bluuebunny/crossref_metadata_2025 huggingface dataset:
Time of Enterotoxin Formation and Release During Sporulation of
Clostridium perfringens
Type A
Authors: Duncan Charles L.
Published: January 2020

Clostridium perfringens
enterotoxin was detected intracellularly about 3 hr after the inoculation of vegetative cells into sporulation medium. The subsequent increase in intracellular enterotoxin concentration roughly paralleled but followed by 2.5 to 5 hr the increase in number of heat-resistant spores. The increase in biologically active toxin coincided with the increase in enterotoxin antigen. Enterotoxin was released from the sporangium with its lysis, concomitantly with the mature spore release.
Metabolism of Phenol and Cresols by Mutants of
Pseudomonas putida
Authors: Bayly R. C. , Wigmore G. J.
Published: January 2020

Mutant strains of
Pseudomonas putida
strain U have been obtained which are deficient in enzymes of the degradative pathways of phenol and cresols. Mutant strains deficient in catechol 2, 3-oxygenase accumulated the appropriate catechol derivative from cresols. A mutant strain which would not grow on either phenol or a cresol was shown to be deficient in both 2-hydroxymuconic semialdehyde hydrolase and a nicotinamide adenine dinucleotide, oxidized form, (NAD
+
)-dependent aldehyde dehydrogenase. When this strain was grown in the presence of phenol or a cresol, the appropriate product of
meta
fission of these compounds accumulated in the growth medium. A partial revertant of this mutant strain, which was able to grow on
ortho
- and
meta
-cresol but not
para
-cresol, was shown to have regained only the hydrolase activity. This strain was used to show that the products of
meta
ring fission of the cresols and phenol are metabolized as follows: (i)
ortho
- and
meta
-cresol exclusively by a hydrolase; (ii)
para
-cresol exclusively by a NAD
+
-dependent aldehyde dehydrogenase; (iii) phenol by both a NAD
+
-dependent dehydrogenase and a hydrolase in the approximate ratio of 5 to 1. This conclusion is supported by the substrate specificity and enzymatic activity of the hydrolase and NAD
+
-dependent aldehyde dehydrogenase enzymes of the wild-type strain. The results are discussed in terms of the physiological significance of the pathway. Properties of some of the mutant strains isolated are discussed.
Relationship Between Methionyl Transfer Ribonucleic Acid Cellular Content and Synthesis of Methionine Enzymes in
Saccharomyces cerevisiae
Authors: Surdin-Kerjan Y. , Cherest H. , de Robichon-Szulmajster H.
Published: January 2020

Derepression of some methionine biosynthetic enzymes (methionine group I enzymes) obtained in methionine limitation has been found to be accompanied by a significant lack of in vivo charging of bulk methionine transfer ribonucleic acid (tRNA
Met
) and in addition by a decreased rate of synthesis of all tRNAs. Under the same conditions, methionyl-tRNA synthetase (MTS) was derepressed rather than repressed. These results are in agreement with those previously published based on studies of a mutant with an impaired MTS (5) and reinforce the idea that the rate of synthesis of methionine group I enzymes can be related to the total content of methionyl (Met)-tRNA
Met
per cell. They also render unlikely that MTS could be a constituent of the regulatory signal.
Effect of Weak Acids on Amino Acid Transport by
Penicillium chrysogenum
: Evidence for a Proton or Charge Gradient as the Driving Force
Authors: Hunter Douglas R. , Segel Irwin H.
Published: January 2020

A variety of weak acids at and below their pK
a
are potent inhibitors of transport in
Penicillium chrysogenum
. The effective compounds include sorbate, benzoate, and propionate (common antifungal agents), indoleacetate (a plant hormone), acetylsalicylate (aspirin), hexachlorophene, and a yellow pigment produced by the mycelia under nutrient-deficient conditions, as well as the classical uncouplers 2,4-dinitrophenol,
p
-nitrophenol, and azide. The results suggest that a proton gradient or charge gradient is involved in energizing membrane transport in
P. chrysogenum
. The unionized form of the weak acids could discharge the gradient by diffusing through the membrane and ionizing when they reach an interior compartment of higher pH. Experiments with 2,4-dinitrophenol and
p
-nitrophenol established that the ionized species are not absorbed by the mycelium to any great extent. The transport inhibitors also caused a decrease in cellular adenosine 5′-triphosphate (ATP) levels, but there was no constant correlation between inhibition of transport and suppression of cellular ATP. A decrease in aeration of the mycelial suspension had the same effect on transport and ATP levels as the addition of a weak organic acid. The effects on transport rates and ATP levels were reversible. The instantaneous inhibition of [
14
C]
l
-leucine transport by NH
4
−
(and vice-versa) in nitrogen-starved mycelia at pH values of 7 or below can be explained by competition for a common energy-coupling system. The inhibition is not observed in carbon-starved mycelia in which the NH
4
+
transport system is absent or inactive (but the general amino acid transport is fully active), or in iodoacetate-treated mycelia in which the NH
4
+
transport system has been differentially inactivated. At pH values greater than 7.0, NH
3
and HPO
4
2−
inhibit transport, presumably by discharging the membrane proton or charge gradient. Aniline counteracts the inhibitory effect of NH
3
and HPO
4
2−
possibly by acting as a proton reservoir or buffer within the membrane.
Evidence for an Extrakaryotic Mutation Affecting the Maintenance of the rho Factor in Yeast
Authors: Handwerker A. , Schweyen R. J. , Wolf K. , Kaudewitz F.
Published: January 2020

A newly isolated, temperature-sensitive mutant of a haploid strain of
Saccharomyces cerevisiae
is described. Its shift to nonpermissive temperature (35 C) resulted in an irreversible change to rho
−
, causing, within four to six generations, more than 90% of the cells to form petite colonies. Genetic analysis revealed extrakaryotic inheritance of this temperature-sensitive mutation. Data presented indicate mutation of a gene in the mitochondrial deoxyribonucleic acid affecting the maintenance of the rho factor.
Manganese Transport in
Bacillus subtilis
W23 During Growth and Sporulation
Authors: Eisenstadt Eric , Fisher Susan , Der Chi-Lui , Silver Simon
Published: January 2020

Manganese is accumulated in
Bacillus subtilis
by a highly specific active transport system. This trace element “pump” is insensitive to added magnesium or calcium and preferentially accumulates manganese in the presence of cobalt, iron, and copper. Manganese uptake in
B. subtilis
is inhibited by cyanide, azide, pentachlorophenol, and
m
-chlorophenyl carbonylcyanide hydrazone. The uptake of manganese follows Michaelis-Menten kinetics, and the net accumulation of manganese is regulated by increasing the
V
max
after exposure to manganese-starvation conditions and by decreasing the
V
max
for manganese uptake during growth in excess manganese. The

K
m

remains constant during these regulatory changes in
V
max
. Manganese accumulated during growth is exchangeable for exogenous manganese and can be released from the cells by toluene (which causes leakage but not lysis) or by lysis with lysozyme. Two stages can be distinguished with regard to intracellular manganese during the process of growth and sporulation. During logarithmic growth,
B. subtilis
maintains a relatively constant internal manganese content, which is a function of the external manganese concentration following approximately a Langmuir adsorption isotherm. At the end of log phase, net accumulation of manganese slows. A second phase of net manganese accumulation begins at about the same time during sporulation as the accumulation of calcium begins. The manganese accumulated during growth and early sporulation is exchangeable and therefore relatively “free”; intracellular manganese is converted later during sporulation into a bound form that cannot be released by toluene or lysozyme.
Control of Arginine Biosynthesis in
Escherichia coli
: Characterization of Arginyl-Transfer Ribonucleic Acid Synthetase Mutants
Authors: Williams A. L. , Williams L. S.
Published: January 2020

The arginyl-transfer ribonucleic acid (Arg-tRNA) synthetase (EC 6.1.1.13, arginine: RNA ligase adenosine monophosphate) mutants, exhibiting nonrepressible synthesis of arginine by exogenous arginine, were employed in studies of several biochemical properties. Two of these mutants possessed Arg-tRNA synthetases with a reduced affinity for arginine, and this enzyme of another mutant had a reduced affinity for arginine-tRNA (tRNA
arg
). The mutant possessing an Arg-tRNA synthetase with an altered

K
m

for tRNA
arg
was found to have reduced in vivo aminoacylation of two of the five isoaccepting species of tRNA
arg
and complete absence of aminoacylation of one of the isoaccepting species.
Fate of Transforming Deoxyribonucleic Acid After Uptake by Competent
Bacillus subtilis
: Nonrequirement of Deoxyribonucleic Acid Replication for Uptake and Integration of Transforming Deoxyribonucleic Acid
Authors: Dubnau D. , Cirigliano C.
Published: January 2020

Studies on transformation of
Bacillus subtilis
using the inhibitor 6-(
p
-hydroxyphenylazo)-uracil show that deoxyribonucleic acid (DNA) replication is not required for the uptake and integration of donor DNA and genetic markers.
Physical Assay of Competence for Specific Mating-Pair Formation in
Escherichia coli
Authors: Walmsley Roger H.
Published: January 2020

The fractions of
Escherichia coli
female and male bacteria that are competent to form specific mating pairs at any time during normal exponential growth have been measured by a physical assay. The competencies of a Hayes- and a Cavali-type donor were 35 and 50%, respectively, in agreement with piliation assays reported by others. The competencies of two recipient strains, PA309 and P678, were found to be 33 and 29%, respectively.
Isolation and Properties of a Ribonuclease-Deficient Mutant of
Salmonella typhimurium
Authors: Wehr C. Timothy
Published: January 2020

A mutant of
Salmonella typhimurium
has been isolated that has less than 5% of the ribonuclease activity of the parent strain. Mutant screening and enzyme assays were done in the presence of ethylenediaminetetraacetic acid, a substance that activates ribonuclease I and inhibits other known microbial nucleases. Genetic mapping indicates that the mutation is located between the
purE
and
gal
genes on the
Salmonella
chromosome. A ribonuclease-deficient mutant that carries a deletion in the
pyrF
gene is unable to utilize ribonucleic acid as a pyrimidine source, whereas the
pyrF
parent with normal ribonuclease activity will grow. This suggests that the enzyme may perform a scavenge function in the utilization of exogenous ribonucleic acid. Loss of this enzyme seems to have no detrimental effects on the growth of
Salmonella
.
Stimulation by Cyclic Adenosine Monophosphate of Plasmid Deoxyribonucleic Acid Replication and Catabolite Repression of the Plasmid Deoxyribonucleic Acid-Protein Relaxation Complex
Authors: Katz Leonard , Kingsbury David T. , Helinski Donald R.
Published: January 2020

Colicinogenic factors ColE1 and ColE2 are bacterial plasmids that exist in
Escherichia coli
as supercoiled deoxyribonucleic acid (DNA) and as strand-specific, relaxation complexes of supercoiled DNA and protein. Newly replicated ColE1 DNA becomes complexed with protein after the replication event. This association of DNA and protein can take place under conditions in which DNA or protein synthesis is arrested. The addition of cyclic adenosine monophosphate (c-AMP) to normal cells growing in glucose medium results in a six- to tenfold stimulation in the rate of synthesis of the protein component(s) of the complex and a three- to fivefold stimulation in the rate of ColE1 DNA replication. Employing mutants deficient in catabolite gene activator protein or adenylate cyclase, it was shown that synthesis of both the plasmid-determined protein colicin E1 and the protein component(s) of the ColE1 relaxation complex is mediated through the c-AMP-catabolite gene activator protein system. Addition of c-AMP to ColE2-containing cells results in the stimulation of synthesis of ColE2 DNA and relaxation protein(s) as well as in the production of a protein component of the ColE2 relaxation complex that renders it sensitive to induced relaxation by heat treatment. In the case of ColE2, synthesis of the relaxation protein(s) is not dependent upon catabolite gene activator protein.
Membrane Translocation of Mannitol in
Escherichia coli
Without Phosphorylation
Authors: Solomon Ellen , Miyai Kenji , Lin E. C. C.
Published: January 2020

Galactosyl-mannitol can be transported into cells of
Escherichia coli
by β-galactoside permease and can be hydrolyzed rapidly to mannitol and galactose by β-galactosidase. When a mutant strain lacking enzyme I of the phosphoenolpyruvate phosphotransferase system and constitutive in the lactose system was presented with galactosyl-mannitol in which the mannitol moiety was labeled with
3
H, the liberated mannitol remained inside the cell if the Enzyme II complex of the phosphoenolpyruvate phosphotransferase system for mannitol was uninduced. It is postualted that one of the enzyme II proteins can still catalyze translocation of mannitol across the cell membrane even when phsophorylation is not possible.
Subapical Wall Synthesis and Wall Thickening Induced by Cycloheximide in Hyphae of
Aspergillus nidulans
Authors: Sternlicht E. , Katz Dvorah , Rosenberger R. F.
Published: January 2020

Hyphae of
Aspergillus nidulans
continued to synthesize all the major polysaccharide components of the cell wall when cycloheximide was added to cultures. In the presence of cycloheximide, hyphae did not elongate, but electron microscopy showed that the walls became thicker around the cell. The conclusion that cycloheximide changed wall synthesis from extension at the apex to subapical thickening was supported by grain distributions on radioautograms of mutant hyphae labeled with galactose. These findings are discussed in relation to the control of hyphal wall synthesis and are compared with the effects of protein synthesis inhibitors on wall formation in gram-positive bacteria.
Inhibition of Spore Outgrowth and Vegetative Growth of
Bacillus stearothermophilus
by Dipicolinate,
Authors: Fields Marion L. , Frank Hilmer A.
Published: January 2020

Spores of
Bacillus stearothermophilus
germinated in the presence of sodium dipicolinate (DPA) but did not elongate after the emergence stage of outgrowth. Vegetative growth also was inhibited by Na
2
DPA.
Measurement of the Cyanophycin Granule Polypeptide Contained in the Blue-Green Alga
Anabaena cylindrica
Authors: Simon Robert D.
Published: January 2020

An assay was developed to determine the amount of cyanophycin granules in blue-green algae. The amount of this polypeptide in cells of
Anabaena cylindrica
was measured as a function of culture age and was compared with changes in other proteinaceous cellular components. The data presented support the notion that the cyanophycin granule is a cellular nitrogen reserve.
Colicin B: Mode of Action and Inhibition by Enterochelin
Authors: Guterman Sonia K.
Published: January 2020

Adsorption of colicin B to a sensitive strain of
Escherichia coli
results in rapid cessation of deoxyribonucleic acid, ribonucleic acid, and protein synthesis. Some classes of mutants insensitive to colicin B hyperexcrete a colicin inhibitor into their growth medium. This inhibitor functions by preventing adsorption of colicin B and does not rescue cells to which colicin has already adsorbed. The inhibitor is insensitive to nucleases, proteolytic enzymes, and lysozyme and is not extracted into organic solvents. The inhibitory material has a low molecular weight, which rules out identification as lipopolysaccharide, although purified lipopolysaccharide has some inhibitory activity. Evidence is presented that the inhibitor is enterochelin, an iron chelator which is the cyclic trimer of 2,3-dihydroxybenzoylserine. Enterochelin does not inhibit colicin M, a colicin that is produced by many strains colicinogenic for colicin B.
Regulation of Intracellular Proteolysis in
Escherichia coli
Authors: Pine Martin J.
Published: January 2020

Individual nitrogenous metabolites have been examined as regulating agents for the breakdown of intracellular proteins in
Escherichia coli
. Generally, NH
4
+
is the most effective regulator. Its depletion progressively increases the basal proteolytic rate to maximum in most strains when the doubling time is increased to 2 h. In
E. coli
9723, the rate is further increased at longer doubling times. Amino acids have individual effects on intracellular proteolysis. The basal rate in amino acid-requiring auxotrophs of
E. coli
9723 is stimulated weakly by starvation for histidine, tryptophan, or tyrosine, moderately by four other amino acid depletions, and more strongly by eight others. The degree of stimulation roughly correlates with the frequency of the amino acid in the cell proteins. Amino acid analogues that incorporate extensively into protein generally slightly inhibit intracellular proteolysis, except for selenomethionine, which is slightly stimulatory. Metabolic inhibitors were studied at graded concentrations. Chloramphenicol inhibits the basal level of intracellular proteolysis when protein synthesis is slightly or moderately inhibited, and stimulates proteolysis slightly at higher levels. Graded inhibition of ribonucleic acid synthesis with rifampin progressively stimulates intracellular proteolysis. Uracil depletion is also stimulatory. Inhibition of deoxyribonucleic acid synthesis with mitomycin C or by thymine starvation slightly inhibits intracellular proteolysis. Intracellular proteolysis is postulated to be regulated primarily by active ribosomal function. At 43 to 45 C, intracellular proteolysis becomes maximally induced and unresponsive to normal regulatory control by metabolites. Most regulation is directed towards the breakdown of the more stable cell proteins. Total proteolysis in all cell proteins is no more than doubled by the most effective conditions of starvation.
A Regulatory Gene of Phenylalanine Biosynthesis (
pheR
) in
Salmonella typhimurium
Authors: Gollub E. G. , Liu K. P. , Sprinson D. B.
Published: January 2020

4-Fluorophenylalanine-resistant mutants of
Salmonella typhimurium
were isolated in which synthesis of chorismate mutase P-prephenate dehydratase (specified by
pheA
) was highly elevated. Transduction analysis showed that the mutation affecting
pheA
activity was not linked to
pheA
, and conjugation and merodiploid analysis indicated that it was in the 95- to 100-min region of the
Salmonella
chromosome. Evidence is presented for the hypothesis that the mutation responsible for constitutivity of chorismate mutase P-prephenate dehydratase occurred in
pheR
, a gene specifying a cytoplasmic product that affected
pheA
.
pheR
mutants were found to carry a second mutation,
tyrO
. The
tyrO
mutation acts
cis
to cause increased levels of the tyrosine biosynthetic enzymes 3-deoxy-
d
-arabinoheptulosonate 7-phosphate synthetase (tyr) and prephenate dehydrogenase, but it has no effect on regulation of
pheA
.
Ambiguity in a Polypeptide-Synthesizing Extract from
Saccharomyces cerevisiae
Authors: Schlanger Gladys , Friedman S. Marvin
Published: January 2020

Environmental factors known to induce ambiguity in bacterial extracts were tested in an in vitro cytoplasmic polypeptide-synthesizing system derived from
Saccharomyces cerevisiae
. Increasing concentrations of magnesium, spermine, and spermidine resulted in extensive leucine-phenylalanine ambiguity in polyuridylic acid-directed polypeptide synthesis. Kinetic studies showed that spermine-mediated stimulation of leucine incorporation occurred when phenylalanine was being actively incorporated. In addition to leucine, the amino acids isoleucine and serine were incorporated in the presence of added magnesium and spermine. Ambiguity in the presence of a high Mg
2+
concentration was decreased when the pH of the reaction mixture was lowered. Ethanol and neomycin enhanced ambiguity to a small, but significant, extent. Streptomycin and temperature had no effect on ambiguity. Leucine, isoleucine, and serine were not attached to phenylalanine transfer ribonucleic acid (tRNA) when the aminoacylation reaction was performed at increasing Mg
2+
and spermine concentrations. On the other hand, increasing levels of Mg
2+
and spermine stimulated the incorporation of leucine from tRNA into polypeptide during the transfer reaction. The formal similarity between the findings in the yeast and
Escherichia coli
systems implies the existence of a tRNA-screening site on the yeast ribosome comparable to that suggested for bacteria. A proposal is made as to the manner in which this site may function to produce the ambiguous codon translation observed.
Relationship Between Prophage Induction and Transformation in
Haemophilus influenzae
Authors: Setlow Jane K. , Boling M. E. , Allison D. P. , Beattie K. L.
Published: January 2020

The interaction between transformation and prophages of HP1
c
1, S2, and a defective phage of
Haemophilus influenzae
has been investigated by measurement of (i) the effect of prophage on transformation frequency and (ii) the effect of transformation on phage induction. The presence of any of the prophages does not appreciably alter transformation frequencies in various Rec
+
and Rec
−
strains. However, exposure of competent lysogens to transforming deoxyribonucleic acid (DNA) may induce phage but only in Rec
+
strains, which are able to integrate transforming DNA into their genome. Transformation of Rec
+
lysogens with DNA irradiated with ultraviolet (UV) light causes the production of even more phage than results from unirradiated DNA, but this indirect UV induction is not as effective as direct induction by UV irradiation of lysogens. Both types of UV induction are influenced by the repair capacity of the host. Wild-type cells contain a prophage and can be induced by transformation to produce a defective phage, which kills a small fraction of the cells. Defective phage in wild-type cells are also induced by
H. parainfluenzae
DNA, and a much larger fraction of the cells is killed. Strain BC200, which is highly transformable but is not inducible for defective phage, is not killed by
H. parainfluenzae
DNA, suggesting that wild-type cells are killed by killed by this DNA because of phage induction. A minicell-producing mutant, LB11, has been isolated. Some phage induction occurs in this strain when the cells are made competent, unlike the wild type. A large majority of LB11 cells surviving the competence regime are killed by exposure to transforming DNA.
Use of External, Biosynthetic, and Organellar Arginine by
Neurospora
Authors: Subramanian K. N. , Weiss Richard L. , Davis Rowland H.
Published: January 2020

The fate of very low amounts of
14
C-arginine derived from the medium or from biosynthesis was studied in
Neurospora
cells grown in minimal medium. In both cases, the label enters the cytoplasm, where it is very briefly used with high efficiency for protein synthesis without mixing with the bulk of the large, endogenous pool of
12
C-arginine. The soluble
14
C-arginine which is not used for protein synthesis is sequestered in a vesicle with the bulk of the endogenous arginine pool. After this time, it is selectively excluded from use in protein synthesis except by exchange with cytoplasmic arginine. The data suggest that in vivo, the non-organellar cytoplasm contains less than 5% of the soluble, cellular arginine. The cellular organization of
Neurospora
described here also prevents the catabolism of arginine. Our results are discussed in relation to previous work on amino acid pools of other eukaryotic systems.
Characterization of Excision Repair in
Neurospora crassa
Authors: Worthy Thomas E. , Epler J. L.
Published: January 2020

The excision of pyrimidine dimers from the deoxyribonucleic acid (DNA) of
Neurospora crassa
was examined. Postirradiation incubation in the presence of several chemicals known to inhibit various repair systems indicated that caffeine reduced the rate of excision twofold, but did not inhibit excision completely as did proflavine and quinacrine. Examination of the time course of excision showed that repair occurs at a relatively rapid rate: approximately 60 dimers excised per min after 500 ergs/mm
2
. Further evidence for rapid excision was obtained by sedimentation analysis of DNA; the maximal number of breaks introduced during repair was three, suggesting that breaks are repaired almost as fast as they are made and that only a few dimers are repaired at a time. Repair synthesis was measured by prelabeling the DNA with
15
N and D
2
O, and then subjecting the DNA to equilibrium density gradient centrifugation after postirradiation incubation with
32
P. Accumulation of single-strand breaks with increasing dose of ultraviolet radiation suggested that the limiting step was subsequent to the incision and excision steps of repair. Equilibrium CsCl centrifugation demonstrated that the limiting step in excision was repair synthesis.
Derepression of Anthranilate Synthase in Purified Minicells of
Escherichia coli
Containing the Col-
trp
Plasmid
Authors: Frazer Anne Cornish , Curtiss Roy
Published: January 2020

Purified minicells of
Escherichia coli
K-12 containing the plasmid Col-
trp
+
or Col-
trpA2
could be derepressed for the synthesis of anthranilate synthase, the first enzyme encoded in the
trp
operon. Non-plasmid-containing, deoxyribonucleic acid-deficient minicells could not be derepressed. Derepressed enzyme synthesis was initiated by
l
-tryptophan starvation. The kinetics of derepression were studied with minicells containing the Col-
trpA2
plasmid. The derepression curves were biphasic with a rapid initial rate of enzyme synthesis followed by a slower rate of synthesis. The presence of
l
-tryptophan (20 to 50 μg/ml) or chloramphenicol (200 μg/ml) abolished enzyme synthesis. The presence of rifamycin SV (280 μg/ml) partially inhibited enzyme synthesis after at least 3.5 min of exposure. The ratio of minicell-to-cell synthetic capacity was 1:2.4 when compared on the basis of derepressed enzyme activity per unit cell volume. This work demonstrates that plasmid-containing minicells are capable of considerable functional protein and messenger ribonucleic acid synthesis and that the regulation of at least the
trp
operon is similar in minicells to that observed in cells.
Properties of a
Streptococcus sanguis
(Group H) Bacteriocin and Its Separation from the Competence Factor of Transformation
Authors: Schlegel Richard , Slade Hutton D.
Published: January 2020

STH
1
, a streptocin elaborated by group H streptococcus strain Challis, is lethal for group H streptococcus strain Wicky and is produced maximally during the exponential growth phase of liquid medium cultures. Crude streptocin preparations are resistant to oxidation and display a biphasic pH stability (stability being maximal at pH 5.0 and 10.0). Survivor studies indicate that streptocin-mediated killing is a “one-hit” phenomenon and proceeds rapidly. The streptocin has been purified 50-fold with (NH
4
)
2
SO
4
fractionation and Sephadex G100 chromatography and appears to exist in equilibrium between two molecular weight forms. Low ionic strength and neutral pH buffers favor the isolation of the 110,000 molecular weight form, whereas high ionic strength and alkaline pH conditions facilitate isolation of the 28,000 to 30,000 molecular weight form. These findings suggest an association-dissociation relationship between macromolecules of 28,000 to 30,000 molecular weight. Purified STH
1
has no “competence factor” (CF) activity. In addition, CF has no STH
1
activity and displays no inhibitory effect on exponential-phase Wicky cultures as determined by absorbancy measurements. It appears, therefore, that initiation of the competent state for transformation in strain Wicky is not necessarily accompanied by gross alterations in cell growth.
Repression of Enzyme Synthesis of the Pyrimidine Pathway in
Salmonella typhimurium
Authors: Williams James C. , O'Donovan Gerard A.
Published: January 2020

It has been reported by other workers that a uridine and probably also a cytidine nucleotide are required for maximal repression of aspartate transcarbamylase encoded by the gene
pyrB
in
Salmonella typhimurium
. We have identified the repressing metabolites for three more biosynthetic enzymes, namely, dihydroorotate dehydrogenase (encoded by
pyrD
), orotidine-5′-monophosphate pyrophosphorylase (encoded by
pyrE
), and orotidine-5′-monophosphate decarboxylase (encoded by
pyrF
), as well as examining the repression profiles of aspartate transcarbamylase in more detail. Using a specially constructed strain of
S. typhimurium
(JL1055) which lacks the enzymes for the interconversion of cytidine and uridine compounds, thus allowing the independent manipulation of endogenous cytidine and uridine nucleotides, we found that a cytidine compound is the primary effector of repression in all cases except for aspartate transcarbamylase where little repression is observed in excess cytidine. For aspartate transcarbamylase, we found that the primary repressing metabolite is a uridine compound.
Preparation of Metabolically Active
Staphylococcus aureus
Protoplasts by Use of the
Aeromonas hydrophila
Lytic Enzyme
Authors: Coles N. W. , Gross R.
Published: January 2020

Stable, metabolically active protoplasts of
Staphylococcus aureus
have been prepared by the use of a staphylolytic enzyme produced by
Aeromonas hydrophila
. Respiratory and glycolytic rates and synthesis of nucleic acids, protein, and lipid in these protoplasts, stabilized variously in 1.1 M sucrose, 0.37 M sodium succinate, or 0.37 M sodium sulfate, have been shown to be comparable with the same parameters in intact cells under the same conditions.
Amino Acid Transport in a Polyaromatic Amino Acid Auxotroph of
Saccharomyces cerevisiae
Authors: Greasham Randolph L. , Moat Albert G.
Published: January 2020

The initiation of growth of a polyaromatic auxotrophic mutant of
Saccharomyces cerevisiae
was inhibited by several amino acids, whereas growth of the parent prototroph was unaffected. A comparative investigation of amino acid transport in the two strains employing
14
C-labeled amino acids revealed that the transport of amino acids in
S. cerevisiae
was mediated by a general transport system responsible for the uptake of all neutral as well as basic amino acids. Both auxotrophic and prototrophic strains exhibited stereospecificity for
l
-amino acids and a

K
m

ranging from 1.5 × 10
−5
to 5.0 × 10
−5
M. Optimal transport activity occurred at pH 5.7. Cycloheximide had no effect on amino acid uptake, indicating that protein synthesis was not a direct requirement for amino acid transport. Regulation of amino acid transport was subject to the concentration of amino acids in the free amino acid pool. Amino acid inhibition of the uptake of the aromatic amino acids by the aromatic auxotroph did not correlate directly with the effect of amino acids on the initiation of growth of the auxotroph but provides a partial explanation of this effect.
Genetic Analysis of
thr
Mutations in
Salmonella typhimurium
Authors: Stuttard Colin
Published: January 2020

Previous workers divided threonine-requiring (Thr
−
) strains of
Salmonella
into three phenotypes with mutations in four complementation groups. The mutations were deemed to define four genes in the order
thrD-C-A-B
at minute zero on the
Salmonella
linkage map. In the present study 12 of these mutants were reexamined together with eight new Thr
−
strains. The three phenotypes were: homoserine-requiring (Hom
−
); Thr
−
, feeders of Hom
−
strains; Thr
−
, nonfeeders. Exact correlation between these phenotypic groups and three complementation groups was confirmed by abortive transduction. No evidence was found for intergenic complementation between mutations in Hom
−
strains. It is proposed that
thr
mutations define three genes rather than four and that these be renamed
thrA
(Hom
−
),
thrB
(Thr
−
feeders), and
thrC
(Thr
−
nonfeeders) to correspond with the sequence of reactions in threonine biosynthesis. Double mutant
trpRthr
strains were used in reciprocal three-point transduction tests to establish the order of
thr
mutation sites. Although revisions were made in the classification or location of several mutations, there was an overall correlation of complementation group, phenotype, and map position. The present data provide a basis for further correlation of threonine genes and biosynthetic enzymes, and analysis of cross regulation in aspartate amino acid biosynthesis in
Salmonella
.
Amino Acid and Peptide Requirement of
Fusiformis necrophorus
Authors: Wahren Ann , Holme Tord
Published: January 2020

Uptake of individual amino acids and peptides by
Fusiformis necrophorus
was studied in growing cultures and resting cell suspensions. The cells were able to incorporate 16 of 17
14
C-labeled amino acids into cell protein, the exception being proline. Proline could neither be formed by the cells from any of the other tested amino acids nor be synthesized from glucose or serine when these were used as energy sources. The addition of di- and tripeptides, the octapeptides vasopressin and oxytocin, and the poly (24) peptide ACTH did not stimulate cell growth, but a marked stimulatory effect was noted after the addition of poly-
l
-proline (mean molecular weight 2,000). It is concluded that cells of
F. necrophorus
(i) possess transport systems for most amino acids but not for proline, (ii) are dependent on exogenous proline in the form of proline-containing peptides for growth, and (iii) may be cultivated in a defined amino acid medium provided the proline requirement is met by the addition of a proline-containing peptide.
Crystal Formation by a Ribonucleic Acid Polymerase Mutant of
Bacillus subtilis
Authors: Santo Leatrice Y. , Doi Roy H.
Published: January 2020

A crystalline inclusion has been observed in a ribonucleic acid polymerase mutant of
Bacillus subtilis
which is conditionally temperature sensitive only during sporulation. The crystal is formed at the permissive temperature in 1 to 2% of the sporulating (stage III–IV) cells; about 85% of the cells sporulate normally, while the cells with crystals do not sporulate. The wild type does not form crystals at either the permissive (30 C) or the nonpermissive (47 C) temperatures. The crystal may result from altered transcription during sporulation at 30 C.
Wall Synthesis by
Pediococcus cerevisiae
and by a Substrain That Requires Methicillin for Growth
Authors: Wilkinson B. J. , White P. J.
Published: January 2020

Pediococcus cerevisiae
and
P. cerevisiae
CRD synthesized peptidoglycan when incubated in a wall synthesis solution inadequate to allow growth.
Mode of Action of Glycine on the Biosynthesis of Peptidoglycan
Authors: Hammes W. , Schleifer K. H. , Kandler O.
Published: January 2020

The mechanism of glycine action in growth inhibition was studied on eight different species of bacteria of various genera representing the four most common peptidoglycan types. To inhibit the growth of the different organisms to 80%, glycine concentrations from 0.05 to 1.33 M had to be applied. The inhibited cells showed morphological aberrations. It has been demonstrated that glycine is incorporated into the nucleotide-activated peptidoglycan precursors. The amount of incorporated glycine was equivalent to the decrease in the amount of alanine. With one exception glycine is also incorporated into the peptidoglycan. Studies on the primary structure of both the peptidoglycan precursors and the corresponding peptidoglycan have revealed that glycine can replace
l
-alanine in position 1 and
d
-alanine residues in positions 4 and 5 of the peptide subunit. Replacement of
l
-alanine in position 1 of the peptide subunit together with an accumulation of uridine diphosphate-muramic acid (UDP-MurNAc), indicating an inhibition of the UDP-MurNAc:
l
-Ala ligase, has been found in three bacteria (
Staphylococcus aureus, Lactobacillus cellobiosus
and
L. plantarum
). However, discrimination against precursors with glycine in position 1 in peptidoglycan synthesis has been observed only in
S. aureus
. Replacement of
d
-alanine residues was most common. It occurred in the peptidoglycan with one exception in all strains studied. In
Corynebacterium
sp.,
C. callunae, L. plantarum
, and
L. cellobiosus
most of the
d
-alanine replacing glycine occurs C-terminal in position 4, and in
C. insidiosum
and
S. aureus
glycine is found C-terminal in position 5. It is suggested that the modified peptidoglycan precursors are accumulated by being poor substrates for some of the enzymes involved in peptidoglycan synthesis. Two mechanisms leading to a more loosely cross-linked peptidoglycan and to morphological changes of the cells are considered. First, the accumulation of glycine-containing precursors may lead to a disrupture of the normal balance between peptidoglycan synthesis and controlled enzymatic hydrolysis during growth. Second, the modified glycine-containing precursors may be incorporated. Since these are poor substrates in the transpeptidation reaction, a high percentage of muropeptides remains uncross-linked. The second mechanism may be the more significant in most cases.
Association of Lysozyme with Ribosomes and Ribosome Precursor Particles
Authors: Dimmitt Kathleen , Sypherd Paul S.
Published: January 2020

Lysozyme, used to prepare osmotically fragile cells, combines with ribosomal subunits unless salt is present in excess of 50 mM. The binding of lysozyme to precursor ribonucleoprotein particles can result in their conversion to particles which sediment as mature ribosomes.
Mutant of
Escherichia coli
K-12 Defective in the Transport of Basic Amino Acids
Authors: Celis T. F. R. , Rosenfeld H. J. , Maas W. K.
Published: January 2020

Escherichia coli
K-12 possesses two active transport systems for arginine, two for ornithine, and two for lysine. In each case there is a low- and a high-affinity transport system. They have been characterized kinetically and by response to competitive inhibition by arginine, lysine, ornithine and other structurally related amino acids. Competitors inhibit the high-affinity systems of the three amino acids, whereas the low-affinity systems are not inhibited. On the basis of kinetic evidence and competition studies, it is concluded that there is a common high-affinity transport system for arginine, ornithine, and lysine, and three low-affinity specific ones. Repression studies have shown that arginine and ornithine repress each other's specific transport systems in addition to the repression of their own specific systems, whereas lysine represses its own specific transport system. The common transport system was found to be repressible only by lysine. A mutant was studied in which the uptake of arginine, ornithine, and lysine is reduced. The mutation was found to affect both the common and the specific transport systems.
Escherichia coli
K-12 Mutants Altered in the Transport Systems for Oligo- and Dipeptides
Authors: De Felice Maurilio , Guardiola John , Lamberti Alessandro , Iaccarino Maurizio
Published: January 2020

Two mutants of
Escherichia coli
K-12, defective in the oligopeptide and dipeptide transport system, are described. A mutant defective in the oligopeptide transport system (
opp-1
) was isolated as resistant to the inhibitory action of triornithine; this mutant is also resistant to glycylglycylvaline and does not concentrate
14
C-glycylglycylglycine, although it is still as sensitive as the parental strain to glycylvaline and valine. Starting from the
opp-1
strain, a mutant defective also in the dipeptide transport system (
dpp-1
) was isolated; this mutant is resistant to the inhibitory action of glycylvaline, valylleucine, and leucylvaline and does not concentrate
14
C-glycylglycine, although it is still as sensitive as the parental strain to valine. The apparent kinetic constants for oligopeptide and dipeptide transport were measured. The
opp
marker is co-transducible with
trp
at 27 min on the
E. coli
genetic map. The
dpp
locus is separated from
opp
and is located between
proC
(10 min) and
opp
.
Genetic Control of the Transport of Hexose Phosphates in
Escherichia coli
: Mapping of the
uhp
Locus
Authors: Kadner Robert J.
Published: January 2020

A number of mutations affecting the transport of hexose phosphates in
Escherichia coli
were ordered within the
uhp
locus. Three-point crosses by transduction or conjugation allowed the ordering of the alleles relative to the adjacent
pyrE
marker. The same linear map was obtained by both methods. This, combined with the regulatory properties of revertants of these mutants, allowed a tentative identification of two genes, one presumably coding for the transport system (
uhpT
) and the other(s) specifying a regulatory element (
uhpR
). The order of these is
pyrE-uhpT-uhpR
. Mutants exhibiting constitutive expression of the transport system were isolated. This behavior is genetically linked to the
uhp
locus, but more precise localization was not possible.
Relationship between Dimorphology and Respiration in
Mucor genevensis
Studied with Chloramphenicol
Authors: Clark-Walker G. D.
Published: January 2020

Growth of
Mucor genevensis
, a facultatively anaerobic dimorphic mold, in high concentrations of chloramphenicol (4 mg/ml) leads to increased numbers of yeast-like cells and small club-like mycelial forms. This change in morphology is accompanied by a threefold increase in the mass doubling time, the loss of cyanide-sensitive respiration, and the development of cyanide-insensitive respiration. Associated with these changes is the absence of cytochromes
aa
3
and
b
and the inability of the organism to utilize ethanol; in addition, mitochondria appear more numerous and have less internal membrane. A further inhibitory action of the antibiotic, other than eliminating functional mitochondria, appears likely since microaerobic cultures which lack respiratory ability have twice the mass doubling time in the presence of the drug. Although a small inhibition of amino acid incorporation by cytoplasmic ribosomes is found with a high chloramphenicol concentration, it is insufficient to account for the effect on growth of the microaerobic culture. The nature of this additional effect of chloramphenicol remains to be determined, but it has been shown that increasing the glucose concentration can partially reverse this action of the antibiotic. The effect of the drug on the morphology of the organism is not as dramatic as that of phenethyl alcohol in producing yeast-like forms. However, in view of the action of chloramphenicol in eliminating functional mitochondria in
M. genevensis
the suggestion that phenethyl alcohol exerts its effect in promoting yeast-like morphology by uncoupling oxidative phosphorylation should be re-examined.
Gene Transmission Among Strains of
Erwinia amylovora
Authors: Chatterjee Arun K. , Starr Mortimer P.
Published: January 2020

Stable donor strains of
Erwinia amylovora
were obtained from strain EA178R
1
(harboring an
Escherichia coli
F′
lac
) by selection for clones resistant to curing by acridine orange. These donor strains (EA178R
1
-99 and EA178R
1
-111) transfer chromosomal markers (
arg, cys, gua, ilv, met, pro, ser, trp
); the frequency of the appearance of recombinants prototrophic for Cys, Gua, Met, Ser, and Trp is highest (> 10
−5
), followed by recombinants prototrophic for Arg, Ilv, and Pro (10
−7
to 10
−5
). The results of interrupted matings, as well as the frequency of transmission of various markers, suggest that
cys
is transferred as an early marker by both donor strains. The Hfr state of these donor strains is rather likely on the basis of the following observations. The donor strains exhibit a relatively efficient and possibly oriented chromosome transfer; the Lac
+
character is not cured by acridine orange in these donor strains; and these donor strains do not transfer F.
Isocitrate Lyase from a Thermophilic
Bacillus
: Effect of Salts on Enzyme Activity
Authors: Griffiths M. W. , Sundaram T. K.
Published: January 2020

The isocitrate lyase from a thermophilic
Bacillus
is activated about threefold by a variety of salts. Such strong stimulation of activity is not seen with isocitrate lyase from the mesophiles,
Bacillus licheniformis, Bacillus megaterium, Escherichia coli
, and
Aspergillus nidulans
. The salt activation is markedly pH-dependent. At pH values above 8.6, salt (KCl) indeed inhibits the enzyme activity. Potassium chloride also causes a significant shift of the pH optimum of the enzyme towards the acid side. As the temperature of the enzyme reaction is raised, activation becomes progressively weaker. Potassium chloride also affords considerable protection against enzyme denaturation at 55 C. The activation and the stabilization, however, appear to be independent effects. Of six other enzymes in the thermophile that were examined, isocitrate dehydrogenase was equally strongly activated by KCl and malate synthase was less strongly, but significantly, activated; citrate synthase, malate dehydrogenase, glutamate dehydrogenase, and lactate dehydrogenase were unaffected or slightly inhibited by KCl. The property of being strongly activated by salt appears to be a peculiar characteristic of the thermophile isocitrate lyase and possibly evolved concomitantly with its thermostability.
Occurrence of Phosphonosphingolipids in
Bdellovibrio bacteriovorus
Strain UKi2
Authors: Steiner S. , Conti S. F. , Lester Robert L.
Published: January 2020

The major phospholipids of two strains of
Bdellovibrio bacteriovorus
were characterized. Both strain UKi1, which is obligately saprophytic, and strain UKi2, which is facultatively parasitic, contained phosphatidylethanolamine and phosphatidylglycerol as their major glycerophosphatides. A branched, 15-carbon fatty acid is the major component of these alkali-labile lipids. Absent from UKi1 but present in UKi2 were three alkali-stable lipids (compounds 8, 9, and 11) which appear to be phosphosphingolipids. After acid hydrolysis, both compound 8 and 9 yield the identical phosphorus-containing substance that is water soluble, dipolar ionic, and ninhydrin positive. This substance appears to contain a C-P bond since P
i
could not be released from this substance by treatment with alkaline phosphatase or by very harsh mineral acid treatment. Based on chromatographic comparisons, this phosphonate appears to be a novel lipid constituent. Upon degradation, compound 8 yields 1 mol of dihydroxy long-chain base and compound 9 yields 1 mol of a trihydroxy long-chain base. These bases appear to have a 17-carbon, possibly branched, structure based on gas-liquid chromatography retention times. Degradation of both sphingolipids yields a mixture of hydroxy fatty acids, the major component being a branched, 15-carbon hydroxy acid.