bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical and Ultrastructural Studies on the Cell Walls of the Yeastlike and Mycelial Forms of
Histoplasma farciminosum
Authors: San-Blas Gioconda , Carbonell Luis M.
Published: January 2020

The cell wall of the yeast form of
Histoplasma farciminosum
contains 13.2% β-1,3-glucan, 1.0% galactomannan, and 25.8% chitin, whereas the cell wall of mycelial form has 21.8, 4.5, and 40%, respectively, for the same polymers. Also, the cell wall of the yeast form contains α-1,3-glucan (13.5%) and an unidentified polymer (21.5%). Chitin, one of the structural polymers of both yeast and mycelial cell walls, is identified as thin isolated fibers (4 nm wide) or in thick bundles (50 nm wide) of fibers. β-(1-3)-Glucan is also found as thin isolated fibers indistinguishable from isolated fibers of chitin. Fibers 14 nm wide and resembling α-(1-3)-glucan fibers of other fungi are found in the yeast form. The results reported here do not give support to the proposal for a different taxonomic classification.
Statistical Estimate of the Total Number of Operons Specific for
Bacillus subtilis
Sporulation
Authors: Hranueli D. , Piggot P. J. , Mandelstam J.
Published: January 2020

As an alternative to exhaustive mapping, an attempt has been made to obtain a rough estimate of the total number of sporulation operons by statistical treatment. Sixteen sporulation mutants taken at random were characterized biochemically and morphologically. The mutations they contained were mapped to determine whether they fell into any one of 23 known operons. From the proportion that do so (10/16), it is calculated that the most probable number of sporulation operons is 37 (68% confidence limits of 31 and 46). If allowance is made for the fact that two of the operons apparently contain mutagenic “hot spots” and the calculation is amended accordingly, the most probable numbers of operons becomes 42 (limits 33 and 59).
Culture Medium for Enterobacteria
Authors: Neidhardt Frederick C. , Bloch Philip L. , Smith David F.
Published: January 2020

A new minimal medium for enterobacteria has been developed. It supports growth of
Escherichia coli
and
Salmonella typhimurium
at rates comparable to those of any of the traditional media that have high phosphate concentrations, but each of the macronutrients (phosphate, sulfate, and nitrogen) is present at a sufficiently low level to permit isotopic labeling. Buffering capacity is provided by an organic dipolar ion, morpholinopropane sulfonate, which has a desirable pK (7.2) and no apparent inhibitory effect on growth. The medium has been developed with the objectives of (i) providing reproducibility of chemical composition, (ii) meeting the experimentally determined nutritional needs of the cell, (iii) avoiding an unnecessary excess of the major ionic species, (iv) facilitating the adjustment of the levels of individual ionic species, both for isotopic labeling and for nutritional studies, (v) supplying a complete array of micronutrients, (vi) setting a particular ion as the crop-limiting factor when the carbon and energy source is in excess, and (vii) providing maximal convenience in the manufacture and storage of the medium.
Photoinactivation of Ammonia Oxidation in
Nitrosomonas
Authors: Hooper Alan B. , Terry Kathleen R.
Published: January 2020

Photoinactivation of ammonia oxidation in cells of
Nitrosomonas
was shown to follow first-order kinetics with a rate constant proportional to incident light intensity. The action spectrum for photoinactivation consisted of a broad peak in the ultraviolet range, where both hydroxylamine and ammonia oxidation were affected, and a shoulder at approximately 410 nm where only ammonia oxidation was affected. In photoinactivated cells, hydroxylamine but not ammonia was oxidized to nitrite and hydroxylamine but not ammonia caused reduction of cytochromes in vivo. The amount per cell of the following constituents was not measurably altered by photoinactivation: cytochromes
b, c, a
, and P460; ubiquinone; phospholipid; free amino acids; hydroxylamine-dependent nitrite synthetase; nitrite reductase;
p
-phenylenediamine oxidase; and cytochrome
c
oxidase. Malonaldehyde or lipid peroxides were not detected in photoinactivated cells. Photoinactivation was prevented (i) under anaerobic conditions, (ii) in the presence of methanol, allylthiourea, thiosemicarbazide, hydroxylamine, ethylxanthate, or CO at concentrations wich caused 100% inhibition of ammonia oxidation, and (iii) at concentrations of ammonia or hydroxylamine which gave a rapid rate of nitrite production. Recovery of ammonia oxidation activity in 90% inactivated cells took place in 6 h, required an energy and/or nitrogen source, and was inhibited by 400 μg of chloramphenicol per ml.
Transport of Biosynthetic Intermediates: Regulation of Homoserine and Threonine Uptake in
Escherichia coli
Authors: Templeton Bonnie A. , Savageau Michael A.
Published: January 2020

Homoserine is transported by a single system that it shares with alanine, isoleucine, leucine, phenylalanine, threonine, valine and perhaps cysteine, methionine, serine, and tyrosine. We investigated the regulation of this transport system and found that alanine, isoleucine, leucine, methionine, and valine each repress the homoserine-transporting system. From the concentration resulting in 50% repression of this transport system and the maximal amount of repression, we ranked the amino acids according to their effectiveness in repressing homoserine transport (in decreasing order): leucine>methionine>alanine>valine>isoleucine. The exponential rate of decrease in transport capacity after leucine addition equals the exponential growth rate of the culture, and protein synthesis is necessary for the derepression seen when leucine is removed. Threonine, in addition to using the above system, is transported by a second system shared with serine. We present further evidence for this serine-threonine transport system and show that it is not regulated like the homoserine-transporting system.
Induction of
Neurospora crassa
Laccase with Protein Synthesis Inhibitors
Authors: Froehner Stanley C. , Eriksson Karl-Erik
Published: January 2020

Rapidly growing
Neurospora crassa
does not produce laccase (
p
-diphenol:oxygen oxidoreductase; EC 1.10.3.2). Low concentrations of cycloheximide induce the production of this enzyme, most of which is secreted into the media. In general, limited inhibition of protein synthesis seems to derepress laccase synthesis since actinomycin D and, to a limited extent, puromycin also induce laccase production. Similarities in the conditions of laccase and tyrosinase induction, plus investigations with two tyrosinase regulatory mutants, suggest that the production of these two phenol oxidases is controlled by the same mechanism. As shown by polyacrylamide gel electrophoresis, most of the 10 to 12 proteins normally present in the medium virtually disappear during cycloheximide treatment. In contrast, the amounts of two proteins that are present in only very minor quantities, if at all, in normal culture filtrates increase dramatically. One of these proteins co-migrates with laccase, whereas the other has not been identified.
Purification and Properties of
Neurospora crassa
Laccase
Authors: Froehner Stanley C. , Eriksson Karl-Erik
Published: January 2020

Extracellular
Neurospora
laccase (
p
-diphenol:oxygen oxidoreductase; EC 1.10.3.2) has been purified to apparent homogeneity by classical purification techniques. The enzyme, which consists of mainly one form, has a molecular weight of 64,800 and contains 11% carbohydrate. The ultraviolet, visible, and electron paramagnetic resonance spectra indicate that both type I and type II copper are present, as described for the
Polyporus versicolor
enzyme. With the exception of phloroglucinol, only
para
- and
ortho
-diphenols serve as effective substrates for the enzyme. Like the extracellular form, intracellular laccase is a glycoprotein as shown by its ability to bind to Concanavalin A Sepharose. Other studies, including gel filtration and ion-exchange chromatography, revealed no differences between the intracellular and extracellular enzymes, suggesting that intracellular laccase is destined for excretion by the cell.
Dark-Field Electron Microscopy of Thin Sections of
Trichosporon cutaneum
Authors: Weibull Claes
Published: January 2020

Dark-field electron micrographs of aldehyde-fixed, unstained yeast-phase cells of
Trichosporon cutaneum
exhibit remarkable contrast and good resolution when the sections studied are less than 25 nm thick and conical illumination is used.
Ammonia or Ammonium Ion as Substrate for Oxidation by
Nitrosomonas europaea
Cells and Extracts
Authors: Suzuki Isamu , Dular Usha , Kwok S. C.
Published: January 2020

The effect of pH on the

K
m

values for ammonia was studied in its oxidation by
Nitrosomonas
cells and cell-free extracts. The

K
m

values decreased markedly with increasing pH, suggesting (NH
3
) rather than (NH
4
+
) as the actual substrate for oxidation.
Glucose Metabolism in
Neisseria gonorrhoeae
Authors: Morse Stephen A. , Stein Stefanie , Hines James
Published: January 2020

The metabolism of glucose was examined in several clinical isolates of
Neisseria gonorrhoeae
. Radiorespirometric studies revealed that growing cells metabolized glucose by a combination on the Entner-Doudoroff and pentose phosphate pathways. A portion of the glyceraldehyde-3-phosphate formed via the Entner-Doudoroff pathway was recycled by conversion to glucose-6-phosphate. Subsequent catabolism of this glucose-6-phosphate by either the Entner-Doudoroff or pentose phosphate pathways yielded CO
2
from the original C6 of glucose. Enzyme analyses confirmed the presence of all enzymes of the Entner-Doudoroff, pentose phosphate, and Embden-Meyerhof-Parnas pathways. There was always a high specific activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) relative to that of 6-phosphogluconate dehydrogenase (EC 1.1.1.44). The glucose-6-phosphate dehydrogenase utilized either nicotinamide adenine dinucleotide phosphate or nicotinamide adenine dinucleotide as electron acceptor. Acetate was the only detectable nongaseous end product of glucose metabolism. Following the disappearance of glucose, acetate was metabolized by the tricarboxylic acid cycle as evidenced by the preferential oxidation of [1-
14
C]acetate over that of [2-
14
C]acetate. When an aerobically grown log-phase culture was subjected to anaerobic conditions, lactate and acetate were formed from glucose. Radiorespirometric studies showed that under these conditions, glucose was dissimilated entirely by the Entner-Doudoroff pathway. Further studies determined that this anaerobic dissimilation of glucose was not growth dependent.
Effect of Cyclic Guanosine 3′,5′-Monophosphate on the Synthesis of Enzymes Sensitive to Catabolite Repression in Intact Cells of
Escherichia coli
Authors: Artman Michael , Werthamer Seymour
Published: January 2020

Cyclic guanosine 3′,5′-monophosphate inhibits the synthesis of β-galactosidase and tryptophanase in cultures of
Escherichia coli
growing in minimal media with glucose or glycerol as the carbon source. Cyclic guanosine 3′,5′-monophosphate acts at the transcriptional level in the
lac
operon, it exerts its action at the promoter site of the operon, and requires the presence of functional cyclic adenosine 3′,5′-monophosphate receptor protein.
Effects of Ammonium,
l
-Glutamate, and
l
-Glutamine on Nitrogen Catabolism in
Aspergillus nidulans
Authors: Hynes M. J.
Published: January 2020

During growth of
Aspergillus nidulans
in medium containing ammonium the specific activities of most enzymes involved in catabolism of nitrogen sources are low (ammonium repression). The
gdhA10
lesion, which results in loss of nicotinamide adenine dinucleotide phosphate-linked glutamate dehydrogenase activity, has been shown to lead to partial relief of ammonium repression of three amidase enzymes as well as histidase. The
areA102
lesion led to altered levels of these enzymes but did not greatly affect ammonium repression. The double mutant
areA102,gdhA10
was almost completely insensitive to ammonium repression of two of the amidase enzymes and histidase. This suggests that an interaction between the
areA
and
gdhA
genes in determining responses to ammonium occurs. Growth of mycelium in medium containing
l
-glutamate has been found to result in lowered levels of all four enzymes, and this occurs in strains insensitive to ammonium repression. Very strong repression in all strains occurred during growth in medium containing
l
-glutamine. Relief of these repressive effects of glutamate and glutamine was blocked by cycloheximide. Glutamate and glutamine had similar effects on the production of extracellular protease activity, and growth on glutamine led to low levels of urate oxidase. In contrast to the above enzymes, nitrate reductase was insensitive to the effects of glutamine and glutamate, even though this enzyme is very sensitive to ammonium repression. Although other possibilities exist, it is suggested that there may be mechanisms of general control of nitrogen-catabolic enzymes other than ammonium repression.
Mis-Regulation of 3-Deoxy-
d
-Arabino-Heptulosonate 7-Phosphate Synthetase Does Not Account for Growth Inhibition by Phenylalanine in
Agmenellum quadruplicatum
Authors: Jensen Roy A. , Stenmark-Cox S. , Ingram Lonnie O.
Published: January 2020

The growth of the blue-green bacterium,
Agmenellum quadruplicatum
, is inhibited in the presence of
l
-phenylalanine. This species has a single, constitutively synthesized 3-deoxy-
d
-arabino-heptulosonate 7-phosphate (DAHP) synthetase.
l
-Phenylalanine inhibits DAHP synthetase non-competitively with respect to both substrate reactants. Other aromatic amino acids do not inhibit the activity of DAHP synthetase. A common expectation for branch-point enzymes such as DAHP synthetase is a balanced pattern of feedback control by all of the ultimate end products. It seemed likely that growth inhibition might equate with defective regulation within the branched aromatic pathway. Accordingly, the possibility was examined that mis-regulation of DAHP synthetase by
l
-phenylalanine in wild-type cells causes starvation for precursors of the other aromatic end products. However, the molecular basis for growth inhibition cannot be attributed to
l
-phenylalanine inhibition of DAHP synthetase for the following reasons: (i) DAHP synthetase enzymes from
l
-phenylalanine-resistant mutants are more, rather than less, sensitive to feedback inhibition by
l
-phenylalanine. (ii) Shikimate not only fails to antagonize inhibition, but is itself inhibitory. (iii) Neither the sensitivity nor the completeness of
l
-phenylalanine inhibition of the wild-type enzyme in vitro appears sufficient to account for the potent inhibition of growth in vivo by
l
-phenylalanine. The dominating effect of
l
-phenylalanine in the control of DAHP synthetase appears to reflect a mechanism that prevents rather than causes growth inhibition by
l
-phenylalanine. The alteration of the control of DAHP synthetase in mutants selected for resistance to growth inhibition by
l
-phenylalanine did indicate that the cause for this metabolite vulnerability can be localized within the aromatic amino acid pathway. Apparently, an aromatic intermediate (between shikimate and the end products) accumulates in the presence of
l
-phenylalanine, causing toxicity by some unknown mechanism. It is concluded that phenylpyruvate, potentially formed by transamination of
l
-phenylalanine, is an unlikely cause of growth inhibition. Although several significant questions remain unanswered, our results suggest that single-effector control of DAHP synthetase, the first regulatory enzyme activity of a branched pathway, may be more appropriate than it would seem a priori.
Apparent Mutagenic Effect of Induction of Lambda Prophage Inserted Between
lysA
and
thyA
Authors: Chung Shiau-Ta , Greenberg G. Robert
Published: January 2020

Induction of a heat-inducible abnormal lambda prophage inserted between
lysA
and
thyA
in
Escherichia coli
resulted in a number of auxotrophic mutants in the surviving cured-cell populations. These mutants could not be accounted for by deletions arising on formation of lambda hybrid particles carrying regions adjacent to the insertion site. The properties of these mutants, which were almost all spontaneously revertable, have been described and mapped by F′ episome complementation. Tentatively, it was suggested that induction of the lambda lysogen leads to a mutagenic state.
Differential Thermolability of Exonuclease and Endonuclease Activities of the
recBC
Nuclease Isolated from Thermosensitive
recB
and
recC
Mutants
Authors: Kushner Sidney R.
Published: January 2020

The
recBC
nuclease (also called exonuclease V) has been partially purified from
Escherichia coli
K-12 strains carrying the thermosensitive
recB270, recC271
, and
recB270 recC271
mutations. Of the multiple activities associated with the enzyme, only the adenosine 5′-triphosphate-dependent exonucleolytic hydrolysis of duplex deoxyribonucleic acid (DNA) is abnormally thermolabile. The exo- and endonucleolytic degradation of single-stranded DNA is no more thermosensitive than that catalyzed by the wild-type enzyme. These results suggest that the defects in genetic recombination, DNA repair, and the maintenance of cell viability observed in
recBC
mutants in vivo result primarily from the specific loss of adenosine 5′-triphosphate-dependent exonuclease active on duplex DNA.
Molecular Nature of the Deoxyribonucleic Acid of a Thermosensitive R Factor, Rts1
Authors: DiJoseph Carl G. , Kaji Akira
Published: January 2020

The deoxyribonucleic acid of the thermosensitive R factor, Rts1, has been examined by the technique of sedimentation in alkaline sucrose, electron microscopy, and radiation target size. All these methods yielded a molecular weight of approximately 120 million for Rts1 deoxyribonucleic acid in
Escherichia coli
. Sedimentation analysis revealed that Rts1 deoxyribonucleic acid in
Proteus mirabilis
was also 120 million daltons. Rts1 did not segregate into
E. coli
minicells under the conditions where another smaller non-thermosensitive R factor could.
Synthesis of Colicin E1 in a Cell-Free System
Authors: Eichenlaub R.
Published: January 2020

Colicin E1 was synthesized in a cell-free system. The in vitro synthesis was found to be dependent on the Col E1 DNA concentration and was not enhanced by the addition of mitomycin C.
Assay and regulation of S-adenosylmethionine synthetase in Saccharomyces cerevisiae and Candida utilis
Authors: Holcomb E R , Shapiro S K
Published: January 2020

A simple and sensitive assay for S-adenosylmethionine (SAM) synthetase is described which depends on the quantitative separation of the product, [14CH3]S-adenosylmethionine, from the substrate, L-[14CH3]methionine, on a Bio-Rex 70 column. L-Methionine protects the enzyme during preparation of cell extracts by sonic treatment but causes repression of enzyme activity during growth of Candida utilis. The presence of 5 mM methionine in the growth medium repressed SAM synthetase specific activity threefold compared to the specific acitivity of the enzyme isolated from cells grown in unsupplemented medium. Conversely, the presence of methionine in the growth medium resulted in an 80-fold increase in the intracellular concentration of SAM as compared to the Sam accumulated intracellularly in unsupplemented cultures.
Recombination and the Escherichia coli K-12 sex factor F
Authors: Willetts N S
Published: January 2020

Recombination between two Flac tra minus elements to give Flac tra plus recombinants was measured in Rec plus and Rec minus strains of Escherichia coli K-12. Polar tra mutations were used to increase the proportion of tra plus recombinants among the parental Flac tra minus elements transferred by complementation. The kinetics, measured in a rec plus strain, showed that recombination began about 1 h after the initiation of mating and was completed about 1 h later. Recombination was abolished in a recA minus strain, reduced by two-thirds in a recF minus strain, and unaffected in recB minus and recC minus strains. It is proposed that the part not due to the RecF pathway results from a RecBC- and RecF-independent system for formation of single-stranded joins. One such join could be followed either by transfer and a site-specific recombination event, or by a second single-stranded join and then transfer: in either case replication and inheritance of the recombinant molecule would be dependent upon the F transfer replication system. Chromosome mobilization by an F' element was normal in a recB plus recF minus strain, and was reduced only fourfold in a recB minus recF plus strain: in the latter strain, both the RecF pathway and the system for single-stranded joins may have contributed to mobilization. Measurement of post-conjugational chromosomal recombination in exponential-phase recipient cells carrying surface exclusion-deficient Flac mutants indicated that F does not itself determine a generalized recombination system able to replace the RecA plus product or the RecBC and RecF pathways.
Composition of the first enzyme of histidine biosynthesis isolated from wild-type and mutant operator strains of Salmonella typhimurium
Authors: Parsons S M , Lipsky M
Published: January 2020

The first enzyme of histidine biosynthesis in Salmonella typhimurium, adenosine triphosphate phosphoribosyltransferase (EC 2.4.2.17), has been purified from two bacterial strains containing histidine operator deletions and compared to the eenzyme from a strain that has a normal operator. The enzymes isolated in different ways also are compared. Evidence as to the separateness of the operator and first structural gene or covalent modification of the first enzyme was sought. Specific activity, histidine feedback inhibition, amino acid analysis, discontinuous-gel electrophoresis, and gel filtration of the native enzyme, and Ouchterlony double-immunodiffusion tests were carried out. The purified enzyme contains little phosphorous and has five cysteine residues per subunit, which all are readily titratable. No evidence for differences in the enzyme preparations was obtained. Thus, no evidence for overlap of the histidine operator with the first structural gene was obtained.
Erythritol catabolism by Brucella abortus
Authors: Sperry J F , Robertson D C
Published: January 2020

Cell extracts of Brucella abortus (British 19) catabolized erythritol through a series of phosphorylated intermediates to dihydroxyacetonephosphate and CO-2. Cell extracts required adenosine 5'-triphosphate (ATP), nicotinamide adenine dinucleotide (NAD), Mg2+, inorganic orthophosphate, and reduced glutathione for activity. The first reaction in the pathway was the phosphorylation of mesoerythritol with an ATP-dependent kinase which formed d-erythritol 1-phosphate (d-erythro-tetritol 1-phosphate). d-Erythritol 1-phosphate was oxidized by an NAD-dependent dehydrogenase to d-erythrulose 1-phosphate (d-glycero-2-tetrulose 1-phosphate). B. abortus (US-19) was found to lack the succeeding enzyme in the pathway and was used to prepare substrate amounts of d-erythrulose 1-phosphate. d-Erythritol 1-phosphate dehydrogenase (d-erythro-tetritol 1-phosphage: NAD 2-oxidoreductase) is probably membrane bound. d-Erythrulose 1-phosphate was oxidized by an NAD-dependent dehydrogenase to 3-keto-l-erythrose 4-phosphate (l-glycero-3-tetrosulose 4-phosphate) which was further oxidized at C-1 by a membrane-bound dehydrogenase coupled to the electron transport system. Either oxygen or nitrate had to be present as a terminal electron acceptor for the oxidation of 3-keto-l-erythrose 4-phosphate to 3-keto-l-erythronate 4-phosphate (l-glycero-3-tetrulosonic acid 4-phosphate). The beta-keto acid was decarboxylated by a soluble decarboxylase to dihydroxyacetonephosphate and CO-2. Dihydroxyacetonephosphate was converted to pyruvic acid by the final enzymes of glycolysis. The apparent dependence on the electron transport system of erythritol catabolism appears to be unique in Brucella and may play an important role in coupling metabolism to active transport and generation of ATP.
Ultrastructure of lipopolysaccharide isolated from Thermoplasma acidophilum
Authors: Mayberry-Carson K J , Roth I L , Smith P F
Published: January 2020

The fine structure of lipopolysaccharide isolated from Thermoplasma acidophilum was examined by electron microscopy. Negative staining of the lipopolysaccharide revealed long, ribbon-like structures with some branching. The average width of the lipopolysaccharide ribbons was 5 nm. Treatment of the lipopolysaccharide with 0.5% sodium dodecyl sulfate resulted in the dissociation of the ribbon-like structures to spherical- and vesicular-shaped particles and some short, rodlike structures. Results suggest that the lipopolysaccharide from T. acidophilum is morphologically similar to lipopolysaccharide isolated from gram-negative bacteria.
Fruiting-body formation and myxospore differentiation and germination in Mxyococcus xanthus viewed by scanning electron microscopy
Authors: Shimkets L , Seale T W
Published: January 2020

Streaming cells, fruiting bodies, and single cells undergoing myxospore differentiation and germination were examined in the FB strain of Myxococcus xanthus by scanning electron microscopy. Myxospores differentiated in fruiting bodies differed in size, in kinetics of germination, in the fate of the myxospore capsule, and in the external structure of the walls of newly emerged cells when compared with myxospores differentiated in liquid medium after glycerol induction. Vegetative cells outgrowing from glycerol-induced myxospores were regularly pleomorphic, a condition that persisted through the first cell division.
Glucose transport-deficient mutant of Neurospora crassa with an unusual rhythmic growth pattern
Authors: Halaban R
Published: January 2020

A new mutant of Neurospora crassa has been isolated from the patch strain. The phenotype of the new mutant includes the periodic production of sparse and dense aerial hyphae and the inability to utilize carbohydrates. The biochemical lesion was identified as a deficiency in the low-affinity glucose transport system. The high-affinity transport system appeared normal. External conditions such as medium composition, temperature change, and light-dark cycles affected the rhythm of hyphal production to a different extent in the mutant from that in the parental strain. The lesion in the mutant was mapped on the far left arm of linkage group IV.
Endonuclease from
Dictyostelium discoideum
That Attacks Ultraviolet-Irradiated Deoxyribonucleic Acid
Authors: Deering R. A. , Jensen D. S.
Published: January 2020

An endonuclease activity yielding single-strand breaks in ultraviolet light-irradiated φX-174 RF I DNA in vitro has been detected in homogenates of the amoebae of the cellular slime mold,
Dictyostelium discoideum
.
Role of Ribonucleic Acid Synthesis in Replication of Deoxyribonucleic Acid
Authors: Pato Martin L.
Published: January 2020

An experiment previously interpreted to show a ribonucleic acid requirement for propagation of deoxyribonucleic replication is reexamined and the earlier interpretation is shown to be incorrect.
Capacity of the outer membrane of a gram-negative marine bacterium in the presence of cations to prevent lysis by Triton X-100
Authors: Unemoto T , MacLeod R A
Published: January 2020

Cells of marine pseudomonad B-16 (ATCC 19855) washed with a solution containing 0.3 M NaCl, 50 mM MgCl2, and 10 mM KCl (complete salts) could be protected from lysis in a hypotonic environment if the suspending medium contained either 20 mM Mg2+, 40 mM Na+, or 300 mM K+. When the outer double-track layer (the outer membrane) of the cell envelope was removed to yield mureinoplasts, the Mg2+, Na+ or K+, requirements to prevent lysis were raised to 80, 210, and 400 mM, respectively. In the presence of 0.1% Triton X-100, 220, 320, and 360 mM Mg2+, Na+ or K+, respectively, prevented lysis of the normal cells. Mureinoplasts and protoplasts, however, lysed instantly in the presence of the detergent at all concentrations of Mg2+, Na+, or K+ tested up to 1.2 M. Thus, the structure of the outer membrane appears to be maintained by appropriate concentrations of Mg2+ or Na+ in a form preventing the penetration of Triton X-100 and thereby protecting the cytoplasmic membrane from dissolution by the detergent. K+ was effective in this capacity with cells washed with complete salts solution but not with cells washed with a solution of NaCl, suggesting that bound Mg2+ was required in the cell wall membrane for K+ to be effective in preventing lysis by the detergent. At high concentrations (1 M) K+ and Mg2+, but not Na+, appeared to destabilize the structure of the outer membrane in the presence of Triton X-100.
Accumulation of arsenate, phosphate, and aspartate by Sreptococcus faecalis
Authors: Harold F M , Spitz E
Published: January 2020

Uptake of arsenate and phosphate by Streptococcus faecalis 9790 is strictly dependent on concurrent energy metabolism and essentially unidirectional. targinine supports uptake only in presence of glycerol or related substances; glycerol is not directly involved in transport but depletes the cellular orthophosphate pool and thus relieves feedback inhibition of transport. Uptake of phosphate and arsenate is stimulated by K+ and by other permeant cations. The results suggest that electroneutrality is preserved by compensatory movement of either H+ or OH minus. Ionophores and N,N'-dicyclohexylcarbodiimide, which prevent establishment of a proton motive force, block the accumulation of thiomethylgalactoside and of threonine but not that of arsenate or phosphate. We conclude that arsenate accumulation requires adenosine 5'-triphosphate but is not driven by the proton-motive force. However, conditions and reagents that lower the cytoplasmic pH do inhibit accumulation of arsenate and phosphate, suggesting that uptake depends on the capacity of the cells to maintain a neutral or alkaline cytoplasm. We therefore propose that phosphate accumulation is an electroneutral exchange for OH driven by adenosine 5'-triphosphate or by a metabolite thereof. Accumulation of aspartate and glutamate also requires adenosine 5'-triphosphate but not the proton-motive force and may involve a similar mechanism.
Conjugational transfer of genes determining plant virulence in Erwinia amylovora
Authors: Pugashetti B K , Starr M P
Published: January 2020

A stable virulent donor strain (EA 178R1-99) of Erwinia amylovora can transfer, by conjugation during a 3-h mating period, the gene or genes which determine(s) plant virulence to avirulent recipient strains (EA178-M64S1 and EA178-M173S1) of Escherichia amylovora. The virulence of over 200 recombinant clones was tested; they all were as virulent on immature Bartlett pear fruits (and, in the smaller series of strains tested, also, on Pyracantha twigs) as was the parent donor strain. Although the avirulent recipeint strains are amino acid auxotrophs, addition of the required amino acids to the inocula in plant virulence trials does not of itself restore virulence. Two small series of prototrophic revertant clones were selected from the auxotrophic avirulent recipient strains; only nine of the 21 prototrophic revertant clones regained virulence, whereas the other 12 prototrophic revertant clones remained avirulent, again suggesting a lack of parallelism between nutritional status and virulence in this system. Preliminary interrupted mating trials, carried out at 15-min intervals over 3 h, show that ser is transferred during the first 15 min, that pro starts entering at about 75 min (and with a higher frequency later), and that lac (originating from an integrated Escherichia coli F'lac) enters toward the end of the 3-h mating period and at a reduced frequency compared to the other markers. The gene or genes which determine(s) plant virulence in this Escherichia amylovora donor strain appear(s) to be transferred readily and seemingly completely to recipient strains during the first 15 min of a 3-h mating period. Exposure of the virulent donor strain to acridine orange or ethidium bromide does not result in loss of virulence, suggesting (but, of course, not proving conclusively) that the determinant(s) of virulence in Escherichia amylovora might be chromosomal rather than extrachromosomal.
Characterization of an inhibitor of ribonucleic acid polymerase from the mycelial phase of Histoplasma capsulatum
Authors: Boguslawski G , Kobayashi G S , Schlessinger D , Medoff G
Published: January 2020

An inhibitor of ribonucleic acid polymerases has been obtained from the mycelial phase of Histoplasma capsulatum and partially characterized. The inhibitor, called histin, was purified 200-fold by heat treatment at 100 C and electrophoresis on polyacrylamide gels. Histin moved in electrophoresis as if negatively charged; it was insensitive to treatment with ribonuclease of deoxyribonuclease but was completely digested by Pronase. Sucrose gradient centrifugation suggests a molecular weight of 24,000. The possibility of a regulatory role for histin in the life cycle of H. capsulatum is discussed.
Fate of heterologous deoxyribonucleic acid in Bacillus subtilis
Authors: Piechowska M , Soltyk A , Shugar D
Published: January 2020

CsCl density gradient fractionation of cell lysates was employed to follow the fate of Escherichia coli, phage T6, and non-glucosylated phage T6 deoxyribonucleic acid (DNA) after uptake by competent cells of Bacillus subtilis 168 thy minus trp minus. Shortly after uptake, most of the radioactive Escherichia coli or non-glucosylated T6 DNA was found in the denatured form; the remainder of the label was associated with recipient DNA. Incubation of the cells after DNA uptake led to the disappearance of denatured donor DNA and to an increase in the amount of donor label associated with recipient DNA. These findings are analogous to those previously reported with homologous DNA. By contrast, T6 DNA, which is poorly taken up, appeared in the native form shortly after uptake and was degraded on subsequent incubation. The nature of the heterologous DNA fragments associated with recipient DNA was investigated with Escherichia coli 2-H and 3-H-labeled DNA. Association of radioactivity with recipient DNA decreased to one-fourth in the presence of excess thymidine; residual radioactivity could not be separated from recipient DNA by shearing (sonic oscillation) and/or denaturation, but was reduced by one-half in the presence of a DNA replication inhibitor. Residual radioactivity associated with donor DNA under these conditions was about 5% of that originally taken up. Excess thymidine, but not the DNA replication inhibitor, also decreased association of homologous DNA label with recipient DNA; but, even in the presence of both of these, the decrease amounted to only 60%. It is concluded that most, or all, of the Escherichia coli DNA label taken up is associated with recipient DNA in the form of mononucleotides via DNA replication.
Lipophilic chelator inhibition of electron transport in Escherichia coli
Authors: Crane R T , Sun I L , Crane F L
Published: January 2020

The lipophilic chelator bathophenanthroline inhibits electron transport in membranes from Escherichia coli. The less lipophilic 1,10-phenanthroline, bathophenanthroline sulfonate, and alpha,alpha-dipyridyl have little effect. Reduced nicotinamide adenine dinucleotide oxidase is more sensitive to bathophenanthroline inhibition than lactate oxidase activity. Evidence for two sites of inhibition comes from the fact that both reduced nicotinamide adenine dinucleotide menadione reductase and duroquinol oxidase activities are inhibited. Addition of uncouplers of phosphorylation before bathophenanthroline protects against inhibition.
Fate of transforming bacteriophage HP1 deoxyribonucleic acid in Haemophilus influenzae lysogens
Authors: Stuy J H
Published: January 2020

The biological fate of temperate phage HP1 deoxyribonucleic acid (DNA) was followed after uptake by defectively lysogenic competent Haemophilus influenzae cultures. The similar inactivation kinetics of three single phage genetic markers and of their triple combination indicated a complete rather than partial destruction of about half of the adsorbed DNA molecules. Intracellular DNA breakdown products were tentatively identified by hydroxyapatite column chromatography as short single strands and extensively damaged short double strands. Integrated donor DNA (after single-strand insertion?) was still highly efficient for triple-marker co-transformation. This suggests that whole or nearly whole donor DNA molecules were integrated. Some donor DNA was never integrated but remained largely unaltered. This DNA fraction did not contain significant amounts of recipient prophage marker activity. It is concluded that it had not participated in some kind of reciprocal recombination event involving the recipient chromosome. Since very similar phage DNA marker inactivation rates were observed after adsorption by competent nonlysogenic recipients (transfection), the relationship between biological inactivation of adsorbed donor phage DNA and its integration in lysogenic recipients is not clear.
Rate stimulation of deoxyribonucleic acid synthesis after inhibition
Authors: Zaritsky A
Published: January 2020

The degree to which the rate of deoxyribonucleic acid synthesis in thy- cultures of Escherichia coli is stimulated after a period of thymine starvation is shown to be a function of the concentration of thymine present as well as of the culture doubling time. Inhibition of deoxyribonucleic acid synthesis by nalidixic acid yields comparable results. Periods of thymine starvation exceeding one doubling time appear to cause an irreversible inactivation of a fraction of the replication forks in the culture.
Interaction of the expression of two membrane genes, acrA and plsA, in Escherichia coli K-12
Authors: Nakamura H , Tojo T , Greenberg J
Published: January 2020

The mutation acrA1, leading to acriflavine sensitivity through disorganization of the plasma membrane, is located between proC and purE on the Escherichia coli K-12 chromosome. Gene plsA has been reported to determine biosynthesis of membrane phospholipid and to be located very near acrA (1). Genes acrA and plsA fall into different cistrons and are arranged in the order proC-acrA-plasA-purE. The genes were shown to interact with each other. Introduction of acrA mutation into a plsA temperature-sensitive mutant mitigated the heat sensitivity. Plasmid (F-gal+) stability in acrA mutants was restored by introduction of the plasA mutation into the acrA cells. When an Hfr plsA donor was conjugated with an acrA recipient, or when reciprocally conjugated, the exogenotes were eliminated at high frequency during subsequent subcultivation in broth. However, the exogenotes were not eliminated in all other allelic combinations of genes acrA and plsA. When an F-gal+ plasmid was introduced into the unstable heterozygotes (acrA+plsA/acrApls1+), the plasmids were stably hosted, whereas the acrA+ plasA exogenotes were spontaneously lost at a high frequency. On the other hand, when the unstable heterozygotes carrying F-gal+ were cultured in acriflavine-containing medium, the F-gal+ plasmids were preferentially eliminated but the acrA+plasA exogenotes were not affected. The results suggest that the organization of the plasma membrane controls the recombination of the exogenotes introduced into zygotes.
Microbial transformation of artificial estrogens of the allenolic group
Authors: Maugras M , Lorrain M , Lematre J , Granger P
Published: January 2020

When 2,2-dimethyl 3-(2'-naphthyl 6'-hydroxy) pentanoic acid, an artificial estrogen of the allenolic acid group, was added to an exponential-phase growth culture of Neurospora crassa (in Horowitz medium), it was transformed into its hydroxylated derivative, 2,2-dimethyl 3-(2'-naphthyl 4',6'-dihydroxy)pentaoic acid. To study this transformation, radioactive 2-methyl-[2-14-C=A1methyl 3-(2'-naphthyl 6'-hydroxy) pentanoic acid has been prepared. The rate of metabolism of allenolic acids varies in the same way as their estrogenic activity.
Role of adenylate kinase in the regulation of macromolecular biosynthesis in a putative mutant of Escherichia coli defective in membrane phospholipid biosynthesis
Authors: Glaser M , Nulty W , Vagelos P R
Published: January 2020

The regulation of macromolecular biosynthesis was studied in a temperature-sensitive mutant of Escherichia coli previously identified as containing a single mutation causing a thermolabile sn-glycerol-3-phosphate acyltransferase, the first enzyme of the pathway for phospholipid biosynthesis. When this mutant was shifted to a nonpermissive temperature, phospholipid synthesis, as well as ribonucleic acid, deoxyribonucleic acid, and protein synthesis, decreased in a coordinate manner, suggesting the existence of a common regulatory mechanism. During the same time that the rate of macromolecular synthesis was decreasing at the nonpermissive temperature, the intracellular concentration of adenosine 5'-triphosphate dropped dramatically and the concentration of adenosine monophosphate increased. The concentration of adenosine 5'-diphosphate dropped, but not as markedly. The decrease in macromolecular synthesis and the changes in the adenine nucleotide concentrations can now be attributed to a thermolabile adenylate kinase. The inactivation of adenylate kinase prevented the cell from converting adenosine 5'-monophosphate to adenosine 5'-diphosphate and consequently from making adenosine 5'-triphosphate. This in turn caused a decrease in the rate of macromolecular synthesis and cell growth. Adenylate kinase, therefore, is a key enzyme in controlling the rate of cell growth. The nature of the possible relationship between adenylate kinase and glycerol-3-phosphate acyltransferase is discussed.
Effect of uncouplers on "downhill" beta-galactoside transport in energy-depleted cells of Escherichia coli
Authors: Cecchini G , Koch A L
Published: January 2020

Galactoside permease-containing cells of Escherichia coli can be depleted of energy reserves so that the "downhill" cellular hydrolysis of o-nitrophenyl-beta-d-galactopyranoside (ONPG) no longer takes place. Treatment of such energy-depleted cells with proton-conducting agents such as carbonylcyanide m-chlorophenylhydrazone results in stimulation of ONPG transport. The same agents lower transport of non-energy-depleted cells towards the same levels that result from stimulation of the energy depleted cells. Of course, these agents prevent "uphill" accumulation against a concentration gradient under all conditions. Since uncouplers allow normal and energy-depleted cells to assume the same facilitated transport capability, these results lend support to the chemiosmotic hypothesis of Mitchell that comigration of charge is necessary for the transport of neutral galactosides. Our results imply that a potential favorable to transport is maintained by metabolism in non-energy-depleted cells, whereas an unfavorable potential is developed in the initial instant of time when energy-depleted cells are given ONPG.
Mode of action of alpha-dehydrobiotin, a biotin analogue
Authors: Eisenberg M A
Published: January 2020

Alpha-Dehydrobiotin, like biotin, represses coordinately the 7,8-diaminopelargonic acid aminotransferase and the dethiobiotin synthetase enzymes that are encoded on the l and r strands, respectively, of the bioA operon. The rate of synthesis for both enzymes is inhibited about 80% in the presence of alpha-dehydrobiotin. Homobiotin and alpha-methylbiotin are less effective than alpha-dehydrobiotin in repressing the synthesis of the two enzymes. The selective repression of transcription from l and by alpha-dehydrobiotin and homobiotin, previously reported in hybridization experiments, is not observed at the enzyme level. A combination of equal concentrations of biotin and alpha-dehydrobiotin which was reported to enhance selectively the level of messenger ribonucleic acid transcribed from the l strand does not increase the rate of synthesis of the aminotransferase enzyme. Instead, the enzymes encoded on both strands are essentially completely inhibited as with biotin alone. Strain differences have been ruled out to account for the different results obtained by the two methodologies. Our evidence would suggest that alpha-dehydrobiotin acts like biotin, presumably as the co-repressor, in the repression of the bioA operon. The low rates of enzyme synthesis observed in the presence of the biotin analogue is the result of incomplete repression due to a lower affinity of either the analogue for the repressor or of the co-repressor/repressor complex for the operator. While our evidence would support the concept of a two promoter/operator complex, both would have to respond equally to biotin and its analogues. The evidence, however, does not rule out other possible alternative models for the regulation of the biotin operon.
Phospholipid composition and cardiolipin synthesis in fermentative and nonfermentative marine bacteria
Authors: Diervo A J , Reynolds J W
Published: January 2020

Twenty biochemically distinct isolates of marine bacteria, comprising a collection of gram-negative, motile, straight and curved rod-shaped organisms, were separated into fermentative and nonfermentative groups. The isolates were analyzed fro phospholipid composition and the activities of the enzymes, cardiolipin synthetase, and a phosphilipase were determined. The phospholipid compositions of all isolates were generally similar. Phosphatidylethanolamine and phosphatidylglycerol were the major phospholipid classes detected. The absence of cardiolipin in most of the nonfermentative isolates was the most striking observation noted. This was verified chromatographically and by the absence of cardiolipin synthetase activity. In isolates which had cardiolipin, it apparently was synthesized by the condensation of two molecules of phosphatidylglycerol, a mechanism similar to that observed in terrestrial bacteria. Possible correlations between the presence of cardiolipin and Mg-2+ requirements for growth are discussed.
Mechanism of the isomerization of isopentenyl pyrophosphate in Rhodotorual rubra-1
Authors: Hayman E P , Chichester C O , Simpson K L
Published: January 2020

Stereospecifically labeled mevalonic acid was incorporated into the carotenoids of Rhodotorula. The randomized results are discussed in relation to mechanisms proposed for the conversion of isopentenyl pyrophosphate to dimethylallyl pyrophosphate and the prenol transferase enzyme system to Rhondotorula rubra.
Regulation of the Escherichia coli methylgalactoside transport system by gene mglD
Authors: Robbins A R
Published: January 2020

Constitutive activity of the methylgalactoside transport system of Escherichia coli K-12 is shown to result from mutation of a genetic locus distinct from the two previously described regulatory loci for this permease. Employing an autoradiographic procedure whereby constitutive and inducible cells can be differentiated, it is demonstrated that this locus, termed mglD, is 20% cotransducible with ptsF by bacteriophage P1. Selection for constitutive mutants among an inducible population yielded cells who mutations mapped in mglD. Cotransduction of mglD with mglB, minus C, and minus A, three genes required for activity of the methylgalactoside transport system, is 95, 88, and 81%, respectively. The results of recombination studies employing three and four factors indicate that the order of genes in this region is ptsF, mglD, B, C, A.