bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutants of
Saccharomyces cerevisiae
That Incorporate Deoxythymidine-5′-Monophosphate Into Deoxyribonucleic Acid In Vivo
Authors: Wickner Reed B.
Published: January 2020

Spontaneous mutants of
Saccharomyces cerevisiae
able to incorporate deoxythymidine-5′-monophosphate (dTMP) into deoxyribonucleic acid (DNA) have been selected based on their ability to grow in the presence of aminopterin and sulfanilamide if dTMP is present. Essentially all mutants (called
tup
) selected in this way required dTMP for growth in the presence of the two drugs, but none required dTMP in the absence of the drugs. Neither thymine nor thymidine would satisfy this requirement. Equimolar amounts of
32
P- and
3
H-base-labeled dTMP were incorporated by the mutants into alkali-stable, deoxyribonuclease-sensitive material. In the presence of aminopterin and sulfanilamide, this incorporation was sufficient to account for a substantial proportion of the thymine residues in the cellular DNA, whereas in the absence of the drugs only about 40% as much of the thymine residues originated from the medium. Of 29 mutants examined, all were recessive and 17 showed 2:2 segregation in crosses with a wild-type strain. The lesions in these mutants fell into four complementation groups: one (
tup1
) occurs on chromosome III; another (
tup3
) is on chromosome II; and a third (
tup4
) was centromere linked. Strains of the genotype α
tup1
mated with lower than normal efficiency with
a
strains, but with higher than normal efficiency with α strains. Strains of genotype
a/α tup1/tup1
failed to sporulate, whereas homozygous diploids for
tup2, tup3
, or
tup4
sporulated normally, as did
a/α tup1
/+ strains.
Mapping of the 5-Methyltryptophan Resistance Locus in
Bacillus subtilis
Authors: Hoch Sallie O'Neil
Published: January 2020

The 5-methyltryptophan resistance locus (
mtr
) in
Bacillus subtilis
, which leads to constitutive production of the tryptophan enzymes, has been mapped on the chromosome. The order of loci is
ser-1—mtr—aroF—aroB—trp—hisB
.
Control of Deoxyribonucleic Acid Synthesis in a
Bacillus subtilis
Mutant Temperature Sensitive for Initiation of Chromosome Replication
Authors: Laurent Simone J.
Published: January 2020

We used a
Bacillus subtilis
mutant described previously, which is temperature sensitive for initiation of replication. The inhibition of deoxyribonucleic acid synthesis occurring at 45 C was shown to be reversed when the temperature is lowered even in the absence of protein synthesis. If the bacteria are returned to 30 C, after a prior period at 45 C, they are able to initiate the first round of replication in the presence of chloramphenicol, but the initiation of the second round still requires protein synthesis. This paper shows that the proteins necessary to initiate the second round of replication can be present in bacteria long before this round is initiated. In addition, the appearance of these proteins seems to be influenced by the length of the previous 45 C period. Although similar reinitiation kinetics are observed at 30 C after prior 45 C periods of 30 or 65 min, the ability to initiate the second round without further protein synthesis appears much earlier after a longer exposure at 45 C. To explain these results, a hypothesis is presented which assumes that two different proteins are both necessary for initiation. Only one of these proteins could be accumulated at 45 C during the inhibition of deoxyribonucleic acid synthesis. A peculiarity of initiation material in mutant Ts 37 is that it may be active at 45 C if it has been exposed previously at 30 C.
Mutations in the
l
-Arabinose Operon of
Escherichia coli
B/r That Result in Hypersensitivity to Catabolite Repression
Authors: Gendron Robert P. , Sheppard David E.
Published: January 2020

Two independent mutants resistant to
l
-arabinose inhibition only in the presence of
d
-glucose were isolated from an
l
-arabinose-sensitive strain containing the
araD139
mutation. Preliminary mapping studies indicate that these mutations are closely linked to the
araIOC
region. Addition of
d
-glucose to growing cultures of these mutants results in a 95 to 98% repression of
ara
operon expression, as compared to a 50% repression of the parental control. Since cultures of both mutant and parental strains undergo a 50% repression of
lac
operon expression upon addition of glucose, the hypersensitivity to catabolite repression exhibited by these mutants is specific for the
ara
operon. Addition of cyclic adenosine monophosphate reverses the catabolite repression of the
ara
operon in both mutant and parent strains to 70 to 80% of the control. It is suggested that in these mutants the affinity of the
ara
operon initiator region for the cAMP-catabolite-activator protein complex may have been altered.
Genetic Characterization of Recombination-Deficient Mutants of
Bacillus subtilis
Authors: Dubnau D. , Cirigliano C.
Published: January 2020

Recombination-deficient (
rec
), radiation-sensitive mutations in
Bacillus subtilis
are grouped in at least seven distinct loci. Map positions are determined for six of these loci.
Ethylene Glycol-Induced Alteration of Conidial Germination in
Neurospora crassa
Authors: Bates W. K. , Wilson J. F.
Published: January 2020

In nutrient medium containing 3.22 M ethylene glycol or glycerol, conidia of
Neurospora crassa
grow as single cells, without forming the germ tubes characteristic of normal morphological germination. Ethylene glycol is more effective than glycerol in producing this response. After growth in ethylene glycol medium for a suitable time, the cells are easily disrupted by an abrupt decrease in osmotic pressure. Osmotic disruption yields intact nuclei and mitochondria, although mitochondrial fractions obtained in this way show significantly reduced concentrations of cytochromes
c
+
c
1
, as compared to those observed for comparable fractions obtained from vegetative hyphae. Cell cultures gradually adapted to lower concentrations of the glycol show a much higher degree of synchrony in the formation of germ tubes than do untreated conidia.
Residual Polarity and Transcription/Translation Coupling During Recovery from Chloramphenicol or Fusidic Acid
Authors: Pastushok Carol , Kennell David
Published: January 2020

Fusidic acid or chloramphenicol was used to inhibit peptide synthesis to 1% of normal in
Escherichia coli
B, strain AS19. After 10 min of inhibition, peptide synthesis could be quickly restored to 80% of the normal rate after washing the bacteria on a filter. However, even in the presence of adenosine 3′-5′-cyclic-monophosphoric acid to block catabolite repression, β-galactosidase, the first enzyme of the lactose operon (
lac
), could only be induced to 10% of normal, and the last enzyme of the operon, galactoside acetyltransferase, even less. The first and last enzymes of the operon for tryptophan synthesis could be derepressed to about 30% of normal. The
lac
ribonucleic acid (RNA) induced during recovery showed a smaller than normal size distribution on sucrose gradients. The operator-proximal or -distal parts of this RNA were specifically labeled. Hybridization to φ80
dlac
deoxyribonucleic acid (DNA) suggested that although the distal parts of the
lac
RNA were barely detectable, initiation was occurring at normal rates in recovery. Either normal levels of distal messenger RNA (mRNA) are made but then rapidly degraded or the mRNA is not completed. The small amount that is made decayed abnormally slowly, probably as a result of slower transcription. Total mRNA decay was multiphasic with all components decaying slower than normal. We propose that there is a residual level of inhibition of peptide synthesis during recovery. The probability that a ribosome is blocked at any codon can be estimated from the data. The longer the message, the less likely its complete translation. We propose that the RNA polymerase can transcribe translatable mRNA for only a finite distance beyond the lead ribosome. Because ribosomes can load at the start of each message in a polycistronic mRNA, the probability that a distal message will be synthesized and translated is a function of the number of more proximal messages and the distances between their ribosome-loading sites.
Binding of Streptococcal Competence Factor by the Spheroplast Membrane of a Group H Streptococcus
Authors: Perry Dennis
Published: January 2020

The binding of streptococcal competence factor (CF) was found to be specific for a strain of streptococcus which was capable of undergoing competence induction. Three other streptococcal strains which could not be induced to competence, did not bind CF. CF binding was independent of time, temperature, age of the culture, and type of growth media employed. Several observations indicated that the receptor sites for CF are located in the bacterial membrane: (i) the retention of CF by spheroplasts, (ii) the binding of CF by isolated membrane fractions, and (iii), the degradation of CF binding capacity of membranes by different chemicals and enzymes.
Heterotrophic Nature of the Cell-Free Protein-Synthesizing System from the Strict Chemolithotroph,
Thiobacillus thiooxidans
Authors: Amemiya K. , Umbreit W. W.
Published: January 2020

A cell-free protein-synthesizing system prepared from the strict chemolithotroph,
Thiobacillus thiooxidans
, was similar to that of heterotrophs. The poly-U directed system had a temperature optimum of 37 C, but in the presence of spermidine (3 mM) the optimum shifted to 45 C. Although growth of the chemolithotroph occurs only in acid conditions, the pH optimum for the cell-free system was pH 7.2. The endogenous-directed activity in the presence or absence of spermidine was maximal at pH 7.8. Spermidine had a stimulatory effect; however, this effect was dependent on the magnesium and tris(hydroxymethyl)aminomethane (Tris) concentrations. At low Tris concentrations (10 mM), spermidine (3 to 5 mM) could completely replace magnesium. When the Tris concentration was increased (50 mM), spermidine could not replace magnesium. Supernatant and ribosomal fractions from
T. thiooxidans
were exchanged with those of
Bacillus thuringiensis
and
Escherichia coli
, and the ribosomal fraction from the chemolithotroph gave good to moderate stimulation when exchanged with the supernatant from the heterotrophs. On the other hand, the supernatant from
T. thiooxidans
gave good stimulation when mixed with ribosomes from
B. thuringiensis
but poor activity with ribosomes from
E. coli
. Both supernatant and ribosomal fractions prepared from stationary phase extracts of
T. thiooxidans
were inactive in the cell-free system.
Electron Microscopy of
Staphylococcus aureus
Cells and Cell Walls After Treatment with Lysozyme
Chalaropsis
Authors: Robinson John P. , Robinson Richard D. , Hash John H.
Published: January 2020

Lysozyme
Chalaropsis
, a β-1,4-
N
,6-O-diacetylmuramidase, attacks the cell wall murein of
Staphylococcus aureus
H in a random manner. In hypertonic sucrose solutions, true protoplasts are produced and, in the process, mesosomal tubules are extruded into the medium.
Metabolism of
d
-Arabinose by
Escherichia coli
B/r
Authors: Boulter Jim , Gielow Bill , McFarland Mary , Lee Nancy
Published: January 2020

The pathway for
d
-arabinose metabolism in
Escherichia coli
B/r has been determined. Evidence is presented to support the following metabolic scheme:
d
-arabinose
d
-ribulose ⇀
d
-ribulose-5-phosphate
d
-xylulose-5-phosphate.
α-α′-Dipyridyl or
Ortho
-Phenanthroline Stimulation of the Soluble Reduced Nicotinamide Adenine Dinucleotide Oxidase from
Bacillus subtilis
Spores and Dipicolinic Acid Inhibition of the Stimulated Enzyme
Authors: Tochikubo Kunio
Published: January 2020

Soluble reduced nicotinamide adenine dinucleotide oxidase activity in extracts of
Bacillus subtilis
spores was stimulated by the addition of not only flavine mononucleotide (FMN) or flavine adenine dinucleotide (FAD) but also α-α′-dipyridyl or
o
-phenanthroline. These chelating agents showed stronger effect on the enzyme from spores than on that from vegetative cells. Activity stimulated by α-α′-dipyridyl or
o
-phenanthroline was inhibited by atabrine or dipicolinic acid, whereas FMN or FAD stimulation was inhibited only by atabrine.
Protein Degradation and Protease Activity During the Life Cycle of
Blastocladiella emersonii
Authors: Lodi W. R. , Sonneborn D. R.
Published: January 2020

Analysis of protein degradation during the life cycle of
Blastocladiella emersonii
showed that (i) protein degradation is especially high during two phases of differentiation (sporulation, 12%/h and germination, 5%/h) in contrast with a much smaller degradation rate in the other phases (growth and zoospores, less than 1%/hr); (ii) protein degradation during germination in growth medium, as well as most of the germination process, is quantitatively unaffected by cycloheximide; (iii) a caseinolytic protease (pH optimum 5.5, apparent molecular weight 55,000 to 60,000) is present in extracts of zoospores and germinating cells; (iv) this protease activity is very low (perhaps absent) in extracts of late growth phase cells, but reappears during induced sporulation; (v) a different class of caseinolytic protease activity (pH optima 7 and 10; apparent molecular weight 25,000 to 30,000) is found in cellular extracts of late growth phase and early phases of sporulation; (vi) the latter class of enzyme activity is released into the medium during later phases of sporulation and is replaced in the cells by the former class. Speculations as to the roles of protein degradation in cell differentiation are discussed.
Physiological Studies of
Bacillus subtilis
Minicells
Authors: Mendelson Neil H. , Reeve John N. , Cole Roger M.
Published: January 2020

Minicells produced by
Bacillus subtilis
strains carrying the
div IV-B1
mutation, (CU 403
div IV-B1
and CU 403
div IV-B1, tag-1
), were purified by a procedure which destroys parental cells with ultrasound, but spares minicells. Such preparations generally contain 10
9
or more minicells/ml and less than 10
4
colony-forming units/ml. Purified minicells are resistant to autolysis in tris(hydroxymethyl)aminomethane buffer, pH 7.5, at 30 C, conditions which result in total lysis of parental cells. Minicells are not completely devoid of autolytic activity, however. The medium in which minicells are produced, the temperature at which purified minicells are incubated, and the genotype of cells from which the minicells are derived all influence the rate of autolysis of purified minicells. These parameters are demonstrated by using minicells obtained from
div IV-B1
and
div IV-B1, tag-1
strains. Ultrastructural differences have been observed in the products of autolysis of these two minicell strains. Minicells are sensitive to low levels of lysozyme and yield miniprotoplasts when the wall is removed in an osmotically protective environment. Although minicells are unable to grow, they can maintain their integrity over long periods of time, which suggests functional energy metabolism in minicells. Direct measurements of adenosine 5′-triphosphate (ATP) levels by the luciferase assay indicated that minicells can produce ATP. Oxygen consumption, measured by standard respirometry techniques, also indicates functional metabolism in minicells. These findings demonstrate that minicells purified by ultrasound are suitable material for study of physiological processes in anucleate cells.
Chemical Characterization of Organisms Isolated from Leprosy Patients
Authors: Beaman Blain L. , Kim Kwang-Shin , Lanéelle Marie A. , Barksdale Lane
Published: January 2020

Chemical analyses of the cell walls of organisms isolated in various parts of the world from cases of lepromatous and tuberculoid leprosy make possible their assignment to one of the three genera:Corynebacterium, Mycobacterium, orPropionibacterium. One, bacterium 22M, remains unassigned. The combined chemical and enzymatic properties attributed to leprosy bacilli freshly harvested from lepromata are found collectively, but not individually, in these three genera.
Isolation and Characterization of Temperature-Sensitive Mutants of Host-Dependent
Bdellovibrio bacteriovorus
109D
Authors: Dunn Joe E. , Windom Gwenyth E. , Hansen K. L. , Seidler Ramon J.
Published: January 2020

A variety of temperature-sensitive mutants of host-dependent
Bdellovibrio bacteriovorus
109D were selected after ethyl methane sulfonate mutagenesis. Mutants that demonstrated plaque-forming ability reversion frequencies of 10
−8
to 10
−9
were chosen for further study. Representatives of these mutants were then characterized by phase-contrast and electron microscopy, temperature-shifted one-step growth experiments, attachment kinetics, and macromolecular capabilities. Representative mutants demonstrate various types of blockage corresponding to the previously described morphological stages of
Bdellovibrio
predatious life cycle, i.e., attachment blockage (109D153), penetration blockage (109D3 and 109D48), and blockage of intracellular growth (109D4 and 109D152). The time of release from temperature repression for the mutant classes was found to correspond to the apparent morphological stage of blockage via temperature-shifted, one-step growth experiments. Mutants characterized as exhibiting blockage in the penetration or intracellular stages of the infection cycle exhibited, at the permissive and nonpermissive temperatures, kinetics of attachment to
Escherichia coli
WP2 similar to those of the wild type. One mutant, 109D153, exhibited depressed attachment at the restrictive temperature even though the
Bdellovibrio
cells were motile. The extent of 38.5 C attachment of 109D153 to
E. coli
is at the same level as that of wild-type 109D to
Bacillus subtilis
, a gram-positive, non-host organism. Subsequent detachments were revealed in the wild-type 109D-
B. subtilis
or mutant 109D153-
Escherichia coli
(38.5 C) cultures. These studies reveal a biphasic attachment phenomenon in the early interaction of
Bdellovibrio
with its host. It appears that, at the restrictive temperature, 109D153 is capable only of the initial, nonspecific type of attachment.
“Killer Character” of
Saccharomyces cerevisiae
: Curing by Growth at Elevated Temperature
Authors: Wickner Reed B.
Published: January 2020

Normal “killer” strains of
Saccharomyces cerevisiae
, when grown at 37 to 40 C, produce almost exclusively nonkiller cells due to loss or mutation of at least part of the non-chromosomal killer genome.
Proteins of the Inner Membrane of
Escherichia coli
: Identification of Succinate Dehydrogenase by Polyacrylamide Gel Electrophoresis with
sdh
Amber Mutants
Authors: Spencer Margaret E. , Guest J. R.
Published: January 2020

The inner or cytoplasmic membrane fraction of the cell envelope of
Escherichia coli
was isolated by isopycnic centrifugation on sucrose gradients. The membrane proteins were analyzed by electrophoresis in sodium dodecyl sulfate-polyacrylamide gels (8.5%), and up to 56 bands were resolved. Different preparations gave very similar patterns of proteins. Succinate dehydrogenase mutants (
sdh
) were isolated which could not grow on succinate minimal medium, although growth on fumarate was unimpaired. The protein patterns of inner membrane preparations from
sdh
amber mutants were compared with the wild type, and one major band was greatly reduced in the mutants. This component, which represented approximately 5% of the inner membrane protein, was restored by introducing an amber suppressor gene (
supU
), which also restored the Sdh
+
phenotype. The band corresponded to a protein with a molecular weight of 67,000 daltons, which is close to that for the large subunits of the succinate dehydrogenases of
Rhodospirillum rubrum
and beef heart mitochondria.
Hemagglutinin in Cell Walls ofChlamydia psittaci
Authors: Tamura Akira , Manire G. P.
Published: January 2020

Intact purified elementary bodies (EB) ofChlamydia psittaciagglutinate chicken erythrocytes in low titer, whereas homogenates of EB and of EB cell walls agglutinate at much higher titers depending on the extent of disruption by shaking and sonication. The hemagglutinin is contained in the cell envelope and can be purified with cell wall fractions. Treatment of cell wall with sodium dodecyl sulfate completely inactivated the hemagglutinin. Purified hemagglutinin was found to have an identical polypeptide composition to EB cell walls. Preparations of purified reticulate forms, the reproductive intracellular form of the organism, were almost totally devoid of hemagglutinin.
Active Transport of Alcohol inCorynebacterium acetophilum
Authors: Murooka Yoshikatsu , Harada Tokuya
Published: January 2020

The transport of alcohols was studied inCorynebacterium acetophilum, which was isolated as a strain growing well on acetate and ethanol. The transport of ethanol was found to be inducible by ethanol,n-propanol,n-butanol, and acetate, whereas transport of methanol occurred by noninducible passive diffusion. The entry of ethanol into the cells occurred against a concentration gradient and showed saturation kinetics with twoKmvalues of 2.4 × 10−5M and 6.0 × 10−5M. Uptake of ethanol was inhibited by sodium azide, sodium cyanide, 2,4-dinitrophenol, andp-chloromercuribenzoate. The transport of ethanol was competitively inhibited by normal alcohols, but not byiso- ortert-alcohols. From these studies, we concluded that an inducible active alcohol transport system mediates the entry of ethanol,n-propanol, orn-butanol into the cells ofC. acetophilum.
Amino-Terminal Sequence of the Tryptophan Synthetase α Chain of
Bacillus subtilis
Authors: Li Shoei-Lung , Hoch Sallie O.
Published: January 2020

The sequence of the 46 NH
2
-terminal residues of the tryptophan synthetase α chain of
Bacillus subtilis
was determined and compared with the corresponding sequences of
Escherichia coli, Shigella dysenteriae, Salmonella typhimurium, Aerobacter aerogenes, Serratia marcescens
, and
Pseudomonas putida
. A deletion of six residues was found at the NH
2
-terminal end of the α chain of
B. subtilis
.
Electron Microscope and Autoradiographic Study of Ultrastructural Aspects of Competence and Deoxyribonucleic Acid Absorption in
Bacillus subtilis
: Ultrastructure of Competent and Noncompetent Cells and Cellular Changes During Development of Competence
Authors: Vermeulen C. A. , Venema G.
Published: January 2020

By means of electron microscope autoradiography of component cultures of
Bacillus subtilis
exposed to [
3
H]thymidine-labeled transforming deoxyribonucleic acid competent and noncompetent cells can be distinguished. Competence is not limited to a specific phase of the cell division cycle. With serial section electron microscopy of competent and noncompetent cells, two types of mesosomal structures are observed: mesosomes connected to the plasma membrane only (plasma membrane mesosomes) and mesosomes which are additionally connected to the nuclear bodies (nuclear mesosomes). The two types show different cellular distributions. Especially the number of nuclear mesosomes is higher in competent than in noncompetent cells. This, and the observation that the increase and decrease of competence is correlated with both the number of cells carrying nuclear mesosomes and the number of nuclear mesosomes per cell, suggests that mesosomes are involved in the acquisition of competence.
Intracellular and Extracellular Nucleotides and Related Compounds During the Development of
Myxococcus xanthus
Authors: Hanson Charles W. , Dworkin Martin
Published: January 2020

Changes in nucleotide pools and extracellular nucleotides during the developmental cycle of the myxobacterium
Myxococcus xanthus
were determined using a high-pressure liquid chromatography nucleotide analyzer. A general increase in all nucleotide pools occurred during the morphological phase of glycerol conversion of vegetative cells to myxospores. The levels of the nucleoside triphosphate pools remained high as the myxospore matured and throughout subsequent germination. Oxidized nicotinamide adenine dinucleotide levels were elevated in the dormant myxospore and then declined during germination. The adenylate energy charge value was 0.85 ± 0.02 for vegetative cells, germinating myxospores, and 6-h-old myxospores. It was interesting that the value for the so-called dormant myxospore was the same as that characteristic of physiologically active cells. The germinating myxospores excreted large quantities of uracil along with lesser quantities of purine nucleoside monophosphates. Although the source of the extracellular uracil cannot be determined from these experiments, it may have been derived from a shift in base ratios accompanying an assumed ribonucleic acid turnover during germination.
Complementation In Vitro Between Mutationally Altered β2subunits ofEscherichia coliTryptophan Synthetase
Authors: Kida Setsuko , Crawford Irving P.
Published: January 2020

Cross-reacting β2subunits (CRMs) were purified from eighttrpBmissense mutants to test for complementation in vitro after urea dissociation and reaggregation. One CRM (B290, demonstrating “repairability,” i.e., the appearance of enzymatic activity on combination with α subunits) was clearly positive with four others, all “non-repairable” CRMs resulting from mutations at three different but neighboring sites. One complementing pair, B290-B248, was studied in more detail and found, upon mixing purified proteins, to give complementation in the absence of denaturants. Complementation activity was low in each case. To study the mechanism of the modest increases in activity, we used a reduced β2subunit as an artificial CRM to form hybrids where both the amount of activity due to complementation and the amount of hybrid could be measured. (In a reduced β2subunit, the two pyridoxal phosphate cofactors have been chemically reduced by sodium borohydride and are covalently attached to lysine residues. This abolishes activity in the tryptophan synthetic reaction and causes the protein to migrate much faster than normal in acrylamide gel electrophoresis.) Reduced β2subunit formed hybrid dimers with the non-repairable CRMs B244 and B248 at pH 6.0, but no enzymatic activity appeared. On the other hand, when reduced β2subunit was mixed with B290 CRM at pH 6.0 to 6.6, an activity increase was seen that was proportional to the amount of hybrid. We conclude that hybrid formation is essential for complementation and that the mechanism of complementation in this system is the correction of a repairable active site on the B290 β chain by a conformational change occuring when hybrid dimer is formed. This type of complementation must be restricted to a small class of CRMs having a conformationally deformed active site. From the amount of hybrid present and the increase in activity, a specific activity of 50 U/mg was calculated for the hybrid containing reduced and B290 β chains. This value is slightly less than but close to the activity of the hybrid formed between reduced and normal β chains, shown earlier to have half the specific activity of the normal dimer.
Homoserine Kinase from
Escherichia coli
K-12: Properties, Inhibition by
l
-Threonine, and Regulation of Biosynthesis
Authors: Theze J. , Kleidman L. , Girons I. Saint
Published: January 2020

We have partially purified homoserine kinase from a genetically derepressed strain of
Escherichia coli
K-12. The optimum pH of the enzyme-substrate reaction was 7.8 and the

K
m

values for
l
-homoserine and adenosine 5′-triphosphate were both 3 × 10
−4
M. K
+
(or NH
4
+
) as well as Mg
2+
were required for its activity. The sedimentation coefficient determined by ultracentrifugation in a sucrose density gradient was 5.0 ± 0.25
S
.
l
-Homoserine was an excellent protector against heat inactivation of homoserine kinase.
l
-Threonine was a competitive inhibitor of homoserine kinase, suggesting that end-product inhibition of this enzyme plays a role in vivo in the overall regulation of threonine biosynthesis. The specific activity of aspartokinase I-homoserine dehydrogenase I and of homoserine kinase showed a strong positive correlation in extracts from strains under widely varying conditions of genetic or physiological derepression; it was concluded that these two enzymes are coordinately regulated in
E. coli
K-12.
Proteinase Produced byChlamydia psittaciin L Cells
Authors: Stokes Gerald V.
Published: January 2020

L cells (mouse fibroblasts) infected withChlamydia psittaci(strain meningopneumonitis) produced a proteinase differing in solubility in ammonium sulfate from the proteinase of uninfected L cells. Synthesis of the enzyme was inhibited by chloramphenicol but not by cycloheximide, indicating that the new proteinase in infected L cells was synthesized byChlamydia psittaci. The chlamydial proteinase had no demonstrable ion requirements and was not inhibited by a variety of inhibitors of proteinase activity. Gel filtration experiments suggested a molecular weight of approximately 250,000. The proteinase appeared in infected L cells at the time host cells began to die and the large chlamydial cells began to reorganize into small ones. Some possible functions for the chlamydial proteinase were proposed.
Activity of Uridine Diphosphate
N
-Acetylglucosamine-4-Epimerase During Spherulation of
Physarum polycephalum
Authors: Hiatt William R. , Whiteley H. R.
Published: January 2020

The specific activity of uridine diphosphate
N
-acetylglucosamine-4-epimerase increases during spherulation of
Physarum polycephalum
, a process that involves the synthesis of galactosamine walls. This increase is prevented by the addition of cycloheximide.
Cold-Sensitive Mutant of
Salmonella typhimurium
Defective in Nucleosidediphosphokinase
Authors: Ginther Charles L. , Ingraham John L.
Published: January 2020

A cold-sensitive mutant of
Salmonella typhimurium
defective in nucleosidediphosphokinase (ATP:nucleosidediphosphate phosphotransferase, EC 2.7.4.6) has been isolated and characterized. The mutant contains only 2% of the enzyme activity found in the parent, and the heat lability of this activity is 10 times that from the parent at 33 C. Mutant extracts lack the ability to convert any of 11 nucleoside diphosphates tested to the corresponding nucleoside triphosphates, but the nucleosidemonophosphatase activities are normal. Although the nucleoside triphosphate pools of the mutant are depressed significantly at the restrictive temperature (20 C), they are slightly elevated at the permissive temperature (37 C). The levels of guanosine pentaphosphate and guanosine tetraphosphate are dramatically increased. Two representative enzymes of pyrimidine de novo synthesis, aspartic transcarbamylase and dihydroorotate dehydrogenase, are fully repressed at both 37 and 20 C. Intracellular pools of uridine diphosphate are depressed at both permissive and restrictive temperature.
Inhibition of the Development of Competence in
Streptococcus sanguis
(Wicky) by Reagents that Interact with Sulfhydryl Groups: Discernment of the Competence Process
Authors: Ranhand Jon M.
Published: January 2020

Reagents that interact with sulfhydryl groups are shown to inhibit competence factor (CF)-induced competence development in
Streptococcus sanguis
(Wicky) strain WE4 (Wicky 4 Ery
R
). Inhibition is correlated with specific inhibition of either the function or biosynthesis of three competent cell-related proteins and is reversed by either 2-mercaptoethanol or dithiothreitol. Mercuric chloride (5 μM) or
N
-ethylmaleimide (NEM; 50 μM) inhibited (i) the function but not the biosynthesis or activation of the competent cell-associated autolysin; (ii) the biosynthesis of a competent cell-associated protein of unknown function, demonstrated by polyacrylamide gel electrophoresis of acidified phenol extracts; and (iii) the biosynthesis or activation of distinct deoxyribonucleic acid (DNA)-binding sites. Neither reagent at the indicated concentration interfered with the uptake of CF by cells or with the uptake and expression of DNA by competent cells. Neither reagent inactivated CF or genetic markers coded by the transforming DNA, nor did they inhibit cell growth or viability appreciably. The data reveal that either mercuric chloride or NEM can differentially inhibit induced protein synthesis and, in addition, conclusively show that some autolytic activity is essential for the onset of the competent state.
Development of Auxotrophy by Streptomycin-Resistant Mutation
Authors: Chakrabarti S. L. , Maitra P. K.
Published: January 2020

Several streptomycin-resistant mutants of
Escherichia coli
have been isolated which require exogenous isoleucine for growth. The majority of these strains were of streptomycin-dependent phenotype. If grown in the absence of streptomycin, these streptomycin-dependent auxotrophs (Sm
d-aux
) strains were unable to produce β-galactosidase and aldolase activities and also failed to exhibit donor properties in conjugation. Genetic analysis indicated that the isoleucine requirement of these strains could be caused by a mutation at the
strA
locus.
Ribonucleic Acid Regulation in Permeabilized Cells of
Escherichia coli
Capable of Ribonucleic Acid and Protein Synthesis
Authors: Atherly Alan G.
Published: January 2020

A cell permeabilization procedure is described that reduces viability less than 10% and does not significantly reduce the rates of ribonucleic acid and protein synthesis when appropriately supplemented. Permeabilization abolishes the normal stringent coupling of protein and ribonucleic acid synthesis.
Mapping Loci for Surface Exclusion and Incompatibility on the F Factor of
Escherichia coli
K-12
Authors: Willetts Neil
Published: January 2020

A series of Hfr deletion strains carrying deletions extending different distances into the integrated F factor have been used to map loci for surface exclusion (
traS
) and for incompatibility (
inc
) on the
Escherichia coli
K-12 sex factor F.
traS
mapped between
traG
and
traD
. It forms a part of the large operon, including all the known transfer genes except
traJ
, and is co-controlled with these. The product of
traS
is not required for formation of the F pilus.
inc
mapped between the φ
R
11
locus and the origin of transfer; it is therefore one of the earliest loci transferred during conjugation.
Mutants of
Escherichia coli
B/r Defective in Deoxyribonucleic Acid Initiation:
dnaI
, a New Gene for Replication
Authors: Beyersmann D. , Messer W. , Schlicht M.
Published: January 2020

Mutagenized
E. coli
B/r cells were subjected to a procedure designed to select mutants temperature-sensitive for initiation of deoxyribonucleic acid (DNA) replication. Seventeen mutants exhibiting limited residual DNA synthesis at 42 C were obtained and the
dna
−
sites were mapped genetically. Sixteen of the sites map near
dnaA, dnaB
, and
dnaC
. One mutant (
dna-208
) maps in a new location between the
trp
and
his
genes. We propose to call this mutant
dnaI208
. In complementation experiments
dnaC
+
and
dnaI
+
were dominant to
dnaC
−
and
dnaI
−
alleles, respectively. However,
dnaA
−
was dominant to the wild-type allele
dnaA
+
. All
dnaA
mutants and four out of six
dnaC
mutants could be suppressed by F factor integration. The pattern of suppression was specific for each mutant.
R-Factor-Mediated Nuclease Activity Involved in Thymineless Elimination
Authors: Tweats D. J. , Pinney R. J. , Smith J. T.
Published: January 2020

R-factor 1818 (R-1818) had no effect on the efficiency of plating of ligase-deficient phage T4 mutants on strains ofEscherichia colicontaining excess, normal, or defective ligase. However, if the R+bacterial strain that overproduced ligase was first starved of thymine, its ability to propagate ligase-deficient phage was reduced by as much as fivefold compared with the burst size on the thymine-starved R−strain. In contrast, it was found that after ultraviolet irradiation of the host the phage burst size was higher on the R+ligase overproducing strain than the R−derivative. The maximal level of R-factor elimination produced by thymine starvation was inversely related to the ligase level of the host. Ultraviolet irradiation did not cure the R factor from strains containing wild-type levels of ligase, but did cause elimination from strains with excess or defective ligase. The results suggest that R-1818 codes for a nuclease that is induced by thymine starvation and which, possibly in conjunction with host-mediated nucleases, is responsible for its elimination under these conditions.
flrB, a Regulatory Locus Controlling Branched-Chain Amino Acid Biosynthesis in Salmonella typhimurium
Authors: Friedberg Devorah , Mikulka Thomas W. , Jones Judith , Calvo Joseph M.
Published: January 2020

Salmonella typhimurium
strain CV123 (
ara-9 gal-205 flrB1
), isolated as a mutant resistant to trifluoroleucine, has derepressed and constitutive levels of enzymes forming branched-chain amino acids. This strain grows more slowly than the parent at several temperatures, both in minimal medium and nutrient broth. It overproduces and excretes sizeable amounts of leucine, valine, and isoleucine in comparison with the parental strain. Both
leuS
(coding for leucyl-transfer ribonucleic acid [tRNA]synthetase) and
flrB
are linked to
lip
(min 20 to 25) by P1 transduction, whereas only
leuS
is linked to
lip
by P22 transduction. Strain CV123 containing an F′
lip
+
episome from
Escherichia coli
has repressed levels of leucine-forming enzymes, indicating that
flrB
+
is dominant to
flrB
. Leucyl-tRNA synthetase from strain CV123 appears to be identical to the leucyl-tRNA synthetase in the parent. No differences were detected between strain CV123 and the parent with respect to tRNA acceptor activity for a number of amino acids. Furthermore, there was no large difference between the two strains in the patterns of leucine tRNA isoaccepting species after fractionation on several different columns. Several other
flrB
strains exhibited temperature-sensitive excretion of leucine, i.e., they excreted leucine at 37 C but not 25 C. In one such strain, excretion at 37 C was correlated with derepression of some enzymes specified by
ilv
and
leu
. These latter results suggest that
flrB
codes for a protein.
Effect of Molybdenum Starvation and Tungsten on the Synthesis of Nitrogenase Components in
Klebsiella pneumoniae
Authors: Brill Winston J. , Steiner Ann L. , Shah Vinod K.
Published: January 2020

Klebsiella pneumoniae
M5a1 grows well in the presence or absence of molybdenum in media containing excess NH
4
+
. However, growth on N
2
is completely dependent on the presence of molybdenum in the medium. Tungstate competes with the molybdate requirement during growth on N
2
. In molybdenum-depleted medium, neither protein component of nitrogenase is active and neither component can be detected antigenically. These data provide evidence that molybdenum is an inducer of nitrogenase synthesis.
Apparent Average Length of the Transcriptional Unit in Bacteria
Authors: Konrad Michael W.
Published: January 2020

The kinetics of radioactive phosphate incorporation into the adenosine and guanosine nucleoside triphosphate termini of bacterial ribonucleic acid (RNA) was studied. Knowledge obtained in a previous investigation of the kinetics of phosphate incorporation into their precursors, adenosine 5′-triphosphate and guanosine 5′-triphosphate, allowed calculation of the average half-lives of these termini, which were found to be approximately 170 s at 21.5 C for both. The ratio between the number of nucleotides incorporated into the interior of RNA chains per second and the number of termini synthesized per second was calculated by several methods and found to be between 4,000 and 8,000. Assuming that the initiation of synthesis of a RNA chain by deoxyribonucleic acid-dependent RNA polymerase always produces a triphosphate termini and that some termini do not have half-lives so short as to not be seen in this study (less than 10 s), this is the apparent average length of the transcriptional unit. The implication of these findings to the genetic organization of transfer RNA genes is discussed.
Septum of
Geotrichum candidum
or Valva of a Centric Diatom?
Authors: Schnepf E.
Published: January 2020

It is suggested that the structures which have been interpreted as immature septa of
Geotrichum candidum
by Hashimoto et al. represent valvae of a centric diatom.
β-β′ Subunits of Ribonucleic Acid Polymerase in Episome-Free Minicells of
Escherichia coli
Authors: Rogerson Allen C. , Stone Jane E.
Published: January 2020

Episome-free minicells of
Escherichia coli
, previously shown to lack ribonucleic acid polymerase activity, do contain the β-β′ subunits of the polymerase.
Changes inMicrosporum gypseumMycelial Wall and Spore Coat Glycoproteins During Sporulation and Spore Germination
Authors: Page W. J. , Stock J. J.
Published: January 2020

Ethylenediamine-soluble glycoproteins were extracted from isolatedMicrosporum gypseumhyphal walls during sporulation and from spore coats before and after germination. This study was carried out to identify a sporulation-specific cell wall protein that possibly served as a substrate for the alkaline protease which initiated the macroconidial germination of this fungus. Analyses revealed that water-insoluble glycoprotein accounted for 10% of the ungerminated spore coat but only for 4 to 5% of the mycelial wall dry weight. This fraction was modified in its amino acid composition during sporulation, and it decreased in protein content during spore germination. Water-soluble glycoprotein, which accounted for approximately 3 to 3.5% of either the spore coat or mycelial wall dry weight, was of similar amino acid composition from both sources and did not decrease in protein content upon spore germination. The water-insoluble glycoprotein was found to be rich in leucine, aspartic acid, glycine, glutamic acid, and phenylalanine residues. The water-soluble glycoprotein was rich in proline, threonine, glycine, serine, glutamic acid, and alanine.
Accumulation of Toxic Concentrations of Methylglyoxal by Wild-Type
Escherichia coli
K-12
Authors: Ackerman Rollie S. , Cozzarelli Nicholas R. , Epstein Wolfgang
Published: January 2020

Wild-type strains of
Escherichia coli
K-12 accumulate toxic concentrations of methylglyoxal when grown in medium containing adenosine 3′,5′-monophosphate and either
d
-xylose,
l
-arabinose, or
d
-glucose-6-phosphate, independent of the presence of other carbon sources. Mutations at a locus called
cxm
specifically block methylglyoxal formation from xylose in the presence of adenosine 3′,5′-monophosphate. Accumulation in medium containing xylose, studied in some detail, is dependent on the ability to utilize xylose and is associated with an increased rate of xylose utilization without changes in levels of xylose isomerase. These results suggest that adenosine 3′,5′-monophosphate results in induction of excessively high levels of an early rate-limiting step in xylose metabolism. This step may be the transport of xylose into the cell. The resulting excessive rates of xylose catabolism could stimulate methylglyoxal formation by overburdening late steps in glycolysis.
Mutations Partially Inactivating the Lactose Repressor of
Escherichia coli
Authors: Shineberg B.
Published: January 2020

After treatment with
N
-methyl-
N
′-nitro-
N
-nitrosoguanidine, 133 independent mutants of a haploid strain of
Escherichia coli
able to use phenyl-β-galactoside as a carbon source were obtained. The galactoside was specific in selecting for mutants with increases in their uninduced levels of β-galactosidase. Virtually all mutants (37 in a subsample of 38) carried mutations in the
lac
repressor gene. There were two classes of repressor mutants. As well as the commonly identified class of mutants with completely inactivated repressors, there was a frequent class of mutants (21/37) whose repressors were partially inactivated. Most of these (15/21) repressed β-galactosidase synthesis 4 to 50 times less than wild type, but were more numerous in the lower part of this range. Their β-galactosidase was inducible to levels characteristic of the parent strain. The repressor activities were diverse and stably expressed under routine growth conditions. The decreased activity did not result from the formation of temperature-sensitive repressors. None of the mutants with completely inactivated repressors appeared to carry UAG or UGA chain-terminating codons. On the assumption that the partially defective repressor mutants carried missense mutations, it is argued that missense mutations in the
lac
repressor gene modify the repressor's affinity for the operator with high probability. An explanation is proposed for the apparent sensitivity of this repressor function to partial inactivation as the result of amino acid substitutions.
Regulatory Aspects of
l
-Glutamate Transport in
Aspergillus nidulans
Authors: Pateman J. A. , Kinghorn J. R. , Dunn Etta
Published: January 2020

Wild-type cells of
Aspergillus nidulans
synthesize a transport system which appears to be specific for
l
-glutamate and
l
-aspartate. The system is energy dependent and concentrates
l
-glutamate at least 60-fold. In cells grown in the presence of 1% sucrose,
l
-glutamate uptake activity is regulated by ammonium control, although it is not certain whether this is at the level of transcription or translation. Mutants that are insensitive to ammonium control of certain other unrelated systems, e.g., nitrate reductase, are also insensitive, except in the case of one class of ammonium-insensitive mutants, to ammonium control of
l
-glutamate transport. The activity of this transport system is specifically impaired in a mutant at the
aauA
locus. This mutation results in poor growth with
l
-glutamate or
l
-aspartate as the sole carbon or nitrogen source and is recessive in the heterozygous diploid
aauA1
/+ for transport and growth characteristics. The likelihood that the mutation results in a defect of the transport mechanism rather than abnormal ammonium control is discussed.
Distinctive Renal Lesion of Spirochete-Infected Brine Shrimp
Authors: Tyson Greta E.
Published: January 2020

In spirochete-infected
Artemia
, the renal tubule exhibited a lesion consisting of a group of spirochetes situated in an indentation of the base of the epithelium and involving discontinuity of the basal lamina.
Presence of Amino Acid Dehydrogenases and Transaminases in
Myxococcus xanthus
During Vegetative Growth and Myxospore Formation
Authors: Kottel Randall H. , Orlowski Michael , White David , Grutsch James
Published: January 2020

The following enzymatic activities were demonstrated in
Myxococcus xanthus
during growth and myxospore formation:
l
-alanine dehydrogenase (EC 1.4.1.1),
l
-glutamic acid dehydrogenase (EC 1.4.1.2), glycine dehydrogenase (EC 1.4.1.5),
l
-glutamic glyoxylate aminotransferase (EC 2.6.1.4), and
l
-alanine glyoxylate aminotransferase (EC 2.6.1.12).
Orthophosphate Requirement for the Formation of Phosphoenolpyruvate from Pyruvate by Enzyme Preparations from Photosynthetic Bacteria
Authors: Buchanan Bob B.
Published: January 2020

The formation of phosphoenolpyruvate from pyruvate and adenosine 5′-triphosphate by enzymes from photosynthetic bacteria required inorganic phosphate, thus indicating that these organisms utilize pyruvate, orthophosphate dikinase rather than phosphoenolpyruvate synthase in photosynthesis.
Complementation Between Different Mutations in the
ilvA
Gene of
Escherichia coli
K-12
Authors: Favre Renée , Iaccarino Maurizio , Levinthal Mark
Published: January 2020

An
ilvA
mutation carried by a ø80i
λ
dilv
transducing phage complemented some
ilvA
mutations and did not complement others. Complementation was accompanied by appearance of threonine deaminase activity in vivo. These results divided the
ilvA
mutations into two sets which formerly appeared to define two cistrons.