bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine Structure of
Cryptococcus neoformans
Grown In Vivo as Observed by Freeze-Etching
Authors: Takeo K. , Uesaka I. , Uehira K. , Nishiura M.
Published: January 2020

Cryptococcus neoformans
grown in the parasitic state was observed by the freeze-etching technique and was compared with that grown on culture media. Unlike other yeasts, this organism grown in vivo is very often devoid of the “ordinary” invaginations. The membrane of the cell grown in vivo was almost free from concavity and convexity except for many round depressions which represent the surface view of paramural bodies. Some of the paramural bodies were found to be multivesicular systems. Most were spherical invaginations containing a single vesicle or its ghost remaining after secretion of the vesicles. In clear contrast to the cell grown in vitro, the in vivo cell contained a great number of vesicles in the cytoplasm. These seemed to show high-secretion activity in
C. neoformans
grown in the parasitic state. On transfer from in vitro to in vivo, this organism enlarged the cell wall, capsule, and cell body. The appearance of a large vacuole, accumulation of storage organelles, and the existence of rodlike structures, seemingly lipid deposits, were also noted in the cytoplasm of the cell grown in vivo. the meaning of these results as well as the mode of capsular production are discussed.
Amino Terminal Sequence of the Tryptophan Synthetase Alpha Chain of
Serratia marcescens
Authors: Li Shoei-Lung , Drapeau Gabriel R. , Yanofsky Charles
Published: January 2020

The sequence of the amino terminal 28 residues of the tryptophan synthetase α chain of
Serratia marcescens
is presented and compared with the related sęquences of α chains of other bacteria.
Transcription of Spontaneously Released Bacterial Deoxyribonucleic Acid in Frog Auricles
Authors: Stroun Maurice , Anker Philippe
Published: January 2020

After frog auricles have been in contact with a suspension of bacteria or bacteria-free supernatant fluid, newly synthesized bacterial ribonucleic acid (RNA) is recovered in animal cells. It appears that the presence of bacterial deoxyribonucleic acid (DNA)-dependent RNA polymerase is necessary for the transcription of bacterial DNA in the host cells. This phenomenon seems to be related to a transfer of DNA and DNA-dependent RNA polymerase from bacteria into animal cells.
X-ray Sensitivity and Repair Capacity of apolA1 exrAStrain ofEscherichia coliK-12
Authors: Youngs David A. , Smith Kendric C.
Published: January 2020

ApolA1 exrAstrain ofEscherichia coliK-12 was constructed. It was found to be more sensitive to aerobic or anoxic X irradiation than were mutants containing eitherpolA1orexrAalone. The ability ofpolA1 exrAand related strains to repair X-ray-induced single-strand breaks in deoxyribonucleic acid DNA was examined. ThepolA1strain was deficient in type II (buffer) repair but not in type III (growth medium-dependent) repair. TheexrAstrain was not deficient in type II repair but was deficient in type III repair (similar torecstrains). The double mutantpolA1 exrAwas deficient in both type II and type III repair. Thus, the increased X-ray sensitivity of thepolA1 exrAdouble mutant was correlated with its decreased ability to repair X-ray-induced single-strand breaks in DNA. We have tested the hypothesis thatpolA recdouble mutants are not viable because they lack the types II and III systems for the repair of DNA single-strand breaks. Since thepolA1 exrAstrain is viable and is deficient in both of these repair processes, this hypothesis seems not to be correct.
Biosynthesis of Branched-Chain Amino Acids in
Schizosaccharomyces pombe
: Properties of Acetohydroxy Acid Synthetase
1
Authors: McDonald Roderick A. , Satyanarayana T. , Kaplan J. G.
Published: January 2020

The regulatory properties of acetohydroxy acid synthetase (AHAS), the first enzyme in the biosynthetic pathway to valine and the second in the isoleucine pathway, were investigated in the fission yeast
Schizosaccharomyces pombe
. The enzyme was partially purified from crude extracts by protamine sulfate treatment, ammonium sulfate fractionation, and gel filtration through Sephadex G-25. AHAS from
S. pombe
is unique in that its activity shows a single peak around pH 6.5; high sensitivity to feedback inhibition by valine at this pH (

K
i

= 0.1 mM) indicates that the enzyme is involved in valine biosynthesis. Pyruvate saturation kinetics of AHAS extracted from cells grown on glycerol as sole carbon and energy source were normal and hyperbolic. In contrast, the enzyme from glucose-grown cells exhibited sigmoidal saturation kinetics, an effect which disappeared when the synthetase from such cells was partially purified. This phenomenon was shown to be due to competition for pyruvate between AHAS and pyruvate decarboxylase; the latter enzyme is present in large amounts in cells fermenting glucose. Valine inhibition is noncompetitive in nature, and this effector exhibits homotropic cooperative effects; isoleucine is a less-potent inhibitor of AHAS activity. Mercurial treatment reversibly desensitized the enzyme to valine inhibition. On the basis of these data, the
S. pombe
AHAS appears to be an allosteric regulatory enzyme with the properties of a negative V system.
Detection and Characterization of Plasmids in
Pseudomonas aeruginosa
Strain PAO
Authors: Pemberton J. M. , Clark Alvin J.
Published: January 2020

Using a variety of techniques, it has been established that the sex factor FP2 has a density of 1.717 g/cm
3
(corresponding to a guanine plus cytosine [G + C] content of 58%) and a mean circular contour length of 28.5 ± 0.6 μm (corresponding to a molecular weight of 59 × 10
6
). Another sex factor FP39 has a density of 1.719 g/cm
3
(corresponding to a G + C content of 60%) and a mean circular contour length of 26.5 ± 0.5 μm (corresponding to a molecular weight of 55 × 10
6
). It appears that all, or nearly all, of the FP sex factor deoxyribonucleic acid occurs as covalent circular molecules under the conditions employed. In addition, these procedures have been used to demonstrate that strain PAO, a naturally occurring female (i.e., FP
−
) strain of
Pseudomonas aeruginosa
, harbors a number of cryptic plasmids having similar densities to the bulk of the cell deoxyribonucleic acid (1.726 g/cm
3
) and occurring as covalent circular molecules.
Characterization of a Cold-Sensitive
hisW
Mutant of
Salmonella typhimurium
Authors: Brenchley Jean E. , Ingraham J. L.
Published: January 2020

A cold-sensitive mutant of
Salmonella typhimurium
LT2 that grows at 37 C but not at 20 C has altered repression regulation in at least two amino acid biosynthetic pathways (histidine and isoleucine). The lesion conferring cold sensitivity that is linked with
hisW
is recessive. Assays for the acceptance of some amino acids by transfer ribonucleic acid (tRNA) reveal a decreased ability of the mutant tRNA to accept arginine, phenylalanine, and histidine. A mutation in a gene for tRNA maturation is a likely possibility for the mutation producing these effects on growth, regulation, and amino acid acceptance.
Site of Catabolite Inhibition of Carbohydrate Metabolism
Authors: McGinnis James F. , Paigen Kenneth
Published: January 2020

Glucose produces catabolite inhibition during its transport across the cell membrane. Glucose generated intracellularly does not produce catabolite inhibition but does produce catabolite repression.
Ultrastructural Study of Poly-β-Hydroxybutyrate Granules from
Bacillus cereus
Authors: Dunlop Winifred F. , Robards A. W.
Published: January 2020

The freeze-etching technique was used to examine the effects of fracturing and etching on the appearance of poly-β-hydroxybutyrate granules from
Bacillus cereus
. These granules were examined in extracts isolated by hypochlorite or by sonic treatment, and also in fixed and unfixed intact cells; in the latter case they were compared with granules in thin sections of intact cells. After freeze-fracturing, the diameter of the granules in intact cells was between 240 and 720 nm. The granules consisted of a central core, of diameter between 140 and 370 nm, which occupied less than 50% of the volume of the granule and which was either stretched or removed on fracturing; the core was surrounded by an outer coat which may be bounded by a membrane.
Teichoic Acid of a Stabilized L-Form ofStreptococcus pyogenes
Authors: Slabyj Bohdan M. , Panos Charles
Published: January 2020

A stabilized L-form ofStreptococcus pyogenescontinues to synthesize glycerol teichoic acid. This polymer was obtained fromS. pyogenesand its L-form, treated in identical fashion, and compared. Highly purified glycerol teichoic acid from only the L-form was found to be devoid ofd-alanine and to have a shorter chain length. Otherwise, the glycerol teichoic acid from these two organisms was found to be a 1,3-phosphodiester-linked glycerophosphate polymer substituted withd-glucose. Evidence is presented that most, if not all, of the glycerol teichoic acid in this streptococcus lies between the wall and membrane. A possible need for the continued synthesis of a minute amount of glycerol teichoic acid by this L-form for survival is discussed in terms of the known function of teichoic acids in bacteria.
Deoxyribonucleic Acid Synthesis in Synchronously Growing
Mycoplasma gallisepticum
Authors: Quinlan Dennis C. , Maniloff Jack
Published: January 2020

Early log-phase cells of
Mycoplasma gallisepticum
A5969 were synchronized by holding in Eagle minimal essential medium (MEM) for 2 h. When transferred out of MEM into tryptose medium, the cells exhibited synchronous growth. Deoxyribonucleic acid (DNA) synthesis proceeded continuously during this growth but stopped during the period of cell division. One round of DNA replication was observed per cell doubling, and a unique region of DNA was found to be permanently bound to the membrane.
Bi-Directional Chromosomal Replication in
Salmonella typhimurium
Authors: Fujisawa T. , Eisenstark A.
Published: January 2020

Transducing frequencies of phage P22 lysates prepared from
Salmonella typhimurium
exponential cultures in minimal and nutrient broth media were compared. The assumption is that cells grown in a minimal medium will have one replication fork per replication unit, but cells in nutrient broth will have multiple replication forks; therefore, the frequency of genetic markers near the origin of replication will be higher in the nutrient broth culture. Analysis of transduction showed a gradient of marker frequencies from the highest (the
cysG-ilv
region) to the lowest (
purE-trpB
region) in both clockwise and counter clockwise directions. This supports our previous observation that chromosome replication proceeds bidirectionally from the origin between
cysG
(109 min on
S. typhimurium
map) and
ilv
(122 min) to a terminus in
purE-trpB
region (20 to 53 min). Since this method avoids possible artifacts of other methods, the results are assumed to reflect the sequence of chromosome replication in exponentially growing cells. Evidence for the existence of multiple replication forks in nutrient broth-grown cells was supported by the following: (i) the marker frequency data fitted the assumption of multiple replication fork formation; (ii) residual deoxyribonucleic acid increase after inhibition of protein synthesis to complete a round of chromosome synthesis which was 44% in cells grown in a minimal medium and 82% in those in nutrient broth; (iii) segregation patterns of the
3
H-thymidine-labeled chromosome strands during subsequent growth in non-radioactive medium were studied by autoradiography, and the number of replication points per chromosome per cell was estimated as 5.6 for the nutrient broth culture and 2.5 for the minimal medium culture. These data support a model of symmetrical and bidirectional chromosome replication.
Relationships Among Deoxyribonucleic Acid, Ribonucleic Acid, and Specific Transfer Ribonucleic Acids in
Escherichia coli
15T
−
at Various Growth Rates
Authors: Skjold A. Christopher , Juarez Hector , Hedgcoth Charles
Published: January 2020

The levels of macromolecules in
Escherichia coli
15T
−
growing in broth, glucose, succinate, and acetate media were determined to compare relationships among deoxyribonucleic acid (DNA), ribosomal ribonucleic acid (rRNA), transfer RNA (tRNA), and protein in cells at different growth rates. DNA and protein increased in relative amounts with decreasing growth rate; relative amounts of rRNA and tRNA decreased, tRNA making up a slightly larger proportion of RNA. For several amino acid-specific tRNAs studied, acceptor capacities per unit of DNA increased with increasing growth rate. The syntheses of tRNA and rRNA are regulated by similar, yet different, mechanisms. Chromatographic examination on columns of benzoylated diethylaminoethyl-cellulose of isoaccepting tRNAs for arginine, leucine, lysine, methionine, phenylalanine, serine, and valine did not reveal differences in the isoaccepting profiles for rapidly (broth culture) and slowly growing (acetate culture) cells. Therefore, isoacceptors for individual amino acids appear to be regulated as a group. Lower efficiencies of ribosomal function in protein synthesis can be explained, in part, by a low ratio of tRNA to the number of ribosomes available and by a decreasing concentration of tRNA with decreasing growth rate. Data on the tRNAs specific for seven amino acids indicate that the decreasing concentration of tRNA is a general event rather than a severe limitation of any one tRNA or isoaccepting tRNA.
A Bifunctional Enzyme in
Pseudomonas aeruginosa
: a New Pattern in the Organization of Enzymes Concerned with Phenylalanine and Tyrosine Biosynthesis
Authors: Ahmed S. I. , Campbell J. J. R.
Published: January 2020

Two isozymes of chorismate mutase (CA mutase
1
and CA mutase
2
) and two isozymes of prephenate dehydratase (PPA dehydratase
1
and PPA dehydratase
2
) have been found in
Pseudomonas aeruginosa
. The activities CA mutase
2
-PPA dehydratase
2
catalyzing phenylalanine biosynthesis have been purified almost 40-fold and were found to be associated as a bifunctional enzyme or an enzyme complex. The enzymes specific for tyrosine biosynthesis did not appear to manifest such physical association. Thus, the organization of enzymes concerned with phenylalanine and tyrosine biosynthesis in
P. aeruginosa
is unique and is unlike most other organisms. Single site mutants have been isolated which have lost both CA mutase
2
-PPA dehydratase
2
activities resulting in a requirement for phenylalanine for growth. Single site revertants of these mutants regained both these activities simultaneously and were able to grow on minimal medium. A mutant, r
6
, was also isolated which had normal CA mutase
2
but lacked PPA dehydratase
2
activity.
Molecular Relationships Among the Salmonelleae
Authors: Crosa J. H. , Brenner D. J. , Ewing W. H. , Falkow S.
Published: January 2020

Polynucleotide sequence relatedness studies were carried out to determine the extent of divergence present in members of the tribe
Salmonelleae
and between salmonellae and other enteric bacteria. Typical
Salmonella
were 85 to 100% related. Two groups of biochemically atypical
Salmonella
showed somewhat lower binding to typical salmonellae and to each other.
Arizona
were 70 to 80% related to salmonellae. Two groups of
Arizona
were detected. These groups correlated with the presence of monophasic or diphasic flagellar antigens.
Salmonella
and
Arizona
were no more related to
Citrobacter
than to
Escherichia coli
(45-55%). Relatedness of
Salmonella
and
Arizona
to other enterobacteria ranged from 20 to 40% with klebsiellae and shigellae, to 20 to 25% with erwiniae, and to less than 20% with edwardsiellae and
Proteus mirabilis
.
Resistance to Arsenic Compounds Conferred by a Plasmid Transmissible Between Strains of
Escherichia coli
Authors: Hedges R. W. , Baumberg S.
Published: January 2020

A plasmid, R773, which confers resistance to arsenic compounds, is transmissible between strains of
Escherichia coli
. It is a member of compatibility group F
1
.
Very Long-Chain Fatty Acids in Yeast
Authors: Welch J. W. , Burlingame A. L.
Published: January 2020

Novel fatty acids ranging from 20 to 30 carbons have been found in
Saccharomyces cerevisiae
. These comprise 1 to 2% of the total fatty acid fraction.
Transport of Vitamin B
12
in
Escherichia coli
: Genetic Studies
Authors: Kadner Robert J. , Liggins George L.
Published: January 2020

The chromosomal location of two genetic loci involved in the transport of cyanocobalamin (B
12
) in
Escherichia coli
K-12 was determined. One gene,
btuA
, is believed to code for the transport protein in the cytoplasmic membrane, because a mutant with an alteration in this gene has lost the ability to accumulate B
12
within the cell although normal levels of the surface receptors for B
12
are present. The other locus,
btuB
, apparently codes for the surface receptor on the outer membrane. These mutants have lost the ability to bind B
12
and have greatly reduced transport activity, although growth experiments have shown that they can utilize B
12
for growth, but with decreased efficiency. This surface receptor for B
12
also appears to function as the receptor for the E colicins, because
btuB
mutants are resistant to the E colicins, and mutants selected for resistance to colicin E1 are defective in B
12
binding and transport. The gene order was determined by transduction analysis to be
cyc-argH-btuA-btuB-rif-purD
. In addition, mutations in
metH
, the gene for the B
12
-dependent homocysteine methylating enzyme, were obtained in this study. This gene was localized between
metA
and
malB
.
Regulation of Tyrosine and Phenylalanine Biosynthesis in
Escherichia coli
K-12: Properties of the
tyrR
Gene Product
Authors: Camakaris H. , Pittard J.
Published: January 2020

A spontaneous amber
tyrR
mutant has been isolated in which constitutive synthesis of 3-deoxy-
d
-arabinoheptulosonic acid 7-phosphate (DAHP) synthetase (tyr) and DAHP synthetase (phe) is suppressible by

supC
−
, supD
−
, supF
−

and
supU
−
. This finding suggests the
tyrR
gene product is a protein. Derepression of DAHP synthetase (phe) in this and in seven other spontaneous
tyrR
mutants and in four Mu-1-induced
tyrR
mutants provides further evidence for the involvement of the
tyrR
gene product in phenylalanine biosynthesis. Evidence that the
tyrR
product is a component of repressor, rather than an enzyme involved in its synthesis or modification, comes from a study of a temperature-sensitive
tyrR
mutant. This mutant is of the thermolabile type, since derepression occurs rapidly and in the presence and absence of growth.
Rapid Method for Isolation of Large Quantities of Outer Membrane fromEscherichia coliK-12 and Its Application to the Study of Envelope Mutants
Authors: Wolf-Watz Hans , Normark Staffan , Bloom Gunnar D.
Published: January 2020

A rapid method for the isolation of large quantities of bacterial outer membrane is described. This cell envelope component was removed from plasmolyzed cells ofEscherichia coliK-12 by lysozyme-ethylenediaminetetra-acetic acid treatment, aggregated by lowering the pH to 5.0, and recovered by centrifugation. Aggregates of membrane fragments were clearly identified in an electron microscope. A criterion of homogeneity of the preparation was obtained by isopycnic sucrose gradient centrifugation. A single band appeared at a density of 1.24 g/cc. The cytoplasmic membrane marker, succinate dehydrogenase activity, was 40 times lower in the outer membrane preparation than in complete cell envelope preparations. A rich activity was, however, found for the outer membrane marker, phospholipase A. The compositions of outer membranes from a transductant pair were compared. One transductant was a chain-forming, antibiotic-supersensitiveenvAstrain, whereas the other contained theenvA+allele. TheenvAstrain showed a slightly modified protein pattern and a lower relative content of phosphatidylglycerol.
Dissimilatory Reduction of Inorganic Sulfur by Facultatively Anaerobic Marine Bacteria
Authors: Tuttle Jon H. , Jannasch Holger W.
Published: January 2020

Three strains, selected from a large number of newly isolated, facultatively anaerobic marine bacteria, reduced inorganic sulfur compounds other than sulfate anaerobically in defined culture media in the following different patterns: (i) sulfite and thiosulfate were reduced to sulfide, and tetrathionate was reduced to thiosulfate; (ii) tetrathionate was reduced to thiosulfate only; or (iii) thiosulfate was reduced to sulfide only when pyruvate was the substrate. Comparison of anaerobic growth in the presence or absence of inorganic sulfur compounds indicated true dissimilatory reductions.
Three Kinds of Controls Affecting the Expression of the
glp
Regulon in
Escherichia coli
Authors: Freedberg W. B. , Lin E. C. C.
Published: January 2020

Three kinds of control mechanisms govern the expression of the members of the
glp
regulon for glycerol and
sn
-glycerol 3-phosphate (G3P) catabolism in
Escherichia coli
K-12: specific repression by the product of the
glpR
gene; catabolite repression; and respiratory repression (the effect exerted by exogenous hydrogen acceptors). The operons of the
glp
system show different patterns of response to each control. By growing in parallel a mutant strain with temperature-sensitive repressor (
glpR
ts
) and an isogenic control with a deletion in the regulator gene at progressively higher temperatures, it was possible to show that the synthesis of aerobic G3P dehydrogenase (
glpD
product) is far more sensitive to specific repression than that of either glycerol kinase (
glpK
product) or G3P transport (
glpT
product). Conversely, in the strain with a deletion in the regulator gene, the syntheses of glycerol kinase and G3P transport are more sensitive to catabolite repression than that of the aerobic G3P dehydrogenase. The levels of the two flavoprotein G3P dehydrogenases vary in opposite directions in response to changes of exogenous hydrogen acceptors. For example, the ratio of the aerobic enzyme to the anaerobic enzyme (specified by
glpA
) is high when molecular oxygen or nitrate serves as the hydrogen acceptor and low when fumarate plays this role. This trend is not influenced by the addition of cyclic adenosine 3′,5′-monophosphate to the growth medium. Thus, respiratory repression most likely involves a third mechanism of control, independent of specific or catabolite repression.
Glycerol Assimilation by a Mutant of
Rhodopseudomonas capsulata
Authors: Lueking Donald , Tokuhisa David , Sojka Gary
Published: January 2020

A spontaneous mutant of
Rhodopseudomonas capsulata
, capable of growth on glycerol, has been isolated. The mutant requires CO
2
or malate to assimilate glycerol photosynthetically. This requirement is not manifested aerobically. Glycerokinase (EC 2.7.1.30) and pyridine nucleotide-independent
l
-α-glycerophosphate dehydrogenase (EC 1.1.2.1) activities appear coincidently with the metabolism of glycerol, suggesting that this organism employs these enzymes for glycerol dissimilation.
Kinetics of Glucose Incorporation by
Aphanocapsa
6714
Authors: Pelroy Richard A. , Bassham James A.
Published: January 2020

Photoautotrophic metabolism of CO
2
was compared with glucose metabolism in the facultative unicellular blue-green alga,
Aphanocapsa
6714. Glucose-fed cells incorporated more
14
C into phosphorylated sugar intermediates of the reductive and oxidative pentose phosphate cycles than autotrophic cells. The relative increases were: 140-fold in dark cells; 32-fold in dichlorophenylmethylurea (DCMU)-inhibited cells; and 16-fold in cells assumilating glucose during photosynthetic carbon reduction. On the other hand, incorporation of
14
C from glucose into 3-phosphoglycerate and the amino acid pools of glutamate and aspartate was reduced in dark cells. Rates of protein synthesis in dark and DCMU-inhibited cells were reduced 50 and 80% compared to photoautotrophic cells. In cells assimilating glucose during photosynthesis, rates of
14
C incorporation into the two amino acids and protein were the same as in photoautotrophic cells. Chase experiments, using an excess of
12
C-glucose and CO
2
, revealed slow turnover of carbon in dark cells and intermediate turnover rates in DCMU-inhibited cells, when compared to cells assimilating glucose during photosynthesis.
Superoxide Dismutases of
Escherichia coli
: Intracellular Localization and Functions
Authors: Gregory Eugene M. , Yost Fred J. , Fridovich Irwin
Published: January 2020

Escherichia coli
B contains two superoxide dismutases which differ with respect to their localization within the cell, the nature of their prosthetic metals, their responses to changes in
p
O
2
, and their functions. One of these enzymes, which was liberated from the cells by osmotic shock and which was therefore presumed to be localized in the periplasmic space, is an iron-containing superoxide dismutase. The amount of this iron enzyme did not vary in response to changes in
p
O
2
during growth. In contrast, the other superoxide dismutase was not solubilized by osmotic shock, was a mangano-protein, and was found in greater amounts in cells which had been grown at high
p
O
2
.
E. coli
, which had low levels of the iron-enzyme and high levels of the mangano-enzyme, as a consequence of growth in iron-deficient aerated medium, was killed by exposure to an exogenous flux of O
2
−
which was generated either photochemically or enzymatically. The addition of bovine superoxide dismutase to the suspending medium protected these cells against this stress. On the other hand,
E. coli
, which had high levels of the iron-enzyme and low levels of the mangano-enzyme, as a consequence of growth in iron-rich anaerobic medium, was resistant to exogeneous O
2
−
. On the basis of these and of previously reported results (4a, Yost, F. J. and I. Fridovich, J. Biol. Chem., 1973, in press), it appears that the iron superoxide dismutase, of the periplasmic space, serves as a defense against exogenous O
2
−
, whereas the mangano-superoxide dismutase, in the matrix of these cells, serves to counter the toxicity of endogenous O
2
−
.
Transport Systems for Alanine, Serine, and Glycine in
Escherichia coli
K-12
Authors: Robbins James C. , Oxender Dale L.
Published: January 2020

At least two transport systems serve for the entry of alanine, glycine, and serine into
Escherichia coli
. One of these systems serves mainly for glycine,
d
-alanine, and
d
-serine and to some extent for
l
-alanine, whereas the second serves for
l
-alanine and perhaps
l
-serine. These two transport systems have been characterized by kinetic studies and by inhibition analysis. Reciprocal plots for
l
-alanine entry are distinctly biphasic, giving rise to

K
m

values of about 2 and 27 μM. The major route of glycine entry can be described by a single

K
m

value of about 4 μM. A higher

K
m

value for glycine of around 70 to 100 μM shows that other routes of entry may serve at high concentrations of amino acid. The glycine,
d
-serine and
d
-alanine transport system is defective in a
d
-serine-resistant mutant, strain EM1302. The mutation,
dagA
, is recessive in
dagA/dagA
+
merodiploids and is 7 to 12% linked by phage P1 transduction to the
pyrB
locus of
E. coli. E. coli
with the
dagA
mutation are unable to utilize
d
-alanine as a carbon source, providing an additional basis for selecting such mutants. The remaining
l
-alanine uptake in
dagA
mutants is subject to inhibition by
l
-serine,
l
-threonine, and
l
-leucine. It is also sensitive to osmotic shock treatment and repressed by growth of the cells on
l
-leucine. It appears from a comparison of the properties of the second
l
-alanine system with those of the leucine, isoleucine, and valine system (LIV system) that the LIV system also serves for the transport of
l
-alanine and
l
-threonine and perhaps
l
-serine.
Resistance of
Escherichia coli
to Penicillins: Identification of the Structural Gene for the Chromosomal Penicillinase
Authors: Burman Lars G. , Park James T. , Lindström E. Börje , Boman Hans G.
Published: January 2020

A screening procedure was used to isolate a number of mutants of
Escherichia coli
K-12 with low penicillinase activity. By co-transduction with
purA
, three of the mutants were found to map near 82 min. Penicillinase was purified from one mutant and from a transductant with a temperature-sensitive enzyme. Comparison with wild-type penicillinase revealed similarities in the Ouchterlony immunodiffusion test but differences in the catalytic properties. It is concluded that the mutations have occurred in the structural gene of the chromosomal penicillinase (designated
ampC
). Purified enzyme and a temperature-sensitive mutant were used to investigate whether the penicillinase has a physiological function related to biosynthesis or breakdown of murein. No positive evidence for any such function was obtained.
Conditions Affecting the Isolation from Transformed Cells of
Bacillus subtilis
of High-Molecular-Weight Single-Stranded Deoxyribonucleic Acid of Donor Origin
Authors: Davidoff-Abelson R. , Dubnau D.
Published: January 2020

The deoxyribonucleic acid (DNA) extraction procedure of Piechowska and Fox was evaluated to determine which steps are required for the isolation of high-molecular-weight single-stranded material from transformed cultures of
Bacillus subtilis
. The results indicate that high-molecular-weight single-stranded DNA can be isolated when certain basic proteins are present at the time of lysis. In the absence of such protective agents as lysozyme or
cytC
the single-stranded DNA is degraded. The single-stranded DNA can also be protected by being treated with lysozyme at low temperature. The high molecular weight of this single-stranded material and its kinetics of appearance are consistent with its being an intermediate in the transformation process.
Evidence for the Control by
exrA
and
polA
Genes of Two Branches of the
uvr
Gene-Dependent Excision Repair Pathway in
Escherichia coli
K-12
Authors: Youngs David A. , Smith Kendric C.
Published: January 2020

A
polA1 exrA
strain of
Escherichia coli
K-12 was found to be more sensitive to ultraviolet radiation than the closely related
polA1
or
exrA
strains, but not as sensitive as either the
exrA uvrB
or
recA
strains. The
exrA
and
polA1
mutations both resulted in a deficiency in the repair of single-strand breaks arising in the deoxyribonucleic acid as a result of the excision repair process (incision breaks). These deficiencies were at least partially independent since the double mutant,
polA1 exrA
, was more deficient than a strain containing either the
polA1
or
exrA
mutation alone. These results suggest that the
polA1
and
exrA
mutations result in defects in two different branches of the
uvr
gene-dependent excision repair process. The repair of incision breaks was still observed in the
polA1 exrA
strain after low exposures of ultraviolet radiation, suggesting the existence of a third branch of the excision repair process which is dependent on neither the
polA
nor
exrA
genes. The
polA1
and
polA1 uvrA
strains were not deficient in post-replicational repair. The
exrA
strain was partially deficient in post-replicational repair, but the
polA1 exrA
strain was no more deficient than the
exrA
strain in this repair process. Thus, the increased ultraviolet irradiation sensitivity of the
polA1 exrA
strain relative to the
polA1
and
exrA
strains appears to be related to the effect of the
polA1
and
exrA
mutations on different branches of the
uvr
gene-dependent excision repair process as well as to the effect of the
exrA
mutation on the post-replicational repair process.
Identification, Preliminary Characterization, and Evidence for Regulation of Invertase in
Streptococcus mutans
Authors: Tanzer Jason M. , Brown Albert T. , McInerney Marcia F.
Published: January 2020

Sucrose dissimilation was studied in five strains of
Streptococcus mutans
. Glucose-adapted strain SL-1 makes acid more slowly from sucrose than from glucose; glucose-adapted strain SL-1 gives diauxie growth kinetics in broth containing limiting amounts of both glucose and sucrose. Thus, at least part of the sucrose dissimilative system appears inducible. Sucrase activity was identified in the 37,000 ×
g
soluble cell fraction of five strains. Its intracellular location implies the presence of sucrose permease. The specific activity of the sucrase is higher in sucrose-adapted cells than in cells adapted to glucose or other sugars, further suggesting its inducibility. The enzyme from strain SL-1 was partially purified by diethylaminoethyl-cellulose chromatography and shown to be a single molecule with a molecular weight of about 48,000. The partially purified enzyme is specific for sucrose and produces equimolar glucose and fructose. Since it degrades raffinose, but not melezitose or other α-glucosides, it is an invertase. The invertase has a relatively high

K
m

for its substrate and a pH optimum of 5.5 to 6.2. It is activated by inorganic orthophosphate (P
i
), P
i
functioning as a positive effector. Arsenate can substitute for phosphate. Neither the crude cell-free extract nor the partially purified enzyme preparations has detectable sucrose phosphorylase activity. A possible potent role of the invertase in the regulation of sucrose carbon flow in
S. mutans
is discussed.
Cell Growth and Division in
Escherichia coli:
a Common Genetic Control Involved in Cell Division and Minicell Formation
Authors: Khachatourians George G. , Clark D. Joseph , Adler Howard I. , Hardigree Alice A.
Published: January 2020

Escherichia coli
Div 124(ts) is a conditional-lethal cell division mutant formed from a cross between a mutant that produces polar anucleated minicells and a temperature-sensitive cell division mutant affected in a stage of cross-wall synthesis. Under permissive growth temperature (30 C), Div 124(ts) grows and produces normal progeny cells and anucleated minicells from its polar ends. When transferred to nonpermissive growth temperature (42 C), growth and macromolecular synthesis continue, but cell division and minicell formation are inhibited. Growth at 42 C results in formation of filamentous cells showing some constrictions along the length of the filaments. Return of the filaments from 42 to 30 C results in cell division and minicell formation in association with the constrictions and other areas along the length of the filaments. This gives rise to a “necklace-type” array of cells and minicells. Recovery of cell division is observed after a lag and is followed by a burst in cell division and finally by a return to the normal growth characteristic of 30 C cultures. Recovery of cell division takes place in the presence of chloramphenicol or nalidixic acid when these are added at the time of shift from 42 to 30 C, and indicates that a division potential for filament fragmentation is accumulated while the cells are at 42 C. This division potential is used for the production of both minicells and cells of normal length. The conditional-lethal temperature sensitive mutation controls a step(s) in cross-wall synthesis common to cell division and minicell formation.
Kinetics of the Mating-Specific Aggregation in
Saccharomyces cerevisiae
Authors: Campbell D. A.
Published: January 2020

Procedures are described for obtaining efficient mating (zygote formation) in the heterothallic yeast
Saccharomyces cerevisiae
. The methods separate operationally the initial, mating-specific aggregation from subsequent steps in conjugation. This cell-cell interaction has been characterized. The data support the conclusions that (i) aggregation in liquid suspension is a random collision process, and (ii) only non-budded cells participate in aggregation. A mathematical model for the kinetics of aggregation in liquid suspension has been developed which is in good agreement with the experimental data.
Mutation to Erythromycin Dependence in
Escherichia coli
K-12
Authors: Sparling P. Frederick , Blackman Eleanor
Published: January 2020

A nitrosoguanidine-induced mutant of
Escherichia coli
K-12 strain JC12 was absolutely dependent on erythromycin or related macrolide antibiotics for growth. The only other drugs which permitted growth (lincomycin and chloramphenicol) are, like the macrolides, inhibitors of the 50
S
ribosome. The order of relative effectiveness of these drugs was macrolides > lincomycin > chloramphenicol. Rates of growth with all drugs were concentration dependent. Erythromycin starvation was followed by normal rates of increase in cell mass and macromolecular synthesis for approximately one mass-doubling time, after which macromolecular synthesis abruptly ceased and cell lysis and death occurred. The dependent mutant gave rise spontaneously to revertants to independence with very high frequency (10
−4
). The gene (
mac
) for macrolide dependence is located near minute 25 on the
E. coli
chromosome; it does not result in increased resistance to these drugs. A separate gene for erythromycin resistance (
eryA
) is located in the cluster of ribosomal structural genes near
spc
, close to minute 63. Dependence on macrolides was most clearly evident in strains carrying mutations at both
eryA
and
mac
.
Accumulation of Messenger Ribonucleic Acid Specific for Extracellular Protease in
Bacillus subtilis
168
Authors: Semets E. V. , Glenn A. R. , May B. K. , Elliott W. H.
Published: January 2020

Production of extracellular protease by
Bacillus subtilis
168 in a medium containing low concentrations of amino acids is essentially linear, whereas in a medium containing high levels of amino acids the time course of production is biphasic. Cells harvested from the growth medium are capable of secreting enzyme for 30 min in the presence of rifampin, but the appearance of the enzyme is sensitive to chloramphenicol and pactamycin. The protease messenger ribonucleic acid (mRNA), nevertheless, appears to have a short half-life typical of bacterial messengers, and this indicates that these cells contain a relatively large pool of protease-specific mRNA. This pattern of results is identical to that observed previously with
B. amyloliquefaciens
. Because it has now been found in two distinct organisms, it is concluded that the accumulation of mRNA for extracellular protease, supported by rapid transcription, is a biologically meaningful phenomenon related to extracellular enzyme synthesis rather than aberrant behavior due to a transcriptional control mutation.
Absence of Circular Plasmid Deoxyribonucleic Acid Attributable to a Genetic Determinant for Methicillin Resistance in
Staphylococcus aureus
Authors: Stiffler Paul W. , Sweeney H. M. , Cohen Sidney
Published: January 2020

Plasmid deoxyribonucleic acid was not detected by centrifugal analysis of lysates of penicillinase-negative strains of
Staphylococcus aureus
harboring a determinant of methicillin resistance derived from strain Villaluz. When these strains contained a penicillinase plasmid, the plasmid deoxyribonucleic acid of methicillin-resistant and methicillin-susceptible strains was indistinguishable by the methods employed. The results indicate that the genetic determinant for methicillin resistance in the strains examined was not associated with a circular plasmid comparable to those that have been shown to determine resistance to benzylpenicillin, tetracycline, and chloramphenicol in
S. aureus
.
Germination of
Bacillus megaterium
Spores After Various Extraction Procedures
Authors: Vary James C.
Published: January 2020

The initiation of germination of
Bacillus megaterium
QM B1551 spores, grown in supplemented nutrient broth, has been studied. The initiation properties depend on buffer concentrations and the particular batch of spores. Initiation in
l
-alanine, KBr, calcium dipicolinate, or in buffer alone increases as a function of the spore age; whereas initiation in glucose,
l
-leucine, or
l
-proline remains relatively constant. Extraction of spores with alkali, sodium dodecyl sulfate-dithiothreitol, or lithium diiodosalicylate removes variable amounts of dipicolinic acid, hexosamine, and protein. These extracted spores are still capable of initiation and, in some cases, initiation is stimulated. However, extraction of spores with 8 M urea-10% mercaptoethanol inhibits subsequent initiation.
Growth Properties of
Rhodospirillum rubrum
Mutants and Fermentation of Pyruvate in Anaerobic, Dark Conditions
Authors: Uffen R. L.
Published: January 2020

Mutant C and G1 were obtained earlier from
Rhodospirillum rubrum
S
1
during growth in the dark under strict anaerobic conditions in medium containing sodium pyruvate. Mutant C and mutant G1 grew in the dark with generation times of 5.8 h and 4.6 h, respectively. Mutant C cells grew equally well when switched between anaerobic (dark or light) or aerobic, dark conditions. Mutant G1 cells grew only in the dark (anaerobic or aerobic conditions), but a fraction of cells in anaerobic, dark cultures grew when placed in light. This number increased about 3,000-fold when G1 cells were incubated aerobically in the dark. During anaerobic, dark growth, C and G1 organisms incorporated similar amounts of [2-
14
C
]sodium pyruvate. About 34% of the incorporated radioactivity was found in lipid fractions from C cells that developed chromatophores during dark growth. Similar results were obtained using G1 cells, which formed only trace amounts of photosynthetic structures. Both mutants fermented sodium pyruvate and produced acetate, formate, carbon dioxide, and hydrogen gas. Molar growth yield coefficients indicated that the cells obtained about 1 mol of adenosine triphosphate per mol of sodium pyruvate fermented. Results suggested that pyruvate fermentation during dark growth occurred via a pyruvate formate-lyase or the pyruvate ferredoxin-oxidoreductase pathway, or both.
Ultrastructural Aspects of a Mutant ofSchizophyllum communewith Continuous Nuclear Migration
Authors: Raudaskoski M. , Koltin Y.
Published: January 2020

Study of a mutant of the basidomyceteSchizophyllum communewith continuous migration of nuclei revealed that the mutant is characterized by vacuolization, bundles of fibrillar-like material, and microtubules. The bundles of fibrillar-like material and microtubules extend through degraded septa to adjacent cells and are found in proximity to nuclei.
New Method for the Isolation of Membranes fromMycoplasma gallisepticum
Authors: Goel M. C.
Published: January 2020

Mycoplasma gallisepticumlysed readily in carbonate bicarbonate buffer at pH 9.2 to 10.5. The hemagglutination titer of the lysates was 2- to 16-fold greater than a cell suspension at the same protein concentration in buffered saline. Membranes prepared from cells lysed by this method at pH 10 were relatively free from cytoplasmic contaminants as shown by electron microscopy of thin sections. The membranes retained their hemagglutination activity, gave reactions in immunodiffusion tests identical to those obtained by osmotic lysis and sonic treatment, and showed a similar pattern of protein bands by polyacrylamide disk electrophoresis. When inoculated into rabbits, the membranes gave rise to antibodies active in growth-, metabolic- and hemagglutination-inhibition tests. On the average, membranes obtained by lysis at pH 10 contained 44% of the original cell protein. The method is simple, giving high yields of membranes, and may be adaptable to other mycoplasmas.
Multiplicity of Leucine Transport Systems in
Escherichia coli
K-12
Authors: Rahmanian Mohamad , Claus David R. , Oxender Dale L.
Published: January 2020

The major component of leucine uptake in
Escherichia coli
K-12 is a common system for
l
-leucine,
l
-isoleucine, and
l
-valine (LIV-I) with a Michaelis constant (

K
m

) value of 0.2 μM (LIV-I system). The LIV-binding protein appears to be associated with this system. It now appears that the LIV-I transport system and LIV-binding protein also serve for the entry of
l
-alanine,
l
-threonine, and possibly
l
-serine. A minor component of
l
-leucine entry occurs by a leucine-specific system (L-system) for which a specific leucine-binding protein has been isolated. A mutant has been obtained that shows increased levels of the LIV-I transport activity and increased levels of both of the binding proteins. Another mutant has been isolated that shows only a major increase in the levels of the leucine-specific transport system and the leucine-specific binding protein. A third binding protein that binds all three branched-chain amino acids but binds isoleucine preferentially has been identified. The relationship of the binding proteins to each other and to transport activity is discussed. A second general transport system (LIV-II system) with a

K
m

value of 2 μM and a relatively low

V
max

can be observed in
E. coli
. The LIV-II system is not sensitive to osmotic shock treatment nor to growth of cells in the presence of leucine. This high

K
m

system, which is specific for the branched-chain amino acids, can be observed in membrane vesicle preparations.
Temperature-Sensitive Nonsense Mutations in Essential Genes of
Escherichia coli
Authors: Beckman David , Cooper Stephen
Published: January 2020

Cells containing nonsense mutations in essential genes have been isolated in a strain of
Escherichia coli
that carried the
su4
ts
gene which specifies a temperature-sensitive tyrosine transfer ribonucleic acid. Such cells are unable to form colonies at temperatures which inactivate this suppressor transfer ribonucleic acid. A screening procedure for the identification of mutants that carry temperature-sensitive nonsense mutations in essential genes is described, and certain properties of two such mutants are reported.
Polysomes, Ribonucleic Acid, and Protein Synthesis During Germination of
Neurospora crassa
Conidia
Authors: Mirkes Philip E.
Published: January 2020

The level of polysomes in ungerminated conidia of
Neurospora crassa
depends on the method used to collect spores. Spores harvested and exposed to hydration contain 30% of their ribosomes as polysomes, whereas those not exposed to hydration contain only 3% of their ribosomes as polysomes. During the germination process, the percentage of the ribosomes which sediment as polysomes increases rapidly to a level of approximately 75% during the first 15 to 30 min of germination. This rapid increase has been shown to require a carbon source. During the first 30 min of germination, spores synthesize ribosomal ribonucleic acid (RNA) and heterogeneously sedimenting RNA, i.e., presumptive messenger RNA.
Positioning Flagellar Genes in
Escherichia coli
by Deletion Analysis
Authors: Silverman Michael , Simon Melvin
Published: January 2020

Two methods were devised to select a series of overlapping deletion mutations carried on episomal elements in
Escherichia coli
. The deletions were then used in an analysis of (i) the relative position on the genome of previously described mutant loci in the flagellar genes, (ii) the relative position of a newly defined cistron,
flaN
, and (iii) the orientation and direction of transcription of genes previously assigned to multicistronic transcriptional units. As a result of this analysis and previous work, we report the following arrangement of the flagellar genes in the
his-aroD
region of the
E. coli
genetic map:
his-flaR-flaQ-flaP-flaA-flaE-flaO-flaC-flaB-flaN-hag-flaD-uvrC-flaI-mot- flaG-flaH
. The genes
flaA, P, Q
, and
R, flaB, C, O
and
E
, and
flaG
and
H
are co-transcribed in that order.