bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Colicins E1 and K on Cellular Metabolism
Authors: Fields Kay L. , Luria S. E.
Published: January 2020

Colicins E1 and K inhibited a whole series of energy-dependent reactions in
Escherichia coli
cells, including motility, biosynthesis of nucleic acids, proteins and polysaccharides, and the conversion of ornithine to citrulline. Respiration was only partially affected, and substrates such as glucose continued to be catabolized through the normal pathways, albeit with reduced CO
2
production. The soluble products of aerobic glucose catabolism by colicin-treated cells were analyzed. Pyruvate replaced acetate as the major excreted product, and the following intermediates of glycolysis were excreted in significant amounts: glucose-6-phosphate, fructose-1,6-diphosphate, dihydroxyacetone phosphate, and 3-phosphoglycerate. Anaerobically growing cells manifested a somewhat enhanced tolerance to the colicins. This protection by anaerobiosis appeared to depend on the exclusion of oxygen more than on the extent of fermentative catabolism versus catabolism of the respiratory type. These results are interpreted in terms of possible functions of colicin in lowering the adenosine triphosphate (ATP) content of the cells and in terms of the role of lowered ATP levels in inhibiting many of the energy-requiring reactions.
Comparison of the Action of Colicins E1 and K on
Escherichia coli
with the Effects of Abortive Infection by Virulent Bacteriophages
Authors: Fields Kay L.
Published: January 2020

Abortive infection of certain strains of
Escherichia coli
or
Shigella dysenteriae
with phages of the T-even group or with phage T5 resembles the action of colicin E1 or K on sensitive bacteria, especially in the effects on biosynthetic processes. Tests on transport systems and on adenosine triphosphate levels suggest, however, that different mechanisms are involved in the two cases. Abortive infection appears to cause damage to the permeability barrier of the cell, whereas the colicins interfere more directly with the energy metabolism of the bacteria.
Serum-mediated Immune Cellular Responses to
Brucella melitensis
IV. Infection of Macrophages Under Anaerobic Conditions
Authors: Ralston Doris J. , Elberg Sanford S.
Published: January 2020

Immune mechanisms active against
Brucella
were studied under conditions of oxygen deficiency.
B. melitensis
grew in rabbit serum-Tyrode medium flooded with N
2
and CO
2
gas mixtures. Immune sera from rabbits injected with
B. melitensis
strain Rev I possessed growth-inhibitory activity that operated in anaerobic environments against Rev I and virulent strain 6015. When mixed with macrophages, immune sera mediated even greater inhibition of bacterial growth and slowed the spread of infection throughout the tissue culture. Although under anaerobic conditions the rate of phagocytosis was reduced, the macrophages in immune serum killed significant percentages of
Brucella
, suggesting that an antibacterial mechanism had been activated. Sonic extracts of macrophages prepared and tested under anaerobic conditions depressed the growth rate of strain Rev I. The extracts, however, exhibited no immediate killing capacity when tested in Tyrode solution. A factor from serum was required for depression of the growth rate.
Identification of L Forms by Polyacrylamide-Gel Electrophoresis
Authors: Theodore Theodore S. , King James R. , Cole Roger M.
Published: January 2020

Crude membranes were obtained from L forms by allowing the cells to lyse in distilled water. The crude membranes were washed several times in distilled water, lyophilized, and extracted with phenol-acetic acid-water. The membrane proteins were separated electrophoretically in polyacrylamide gels run at
p
H 4.5. Electrophoretic patterns and densitometric tracings of the gels showed distinct, reproducible intergeneric differences among L forms of
Proteus, Streptobacillus, Staphylococcus
, and
Streptococcus
. Differences within a genus could not be detected except between the group A streptococcal L forms and the one group D F-24 L form. This electrophoretic method offers possibilities for ready identification of L forms through the use of standard reference strains.
Properties of a Cell Fraction That Repairs Damage to the Cell Division Mechanism of
Escherichia coli
Authors: Fisher William D. , Adler Howard I. , Shull Fred W. , Cohen Amikam
Published: January 2020

A factor in bacterial cell extracts which induces cell division in filaments of
Escherichia coli
produced by irradiation was found to be associated with a heat-labile particulate fraction which sediments at about 100
S
. Frozen or lyophilized samples of the cell extracts were stable for considerable periods of time. Fractions purified by centrifugation contained 2% of the total protein of the extract but no measurable ribonucleic acid or deoxyribonucleic acid. The extracts were inactivated by incubation with phospholipase A, lipases, and detergents, but not by incubation with selected nucleases and proteases.
Comparison of Undefined Medium and Its Dialyzable Fraction for Growth of
Mycoplasma
Authors: Pollock Mary E. , Bonner Susan V.
Published: January 2020

In examining the medium used in cultivation of
Mycoplasma
for deoxyribonucleic acid isolation, it was found that an aggregate was present which sedimented with the organisms and which was ethyl alcohol-precipitated during deoxyribonucleic acid purification. To eliminate the contaminating material, a method was devised to obtain only the dialyzable constituents of the medium. This report describes the preparation of a dialysate of soy peptone-yeast extract. The medium, obtained by immersion of the encased dehydrated ingredients in sodium chloride solution for 5.5 hr at approximately 80 C, has been employed as the basal medium for cultivation of a number of
Mycoplasma
species. Comparative growth curves of two saprophytic strains and two parasitic species indicated that multiplication in dialysate, with suitable supplement, followed the pattern typical of the common eubacteria. Thus, by elimination of the sediment which occurred in nondialyzed medium,
Mycoplasma
could be concentrated without concomitant accumulation of contaminating macromolecules.
Alteration of Glucose Metabolism of
Arthrobacter crystallopoietes
by Compounds Which Induce Sphere to Rod Morphogenesis
Authors: Krulwich Terry A. , Ensign J. C.
Published: January 2020

Succinate and several other compounds which induce sphere to rod morphogenesis of
A. crystallopoietes
were found to suppress both catabolism and assimilation of glucose. Diauxic growth patterns resulted from growth on glucose plus any one of these compounds. Glutamate stimulated growth but was not an inducer of morphogenesis. With this compound, diauxic growth and suppression of glucose catabolism or assimilation did not occur. Glucose permease was studied with α-methylglucoside as substrate. The entry system for glucose was found to involve active transport and to have a
K
m
of 8 × 10
−4
m
. It was inducible, was repressed in succinate-grown cells, and was also inhibited by succinate. The exit system was constitutive and appeared to be less sensitive than the entry system to inhibition by azide. The properties of the glucose permease system may account for the slow growth of the organism on glucose and the preferred use of other substrates for growth. Studies of metabolic pathways for glucose metabolism indicated the operation of the Embden-Meyerhof-Parnas (EMP) and pentose phosphate pathways and of the tricarboxylic acid cycle. Cells grown on glucose plus limiting amounts of succinate or other inducers of morphogenesis metabolized the glucose only after exhaustion of the inducers. Under these circumstances, the organisms employed the EMP pathway to a greater extent than when growing on glucose as sole carbon source.
Control of Mixed-Substrate Utilization in Continuous Cultures ofEscherichia coli
Authors: Silver Richard S. , Mateles Richard I.
Published: January 2020

The chemostat culture technique was used to study the control mechanisms which operate during utilization of mixtures of glucose and lactose and glucose andl-aspartic acid by populations ofEscherichia coliB6. Constitutive mutants were rapidly selected during continuous culture on a mixture of glucose and lactose, and the β-galactosidase level of the culture increased greatly. After mutant selection, the specific β-galactosidase level of the culture was a decreasing function of growth rate. In cultures of both the inducible wild type and the constitutive mutant, glucose and lactose were simultaneously utilized at moderate growth rates, whereas only glucose was used in the inducible cultures at high growth rates. Catabolite repression was shown to be the primary mechanism of control of β-galactosidase level and lactose utilization in continuous culture on mixed substrates. In batch culture, as in the chemostat, catabolite repression acting by itself on thelacenzymes was insufficient to prevent lactose utilization or cause diauxie. Interference with induction of thelacoperon, as well as catabolite repression, was necessary to produce diauxic growth. Continuous cultures fed mixtures of glucose andl-aspartic acid utilized both substrates at moderate growth rates, even though the catabolic enzyme aspartase was linearly repressed with increasing growth rate. Although the repression of aspartase paralleled the catabolite repression of β-galactosidase,l-aspartic acid could be utilized even at very low levels of the catabolic enzyme because of direct anabolic incorporation into protein.
Effect of Histoplasmosis on Antibody Response to an Erythrocyte Antigen
Authors: Cozad George C. , Scalarone Gene M.
Published: January 2020

Infection of mice with
Histoplasma capsulatum
depressed their ability to form agglutinins against foreign erythrocytes. Animals previously inoculated with 10
8
yeast cells of
H. capsulatum
showed the most significant depression, occurring when erythrocytes were injected 8 days after infection. The average log
2
hemagglutinin titer was 2.7 compared to 8.0 for the control (noninfected) group. In general, depression of hemagglutinin response in all infected mice was greatest 8 days after infection, but response was back to near normal after 16 days and stayed at that level for the remaining time tested (24 days).
Characterization and Biological Activity of the Monocytosis-producing Agent of
Listeria monocytogenes
Authors: Holder Ian A. , Sword C. P.
Published: January 2020

Experiments directed toward determining the lipids in extracts of
Listeria monocytogenes
containing monocytosis-producing agent (MPA) and the effect of these extracts on several biochemical parameters previously shown to change during experimental
Listeria
infection were conducted. MPA-containing extracts were found to be a complex of lipids with glycerides, glycolipids, and phospholipid being present. No common cell wall carbohydrates were found. A glyceride, designated glyceride A, was determined to cause the characteristic mononuclear response observed in mice injected with MPA-containing extracts. Fasted MPA-treated animals showed less gluconeogenesis than did controls. Blood glucose levels declined in MPA-treated animals. Increases observed in both blood urea nitrogen and plasma glutamic-pyruvic transaminase were greater in the control groups. Incorporation of
14
C-alanine into liver glycogen was depressed in MPA-treated animals. Liver steroid levels in the control groups increased during fasting and remained elevated for the duration of the experiments, while levels in the MPA-treated groups declined initially and showed no increase until 72 hr after injection. MPA appears to affect steroid metabolism and consequently the animals' homeostatic mechanisms seem to be impaired. Possibly as a consequence, carbohydrate metabolism is altered. The apparent effect of MPA on steroid metabolism and on the gluconeogenic process may indicate participation in the carbohydrate derangement observed in experimental
Listeria
infection.
Evidence for Two States of F Pili
Authors: Wendt Louis , Mobach Helen Wedel
Published: January 2020

The addition of phenethyl alcohol (PEA) to cultures of male strains of
Escherichia coli
rapidly prevents the adsorption of the male-specific bacteriophages f1 and f2 to the donor cells. The adsorption of f2 to F pili in cell-free preparations is unaffected by PEA. In a mating system, PEA alters the kinetics of gene transfer in minimal medium but not in broth. Sodium cyanide, azide, and iodoacetate also apparently inhibit f2 adsorption to cells but not to detached F pili. The phage adsorption inhibitory action of PEA is completely reversible in the presence of 100 μg of chloramphenicol per ml.
Arsenic-Lipid Complex Formation During the Active Transport of Arsenate in Yeast
Authors: Cerbón Jorge
Published: January 2020

In studying formation of an arsenic-lipid complex during the active transport of
74
As-arsenate in yeast, it was found that adaptation of yeast to arsenate resulted in cell populations which showed a deficient inflow of arsenate as compared to the nonadapted yeast. Experiments with both types of cells showed a direct correlation between the arsenate taken up and the amount of As-lipid complex formed.
74
As-arsenate was bound exclusively to the phosphoinositide fraction of the cellular lipids. When arsenate transport was inhibited by dinitrophenol and sodium azide, the formation of the As-lipid complex was also inhibited. Phosphate did not interfere with the arsenate transport at a non-inhibitory concentration of external arsenate (10
−9
m
). The As-adapted cells but not the unadapted cells were able to take up phosphate when growing in the presence of 10
−2
m
arsenate.
Anthranilate Synthetase, an Enzyme Specified by the Tryptophan Operon of
Escherichia coli
: Comparative Studies on the Complex and the Subunits
Authors: Ito Junetsu , Yanofsky Charles
Published: January 2020

The properties of the anthranilate synthetase complex and its separated subunits were compared in catalyzing the anthranilate synthetase reaction, chorismate +
l
-glutamine or NH
4
+
→ anthranilate, and the transferase reaction, anthranilate + 5′-phosphorylribosyl-1-pyrophosphate → phosphoribosyl anthranilate. It is shown that anthranilate synthetase component I is activated by normal anthranilate synthetase component II, a component II
CRM
(CRM = immunologically cross-reacting material), and by a presumed fragment of component II produced by a deletion mutant. Significant differences between the complex and its subunits are demonstrated with respect to substrate affinity, thermostability, feedback inhibitor sensitivity, and activity in the presence of various divalent cations. Of particular interest are the findings that the transferase activity of component II is only inhibitable by
l
-tryptophan when the component is in the complex and that this inhibition does not appear to depend upon the feedback-sensitive site of component I.
Effects of Cycloheximide and 5-Fluorouracil on Formation of Low-Molecular-Weight Ribonucleic Acid in Yeast
Authors: Hendricks D. V. , Andrean B. A. G. , De Kloet S. R.
Published: January 2020

The effects of cycloheximide and 5-fluorouracil on the formation of low-molecular-weight ribonucleic acid (RNA) in yeast were investigated. Both compounds were found to affect the synthesis of low-molecular-weight RNA of ribosomal origin more than transfer RNA but less than the high-molecular-weight ribosomal RNA. 5-Fluorouracil-containing transfer RNA was separated from normal transfer RNA by chromatography on diethylaminoethyl cellulose at 80 C in the presence of 7
m
urea.
Effect of Divalent Cations on the Uptake and Oxidation of Substrates by
Pseudomonas aeruginosa
Authors: Eagon R. G. , Asbell Mary A.
Published: January 2020

Evidence is presented that Zn
2+
and certain other multivalent cations inhibit the uptake and oxidation of substrates by
Pseudomonas aeruginosa
and by other bacterial cells. Tris(hydroxymethyl)aminomethane augmented this effect. Inhibition by these multivalent cations could be prevented by incubation of cellular suspensions of
P. aeruginosa
in phosphate buffer. In the case of other microorganisms, incubation in the presence of ethylenediaminetetraacetate also prevented the inhibition. Inhibition by Zn
2+
of the uptake and of the oxidation of substrates could be reversed by the addition of Mg
2+
. Zn
2+
was shown to inhibit noncompetitively the uptake of the three substrates studied,
l
-alanine,
d
-glucose, and citrate.
Mechanism of Autolysis of Isolated Cell Walls of
Staphylococcus aureus
Authors: Tipper Donald J.
Published: January 2020

Autolysis of isolated cell walls of
Staphylococcus aureus
strain Copenhagen was accompanied by the release of 1 mole of N-terminal alanine per mole of glutamic acid. No other N-terminal amino acids and no C-terminal amino acids were released. These observations indicated that complete hydrolysis of
N
-acetylmuramyl-
l
-alanine linkages (“amidase” action) had occurred. This was confirmed by fractionation and analysis of the products. Hydrolysis of 4-
O
-β-
N
-acetylglucosaminyl-
N
-acetylmuramic acid linkages also occurred to a variable extent; on one occasion, complete degradation to disaccharides and hexosamine-free polypeptides (with intact pentaglycine cross-bridges) occurred. In one other instance, hydrolysis within pentaglycine bridges also occurred. Analyses of intact cell walls indicated that, in vivo, glycine endopeptidase activity was negligible and amidase activity was low, but that endo-β-
N
-acetylglucosaminidase hydrolysed about 8% of the
N
-acetylglucosaminyl-
N
-acetylmuramic acid linkages. Autolysis of isolated cell walls was too slow for the enzymes isolated with them to have significant action during this isolation. The possible functions of these autolytic activities are discussed.
Genetic Determinants of Circadian Rhythmicity in
Neurospora
Authors: Sargent Malcolm L. , Woodward Dow O.
Published: January 2020

Timex, a strain of
Neurospora crassa
which exhibits a circadian rhythm of conidia formation in growth-tube cultures, has been found to differ from wild-type strains by two genes. One gene,
inv
, is responsible for an invertase deficiency, whereas the second gene,
bd
, is of unknown function. Both genes map independently from other genes known to induce
Neurospora
rhythmicity. The
inv
gene is not essential for the timex phenotype because
bd
strains express that phenotype on certain media. Although
inv
strains do exhibit some rhythmicity of their own, the rhythmicity apparently is not a direct result of the invertase deficiency, since there is no correlation between invertase level and rhymicity in 29 strains tested. Of the 29 strains tested, 20 exhibited some rhythmicity in growth-tube cultures, suggesting that morphological manifestations of rhythmicity in
Neurospora
may result from the function or the loss of function of numerous genes, or both. There was no correlation in these strains between rhythmicity and (i) genetic background; (ii) geographical origin; or (iii) nutritional requirements.
Gene-Enzyme Relationships in
Neurospora
Invertase
Authors: Sargent Malcolm L. , Woodward Dow O.
Published: January 2020

A spontaneous, single-gene mutation responsible for a total lack of invertase activity in
Neurospora crassa
is described. The mutation is believed to lie in the structural gene for invertase, since an immunologically cross-reacting protein is made by the mutant strain. In addition, there was no evidence for a defect in regulation of invertase activity or synthesis by the following criteria. (i) The invertaseless condition was recessive in heterokaryons; (ii) no invertase inhibitor was found in mutant extracts by mixing experiments; and (iii) none of the several sugars able to induce activity in wild-type strains was able to induce activity in the mutant strain. It was also discovered that most of the wild-type enzyme (55 to 75%) cannot be washed free from the rapidly sedimenting cell debris. This finding provided additional support for the hypothesis that
Neurospora
invertase is located within or about the cell wall.
Pathogenicity of the Trudeau Strain of
Mycobacterium
sp. 607 for Mice
Authors: Hedgecock L. W. , Torres A.
Published: January 2020

A study was made of the pathogenic properties of the Trudeau Culture Collection strain (T-67) of
Mycobacterium
sp. 607 for mice. The organism was highly pathogenic for CF1 mice upon intravenous injection. The animals succumbed soon after intravenous injection of a 14 × 10
6
viable cellular units. The T-67 strain proliferated in the kidneys of the animals but was unable to reproduce in the lungs, liver, and spleen. Destruction of the organisms in the latter organs commenced 24 hr after injection. Tissue bacterial counts showed that the mycobacteria were similarly destroyed in the kidneys after an interval of from 7 to 9 days after injection of the organisms. Histopathological examination of the tissues indicated that the lethal effects of the organism were due primarily to kidney damage. The liver, lungs, and spleen were similarly involved but to a lesser degree. The unique characteristics of the T-67 strain of
Mycobacterium
sp. 607 are discussed.
Toxin Production in
Clostridium botulinum
as Demonstrated by Electron Microscopy
Authors: Duda John J. , Slack John M.
Published: January 2020

Spheroplasts of
Clostridium botulinum
62A were prepared with the use of lysozyme. These spheroplasts were then exposed to ferritin-labeled type A antitoxin. Ultrathin sections of these specimens revealed the ferritin-labeled antibody symmetrically arranged around the outer spore coats but not within the spore cortex. The ferritin-labeled antibody was also observed in the bacterial cytoplasm. Here it was arranged in aggregates and strands, although it was not associated with any identifiable cell structure. Controls included sections of
C. botulinum
spheroplasts treated with a 1.5% solution of ferritin as well as spheroplasts of
C. roseum
and
Bacillus subtilis
treated with conjugated type A antitoxin or a 1.5% solution of ferritin. No intracellular or extracellular ferritin was demonstrable in these specimens.
Isolation of Spheroplast Membranes and Stability of Spheroplasts of
Bacillus stearothermophilus
Authors: Bodman Hollis , Welker N. E.
Published: January 2020

Spheroplasts were prepared by lysozyme digestion of the cell wall and ruptured by suspension in 0.15
m
NaCl, followed by centrifugation at 30,900 ×
g
for 35 min, and by a final suspension in 0.05
m
NaCl for 12 to 16 hr at 5 C. The membrane ghosts were washed four times in tris(hydroxylmethyl)aminomethane (Tris) magnesium buffer and once in distilled water. The intact membranes resembled empty sacs with narrow slits in which the cytoplasm was extruded. A 92% recovery of cell membrane was obtained with all membrane preparations. The spheroplasts do not require a stabilizing medium to keep them from rupturing, and they are stable for 2 to 3 hr when exposed to a temperature of 65 C. The membrane content of the cell increases with age of culture (mid-log, 16.5%; late-log, 17.0%; and stationary, 17.6%) and temperature of growth (55 C, 16.5%; and 65 C, 17.8%), and it is unaffected by composition of the growth medium. The ratio of the protein to lipid content of the membrane increases with the complexity of the medium, age of culture (mid-log, 3.65; late-log, 3.91; and stationary, 4.15), and temperature of growth (55 C, 3.65; and 65 C, 5.22). The ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) content of the membranes was 9.0 to 13.7% and 0.3 to 0.8%, respectively. Reducing sugar (determined as glucose) amounts to 0.9 to 1.0% of the membrane weight and did not significantly vary for the different membrane preparations. Medium composition, age of culture, and temperature of growth have no significant effect on the amount of each amino acid in the membrane. Aspartic acid, glutamic acid, alanine, leucine, and lysine are present in the greatest amount and represent 12.9 to 14.1%, 10.4 to 11.3%, 9.6 to 10.3%, 7.7 to 8.8%, and 7.6 to 8.5% of the membrane peptide, respectively. Prior to the rupture of the spheroplasts, 25.0, 15.7, and 50.0% of the protein, RNA, and DNA, respectively, is lost. In potassium phosphate-magnesium buffer without sucrose, 90% of the protein and RNA and 95% of the DNA is lost from the spheroplasts. In the presence of sucrose, the leakage of RNA and DNA is similar to that observed for spheroplasts suspended in Tris magnesium buffer; however, the leakage of protein is 2.4 times greater.
Mutations to Spectinomycin Resistance Which Alleviate the Restriction of an Amber Suppressor by Streptomycin Resistance
Authors: Kuwano Michihiko , Endo Hideya , Ohnishi Yoshinari
Published: January 2020

Unlike mutations to streptomycin resistance, which restrict the function of an SU II amber suppressor, mutations to spectinomycin resistance have no restrictive effect. Furthermore, mutations to spectinomycin resistance counteract the restrictive action of streptomycin-resistant mutations when combined in a single strain. The mutations to drug resistance, singly or in combination, do not themselves lead to any detectable suppressor activity. The effects on SU II are interpreted in terms of interactions between ribosomal elements.
Terminal Electron Transport in
Leptospira
Authors: Baseman J. B. , Cox C. D.
Published: January 2020

The cytochrome content of three leptospiral strains grown in several media was investigated after it was shown that respiratory inhibitors suppressed oxygen consumption of a water isolate, B
16
, and that two pathogenic serotypes,
pomona
and
schueffneri
, were active catalase producers, whereas B
16
lacked catalase activity. Reduced minus oxidized difference spectra disclosed cytochromes of the
a, c
, and
c
1
types in all strains. Although no spectral evidence suggested the existence of cytochrome
b
components, they could have been masked by cytochrome
c
, and their presence cannot be ruled out. Carbon monoxide difference spectra revealed peaks indicative of a cytochrome oxidase of the
o
type in all strains. Carbon monoxide spectra further suggested that a cytochrome
a
oxidase, possibly
a
1
or
a
3
, and a pigment with absorption spectra different from those of previously characterized cytochromes existed in the two pathogens and not in the water isolate. Physiological reduction of the cytochromes by various metabolic substrates implied that the cytochrome system in
Leptospira
was functional. No effect of the various growth media on the cytochrome patterns of the three strains was observed, indicating that all three strains were capable of synthesis of cytochrome components and did not require heme prosthetic groups present in serum.
Cell Walls and Lysis of
Mortierella parvispora
Hyphae
Authors: Pengra R. M. , Cole M. A. , Alexander M.
Published: January 2020

Walls of
Mortierella parvispora, Pullularia pullulans, Absidia repens, Fusarium oxysporum
, and of several
Penicillium
species varied in their susceptibilities to digestion by glucanase and chitinase. Polysaccharides were present in the residues remaining after enzymatic digestion. Acid hydrolysates of the walls contained glucose, glucosamine, and a small amount of galactose. The walls of
M. parvispora
, which also contained fucose, were the least digested by these two enzymes. Much of the
M. parvispora
wall material was resistant to decomposition by a heterogeneous soil community, and viable hyphae were not lysed by a glucanase-chitinase mixture. Walls of this fungus were fractionated, and the chemical composition of the fractions was determined. The chitin which was abundant in one of the fractions was apparently largely shielded from chitinase hydrolysis by a glucan. The ecological significance of these findings is discussed.
Change in the Absorbancy of Bacterial Suspensions Before Initiation of Growth
Authors: Hurst A.
Published: January 2020

The apparent absorbancy of suspensions of stationary-phase cells of
Streptococcus lactis
strain 354/07 decreased immediately after being placed in fresh media. This optical effect also occurred in defined mixtures of buffer glucose and KCl. CaCl
2
caused the absorbancy to increase. CaCl
2
and KCl together had about the same effect as KCl alone. SrCl
2
could replace CaCl
2
, but it was less effective by a factor of 10
2
. MnCl
2
, MgCl
2
, and NaCl were without effect. The absorbancy did not change when cells were first killed by
p
-chloromercuribenzoate or when the reaction was carried out at 0 C. The rate of the reaction was dependent on temperature and concentration of glucose and salts. Gradient centrifugation suggests that this optical effect was caused by change in the refractive index of the test organism rather than by change in volume. Nine other organisms representing four additional genera gave the same optical effect as
S. lactis
354/07. Two other organisms reacted feebly whereas another strain of
S. lactis
reacted in the opposite way, the absorbancy of the suspension increasing instead of decreasing. Spores of
Bacillus cereus
did not respond.
Corepressor System for Catabolite Repression of the
lac
Operon in
Escherichia coli
Authors: Dobrogosz Walter J.
Published: January 2020

Acetylated amino sugars, normally used in the biosynthesis of cell walls and cell membranes, were found to play a role as corepressors for catabolite repression of the
lac
operon in
Escherichia coli
. This conclusion was derived from studies conducted on mutants of
E. coli
that were able to assimilate an exogenous source of
N
-acetylglucosamine (AcGN) but were unable to dissimilate or grow on this compound. At concentrations less than 10
−4
m
, AcGN caused severe catabolite repression of β-galactosidase synthesis in cultures grown under either nonrepressed or partially repressed conditions. This repression occurred in the absence of any effect of AcGN on either the carbon and energy metabolism or the growth of the organism. In addition, this repression by AcGN occurred in a mutant strain that is constitutive for β-galactosidase production, demonstrating that the AcGN effect does not involve the uptake of inducer. This model for the corepressor system of catabolite repression is discussed in relation to the existing theories on repression of the
lac
operon.
Nitrogen Fixation by
Rhodospirillum rubrum
Grown in Nitrogen-limited Continuous Culture
Authors: Munson T. O. , Burris R. H.
Published: January 2020

Cell-free extracts of the photosynthetic bacterium
Rhodospirillum rubrum
were inconsistent in reducing N
2
. An internally illuminated fermentor, designed for the continuous culture of this organism on N
2
under nitrogen-limited conditions, produced cells which yielded cell extracts with consistent activity for cell-free N
2
fixation. A nitrogen-limited continuous culture, supplied ammonia rather than N
2
, gave cell-free extracts with even more active N
2
fixation. Extracts of cells grown in the fermentor with glutamate nitrogen as the limiting nutrient in continuous culture did not reduce N
2
, but whole cells fixed
15
N-enriched N
2
. The discovery that cells from ammonia and glutamate nitrogen-limited continuous cultures are capable of N
2
reduction suggests that
R. rubrum
cells produce the N
2
-reducing enzymes in response to conditions of nitrogen deficiency rather than in response to the presence of N
2
. Examination of the effect of the pN
2
on N
2
reduction by cell-free preparations of
R. rubrum
indicated that the
K
(N
2
) is approximately 0.071 atm. Cell-free extracts from
R. rubrum
were tested for their ability to reduce substrates other than N
2
.
Characterization of Excess Deoxyribonucleic Acid Synthesized by Pneumococci in the Presence of Polyadenylic Acid and Deoxyribonucleic Acid Precursors
Authors: Firshein William , Schwenzfeier C. Willy
Published: January 2020

Excess deoxyribonucleic acid (DNA) synthesized by cell suspensions of encapsulated pneumococci in the presence of polyadenylic acid plus all eight of the naturally occurring deoxyribonucleosides and deoxyribonucleotides has been characterized in several ways. The DNA represents complete molecules, is synthesized by a relatively large population at a steady rate, and is replicated in a semiconservative manner.
Some Properties of Excision-defective Recombination-deficient Mutants of
Escherichia coli
K-12
Authors: Howard-Flanders Paul , Theriot Lee , Stedeford J. Brian
Published: January 2020

Strains of
Escherichia coli
that carry the mutation
uvrA6
show no measurable excision of pyrimidine dimers and are easily killed by ultraviolet (UV) light, whereas strains that carry
recA13
are defective in genetic recombination and are also UV-sensitive. An Hfr strain carrying
uvrA6
was crossed with an F
−
strain carrying
recA13
. Among the recombinants identified, one carrying
uvrA recA
proved to be of exceptional sensitivity to UV light. It is estimated from the UV dose (0.2 erg/mm
2
at 253.7 nm) required to reduce the number of colony-forming cells by one natural logarithm that about 1.3 pyrimidine dimers were formed in a genome of 5 × 10
6
base pairs for each lethal event. This double mutant is 40 times more UV-sensitive than the excision-defective strain carrying
uvrA6
. The replication of one pyrimidine dimer is generally a lethal event in strains carrying
recA13
. Spontaneous breakdown and UV-induced breakdown of the deoxyribonucleic acid (DNA) of cells of the various genotypes were estimated by growing the cells in medium containing
3
H-thymidine and measuring both acid-precipitable and acid-soluble radioactivity. The UV-induced degradation in strains with
recA13
did not require the
uvr
+
genes and hence appears to depend upon a mechanism other than dimer excision. The greater level of survival after irradiation in Rec
+
as compared to Rec
−
bacteria may be due to a recovery mechanism involving the reconstruction of the bacterial chromosome through genetic exchanges which occur between the newly replicated sister duplexes and which effectively circumvent the damaged bases remaining in the DNA.
Separation of Folic Acid Reductase from
Streptococcus faecium
(ATCC 8043)
Authors: Speck Eugene L. , Affronti Lewis F.
Published: January 2020

A strain of
Streptococcus faecium
(ATCC 8043) which is highly resistant to the antifolic acid compound, amethopterin, was gently ruptured by exposing protoplasts of the organism to a hypotonic solution. The crude lysate resulting there-from was treated by various chemical and physical techniques designed to separate folic acid reductase from dihydrofolic acid reductase. In the process, the enzyme was purified approximately 160-fold; however, throughout the process, the enzyme preparation maintained the ability to reduce folic acid to tetrahydrofolic acid. Attempts to isolate mutants showing a deficiency in either folic acid reductase or dihydrofolic acid reductase were unsuccessful. Based on these results, it is concluded that folic acid is reduced to tetrahydrofolic acid by one enzyme in
S. faecium
(ATCC 8043). The crude lysate was also subjected to ultracentrifugation. An analysis of the supernatant fluid and the sediment indicated that the reductive activity is located in the soluble fraction of the cell.
Replication of the Bacterial Chromosome: Location of New Initiation Sites After Irradiation
Authors: Billen Daniel
Published: January 2020

New loci of replication along the bacterial chromosome are observed after irradiation of
Escherichia coli
. It was conjectured that, after X-irradiation, the new initiation site was random with respect to the fixed-origin, whereas, after ultraviolet light exposure, it was selective and appeared to be from the fixed-origin. Evidence presented here shows that, after X-irradiation of
E. coli
, the new initiation site(s) for the onset of deoxyribonucleic acid replication is induced at chromosomal regions not restricted to the fixed-origin. After ultraviolet light exposure, the new initiation site is preferentially from the fixed-origin. In these studies amino acid starvation was used to synchronize chromosome replication and to allow for differential radioisotopic labeling of the chromosomal origin and terminus. To facilitate interpretation, growing cells actively replicating their chromosome were compared with cells lacking growth points at the time of irradiation. The role of these new replication sites in the observed kinetics of deoxyribonucleic acid replication following X-ray or ultraviolet light exposure is discussed.
Assimilation and Metabolism of Exogenous Organic Compounds by the Strict Autotrophs
Thiobacillus thioparus
and
Thiobacillus neapolitanus
Authors: Johnson Emmett J. , Abraham S.
Published: January 2020

The assimilation and utilization of the individual carbon atoms of pyruvate and acetate by cells of
Thiobacillus thioparus
and
T. neapolitanus
, in the presence and absence of an energy source, were studied by use of radioactive substrates. Both organisms produced
14
CO
2
from
14
C-labeled pyruvate, but more came from carbon 1 than from carbons 2 or 3. The conversion of the carbons of acetate to CO
2
by both organisms was much less than that from any of the pyruvate carbons. When labeled pyruvate and acetate were incubated with these organisms, small amounts of radioactivity were found in the tricholoacetic acid-soluble material, nucleic acids, and lipids, and larger amounts were found in the protein fraction. The composition of the incubation medium affected the amount of utilization and incorporation of labeled substrates by both organisms. The presence of an exogenous energy source (Na
2
S
2
O
3
) suppressed incorporation of the labeled substrates into various cellular components by
T. thioparus
, but enhanced incorporation by
T. neapolitanus
. When
14
C-pyruvate was used as a substrate, as many as 12 radioactive compounds were found in the water-soluble fraction in the experiments with
T. neapolitanus
, whereas no more than three radioactive compounds were detected in this fraction in the experiments with
T. thioparus
. Of the total
14
C activity found in the water-soluble fractions, malic acid contained the highest percentage. These findings are discussed in light of the overall metabolism of these two sulfur-oxidizing obligate chemoautotrophs, as well as in relation to the biochemical basis of chemoautotrophy.
Two Forms of
d
-Glycerate Kinase in
Escherichia coli
Authors: Ornston M. K. , Ornston L. N.
Published: January 2020

Escherichia coli
K-12 synthesizes two chromatographically distinct forms of glycerate kinase which differ both in their thermolability and in the dependence of their activity upon
pH
. One enzymatic form, GK I, is found in cells grown with glycerate, glucarate, or glycolate. Of these compounds, glycolate is the only carbon source that elicits the synthesis of the second enzymatic form, GK II.
Stimulation of Fermentation and Yeast-like Morphogenesis in
Mucor rouxii
by Phenethyl Alcohol
Authors: Terenzi H. F. , Storck R.
Published: January 2020

The germination of fungal spores into hyphae was inhibited by concentrations of phenethyl alcohol (PEA) from 0.05 to 0.3%. Spores of
Mucor
formed budding spherical cells instead of filaments. These cells were abundant in cultures of
Mucor rouxii
at 0.22% PEA, provided that the carbon source was a hexose at 2 to 5%. Morphology was filamentous with xylose, maltose, sucrose, or a mixture of amino acids. Removal of PEA resulted in the conversion of yeast-like cells into hyphae. PEA did not inhibit biosynthesis of cytochromes or oxygen uptake, but it stimulated CO
2
and ethyl alcohol production. PEA had no effect on the rate of oxygen uptake, but it inhibited the oxidative-phosphorylation activity of mitochondria. These results suggested that growth inhibition by PEA could result from uncoupling of oxidative phosphorylation and that, in
Mucor
, yeast-like morphology and fermentation were linked.
Regulation of Branched-Chain Amino Acid Biosynthesis in
Salmonella typhimurium
: Isolation of Regulatory Mutants
Authors: Calvo J. M. , Freundlich M. , Umbarger H. E.
Published: January 2020

5′,5′,5′-Trifluoro-
dl
-leucine inhibited the activity of α-isopropylmalate synthetase (the initial enzyme unique to leucine biosynthesis) as well as the growth of
Salmonella typhimurium
. Mutants of
S. typhimurium
resistant to the analogue were isolated and characterized. In most cases, they overproduced and excreted leucine or leucine, valine, and isoleucine as a result of an alteration in the regulation of branched-chain amino acid biosynthesis. Biochemical and genetic tests allowed the mutants to be grouped into three classes: I, a moderately large group (13%) which had high, constitutive leucine biosynthetic enzyme levels and mutant sites linked to the leucine operon (operator constitutive); II, a single mutant in which the mutant site was linked to the leucine operon and in which α-isopropylmalate synthetase was not inhibited by leucine (feedback negative); III, a majority type which had constitutive levels of leucine, valine, and isoleucine biosynthetic enzymes and mutant sites unlinked to the leucine operon. Mutants of class I provide important evidence for the concept of an operon organization of genes involved in leucine biosynthesis. The properties of class III mutants indicate that there is some element involved in regulation which is common to the three pathways.
Cold-sensitive Mutations in
Salmonella typhimurium
Which Affect Ribosome Synthesis
Authors: Tai Phang-Cheng , Kessler Donald P. , Ingraham John
Published: January 2020

A number of mutations (45) expressed as cold-sensitive conditional lethal pheno-types were screened by transduction for their linkage to the streptomycin-resistance locus; 7 showed such linkage. Of these, two were studied in greater detail. The sedimentation profiles of ribosomes from cultures grown at low temperature differed from wild type and from one another. Both mutants lost ribonucleic acid control at low temperature. It is suggested that a high proportion of mutants expressing a cold-sensitive phenotype harbor mutations in genes affecting ribosome synthesis or regulation.
d
-Mannitol Metabolism by
Aspergillus candidus
Authors: Strandberg Gerald W.
Published: January 2020

Pathways of mannitol biosynthesis and utilization in
Aspergillus candidus
NRRL 305 were studied in cell-free extracts of washed mycelia prepared by sonic and French pressure cell treatments. A nicotinamide adenine dinucleotide-linked mannitol-1-phosphate (M1P) dehydrogenase was found in French pressure cell extracts of
d
-glucose-grown cells, whereas a specific mannitol-1-phosphatase was present in extracts prepared by both methods. The existence of these two enzymes indicated that mannitol may be synthesized in this organism by the reduction of fructose-6-phosphate. A specific nicotinamide adenine dinucleotide phosphate-linked mannitol dehydrogenase was also identified in both extracts. This enzyme may have been involved in mannitol utilization. However, the level of the mannitol dehydrogenase appeared to be substantially reduced in extracts from mannitol-grown cells, whereas the level of M1P dehydrogenase was increased. A hexokinase has been identified in this organism. Fructose-6-phosphatase, glucose isomerase, and mannitol kinase could not be demonstrated.
Phosphatidic Acid Synthesis in
Escherichia coli
Authors: Kito Makoto , Pizer Lewis I.
Published: January 2020

The kinetic properties of acyl-coenzyme A (CoA):
l
-α-glycerol-phosphate trans-acylase (EC 2.3.1.15) from
Escherichia coli
were studied. At 10 C, a temperature at which the reaction was proportional to time and enzyme concentration, the enzyme had an apparent
K
m
of 60 μ
m
for
l
-α-glycerol-phosphate. The curve describing the velocity of the reaction as a function of palmitoyl-CoA concentration was sigmoid but the plot of v
−1
versus [S]
−3
gave a straight line. A
K
m
of about 11 μ
m
was calculated for palmitoyl-CoA. Adenosine triphosphate specifically inhibited the reaction, being a noncompetitive inhibitor in respect to
l
-α-glycerol phosphate. Inhibition only occurred with high concentrations of palmitoyl-CoA, and maximal inhibition was 60%.
Salmonella abony-Salmonella typhimurium
Recombinant Nonvirulent for the Mouse
Authors: Krishnapillai V. , Karthigasu K.
Published: January 2020

A previous genetic investigation involving a mouse-nonvirulent
Salmonella abony
donor (high frequency of recombination) and a virulent
S. typhimurium
recipient indicated that two unlinked “low-virulence” loci determined nonvirulence. A nonvirulent recombinant was analyzed to determine the basis for its nonvirulence. The recombinant was smooth (like the parental strains) and prototrophic. The doubling time in mouse serum of the recombinant and the
S. abony
parent (both streptomycin-resistant) was longer than that of the wild-type streptomycin-sensitive ancestor of the
S. typhimurium
recipient. The virulent recipient also grew poorly in serum. However, the nonvirulence of the recombinant was probably not due to its inheritance of the streptomycin-resistance allele from the donor, because other recombinants were streptomycin-resistant but still virulent. Unlike the nonvirulent
S. abony
(but like the
S. typhimurium
), the recombinant was insusceptible to rapid intravenous clearance in normal mice. It therefore appears that neither of the “low-virulence” loci determine diminished virulence by enhancing phagocytosis. Clearance of the recombinant was enhanced by opsonization with immune serum. Counts of viable bacteria in the blood, liver, and spleen of normal mice after intravenous challenge showed that the recombinant, like the
S. abony
donor, failed to proliferate in the tissues, whereas the virulent
S. typhimurium
did so markedly. It is concluded that the nonproliferation of the recombinant was determined by one or both of the “low-virulence” loci from the nonvirulent
S. abony
donor.
Suppressor System in
Bacillus subtilis
168
Authors: Georgopoulos C. P.
Published: January 2020

Multiple auxotrophic strains of
Bacillus subtilis
168 were tested for joint one-step reversion of two or more auxotrophic markers to the wild-type phenotype. Mu8u5u5, a strain requiring leucine, methionine, and threonine, yielded revertants that grew without added methionine or threonine and proved to have a suppressor gene. When transferred by transformation with deoxyribonucleic acid, this suppressor gene also suppressed the adenine mutation in another strain, Mu8u5u6. The one-step double revertants fell into two distinct classes: strains of class
su
+
I
grow well in broth; strains of class
su
+
II
grow poorly. Strains
su
+
II
tend to revert frequently to the
su
+
I
or
su
−
state. Conditional lethal mutants of phage φe were isolated which can grow on the
su
+
and not on the
su
−
strains.
Characterization of a β-Galactosidase Formed Between a Complementary Protein and a Peptide Synthesized De Novo
Authors: DeVries Joanne K. , Zubay Geoffrey
Published: January 2020

In a cell-free system, φ80d
lac
can be transcribed, and the resulting ribonucleic acid can be translated to yield a product which interacts with an enzymatically inactive
z
protein to produce active enzyme. The inactive
z
protein is produced by
Escherichia coli
strain 21, which contains a deletion in the first part of the gene for β-galactosidase and appears to exist as a dimer. The enzyme formed in the cell-free system appears to be composed of one strain 21
z
protein dimer and one newly synthesized polypeptide chain with a molecular weight of about 3 × 10
4
. The estimated size of this complementing segment is in good agreement with Ullmann, Jacob, and Monod's estimate of the size of the α region of β-galactosidase. Using α fragments produced by autoclaving or guanidine treatments, we found that the active portion of α seems to be smaller than the full α region. We also found, using α produced by the autoclaving technique, that active dimer undergoes conversion to tetramer as the amount of α is increased. Evidently, the binding of α favors this conversion, but it is unlikely that the conversion of dimer to tetramer per se results in increased enzyme activity.