bluuebunny/crossref_metadata_2025 huggingface dataset:
Nucleotide Composition of Deoxyribonucleic Acid of Some Species ofCryptococcus, Rhodotorula, andSporobolomyces
Authors: Storck R. , Alexopoulos C. J. , Phaff H. J.
Published: January 2020

The buoyant density of deoxyribonucleic acid (DNA) from nine species and two varieties ofCryptococcus, three species and two varieties ofRhodotorula, and six species ofSporobolomyceswas determined by CsCl density gradient equilibrium centrifugation. Several species were represented by two to four different strains. Expressed in moles per cent of guanine plus cytosine (GC content) the ranges were 49 to 65%, 52 to 70%, and 51 to 65% forCryptococcus, Rhodotorula, andSporobolomyces, respectively. For each genus, the GC content was distributed into two discrete groups with averages ranging from 52 to 54 and 60 to 66, respectively. An analysis of these results suggested that the determination of GC content of DNA had a taxonomic value for these yeast genera.
Chromosomal Location of Genes Regulating Resistance to Bacteriophage in
Bacillus subtilis
Authors: Young F. E. , Smith C. , Reilly B. E.
Published: January 2020

Many of the viruses which infect
Bacillus subtilis
require glucosylated polyglycerol teichoic acid for adsorption. These mutants can be divided into three classes on the basis of enzymatic defects and growth on galactose-minimal medium. Transduction with phage PBS1 reveals that two of these,
gtaA
and
gtaB
, are linked to
hisA1
, whereas the
gtaC
locus is linked to
argC
. Analysis by deoxyribonucleic acid-mediated transformation indicates that these loci exist in a cluster between the
hisA1
and
argC4
loci. Anomalies in mapping in the group II region of the chromosome exist. The basis of these anomalies is discussed.
Selective Inhibition of Bacterial Enzymes by Free Fatty Acids
Authors: Ferdinandus John , Clark J. B.
Published: January 2020

Octanoic acid inhibits, in vitro, the bacterial enzymes glucose-6-phosphate dehydrogenase, phosphofructokinase, pyruvate kinase, fumarase, lactate dehydrogenase, and the malic enzyme of
Arthrobacter crystallopoietes
. The free fatty acid appears to act as an inhibitor of lipogenesis, although it does not affect the rate of gluconeogenesis. To demonstrate that this inhibition may be of physiological significance in vivo, those enzymes not involved in lipogenesis, such as fructose-1, 6-diphosphatase, phosphoglucomutase, phosphohexoisomerase, aconitase, nicotinamide adenine dinucleotide phosphate (NADP) isocitrate dehydrogenase, NADP glutamate dehydrogenase, malate dehydrogenase, and isocitrate lyase, were assayed and found not to be inhibited by the free fatty acid.
Kinetics of Induction of the Lactose Operon on an Episome inSalmonella typhimurium
Authors: Ballesteros-Olmo A. , Kovach John S. , Van Knippenberg Peter , Goldberger Robert F.
Published: January 2020

A kinetic study of induction of the enzymes of the lactose operon was carried out under conditions known to affect the kinetics of derepression of the enzymes of the histidine operon. The results show that the lactose system is similar to the histidine system in its responsiveness to conditions thought to affect the formylating capacity of the cell. This was demonstrated in the following ways: (i) trimethoprim, which is known to reduce the formylating capacity of the cell, gives rise to a relatively long interval between the times of induction of β-galactosidase and transacetylase; (ii) under conditions in which the histidine operon is derepressed, chloramphenicol causes a prolongation of the interval between the times of induction of the two enzymes, and this prolongation is reversed by adenine, methionine, and serine, compounds known to enrich the one-carbon pool of the cell; and (iii) 4-amino-5-imidazolcarboxamide ribonucleoside, a compound which may act as a drain for formyl groups, reverses the effect of the latter compounds. The finding that the interval between the times of induction of the two enzymes is shortened under conditions expected to maintain a relatively high intracellular fo rmylating capacity suggests that under certain conditions translation of the polycistronic messenger ribonucleic acid of the lactose operon may be initiated at more than one site or may proceed more rapidly from the operator end.
Changes in the Plasma Membrane of
Escherichia coli
During Magnesium Starvation
Authors: Fiil Annelise , Branton Daniel
Published: January 2020

The effect of Mg
++
starvation on the structure of the
Escherichia coli
cell membrane was studied with the freeze-etch technique. Special attention was paid to changes within the plane of the membrane, which in normal exponentially growing cells has a netlike arrangement of particles 2 to 6 nm in diameter. During Mg
++
starvation, a paracrystalline particle pattern appeared on the plasma membrane, and large areas devoid of particles were seen. Although these changes are reproducibly associated with Mg
++
starvation of the bacteria, no decrease in the Mg
++
content of the cell envelope per se was detected, even after 24 hr of Mg
++
deprivation. The structural changes caused by Mg
++
deprivation appeared to involve specific and permanent alterations in membrane development. The absence of other nutrients or divalent cations did not induce similar alterations.
Structure of Exocellular Polymers and Their Relationship to Bacterial Flocculation
Authors: Friedman Barry A. , Dugan Patrick R. , Pfister Robert M. , Remsen Charles C.
Published: January 2020

Several gram-negative, polarly flagellated rods were isolated on the basis of their flocculent growth habit. Some of the isolates possessed a capsular matrix which is composed of exocellular fibrils. Other isolates did not appear to have a capsular matrix when examined with a bright-field microscope with or without the aid of stains. However, these latter type isolates did possess exocellular material which can be demonstrated by adsorption of a fluorescent dye under an ultraviolet microscope. Electron microscopic examination demonstrated that the exocellular material around all isolates examined is fibrillar. The fibrils were susceptible to cellulase although all fibrils did not appear to be identical. It is postulated that the exocellular polymers were responsible for the flocculent growth habit of the bacteria, and that the process of bacterial flocculation produced by synthetic polyelectrolytes was essentially the same as that caused by naturally produced exopolymers.
Crystalline Inclusions of Bacterium 22M
Authors: Kim Kwang S. , Barksdale Lane
Published: January 2020

Crystalline inclusions occur in bacterium 22M. Arrays consist of parallel rows of polyhedral subunits (7.5 nm in diameter), 2.0 nm apart, with a distance of 3.0 nm between rows.
Resistance of Vegetative Cells and Microcysts of
Myxococcus xanthus
Authors: Sudo Sara Z. , Dworkin Martin
Published: January 2020

The resistance of vegetative cells and of microcysts of
Myxococcus xanthus
to several destructive agents was compared. Fruiting-body microcysts were 300 times more resistant to 60 C, 5.4 times more resistant to ultraviolet light, and 19.3 times more resistant to sonic vibration than were vegetative cells. Whereas resistance to sonic vibration developed during the conversion of rods to refractile spheres, resistance to heat did not appear until after the conversion was complete. Both vegetative cells and microcysts of the yellow variant of this strain were more resistant to ultraviolet irradiation than was the tan variant.
Induction by Mercuric Ion of Extensive Degradation of Cellular Ribonucleic Acid in
Escherichia coli
Authors: Beppu Teruhiko , Arima Kei
Published: January 2020

Low concentrations of HgCl
2
were found to induce extensive degradation of ribonucleic acid (RNA) in exponentially growing
Escherichia coli
cells but not in stationary-phase cells. Whereas 80% of cellular RNA was degraded during 90 min of incubation with 10
−5
m
HgCl
2
at 37 C, HgCl
2
caused only slight degradation in stationary cells, even when present at concentrations higher than 5 × 10
−5
m
. Inhibition of RNA synthesis occurred at almost the same concentration of HgCl
2
as degradation, and the ability of stationary-phase cells to synthesize RNA was also resistant to HgCl
2
. The transition of cells from complete sensitivity to HgCl
2
to a fully insensitive state took place simultaneously with the cessation of growth.
p
-Chloromercuribenzoate was also found to induce remarkable degradation of RNA. In
E. coli
Q13, a mutant deficient for ribonuclease I, no degradation of RNA was evident, even in the exponential growth phase. 3′-Mononucleotides but not 5′-mononucleotides were found among the degradation products of cellular RNA. 2′,3′-Cyclic mononucleotides were produced when RNA was degraded by the cell-free extracts of the Hg treated cells. Almost complete unmasking of the latent ribonuclease occurred in the particle fraction containing subribosomal particles of the Hg-treated cells. These data suggest that the incubation of exponentially growing
E. coli
cells with HgCl
2
led to the unmasking of ribonuclease I, which resulted in the extensive degradation of cellular RNA. The activation of ribonuclease by HgCl
2
in the isolated particulate fraction of
E. coli
K-12 which occurred in vitro suggested the presence of an Hg-sensitive inhibitor for ribonuclease I.
Relative Rates of Lysis of Staphylococcal Cell Walls by Lytic Enzymes from Various Bacteriophage Types
Authors: Schuytema Eunice C. , Glenn H. L. , Doughty C. C.
Published: January 2020

Lytic enzymes were isolated from 14 strains of phage-infected
Staphylococcus aureus
. Cell walls were prepared from the same uninfected strains of bacteria. Comparison of the lytic rates was made for each enzyme, with each of the cell walls as substrate. Differences in the rate of substrate utilization of the various cell wall types exceeded 10-fold. Cell walls from strains 42E, 29, and 77 were the best substrates, whereas cell walls from strains 3C, 80, and 187 were the poorest substrates. The cell wall amino acid composition is discussed as related to lytic enzyme specificity. A possible explanation of phage typing of staphylococcal cells, based on enzyme activity and cell wall composition, is presented.
Pediococci Residing on Plants
Authors: Mundt J. Orvin , Beattie Wanda Graham , Wieland Frederick R.
Published: January 2020

The pediococci residing on plants resemble the lactobacilli, but they differ from the streptococci in their limited distribution and low population level on plants. They are a subgroup within the genus
Pediococcus
which grow freely in neutral media and require neither NaCl nor CO
2
. They are most readily recognized by the ability to initiate growth in liquid media, acidified to
p
H 5.0, which contain 1.5% sodium acetate. In stained preparations the cells occur singly and in pairs, short chains, and clusters. The occurrence of two-dimensional tetrads may be rare; this varies with the individual culture and with the culture medium. The terminal
p
H in 2% glucose broth varies from 3.6 to 4.3. Ability to initiate growth at 45 C, production of ammonia from arginine, dissimilation of malate, and fermentation of arabinose are confirmatory characteristics. The subgroup contains only two quite similar, but differentiable, species.
P. acidilactici
initiates growth at 50 C and produces catalase on heated blood medium but does not produce acid-sensitive catalase; a majority of the strains fail to initiate growth at 10 C and many fail to ferment maltose and lactose.
P. pentosaceus
initiates growth at 10 C but not at 50 C and produces acid-sensitive catalase; catalase production on heated blood medium is transient; a majority of the cultures ferment maltose, salicin, and trehalose. No carbohydrate serves reliably to differentiate between the species. The guanine plus cytosine ratio of
P. pentosaceus
deoxyribonucleic acid (DNA) was determined to be 35.1 ± 1.2 and that of
P. acidilactici
DNA is 38.5 ± 0.8.
Specificity of the Induced Bactericidin of the West Indian Spiny Lobster,Panulirus argus
Authors: Weinheimer Peter F. , Acton Ronald T. , Sawyer Susan , Evans E. Edward
Published: January 2020

To investigate the specificity of an inducible hemolymph bactericidin, West Indian spiny lobsters were immunized with a variety of antigens. Bactericidal assays were conducted with strain EMB-1, a gram-negative bacillus isolated from normal lobster intestine. Animals given saline solution with or without 0.3% Formalin exhibited only a slight response similar to sham controls. Injections of type 2 pneumococci or bovine albumin produced slightly higher responses. These were much less pronounced than the homologous response to EMB-1. Formalin exhibited an adjuvant-like effect with EMB-1.
Activity of Diphtheria Toxin II. Early Events in the Intoxication of HeLa Cells
Authors: Duncan James L. , Groman Neal B.
Published: January 2020

The initial steps in the interaction of diphtheria toxin with HeLa cells were studied. It was demonstrated that lethal doses of toxin are rapidly adsorbed to the cell. The kinetics of uptake, as measured by lethality, indicated that a single toxin molecule is able to cause cell death. Studies on the effect of
p
H on intoxication showed that adsorption of toxin occurred over a wide
p
H range but was partially inhibited at high
p
H values. Experiments to determine the influence of the ionic environment on intoxication indicated that adsorption of toxin did not take place in the absence of salts and was partially inhibited in the presence of a polyanion. The evidence indicates that the initial binding of toxin to the cell is electrostatic in nature, involving positively charged surface groups. Attempts to demonstrate specific receptors for the attachment of toxin to cells were unsuccessful, suggesting that toxin adsorption may be a nonspecific process. The effect of energy inhibitors on intoxication was examined. Sodium fluoride, an inhibitor of glycolysis, almost completely prevented intoxication in HeLa cells, whereas inhibitors of respiration and oxidative phosphorylation had no effect. Sodium fluoride did not prevent adsorption of toxin but appeared to inhibit a later step in the intoxication process, perhaps the transport of toxin to subsurface or intracellular levels.
Characteristics of a New Sterol-nonrequiringMycoplasma
Authors: Tully Joseph G. , Razin Shmuel
Published: January 2020

TwoMycoplasmastrains recovered from tissue culture environments were found to grow in complex media devoid of serum or serum fractions containing cholesterol and in a cholesterol-free synthetic medium. Neither strain was capable of synthesizing pigmented carotenoids, although these compounds are present in, and characteristic of, other sterol-nonrequiring mycoplasmas. Serological tests and an analysis of their cell protein patterns obtained by gel electrophoresis indicated that the isolates were similar to each other but distinct from other sterol-nonrequiring serotypes,Mycoplasma laidlawiiandM. granularum, as well as from sterol-requiring species. The existence ofMycoplasmaother thanM. laidlawiiandM. granularumwithout sterol requirements suggested the need for some taxonomic changes in this group of organisms.
Experimental Production of LethalEscherichia coliBacteremia of Pelvic Origin
Authors: Braude A. I. , Douglas H. , Jones Janet
Published: January 2020

To reproduce the syndrome of overwhelmingEscherichia colibacteremia and shock after pelvic instrumentation, a model was developed by feedingE. colivia drinking water to coliform-free rabbits, injecting nitrogen mustard intravenously, and inserting a temperature probe into the rectum. The temperature probe was inserted to mimic pelvic instrumentation of patients and to detect fever. Rabbits fed invasive serotypes ofE. coliall suffered overwhelming bacteremia with high fever and fatal vascular collapse secondary to invasion of pelvic veins as the granulocyte count approached zero. In the absence of granulocytopenia, the rectal temperature probe produced an intensive inflammation with numerous polymorphonuclears and bacteremia did not develop. In the absence of rectal probing, granulocytopenic rabbits developed high fever without bacteremia. This model resembles human bacteremic shock with respect to the endogenous source of the bacteria, the high frequency of bacteremia due toE. coliand other enteric bacilli, the importance of pelvic instrumentation, and the associated immune disturbances such as granulocytopenia.
Control of Isoleucine, Valine, and Leucine Biosynthesis VI. Effect of 5′,5′,5′-Trifluoroleucine on Repression in
Salmonella typhimurium
Authors: Freundlich Martin , Trela John M.
Published: January 2020

The leucine analogue 5′,5′,5′,-trifluoroleucine (fluoroleucine) replaced leucine for repression of the isoleucine-valine biosynthetic enzymes in
Salmonella typhimurium
. In contrast, the analogue had no effect on derepression of the leucine biosynthetic enzymes in leucine auxotrophs grown on limiting amounts of leucine. The effect of fluoroleucine on repression appeared to be specific for leucine since derepression of the isoleucine-valine enzymes due to an isoleucine or valine limitation was not affected by the analogue. The prevention of derepression by fluoroleucine was probably due to repression and not to the formation of false proteins, since the analogue had no effect on the derepression of a number of enzymes unrelated to the isoleucine-valine pathway. Fluoroleucine was able to attach to leucine transfer ribonucleic acid (tRNA) as evidenced by the ability of the analogue to protect about 70% of leucine tRNA from oxidation by periodate. We propose that the differential effects of fluoroleucine on repression are due to differences in the ability of the analogue to bind to the various species of leucine tRNA.
Estimations of Bacterial Growth Rates in Natural Waters
Authors: Jannasch Holger W.
Published: January 2020

Specific growth rates as low as 0.005 hr
−1
(generation times of 20 to 200 hr) of aquatic bacteria in natural waters have been calculated from significant differences between dilution rates and washout rates in a chemostat. The measured growth rates were affected by the treatment of the water samples (type of sterilization) and by competition with the natural microflora for the unknown growth-limiting substrate.
Biochemical Characterization of Lysine Auxotrophs of
Staphylococcus aureus
Authors: Barnes Isabel J. , Bondi Amedeo , Moat Albert G.
Published: January 2020

Lysine biosynthesis in
Staphylococcus aureus
has been studied by use of a series of lysine auxotrophs. The strains were isolated after chemical mutagenesis. The majority of these mutant strains were classified according to the enzymatic step found to be deficient. Specific enzyme assays as well as nutritional tests were used to group the organisms. The enzymes included were dihydrodipicolinate synthetase, dihydrodipicolinate reductase, diaminopimelate epimerase, and diaminopimelate decarboxylase. The accumulation of diaminopimelate in certain mutants and the demonstration of dihydrodipicolinate synthetase and reductase provide the first detailed evidence that
S. aureus
utilizes the diaminopimelate pathway for lysine biosynthesis. A cell-free system was used to study the regulation of these enzymes with the exception of diaminopimelate epimerase. Lysine repressed all of the enzymes tested. The repression appeared to be coordinate in nature. The data presented provide suggestive evidence that the lysine biosynthetic region in
S. aureus
constitutes an operon.
Tricarboxylic Acid Cycle Enzymes and Morphogenesis in
Blastocladiella emersonii
Authors: Khouw Boen Tie , McCurdy Howard D.
Published: January 2020

During exponential growth, ordinary colorless (OC) plants of
Blastocladiella emersonii
consumed little glucose and produced no lactic acid. Similarly, resistant sporangial (RS) plants did not utilize glucose or produce lactic acid during the first 24 hr of exponential growth. During the next 24 hr of RS development, glucose was consumed with the concomitant production of lactic acid which was then reutilized. Lactic acid gradually accumulated again at maturity. Enzyme studies on cell-free extracts indicated the presence of all tricarboxylic cycle enzymes except α-ketoglutarate dehydrogenase at all stages of development of both RS and OC plants. Included among the enzymes detected were an adenosine monophosphate-stimulated, nicotinamide adenine dinucleotide-isocitric dehydrogenase, and citrate-condensing enzyme. When measured on a per plant basis, tricarboxylic cycle enzyme levels increased during the exponential growth of both kinds of plants. Only after the bicarbonate ceased to have effect on RS plant morphogenesis was there a decrease in the levels of the tricarboxylic cycle enzymes when measured on a per plant basis. Specific activity measurements indicated some differences in the differential rates of synthesis among the enzymes studied previous to 36 hr. Preliminary studies utilizing short periods of
14
C-bicarbonate fixation in young RS plants indicated that during the first 4 min most of the label was located in aspartic acid. These results are discussed in terms of previous results and particularly Cantino's hypothesis concerning the relationship between bicarbonate induction and tricarboxylic-cycle enzymes in the morphogenesis of
B. emersonii
.
Chromosomal Location of Ribosomal Protein Cistrons Determined by Intergeneric Bacterial Mating
Authors: O'Neil Dennis M. , Baron L. S. , Sypherd Paul S.
Published: January 2020

Intergeneric mating between
Escherichia coli
and
Salmonella typhosa
was used to locate at least three 30
S
ribosomal proteins near the streptomycin locus in the region of 54 to 66 min of the
E. coli
map. This procedure utilizes differences in the electrophoretic patterns of 30
S
ribosomal protein of the parents. The results show that cistrons for 30
S
proteins of
E. coli
can replace those of
S. typhosa
in the
Salmonella
genome. Moreover, in a diploid hybrid with a
Salmonella
endogenote and an
E. coli
exogenote, both sets of cistrons are expressed.
Bacteria-shaped Gymnoplasts (Protoplasts) of
Bacillus subtilis
Authors: van Iterson W. , den Kamp J. A. F. Op
Published: January 2020

Addition of glucose to the medium in which
Bacillus subtilis
was grown lowered the
p
H and increased the amount of lysylphosphatidylglycerol relative to the phosphatidylglycerol content of the membrane fraction. This change in phospholipid composition was accompanied by changes in the shape and behavior of the gymnoplasts obtained by cell wall removal with lysozyme. These gymnoplasts appeared to retain most of their original cell shape and internal organization, often with preservation of the mesosomes. Cells harvested from neutral growth medium gave the usual spherical gymnoplasts. In a hypotonic medium, the spherical gymnoplasts lysed rapidly, whereas the rod-like gymnoplasts lost only part of their cell content while showing a tendency to preserve the original shape. This type of gymnoplast could not be produced from cells grown in neutral medium by simply raising the magnesium concentration. When this was done the gymnoplasts assumed bizarre shapes; they became compact and susceptible to the tonicity of the medium. Gymnoplasts or protoplasts, produced from bacilli exposed to low
p
H values, were found not to conform to the formulations on “protoplasts” given in 1958 by 13 authors. Cells exposed to a low environmental
p
H during growth seemed to possess a more rigid membrane structure than cells grown at neutral
p
H.
Deoxyribonucleic Acid Base Compositions of Selected Mycoplasmas and L-Phase Variants
Authors: Williams Carol O. , Wittler Ruth G. , Burris Carroll
Published: January 2020

Deoxyribonucleic acid base compositions were determined for 25
Mycoplasma
strains and 6 L-phase variant strains. Values obtained correlated well with the results of other investigators.
Temperature-sensitive Mutants of
Dictyostelium discoideum
Authors: Loomis William F.
Published: January 2020

Three classes of temperature-sensitive mutants of the cellular slime mold
Dictyostelium discoideum
have been isolated. One class contains strains able to grow at 22 C but not at 27 C. Cells of these strains can develop into sorocarps at both temperatures. Another class contains strains which can grow at both temperatures but can only develop at the lower temperature. The third class contains strains unable to grow or develop at 27 C. Those strains whose development is temperature-sensitive appear to carry mutations which affect the cells only during the period of aggregation before the construction of a multicellular sorocarp. When pairs of growth-temperature-sensitive (GTS) strains develop in mixed aggregates, temperature-resistant (TR) cells are formed at a frequency of about 10
−4
. These TR cells transmit the phenotype in a relatively stable hereditary fashion. However, temperature-sensitive segregants can be isolated from TR strains even after six clonal passages. Mixed incubation of pairs of morphologically aberrant GTS strains was found to give rise to TR progeny which develop normally. These progeny clones independently segregate morphologically aberrant strains and temperature-sensitive strains. The results indicate that several temperature-sensitive and morphological mutations are recessive and nonidentical.
New Class of Conditional Colicin-tolerant Mutants
Authors: de Zwaig Rosa Nagel , Luria S. E.
Published: January 2020

A new class of temperature-dependent
tol
mutants of
Escherichia coli
expresses tolerance to colicins only after growth at higher temperatures. Colicin sensitivity or tolerance, acquired by growth at 30 or 41 C, respectively, is not lost upon incubation at the other temperature in the presence of chloramphenicol. The kinetics of conversion from sensitivity to tolerance and vice versa have been analyzed. In one instance, the
tol VIII
temperature-dependent phenotype was due to the modifying role of a
str-r
mutation on the suppression of a
tol VIII
amber mutant by the suppressor mutation
su
II. The bearing of the present findings on the role of the
tol
genes is discussed.
Phosphotransferase System of
Staphylococcus aureus:
Its Requirement for the Accumulation and Metabolism of Galactosides
Authors: Hengstenberg Wolfgang , Penberthy W. K. , Hill Katherine L. , Morse M. L.
Published: January 2020

The phosphotransferase system of
Staphylococcus aureus
was characterized. Mutants defective in enzyme I and heat-stable (HPr) protein as well as in the two components specific to lactose accumulation, factor III and enzyme II, were isolated. Colorimetric assays for each of the components are presented based on the formation of
o
-nitrophenyl-β-
d
-galactoside-6-phosphate by the system and its hydrolysis by the staphylococcal 6-phospho-β-galactosidase. The components were partially purified and their molecular weights were estimated: enzyme I, 100,000 ± 15%; HPr, 10,000 ± 15%; factor III, 30,000 ± 15%; 6-phospho-β-galactosidase, 45,000. Enzyme II is a membrane-bound protein.
Inhibition of Protease Production of Various Bacteria by Ammonium Salts: Its Effect on Toxin Production and Virulence
Authors: Liu Pinghui V. , Hsieh Hsi-Chia
Published: January 2020

Production of protease by many bacteria was found to be inhibited by ammonium salts, and the enzyme production was more sensitive to the salts than was growth of the organisms. Inhibition of protease production by some pathogenic bacteria may result in the recognition of an exotoxin which otherwise would have been digested by the protease. In the case of
Pseudomonas aeruginosa
, qualitatively different toxicities could be demonstrated in the culture fluids, depending on the presence or absence of protease in such a fluid. The toxicity of the culture in the presence of a high titer of protease may be due primarily to the protease, whereas the toxicity exhibited in the absence of protease could be due to proteinacious exotoxin. Producers of high titers of protease tended to be less virulent in vivo than producers of low titers of the enzyme, which exert their toxicities by a separate exotoxin.
Genetic Separation of the Inosinic Acid Cyclohydrolase-Transformylase Complex of
Salmonella typhimurium
Authors: Gots Joseph S. , Dalal Fram R. , Shumas Susan R.
Published: January 2020

Genetic and enzymatic analyses were made with the
purH
mutants of
Salmonella typhimurium
. These mutants are purine auxotrophs which are deficient in the conversion of phosphoribosyl-aminoimidazolecarboxamide (AIC) to inosine-5′-monophosphate (IMP). Two steps are required for this process: phosphoribosyl-AIC transformylase (EC 2.1.2.3) and IMP cyclohydrolase (EC 3.5.4.10). Genetic analysis identified two complementation groups, I and II, and a third group of noncomplementing mutants (I–II). Mutations in gene I lead to complete loss of transformylase activity and no loss of cyclohydrolase activity if the mutation is of the missense type, but partial loss if it is of the chain-terminating type (nonsense or frameshift). Gene II mutants are all of the missense type and show normal transformylase activity but no cyclohydrolase activity. The noncomplementing mutants (I–II) are all of the chain-terminating type and are completely deficient in both activities. The results are explained and discussed in terms of subunit interactions of a stable enzyme complex.
Isolation of an Antigen of
Neisseria gonorrhoeae
Involved in the Human Immune Response to Gonococcal Infection
Authors: Schmale John D. , Danielsson Dan G. , Smith Joseph F. , Lee Linda , Peacock William L.
Published: January 2020

Ion-exchange chromatography was used to isolate a fraction from disrupted gonococci which reacts with sera from patients with gonococcal disease in complement-fixation and gel-diffusion tests. This antigenic fraction was shown to be the same as that previously described as having been isolated by gel filtration. The method reported here has the advantage of greater rapidity of isolation together with some improvement in purity.
Effect of Bacteria on Chemotaxis in the Cellular Slime Molds
Authors: Konijn Theo M.
Published: January 2020

The effect of chemotactic substances, secreted by
Escherichia coli
, on the cellular slime molds was studied by deposition of bacteria near myxamoebae populations. Droplets of a bacterial suspension and a myxamoebae suspension were placed separately, at predetermined distances from each other, on a hydrophobic agar surface of low rigidity. Myxamoebae remained confined inside the droplets, except when they were activated by the bacterial products. The sphere of attraction increased at higher bacterial concentrations. Myxamoebae could be attracted over distances as great as 5 mm. Myxamoebae in droplets close to dense bacterial populations not only were attracted toward the bacteria but also moved out in an opposite direction from the bacteria. There was a gradual decrease of attraction at increasing distances between amoebae and bacteria. The attraction by bacteria or bacterial products was reduced at lower temperatures. Light did not affect the distance over which attraction could be observed. Myxamoebae close to their aggregation phase were most sensitive to the bacterial attractants. Bacterial attractants at high concentrations could disperse aggregates, even when they were in an advanced stage. At still higher concentrations of the bacterial products, cells stopped moving altogether. The bacterial attractants activated different species of cellular slime molds. They appeared to be present not only in
E. coli
but also in all other bacterial species that were tested. These results are discussed in the light of earlier observations on the attraction of cells by aggregates of myxamoebae.
Growth of
Physarum flavicomum
and
Physarum rigidum
in Chemically Defined Minimal Media
Authors: Henney Henry R. , Lynch Thomas
Published: January 2020

Physarum flavicomum, P. polycephalum
, and
P. rigidum
grew at
p
H 4.2 in a medium composed of mineral salts, glucose, biotin, thiamine, hematin, and four amino acids. Important differences in
p
H tolerance were noted among the species. The minimal medium of
P. flavicomum
and
P. polycephalum
contained the amino acids methionine, glycine, and arginine, but valine was also required by
P. rigidum
. Starting with an inoculum of about 0.3 mg of protein per 25 ml of minimal medium,
P. flavicomum
and
P. polycephalum
grew to 23 mg and
P. rigidum
to 12 mg of protein per 25 ml in 3, 2, and 4 weeks, respectively.
P. flavicomum
and
P. polycephalum
grew with valine or leucine replacing arginine in the minimal medium but the growth yields and growth rates were decreased. All three species utilized homocysteine thiolactone in the minimal media in place of methionine. Serine adequately replaced glycine for
P. rigidum
but was inhibitory in the minimal medium of
P. flavicomum
or
P. polycephalum
unless homocysteine thiolactone also replaced methionine. Growth rates of all three organisms were increased in the presence of seven amino acids (original four plus leucine, lysine, and isoleucine).
Thymineless Death in
Escherichia coli:
Inactivation and Recovery
Authors: Cummings Donald J. , Kusy Alvin R.
Published: January 2020

The effects of chloramphenicol (CAP) on the progress of thymineless death (TLD), nalidixic acid (NA) inactivation, ultraviolet (UV) irradiation, and mitomycin C (MC) inactivation were studied in
Escherichia coli
B, B
s−1
, B
s−3
, B
s−12
, and B/r. This was done before, during, and after inactivation. During the progress of inactivation, it was found that at 10 to 20 μg of CAP per ml, up to 50% of the UV-sensitive bacteria survived TLD and about 10% survived NA. In
E. coli
B/r, at these concentrations of CAP, about 10 to 15% of the cells survived TLD and about 20 to 25% survived NA. Concentrations of CAP greater than 25 μg/ml actually increased the sensitivity of
E. coli
B, B
s−1
, B
s−3
, and B
s−12
to inactivation by either TLD or NA; at 150 μg of CAP per ml, the sensitivity of
E. coli
B/r to inactivation also increased. When
E. coli
B cells were incubated in CAP prior to inactivation, the longer the preincubation the longer onset of TLD was delayed; NA inactivation was also affected in that the rate of inactivation after CAP incubation was greatly decreased. Preincubation of
E. coli
B/r with CAP had much less effect on the progress of inactivation. After thymineless death, incubation in CAP plus thymine led to a rapid and almost complete recovery of
E. coli
B and B
s−12
. Lesser recoveries were observed after inactivation due to UV, NA, or MC inactivation.
E. coli
B
s−1
and B/r did not recover viability after any mode of inactivation, and
E. coli
B
s−3
and B
s−12
recovered from UV to about 20% of the initial titer. It was suggested that protein synthesis, in particular proteins involved in deoxyribonucleic synthesis, was a determining factor in these inactivating and recovery events.
Reversion Instability in the Galactose operon of
Escherichia coli
Authors: Morse M. L. , Pollock Beatrice F.
Published: January 2020

The
gal-3
mutation, which had been shown previously to produce unstable revertants, was combined in three instances with
recA
, a mutation which suppresses recombination. Unstable revertants were produced in the
gal-3 recA
recombinants qualitatively as frequently as in the absence of the recA gene, and it is concluded that a recombination mechanism is not the basis of the instability observed.
Respiration in Blue-Green Algae
Authors: Biggins John
Published: January 2020

The low rate of endogenous respiration exhibited by the blue-green algae
Anacystis nidulans
and
Phormidium luridum
was not increased by the addition of respiratory substrates. However, endogenous respiration was inhibited by low concentrations of cyanide and by high carbon monoxide tensions. In addition, the uncouplers dinitrophenol and carbonyl cyanide
p
-trifluoromethoxyphenylhydrazone both stimulated the respiratory rate. The transition of cells from the aerobic steady state to anaerobiosis was accompanied by a decrease in the concentration of cellular nicotinamide adenine dinucleotide phosphate (NADP
+
) and adenosine triphosphate (ATP), whereas the concentration of nicotinamide adenine dinucleotide (NAD
+
) was unchanged. Concomitant with the metabolite decreases were stoichiometric increases io reduced NADP
+
(NADPH), adenosine diphosphate, and adenosine monophosphate. A decrease in ATP was also observed after the addition of uncouplers. These data are interpreted as evidence for the association of oxidative phosphorylation with the oxidation of NADP
+
-linked substrates in these algae. Membrane fragments isolated from the algal cells oxidized succinate, malate, ferrocytochrome
c
, ascorbate-tetramethyl-
p
-phenylenediamine, and reduced 2,6-dichlorophenol indophenol but did not oxidize NADPH or reduced NAD
+
in a cyanide-sensitive system. Oxidative phosphorylation has not yet been demonstrated in these fragments, but a dark ATP-P
i
exchange, distinct from the lighttriggered exchange associated with photosynthesis, is readily observed. This exchange was inhibited by phloridzin, Atabrine, and uncouplers in concentrations which suggest that the mechanism of oxidative phosphorylation in blue-green algae is different from that found in other bacteria and in mitochondria. These results led to the conclusion that the biochemical basis for obligate autotrophy in these organisms does not lie in the metabolic events associated with terminal electron transport and energy conservation.
Deoxyribonucleic Acid Homology and Relative Genome Size in
Mycoplasma
Authors: Peterson Anne M. , Pollock Mary E.
Published: January 2020

The deoxyribonucleic acid homologies of
Mycoplasma laidlawii
type A and type B,
M. pulmonis
(#47 and #63), and
M. hominis
were determined by membrane methodology. The homology data revealed a difference in genome size between
M. laidlawii
type A and type B. This difference also held with stringent conditions of annealing (high temperature). Little or negligible homology was shown to exist between the
M. laidlawii
strains type A and type B and
M. pulmonis
strains 47 and 63 and
M. hominis. M. hominis
showed less than 10% homology to the
M. pulmonis
and
M. laidlawii
strains. Neither of the
M. laidlawii
strains showed more than 2% annealing to the
M. pulmonis
strains. Reaction rate studies are suggested as a means of demonstrating the phylogenetic relationship between the
Mycoplasma
and other microorganisms.
Progressive Changes of Vibrio Serotypes in Germ-free Mice Infected withVibrio cholerae
Authors: Sack R. Bradley , Miller Carl E.
Published: January 2020

Germ-free mice inoculated withVibrio choleraebecame colonized with vibrios throughout the gastrointestinal tract, but they did not become ill. High vibrio concentrations in the feces were observed throughout the 3 months of observation in spite of the presence of serum antibody. Reciprocal conversions of both Inaba and Ogawa serotypes occurred regularly after inoculation and could be correlated temporally with the appearance of serum-agglutinating antibody. Both of these smooth serotype were later progressively replaced by rough vibrios. Rough to smooth serotype reversions were also found in mice inoculated with a rough vibrio strain. Studies employing immunosuppression and selective vaccination suggested that such serotypic changes were a result of the selective effect of antibody within the intestinal lumen.
Escherichia coli ras
Locus: Its Involvement in Radiation Repair
Authors: Walker James R.
Published: January 2020

There are several classes of
Escherichia coli
mutants defective in radiation repair. These include strains defective in pyrimidine dimer excision, in photoreactivation, in recombination, in repair of X-ray damage, and ultraviolet (UV)-conditional mutants which do not divide after UV. Another mutant (
ras
−
) has been isolated. The
ras
−
has increased UV sensitivity, but only slightly increased X-ray sensitivity (1.5-fold increase). Ability to effect genetic recombination, to reactivate irradiated bacteriophage T1, and to be photoreactivated is normal. UV-induced mutation frequency is greatly increased in the mutant. The
ras
−
apparently lacks the ability to repair some UV damage in the bacterial cell but can repair UV damage to bacteriophage DNA. The
ras
locus is located between
lac
and
purE
on the chromosome map.
Effect of Culture Medium Composition and
p
H on the Production of M Protein and Proteinase by Group A Streptococci
Authors: Cohen Jay O.
Published: January 2020

The effects of
p
H, yeast extract, and neopeptone on the production of extracellular proteinase and M protein by group A streptococci were studied with a type 1 strain capable of producing both M protein and proteinase. The strain DS 2036-66 grew moderately well in a semisynthetic broth. M protein was produced without adding peptides to the medium. When added to a medium with 1% glucose, yeast extract (0.1%) was found to stimulate both growth and proteinase formation. Limiting the glucose to 0.25% prevented a drop in
p
H below 6.7 and prevented proteinase formation. Although less growth occurred with limited glucose, M protein of high specific activity was produced with an actual increase in acid-extractable M protein during the stationary phase of growth. When the medium was buffered at
p
H 7.85 with tris(hydroxymethyl)aminomethane buffer, 0.5% neopeptone prevented proteinase formation. This was true even in the presence of 1% glucose and 0.1% yeast extract, which resulted in a fall in
p
H to about 4.8 by 48 hr. Growth was greater than in Todd Hewitt broth, but the specific activity of M protein was considerably less than that found in the medium with glucose limited to 0.25%. Neopeptone was found to have little direct action on crude streptococcal proteinase. Instead, the evidence suggested that neopeptone somehow prevents proteinase elaboration. Yeast extract, on the other hand, appears to stimulate proteinase elaboration. To prevent proteinase formation, neopeptone must be added early, during the logarithmic phase of growth or at the start. In contrast, when yeast extract was added as late as 24 hr, it resulted in the elaboration of extracellular proteinase and in the decline of M protein. When 38 M nontypable strains from the diagnostic laboratory were tested for proteinase activity under conditions similar to those used in the diagnostic laboratory, only six produced much proteinase.
Temperature-sensitive Yeast Mutant Defective in Ribonucleic Acid Production
Authors: Hutchison H. Terry , Hartwell Leland H. , McLaughlin Calvin S.
Published: January 2020

A single, recessive mutation in a nuclear gene confers a temperature-sensitive growth response in a mutant of
Saccharomyces cerevisiae, ts
−
136. The mutant grows normally at 23 C, but exhibits a rapid and preferential inhibition of ribonucleic acid (RNA) accumulation after a shift to 36 C, demonstrating a defect in stable RNA production. Cultures of the mutant which were shifted from 23 to 36 C display the following phenomena which indicate that messenger RNA (mRNA), as well as stable RNA production, is defective. The entrance of pulse-labeled RNA into cytoplasmic polyribosomes is even more strongly inhibited than is net RNA accumulation. The rate of protein synthesis, at first unaffected, decreases slowly; this decrease is paralleled by the decay of polyribosomes to monoribosomes with a half-time of 23 min. The polyribosomes which remain after a 30-min preincubation of the mutant at 36 C are active in polypeptide synthesis in vivo, whereas the monoribosomes which accumulate are not. Furthermore, ribosomes isolated from a culture of the mutant preincubated for 1 hr at 36 C are inactive in polypeptide synthesis in vitro, but can be restored to full activity by the addition of polyuridylic acid as mRNA. We conclude that mutant
ts
−
136 is defective either in the synthesis of all types of cytoplasmic RNA, or in the transport of newly synthesized RNA from the nucleus to the cytoplasm, and that the mRNA of a eucaryotic organism (yeast) is metabolically unstable, having a half-life of approximately 23 min at 36 C.
Inactivation of Bacteriocins in the Intestinal Canal and Oral Cavity
Authors: Kelstrup J. , Gibbons R. J.
Published: January 2020

Colicinogenic
Escherichia coli
colonized gnotobiotic mice harboring susceptible or resistant strains comparably. Intestinal contents and dental plaque containing proteases inactivated several colicins and streptococcal bacteriocins.
Oxidation of Ammonia by Spheroplasts of
Nitrosomonas europaea
Authors: Suzuki Isamu , Kwok S. C.
Published: January 2020

The ammonia-oxidizing activity of
Nitrosomonas europaea
spheroplasts was restored by addition of hydroxylamine or by preincubation with Mg
2+
.
Detection of bacteriuria by luciferase assay of adenosine triphosphate
Authors: Thore A , Anséhn S , Lundin A , Bergman S
Published: January 2020

A selective method for distinguishing bacterial and nonbacterial adenosine triphosphate (ATP) in clinical bacteriological specimens was studied. The method involved incubation of samples with the detergent Triton X-100 and the ATP-hydrolyzing enzyme apyrase. The incubation selectively destroyed ATP in suspensions of various human cells while not affecting the ATP content in microbial cells. ATP remaining in the sample after incubation was extracted in boiling buffer and assayed by the firefly luciferase assay. Application of the method to 469 clinical urine specimens showed that the ATP level after treatment with Triton/apyrase was correlated to bacterial counts and that the sensitivity of the assay was sufficient for the detection of 10(5) bacteria/ml. The ATP levels per bacterial cell remaining in the urine specimen after treatment with Triton/apyrase were close to values observed in laboratory-grown cultures. The specificity and sensitivity of the luciferase assay for the detection of urinary bacteria and its possible use as a bacteriuria screening method are discussed.
Preparation of Stable Sensitized Erythrocytes for Detection of Chlamydial Antibodies
Authors: Lewis Vester J. , Engelman Helen M. , Thacker W. Lanier
Published: January 2020

Sheep erythrocytes were treated with glutaraldehyde before sensitization for the indirect hemagglutination test to assay chlamydial antibodies. This treatment markedly increased stability during storage.
Rapid Hippurate Hydrolysis Method for Presumptive Identification of Group B Streptococci
Authors: Hwang Mei-Na , Ederer Grace Mary
Published: January 2020

A rapid test to detect the hydrolysis of sodium hippurate by beta-hemolytic streptococci within 2 h was developed. All group B streptococci tested were positive using this method and all other groups were negative.
Determination of bacterial cell concentrations by electrical measurements
Authors: Wheeler T G , Goldschmidt M C
Published: January 2020

An instrument was developed to measure the concentration of bacterial suspensions by their electrical characteristics. It employed a square-wave signal generator, a tetra-polar electrode probe, and a voltage detector in the form of an oscilloscope. When electrical measurements were made on washed bacteria obtained from cultures or urine specimens, there was a direct relationship between the concentration of the cells and the electrical characteristics of the system as reflected by voltage changes. As little as 10(3) organisms per ml could be detected. The resolution between readings taken on samples containing 10(3) to 10(9) cells per ml was found to be a function of the input frequency. The maximal resolution between concentration readings was obtained at a input frequency of 10 Hz. Thus, with relatively simple instrumentation, bacterial concentrations could be determined within a few minutes. This technique, therefore, eliminates the more lengthy laboratory procedures as plate counts or the accumulation of measurable metabolic changes (such as the utilization of radioactive or other substrates). This method can efficiently monitor clinical urine specimens when a bacteriuria is suspected.