composed of proteins from peaks 4, 6, and 7. However, it is concluded that these three peaks consist of distinctly different proteins for the following reasons: (i) they have different amino acid compositions, (ii) they show different solubilities in the nonionic detergent, Nonidet P-40, and as shown previously, (iii) peak 6 (protein Y) is related to deoxyribonucleic acid synthesis, and (iv) proteins in peaks 4, 6, and 7 have different resistance to proteolytic enzymes. Although the reasons for the anomalous molecular weight shifts of these peaks are not well understood at present, it is important to solubilize the
E. coli
envelope proteins by the standard method in order to investigate their properties and functions of the envelope proteins.
Development of a Quantitative Immunological Assay for the Study of Spore Coat Synthesis and Morphogenesis
Authors: Horn Diane , Aronson A. I. , Golub E. S.
Published: January 2020

A quantitative assay employing
125
I-labeled antibody has been developed for
Bacillus cereus
T spore coat protein. Populations of antibody molecules with various affinities for inner or outer coat can be prepared by selective adsorption to and elution from different coat preparations. Adsorption to and elution from intact spores results in an antibody preparation at least 15 times more reactive to outer coat. This antibody is useful for measuring the time and extent of spore coat maturation, i.e., outer spore coat formation. Rifampin inhibits the increase in content of this coat antigen.
Electron Microscope Observations on the Effects of Polymixin B Sulfate on Cell Walls ofChlamydia psittaci
Authors: Matsumoto Akira , Higashi Noboru , Tamura Akira
Published: January 2020

The effects of polymixin B sulfate on cell walls of mature elementary body (EB) and of immature developmental reticulate body (RB) ofChlamydia psittaciwere investigated. When purified EB were treated with polymixin (104units per ml or more) at 37 C for 60 min, about 70% of EB was found to be covered with a number of projections. Further incubation did not increase the percentage affected. The infectivity after treatment as assayed by the inclusion counting technique was reduced by 70% of the original titer. These results suggest that EB with the projections are no longer infective. The projections had obscure outlines and were 20 to 40 nm in diameter when seen in thin sections. In the negatively stained preparations, the projections were composed of aggregations of fine particles 4 to 5 nm in diameter. Treatment with sodium dodecyl sulfate at the same concentration used for cell wall isolation removed the projections completely, and the cell walls were converted to rather ragged forms apparently composed of outside and inside layers. When RB cell walls prepared from infected cells at 18 hr after infection were treated with polymixin at the same concentration, the projections having the same morphology with those seen on treated EB cell walls were observed only on the inside surface of cell wall.
Differentiation of Some Enterococci by Gas Chromatography
Authors: Amstein Charles F. , Hartman Paul A.
Published: January 2020

Relative fatty acid compositions of 37 enterococci were examined by gas chromatography.
Streptococcus faecalis, S. faecium
, and
S. faecium
var.
durans
yielded similar fatty acid patterns. Strains of
S. faecium
var.
casseliflavus
, and a motile yellow-pigmented streptococcus, contained very low levels of C
19:0
cyclopropane fatty acid and four unidentified components, compared to the other strains of enterococci examined. There were no significant differences in the fatty acid patterns of enterococci grouped according to plant, animal, or human source.
Freeze-Etching and X-Ray Diffraction of the Isolated Double-Track Layer from the Cell Wall of a Gram-Negative Marine Pseudomonad
Authors: Forge A. , Costerton J. W. , Kerr K. Ann
Published: January 2020

The isolated double-track layer of the cell wall of the gram-negative marine pseudomonad studied here contains a cleavage plane. This finding localizes the single cleavage plane of the cell wall and shows that the molecular architecture of this layer provides the lipid-enriched layer which cleaves preferentially in the frozen cell. The observation that the isolated double-track layer of the cell wall is sufficiently ordered at the molecular level to yield a well-defined X-ray diffraction pattern with a d-spacing of 0.44 nm shows that its molecular architecture is very similar to that of true membranes. This specific d-spacing is produced by the highly ordered packing of the hydrophobic portions of phospholipid molecules. Therefore, the double-track layer of the cell wall has been shown, by these two biophysical means, to have a molecular architecture which would allow it to function as the membrane-like “molecular sieve” layer, whose presence has been deduced from physiological data. This layer is important in the retention of cell wall-associated enzymes and in the control of the movement of large molecules through the cell wall.
Obligate Thymidine Auxotrophs of
Pseudomonas acidovorans
Authors: Kelln Rod A. , Warren R. A. J.
Published: January 2020

The aminopterin technique was adapted for the isolation of thymidine auxotrophs of
Pseudomonas acidovorans
. All the mutants isolated responded to thymidine but not to thymine.
Characterization of Lethal Zygosis Associated with Conjugation in
Escherichia coli
K-12
Authors: Skurray Ronald A. , Reeves Peter
Published: January 2020

When F
−
cells are mixed with an excess of Hfr cells there is a lethal event which results in a decrease in the number of F
−
survivors. We have described and discussed the parameters affecting this phenomenon of lethal zygosis, and these include the cultural conditions of both donor and recipient cells prior to mixing and the use of aeration throughout the period of the experiment. The absence of lethal zygosis with filtrates and supernatant fluids from donors suggests a dependence on direct cell-cell contact as found in conjugation. The phenomenon, which is normally observed in liquid media, also occurs on solid media, and use of these two methods has allowed examination of strains of different mating types. Whereas most Hfr strains capable of producing normal yields of recombinants showed killing activity, no F
+
and only one F′ donor produced lethal zygosis. Only F
−
strains were sensitive to this phenomenon. The relationship between lethal zygosis and the various stages of conjugation is discussed.
Amino Acid Sequence of the Threonine-Containing Mureins of Coryneform Bacteria
Authors: Fiedler Franz , Schleifer Karlheinz , Kandler Otto
Published: January 2020

In a study of the mureins of coryneform bacteria (
Arthrobacter, Brevibacterium, Cellulomonas, Corynebacterium, Erysipelothrix
), 21 threonine-containing strains were found. In several of the strains the amino acid and amino sugar composition of the murein was muramic acid (Mur), glucosamine (GlcNH
2
),
d
-Glu,
l
-Lys,
l
-Thr, and Ala in a molar ratio of 1:1:1:1:1:4 or 5, and in several other strains it was Mur, GlcNH
2
,
d
-Glu,
l
-Lys,
l
-Thr, Ala, and
l
-Ser in a molar ratio of 1:1:1:1:1:3:1. The amino acid sequence of the mureins was determined by analyzing the oligopeptides derived from partial acid hydrolysates. It was shown that there were five different murein types. The peptide subunits attached to the muramic acid are the same, namely
l
-Ala-
d
-GluNH
2
-
l
-Lys-
d
-Ala. In one strain, the α-carboxyl group of
d
-Glu is substituted by
d
-alanine amide. The interpeptide bridges of the different types consist of the peptides
l
-Ala-
l
-Thr-
l
-Ala,
l
-Ala-
l
-Thr,
l
-Ala-
l
-Ala-
l
-Thr,
l
-Ala-
l
-Ala-
l
-Ala-
l
-Thr, or
l
-Ala-
l
-Thr-
l
-Ser which are bound through their C-termini (
l
-Ala,
l
-Thr,
l
-Ser) to the ε-amino group of
l
-Lys of one peptide subunit and by their N-termini (
l
-Ala) to the C-terminal
d
-Ala of an adjacent peptide subunit. Determination of the N- and C-terminal groups in the mureins showed that about 15 to 30% of the interpeptide bridges are not cross-linked.
Mechanism for the Regulation of Cell Division inAgmenellum
Authors: Ingram L. O. , Fisher W. D.
Published: January 2020

We describe a nonlethal temperature-conditional mutant ofAgmenellum quadruplicatumwhich allows dissociation of the processes of growth and cell division. With this system, evidence has been obtained for the regulation of one step in the process of cell division by a small effector molecule. The effector molecule is apparently released into the surrounding medium and can be obtained from lyophilized spent medium by extraction with 80% ethanol. The addition of this extract to serpentine filaments of the SN29 mutant strain stimulates cell division in these filaments and leads to the production of cells approximating normal dimensions within one generation time. The degree of stimulation of cell division is directly related to the amount of extract added. A general hypothesis is presented for the positive regulation of the initiation of cell wall and cell membrane invagination in this organism.
Life Cycle of
Neurospora crassa
Viewed by Scanning Electron Microscopy
Authors: Seale Thomas
Published: January 2020

Scanning electron microscopy was used to examine the major stages of the life cycle of two wild-type strains of
Neurospora crassa
Shear and Dodge (St. Lawrence 3.1a and 74A): mycelia, protoperithecium formation, perithecia, ascospores, ascospore germination and outgrowth, macro and microconidia, and germination and outgrowth of macroconidia. Structures seen at the limit of resolution of bright-field and phase-contrast microscopes, e.g., the ribbed surface of ascospores, are well resolved. New details of conidial development and surface structure are revealed. There appears to be only one distinguishable morphological difference between the two strains. The pattern of germination and outgrowth which seems relatively constant for strain 74A or strain 3.1a, appears to be different for each. Conidia from strain 3.1a almost always germinate from a site between interconidial attachment points; whereas the germ tubes of strain 74A usually emerge from or very near the interconidial attachment site. These germination patterns usually do not segregate 2:2 in asci dissected in order. This observation suggests that conidial germination pattern is not under the control of a single gene.
Initiation and Termination of Bacterial Deoxyribonucleic Acid Replication in Low Concentrations of Chloramphenicol
Authors: Lark Karl G.
Published: January 2020

Escherichia coli
15T
−
can initiate a cycle of deoxyribonucleic acid replication with equal efficiency in the presence of 25 or 50 μg of chloramphenicol/ml. However, these replication cycles are not completed in the presence of these drug concentrations, and the amount of replication decreases with increasing drug concentration.
Formation of Catenated Colicin Factor E1 Deoxyribonucleic Acid Molecules in a Recombination-Deficient Strain ofEscherichia coli
Authors: Inselburg Joseph W.
Published: January 2020

Catenated deoxyribonucleic acid molecules of colicin factor E1 (Col E1) were found with nearly equal frequency in minicells derived fromEscherichia colistrain P678-54recA+(Col E1) and P678-54recA−(Col E1). The result suggests that the recombination function controlled by therecAgene does not influence the formation of catenated Col E1.
Transformation and Transfection in Lysogenic Strains of
Bacillus subtilis
168
Authors: Yasbin Ronald E. , Wilson Gary A. , Young Frank E.
Published: January 2020

Strains of
Bacillus subtilis
lysogenic for either temperate bacteriophage φ105 or SPO2 were reduced to less than 1.0% of the level of transformation of the nonlysogenic strains. Strains lysogenic for both φ105 and SPO2 are virtually nontransformable, indicating that the effect of lysogeny is additive. Lysogenic cultures transfected at essentially wild-type levels with deoxyribonucleic acid (DNA) isolated from bacteriophages φ29 and SPO1. The residual transformation and transfection achieved by the lysogenic cultures changed dramatically during growth in SPII medium, whereas nonlysogenic strains remained competent for 5 hr in SPII medium. Despite a marked reduction in transformation, lysogenic cultures initially irreversibly bound as much DNA as nonlysogenic cultures. After 60 min in SPII medium, there was a rapid decrease in the capacity of lysogenic cells to bind DNA irreversibly. These results, as discussed, indicate that the inhibition of transformation is probably due to an alteration of the cell surface or a differential inactivation of bacterial genes after lysogenic conversion.
Facilitated Diffusion of Monosaccharides in
Saccharomyces cerevisiae
: Experimental Investigation of Kinetic Parameters Without the Assumptions of Symmetry
Authors: Kalsow Carolyn M. , Doyle R. J.
Published: January 2020

Until the question of symmetry or asymmetry in the facilitated diffusion of monosaccharides by
Saccharomyces cerevisiae
is resolved, attempts to study the transport process cannot be based on assumptions of symmetry, such as equal concentrations at equilibrium or kinetic parameters that are equal in opposite directions. The assumptions of symmetry may be circumvented by measuring efflux against water and against various external concentrations of sugar. The measurement of efflux against water eliminates any involvement of influx, and the separate determinations of influx and efflux parameters do not require that the parameters be equal. Furthermore, the use of relative internal concentrations eliminates any necessity of assuming that the equilibrium concentrations are equal. Since the influx and efflux parameters are to be compared, the measurement of influx on effluxing cells allows both sets of parameters to be determined on cells which are physiologically the same. This procedure has been tested by obtaining the kinetic parameters of
l
-sorbose transport. The validity of these parameters was demonstrated by using them to generate theoretical efflux curves that fit the experimental data and by showing that they give the best fit curve to the relationship of velocity and permeant concentration. Although the question of symmetry remains unanswered, this procedure has opened the way for experimental evaluation of the situation and further investigation of the transport process in yeast.
Analysis of Isoaccepting Transfer Ribonucleic Acid Species of
Bacillus subtilis
: Chromatographic Differences Between Transfer Ribonucleic Acids from Spores and Cells in Exponential Growth
Authors: Vold Barbara S.
Published: January 2020

Differences between the transfer ribonucleic acid (tRNA) of spores and exponentially growing cells of
Bacillus subtilis
168 were compared by co-chromatography on reversed-phase column RPC-5. This system gave excellent resolution of isoaccepting species in 1 to 2 hr using a 200-ml gradient. Two methods were used to extract spore tRNAs, a procedure using a Braun homogenizer and a pretreatment with dithiothreitol followed by lysis with lysozyme. Where changes were observed, column elution profiles of spore tRNAs were independent of the extraction method used. Three kinds of changes between the profiles of vegetative cell tRNA and spore tRNA were observed: (i) no change; phe-, val-, ala-, asp-, ileu-, pro-, met-, fmet-, and his-tRNAs, (ii) a change in the ratio of existing peaks; gly-, tyr-, leu-, ser-, thr-, aspn-, and arg-tRNAs, and (iii) the appearance or disappearance of unique peaks; lys-, glu-, and trp-tRNAs.
Structure of the Molybdoferredoxin Complex from
Clostridium pasteurianum
and Isolation of Its Subunits
Authors: Huang T. C. , Zumft W. G. , Mortenson L. E.
Published: January 2020

Highly purified molybdoferredoxin, with a specific activity of 2.6 μmoles of acetylene reduced per min per mg of protein, was obtained from
Clostridium pasteurianum
. The protein at concentrations above 5 mg/ml exists in solution as a tetrameric complex with two subunits each of about 60,000 and 50,000 daltons. Two atoms of molybdenum are present per protein molecule of 220,000 daltons. The
S
0
20, w
was found to be 10.5. The tetramer dissociates into a dimer as demonstrated by a decreasing sedimentation coefficient with decreasing protein concentration. At low
p
H and ionic strength, further dissociation into the monomers is achieved. A method for the isolation of the protein subunits is described.
Ultrastructure of the Cell Wall and Cytoplasmic Membrane of Gram-Negative Bacteria with Different Fixation Techniques
Authors: Silva M. T. , Sousa J. C. F.
Published: January 2020

The ultrastructure of the cytoplasmic membrane and cell wall of two strains of
Escherichia coli, Proteus morganii, P. vulgaris, Acinetobacter anitratum, Moraxella lacunata, Erwinia amylovora, Acinetobacter
sp., and of a plant pathogen, unclassified gram-negative, fixed by the Ryter-Kellenberger procedure, was found to be significantly affected by the use or omission of the uranyl postfixation included in that procedure, and by the presence or absence of calcium in the OsO
4
fixative. The omission of the uranyl treatment results in a less clear profile of both the outer membrane of the cell wall and of the cytoplasmic membrane. The observation of these two membranes is further limited when both uranyl and calcium are omitted. The R-layer and the material covering the surface of the cell wall appear more distinct when the uranyl postfixation is not used. Evidence is given suggesting that the influence of uranyl and calcium ions on the appearance of the outer and cytoplasmic membranes would be primarily due to their action as fixatives, whereas the influence of uranyl on the appearance of the R-layer would be due to a direct action on the peptidoglycan component of this layer. When uranyl acetate is used as a section stain after the embedding in plastic, it improves the observation of the R-layer. In this case, a well contrasted R-layer is consistently observed in all strains studied, provided that the postfixation has been omitted. The frequent difficulty in clearly observing the R-layer in many published micrographs probably results from the common use of uranyl postfixation.
Repair of Single-Strand Deoxyribonucleic Acid Breaks in Ultraviolet Light-IrradiatedHaemophilus influenzae
Authors: Kantor George J. , Barnhart B. J.
Published: January 2020

The wild-type strain and mutants ofHaemophilus influenzae, sensitive or resistant to ultraviolet light (UV) as defined by colony-forming ability, were examined for their ability to perform the incision and rejoining steps of the deoxyribonucleic acid (DNA) dark repair process. Although UV-induced pyrimidine dimers are excised by the wild-type Rd and a resistant mutant BC200, the expected single-strand DNA breaks could not be detected on alkaline sucrose gradients. Repair of the gap resulting from excision must be rapid when experimental conditions described by us are employed. Single-strand DNA breaks were not detected in a UV-irradiated sensitive mutant (BC100) incapable of excising pyrimidine dimers, indicating that this mutant may be defective in a dimer-recognizing endonuclease. No single-strand DNA breaks were detected in a lysogen BC100(HP1c1) irradiated with a UV dose large enough to induce phage development in 80% of the cells.
Histidine Uptake in Mutant Strains of
Neurospora crassa
Via the General Transport System for Amino Acids
Authors: Magill C. W. , Nelson S. O. , D'Ambrosio S. M. , Glover G. I.
Published: January 2020

A transport double mutant of
Neurospora crassa
has been isolated that has only one of the three transport systems capable of
l
-histidine uptake. The substrate specificity of the remaining transport system, termed the general transport system, has been fully characterized with regard to the contributions to binding of the side chain, the α-amino group, and the carboxylate group. The positively charged α-amino group is necessary for binding; the negatively charged carboxylate group is of less importance, since its replacement by a neutral carbonyl functional group does not completely abolish binding. The greatest structural latitude for binding was found in the side chain; affinity for α-amino acids was uniformly high except for
l
-aspartic and
l
-glutamic acids,
l
-asparagine, and
l
-proline. Thus, this transport system is “general” with these restrictions.
Fine Structural Changes of
Acetobacter suboxydans
During Growth in a Defined Medium
Authors: Batzing Barry L. , Claus G. W.
Published: January 2020

Cytological differences were observed between stationary- and exponentialphase cells of
Acetobacter suboxydans
grown in a defined medium. Unstained cells observed with the light microscope just after entering the stationary phase differed from exponentially growing cells in that the former exhibited localized increases in density, particularly in the polar regions. Electron microscopy of thin sections revealed that early stationary-phase cells possessed predominantly polar complexes of intracytoplasmic membranes accompanied by polar increases in ribosomal material. When cultures were allowed to continue far into the stationary phase, cells contained extensive aggregations of membrane-like material as the predominant fine-structural feature. In contrast, thin sections of exponentially growing cells exhibited only occasional indications of intracytoplasmic membranes. Intracytoplasmic membranes heretofore have been observed only rarely in the heterotrophic
Pseudomonadales
.
Genetic Studies Relating to the Production of Transformed Clones Diploid in the Tryptophan Region of the
Bacillus subtilis
Genome
Authors: Audit C. , Anagnostopoulos C.
Published: January 2020

Transformation experiments with
Bacillus subtilis
strains carrying
trpE26
(the marker responsible for the detection of merodiploid clones after transformation or transduction) have established the precise position of this marker on the “aromatic region” of the chromosome, at the distal end of the anthranilate synthetase locus. Integration efficiency of the mutant allele (
trpE26
) seems to be very low. Co-transfer of markers situated on either side of it is almost nil when both donor and recipient carry this mutation. The “exclusion” of
trpE26
does not, however, affect recombination frequencies for nearby markers. To explain these facts we considered the hypothesis of a preferential breakage of the deoxyribonucleic acid (DNA) at the
trpE26
site or that of an insertion mutation. These studies have also demonstrated the establishment of physical linkage of a marker from the exogenote (
hisH2
) to a resident marker (
tyrA1
) in stable and unstable merodiploid clones, thus confirming integration of the donor DNA segment into a genetic structure of the recipient. Furthermore, duplication was shown in merodiploid clones (through reversion and transformation) for a locus of the recipient (
tyrA
) which was not involved in the initial transformation. This suggests that the diploid condition in this region extends beyond the transformed area. Interpretation of the genetic constitution of these partial diploids calls for postulation of the existence of long duplications, a second (incomplete) chromosome, or an episome-like element.
Biosynthesis of Branched-Chain Amino Acids in
Schizosaccharomyces pombe
: Regulatory Properties of Threonine Deaminase
Authors: McDonald Roderick A. , Kaplan J. Gordin
Published: January 2020

Biosynthetic threonine deaminase (TD) from
Schizosaccharomyces pombe
has been partially purified from crude extracts by treatment with protamine sulfate, ammonium sulfate precipitation, and gel filtration through Sephadex G-25. In both crude extracts and purified preparations, TD showed marked stimulation by pyridoxal phosphate. A pH optimum for activity was found at pH 9.0, whereas the inhibition caused by the natural feedback inhibitor,
l
-isoleucine, was maximal at pH 7.4.
l
-Threonine exhibits homotropic cooperative effects at low pH (7.0–8.0), which are eliminated at pH 9.0, and the affinity for substrate (in terms of

K
m

) increased with increasing pH. Enzyme activity could be completely inhibited by isoleucine over a pH range of 7.4 to 9.0; the amount of isoleucine required for 50% inhibition increased with increasing pH. Isoleucine inhibition was pseudocompetitive with respect to substrate and increased the cooperative effects of threonine.
l
-Valine was found to reverse isoleucine inhibition; it also activated the enzyme in a pH range of 7.0 to 8.0 by eliminating the cooperative effects of threonine, thus normalizing the substrate saturation curves at these pH values.
l
-Leucine was shown to be a competitive inhibitor with respect to threonine, and to be able partially to reverse isoleucine inhibition. Treatment of TD with mercurials did not result in desensitization to isoleucine inhibition. However, at pH 10, virtually no sensitivity of the enzyme to isoleucine was observed while activity remained strong, which suggests the existence of separate sites on the TD molecule for binding threonine and isoleucine. A tentative model is presented which unifies the kinetic results reported here in terms of the interactions of TD with its effector molecules.
Regulatory Mutations Affecting the Gluconate System in
Escherichia coli
Authors: Zwaig Noé , Zwaig Rosa Nagel de , Istúriz Tomás , Wecksler Magda
Published: January 2020

A spontaneously arising regulatory mutant of the gluconate system in
Escherichia coli
was isolated. This mutant became constitutive, probably in one step, for gluconate high-affinity transport, gluconokinase, and gluconate-6-P dehydrase. The mutation involved (
gntR18
) is cotransducible with
asd
. Pseudorevertants, derived from a mutant (M2) that shows a long lag for growth on gluconate mineral medium, were also isolated and characterized. They give constitutive levels of gluconokinase and gluconate-6-P dehydrase but lack high-affinity transport function. Genetic experiments performed with one of these pseudorevertants (M4) indicate that it carries a secondary mutation in the
gntR
gene. The M4 phenotype is thus the result of the interaction of expression of a constitutive mutation (
gntR4
) with the mutation of strain M2 (
gntM2
).
Isolation and Properties of Fumarate Reductase Mutants of
Escherichia coli
Authors: Spencer Margaret E. , Guest J. R.
Published: January 2020

Escherichia coli
produces two enzymes which interconvert succinate and fumarate: succinate dehydrogenase, which is adapted to an oxidative role in the tricarboxylic acid cycle, and fumarate reductase, which catalyzes the reductive reaction more effectively and allows fumarate to function as an electron acceptor in anaerobic growth. A glycerol plus fumarate medium was devised for the selection of mutants (
frd
) lacking a functional fumarate reductase by virtue of their inability to use fumarate as an anaerobic electron acceptor. Most of the mutants isolated contained less than 1% of the parental fumarate reduction activity. Measurements of the fumarate reduction and succinate oxidation activities of parental strains and
frd
mutants after aerobic and anaerobic growth indicated that succinate dehydrogenase was completely repressed under anaerobic conditions, the assayable succinate oxidation activity being due to fumarate reductase acting reversibly. Fumarate reductase was almost completely repressed under aerobic conditions, although glucose relieved this repression to some extent. The mutations, presumably in the structural gene (
frd
) for fumarate reductase, were located at approximately 82 min on the
E. coli
chromosome by conjugation and transduction with phage P1.
frd
is very close to the
ampA
locus, and the order of markers in this region was established as
ampA-frd-purA
.
Association of Many Regions of the
Bacillus subtilis
Chromosome with the Cell Membrane
Authors: Ivarie Robert D. , Pène Jacques J.
Published: January 2020

Unsheared lysates of
Bacillus subtilis
168T
−
containing uniformly labeled deoxyribonucleic acid (DNA) were exposed to varying doses of gamma rays to introduce double-strand scissions in the chromosome. From an estimate of the number-average molecular weight and the amount of DNA bound to membrane after irradiation, about 70 to 90 regions of the bacterial chromosome were detected in membrane fractions. Since this number was independent of the molecular weight of the DNA (i.e., the extent of fragmentation of the chromosome), it is thought to represent an upper limit in the number of membrane-binding sites per chromosome.
Thiosulfate- and Sulfide-Dependent Pyridine Nucleotide Reduction and Gluconeogenesis in Intact
Thiobacillus neapolitanus
Authors: Roth Charles W. , Hempfling Walter P. , Conners Judith N. , Vishniac Wolf V.
Published: January 2020

Nicotinamide adenine dinucleotide phosphate (reduced form) is formed more rapidly after the addition of thiosulfate to suspensions of intact
Thiobacillus neapolitanus
in the absence of CO
2
than nicotinamide adenine dinucleotide (reduced form). Measurement of acid-stable metabolites shows this phenomenon to be the result of rapid reoxidation of nicotinamide adenine dinucleotide (reduced form) by 3-phosphoglyceric acid and other oxidized intermediates, which are converted to triose and hexose phosphates, and that, in reality, the rate of nicotinamide adenine dinucleotide (oxidized form) reduction exceeds that of nicotinamide adenine dinucleotide phosphate (oxidized form) by approximately 4.5-fold. The overall rate of pyridine nucleotide reduction by thiosulfate (264 nmol per min per mg of protein) is in excess of that rate needed to sustain growth. Pyridine nucleotide reduction, adenosine triphosphate synthesis, and carbohydrate synthesis are prevented by the uncoupler
m
-Cl-Carbonylcyanide phenylhydrazone. Sodium amytal inhibits pyridine nucleotide reduction and carbohydrate synthesis are prevented by the uncoupler
m
-Cl-carbonylcyanide observations are reproduced when sulfide serves as the substrate. The rate of pyridine nucleotide anaerobic reduction with endogenous substrates or thiosulfate is less than 1% of the aerobic rate with thiosulfate. We conclude that the principal, if not the only, pathway of pyridine nucleotide reduction proceeds through an energy-dependent and amytal-sensitive step when either thiosulfate or sulfide is used as the substrate.
Cyclic Adenosine Monophosphate-Independent Mutants of the Lactose Operon of
Escherichia coli
Authors: Arditti Rita , Grodzicker Terri , Beckwith Jon
Published: January 2020

In
Escherichia coli
the transcription of the lactose operon, like other catabolite-sensitive operons, requires catabolite gene activator protein and 3′,5′-cyclic adenosine monophosphate in addition to ribonucleic acid polymerase. We isolated and analyzed
lac
+
revertants from a
crp
−
strain of
E. coli
. We found that revertants with a higher level of expression only for the
lac
operon lie in the
lac
promoter region. These promoter mutations have no effect on operator or repressor function. Two of the revertants in which the lesions have been more precisely mapped carry mutations in the operator proximal segment of the promoter.
Comparison of Acetohydroxy-Acid Synthetases from Two Extreme Thermophilic Bacteria
Authors: Chin Nena W. , Trela John M.
Published: January 2020

The acetohydroxy-acid synthetases from two extreme bacterial thermophiles,
Thermus aquaticus
and
Bacillus
sp., have been studied. The two enzymes have different pH optima, 8 and 6, respectively, and both are feedback inhibited by valine. The inhibition is of interest because it is not expressed below 60 C, but only at higher temperatures which are optimal for catalytic activity. Valine inhibition in
T. aquaticus
was noncompetitive, whereas in
Bacillus
sp., it was competitive. Isoleucine (10
−3
M) also inhibited the two enzymes, whereas leucine (10
−3
M) did not. There was no concerted feedback when the amino acids were added in together. The sensitivity of the enzymes to valine could not be removed by HgCl
2
. Both enzymes required Mg
2+
and thiamine pyrophosphate for optimal activity, whereas only the enzyme from
T. aquaticus
required flavine adenine dinucleotide in addition. None of these cofactors was essential for the feedback inhibition caused by valine. The enzymes from both bacteria could be repressed, but only in the presence of all three branched-chain amino acids indicating that, as in
Escherichia coli
and
Salmonella typhimurium
, the repression system is multivalent.
Stimulation of Cell Division by Croton Oil in Blue-Green Bacteria
Authors: Ingram Lonnie O'Neal , Fisher W. D.
Published: January 2020

The potent tumor-promoting agent croton oil, which has been shown previously to be strongly mitogenic in mammalian cells, stimulates cell division in snake mutants of the blue-green bacterium
Agmenellum quadruplicatum
.
Phosphorylation of Glycerol inStaphylococcus aureus
Authors: Richey D. P. , Lin E. C. C.
Published: January 2020

Staphylococcus aureusdissimilates glycerol via an adenosine triphosphate-dependent kinase and not by the phosphoenolpyruvate phosphotransferase system.
Deoxyribonucleic Acid Synthesis in
recA
and
recB
Derivatives of an
Escherichia coli
K-12 Strain with a Temperature-Sensitive Deoxyribonucleic Acid Polymerase I
Authors: Monk M. , Kinross J. , Town C.
Published: January 2020

recA
and
recB
derivatives of a strain of
Escherichia coli
with a temperature-sensitive deoxyribonucleic acid (DNA) polymerase I (
polA12
) are inviable at high temperature, but continue to incorporate
3
H-thymine into DNA for extended periods. The DNA made in pulse-chase experiments at high temperature in the
polA12
parent and its double-mutant derivatives has been examined by alkaline sucrose gradient sedimentation analysis. The low-molecular-weight DNA fragments made during short pulses were joined at the same rate in each strain. Furthermore, the resulting high-molecular-weight DNA was of the same size in each case and was stable for at least 50 min. It is concluded that the inviability of the double mutants is due neither to a defect in converting low-molecular-weight DNA intermediates to high molecular weight nor to the presence of unrepaired random breaks in their DNA.
Distribution of Ribosomal Ribonucleic Acid Cistrons Among Yeast Chromosomes
Authors: De Kloet Siwo R.
Published: January 2020

High-molecular-weight deoxyribonucleic acid (DNA) of
Saccharomyces carls bergensis
has been fractionated by sucrose density gradient centrifugation. The main DNA fraction has an average molecular weight of about 500 × 10
6
. A major fraction of the DNA molecules containing sequences homologous to ribosomal ribonucleic acid (RNA) sediments as material of this molecular weight. The remainder sediments as material of a molecular weight of about 250 × 10
6
. The latter fraction contains relatively more ribosomal RNA cistrons than the former. Studies on the buoyant density of high-molecular-weight DNA homologous to ribosomal RNA have led to the conclusion that the ribosomal RNA cistrons occur in groups attached to a relatively large amount of nonribosomal RNA and suggest that ribosomal RNA cistrons are distributed over a number of yeast chromosomes.
Metabolism of Phosphatidylglycerol, Phosphatidylethanolamine, and Cardiolipin of
Bacillus stearothermophilus
Authors: Card George L.
Published: January 2020

The total phospholipid content of
Bacillus stearothermophilus
was constant during exponential growth, increased during the transition from the exponential to stationary phase of growth, and then slowly increased during the stationary phase. The first increase was a result of an increase in phosphatidylethanolamine; the second was a result of an increase in cardiolipin. Cessation of aeration of an exponentially growing culture or suspension in a nongrowth medium resulted in an immediate reduction in the rate of total phospholipid and phosphatidylethanolamine synthesis and a quantitative conversion of phosphatidylglycerol to cardiolipin. Cardiolipin appeared to be synthesized by the direct conversion of two molecules of phosphatidylglycerol to cardiolipin. After a 20-min pulse of
32
P, phosphatidylglycerol showed the most rapid loss of
32
P followed by cardiolipin, whereas phosphatidylethanolamine did not lose
32
P. The loss of
32
P from the total lipid pool, phosphatidylglycerol, and cardiolipin was biphasic, with rapid loss during the first two bacterial doublings followed by a greatly reduced rate of loss. The major loss of
32
P from the total phospholipid pool appeared to be by breakdown of cardiolipin. The loss of
32
P from the lipid pool was energy dependent (i.e., did not occur under anaerobic conditions or in the absence of an energy source) and was dependent on some factor other than the concentration of cardiolipin in the cells. The apparent conversion of phosphatidylglycerol to cardiolipin was independent of energy metabolism. Chloramphenicol reduced the rate of turnover of both phosphatidylglycerol and cardiolipin. The rate of lipid synthesis (all phospholipid components) was constant for about 10 min after the addition of chloramphenicol but diminished markedly after 20 min. Turnover of
32
P incorporated into phospholipid during a 30-min period prior to the addition of chloramphenicol was more rapid after the removal of chloramphenicol than that of
32
P incorporated during a 30-min period in the presence of chloramphenicol.