bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in the Lipid Composition and Fine Structure ofSaccharomyces cerevisiaeDuring Ascus Formation
Authors: Illingworth R. F. , Rose A. H. , Beckett A.
Published: January 2020

Eighty to ninety percent of vegetative cells ofSaccharomyces cerevisiaeDCL 740 incubated in KCl-acetate medium form asci, the majority of which are four-spored. Ascospores are visible in asci after about 24 hr, and spore formation is complete after about 48 hr. The dry weight of the cells increases by about 75% during 48 hr of incubation, while the lipid content of the cells increases by a factor of four. The increase in lipid content is attributed mainly to an increased synthesis of sterol esters and triacylglycerols and to a lesser extent of phospholipids. The phospholipid and sterol compositions do not change appreciably, but there is a marked increase in the proportion of unsaturated fatty acid residues in ascan lipids. Uniformly labeled14C-acetate is incorporated mainly into sterol esters and triacylglycerols and phospholipids. Pulse-labeling by adding acetate-U-14Cto sporulating cultures and harvesting after a further 6 hr of incubation reveal two main periods of acetate incorporation, namely between 0 and 18 hr, and between 24 and 30 hr. Electron micrographs of thin sections through developing asci show that the principal changes in fine structure occur between 18 and 24 hr and include the appearance of numerous electron-transparent vesicles which become aligned around the meiotic nucleus, and the laying down of extensive endoplasmic reticulum membranes. Changes in fine structure are discussed in relation to the alterations in lipid content and composition of asci.
Superoxide Dismutase in
Bacillus popilliae
, a Catalaseless Aerobe
Authors: Yousten Allan A. , Bulla Lee A. , McCord Joe M.
Published: January 2020

Bacillus popilliae
, a cytochrome-containing aerobic organism that lacks catalase and peroxidase, was examined for superoxide dismutase activity. The activity was quite high relative to a wide variety of organisms previously surveyed and was induced by oxygen. No correlation could be made between superoxide dismutase activity and the unexplained death of this organism after completion of exponential growth.
Molecular Structure of an R Factor, Its Component Drug-Resistance Determinants and Transfer Factor
Authors: Milliken Christine E. , Clowes R. C.
Published: January 2020

Plasmid DNA from
Escherichia coli
strains harboring drug resistance either of the infectious or noninfectious kind has been separated by CsCl centrifugation of crude cell lysates in the presence of ethidium bromide and examined by electron microscopy. Plasmid deoxyribonucleic acid (DNA) from an S
+
strain (which has the property of noninfectious streptomycin-sulfonamide resistance) consists of a monomolecular covalently closed circular species of 2.7 μm in contour length (5.6 × 10
6
atomic mass units; amu). DNA from a strain carrying a transfer factor, termed Δ, but no determinant for drug resistance, is a monomolecular covalently closed circular species of 29.3 μm in contour length (61 × 10
6
amu). DNA from either Δ
+
A
+
or Δ
+
S
+
strains, (which are respectively ampicillin or streptomycin-sulfonamide resistant, and can transfer this drug resistance), shows a bimodal distribution of molecules of contour lengths 2.7 μm and 29.3 μm, whereas DNA from a (Δ-T)
+
strain (showing infectious tetracycline resistance) contains only one species of molecule measuring 32.3 μm (67 × 10
6
amu). We conclude that ampicillin resistance is carried by a DNA molecule (the A determinant) of 2.7 μm, and streptomycin-sulfonamide resistance is carried by an independent molecule (the S determinant) of similar size. These molecules are not able to effect their own transfer, but can be transmitted to other cells due to the simultaneous presence of the transfer factor, Δ, which also constitutes an independent molecule, of size 29.3 μm. In general, there appears to be little recombination or integration of the A or S molecules into that of Δ, although a small proportion (5–10%) of recombinant molecules cannot be excluded. In contrast, the third drug-resistance determinant, that for tetracycline resistance (denoted as T), is integrated in the Δ molecule to form the composite structure Δ-T of size 32.3 μm, which determines infectious tetracycline resistance. The Δ
+
A
+
and Δ
+
S
+
strains are defined as harboring
plasmid aggregates
, and the (Δ-T)
+
strain is defined as carrying a
plasmid cointegrate
; the properties of all three strains are characteristic of strains harboring R factors. These results are compatible with the previously published genetic data. The number of Δ molecules per cell appears to be equal to the chromosomal number irrespective of growth phase, and this plasmid can thus be defined as stringently regulated in DNA replication. In contrast, S and A exist as multiple copies, probably in at least a 10-fold excess of chromosomal copy number. S and A can thus be defined as relaxed in the regulation of their DNA replication.
On the Conservation of Aminoacyl-Transfer Ribonucleic Acid Synthetase Genes in
Bacillus
Authors: Hoch James A. , Steinberg William
Published: January 2020

None of the heterologous deoxyribonucleic acid from various bacilli was capable of transforming lysyl- and tryptophanyl-transfer ribonucleic acid (tRNA) synthetase mutants of
Bacillus subtilis
to wild type. It was concluded that there is little conservation of the aminoacyl-tRNA synthetases even though the tRNA cistrons are conserved genetic functions.
Screening Procedure for
Escherichia coli
Mutants Deficient in Ribonuclease I
Authors: Kaplan S.
Published: January 2020

Strains of
Escherichia coli
that possess ribonucleic acid accumulated under
relaxed
growth conditions show a considerable increase in time before the onset of β-galactosidase inducibility. This time dependency can be related to the presence or absence of ribonuclease I.
Succinate Oxidase in
Neurospora
Authors: West David J. , Woodward Dow O.
Published: January 2020

Two kinetically distinct states of succinate oxidase have been detected in the mitochondria of
Neruospora crassa
. One state has a
K
m
for succinate of 4.1 × 10
−3
m
, and the other has a
K
m
for succinate of 3.5 × 10
−4
m
. The high
K
m
state was found in freshly extracted mitochondria from either 20- or 72-hr mycelium. However, the succinate oxidase activity in mitochondria from 20-hr mycelium rapidly deteriorated in vitro, leaving a stable residual activity with the lower
K
m
for succinate. Adenosine triphosphate (ATP) plus Mg
2+
stabilized the high
K
m
state in these preparations. The high
K
m
state of succinate oxidase was further characterized by a two- to threefold increase in activity over the
p
H range 6.6 to 8.0 and by classical competitive inhibition by fumarate and malonate. By contrast, the low
K
m
state of succinate oxidase showed a relatively flat response to
p
H over the range 6.6 to 8.0 and a nonclassical pattern of inhibition by fumarate and malonate, as shown by nonlinear plots of reciprocal velocity versus reciprocal substrate concentration in the presence of inhibitor or reciprocal velocity versus inhibitor concentration at fixed substrate concentrations. The relationship of mycelial age to the in vitro stability of succinate oxidase is considered with reference to probable changes in the relative pool sizes of extra- and intramitochondrial ATP in response to changes in the rate of glycolysis.
Two Genetic Loci for Resistance to Kasugamycin in
Escherichia coli
Authors: Sparling P. Frederick , Ikeya Yoshiko , Elliot Donna
Published: January 2020

There are two loci for resistance to the antibiotic kasugamycin (Ksg) in
Escherichia coli
. Mutations at
ksgA
resulted in 30
S
ribosomal subunit resistance to Ksg. The map location of
ksgA
was near minute 0.5:
ksgA
was 95% cotransducible with
pdxA
, and the apparent gene order was
thr... ksgA... pdxA
. Studies in stable
ksgA/ksgA
+
merodiploids showed that sensitivity was dominant over resistance. Mutations at a second gene (
ksgB
), located between minutes 25 and 39, resulted in phenotypic Ksg
R
indistinguishable from
ksgA
mutations, but ribosomes from
ksgB
strains were sensitive to the drug in vitro. Spontaneous and induced mutations to Ksg
R
were usually of the
ksgA
(ribosomal) type.
Chromatographically Fractionated Complementary Strands of
Bacillus subtilis
Deoxyribonucleic Acid: Biological Properties
Authors: Rudner Rivka , Remeza Virgilija
Published: January 2020

Biological, physical, and chromatographic properties of methylated albuminkieselguhr (MAK)-fractionated complementary strands, designated as light (L) and heavy (H), of
Bacillus subtilis
deoxyribonucleic acid (DNA) are presented. The pattern of transforming activity along the MAK elution profile of alkilidenatured DNA shows that the residually active molecules selectively fractionated ahead of the L strand fraction, whereas the most active self-annealed molecules fractionated preferentially at the trailing end of the H strand fraction. The restoration rate of transforming activity in the late-eluting H molecules was rapid and independent of concentration during the annealing reaction. The data suggest that the self-annealing activity in the H strand is due in part to the formation of intrastrand secondary structures. Hydroxyapatite chromatography of self-annealed L and H strands yielded a major fraction (I) of highly purified strand preparations devoid of transforming activity and hypochromicity, and a minor “nativelike” fraction (II). Sedimentation velocity measurements show that, in addition to the mutual complementary nature of the L and H fractions, they differ in molecular size and possibly configuration.
Salmonella typhimurium
Mutants Lacking Ribonuclease I: Effect on the Polarity of Histidine Mutants
Authors: Bruni Carmelo B. , Rechler Matthew M. , Martin Robert G.
Published: January 2020

Mutants of
Salmonella typhimurium
containing 1 to 2% of wild-type ribonuclease I activity were isolated. The
rns
mutation had no effect on the polarity of mutations in the
S. typhimurium
histidine operon. Even in the presence of an
rns
mutation, it was not possible to obtain strong suppressors of the polarity of two polar mutations in the
his
operon.
Anthranilate Hydroxylase from
Aspergillus niger:
Evidence for the Participation of Iron in the Double Hydroxylation Reaction
Authors: Kumar R. Prema , Sreeleela N. S. , Rao P. V. Subba , Vaidyanathan C. S.
Published: January 2020

Evidence was obtained for the participation of iron in the double hydroxylation reaction catalyzed by anthranilate hydroxylase from
Aspergillus niger
(UBC 814). Omission of iron from the growth medium gave inactive preparations of anthranilate hydroxylase which could be reactivated by incubating the enzyme preparations with ferric citrate. The enzyme was susceptible to inhibition by metal chelating agents. The

K
i

for
o
-phenanthroline, which inhibited the enzyme activity non-competitively with respect to anthranilate, was calculated to be 0.9 mM. The inhibition by
o
-phenanthroline was counteracted by ferric complexes such as ferric-ethylenediaminetetraacetic acid and ferric citrate. Anthranilate afforded protection against inhibition by
o
-phenanthroline.
Microcinematographic Studies of
Mycoplasma hominis
Cells
Authors: Bredt W. , Heunert H. H. , Höfling K. H. , Milthaler Brigitte
Published: January 2020

Cells of two strains of
Mycoplasma hominis
growing in liquid medium on a glass surface were observed continuously, and cinematographic pictures were taken. Most of the observed structures showed reversible changes of their shape, suggesting the presence of contractile material in membrane or cytoplasma. The frequency and speed of such variations were measured. The deformations seem to be related to multiplication. The mechanisms of these phenomena are unknown.
Postmaturational Cleavage of 23
s
Ribosomal Ribonucleic Acid and Its Metabolic Control in the Blue-Green Alga
Anacystis nidulans
Authors: Doolittle W. Ford
Published: January 2020

Data are presented consistent with the notion that the 23
s
ribosomal ribonucleic acid (rRNA) of
Anacystis nidulans
undergoes specific endonucleolytic cleavage in vivo, to produce two fragments with molecular weights of 0.88 × 10
6
and 0.17 × 10
6
daltons. Cleavage occurred at random after 23
s
rRNA formation and was stimulated by light in this organism, an obligately photoautotrophic unicellular blue-green alga. The half-life of intact 23
s
rRNA was about 5 h in illuminated cultures and 10 h in unilluminated cultures. 3-(
p
-Chlorophenyl)-1, 1-dimethylurea, an inhibitor of photosystem II, retarded 23
s
rRNA cleavage in the light. The results are discussed in the context of recent reports of rRNA instability in a variety of eukaryotic and prokaryotic organisms.
Mutants of
Bacillus subtilis
Temperature Sensitive in the Outgrowth Phase of Spore Germination
Authors: Galizzi A. , Gorrini F. , Rollier A. , Polsinelli M.
Published: January 2020

Thirteen thermosensitive mutants of
Bacillus subtilis
defective in the outgrowth phase of spore germination were isolated. The spores of the mutants grow into vegetative cells at 35 C but not at 47 C, whereas the vegetative cells grow equally well at both temperatures. At 47 C all the mutant spores are able to initiate germination, but the process stops at an early phase of outgrowth in one strain and in a late phase in the other 12 strains. The spore of the latter gives rise to a swollen cell unable to divide. In all mutants, the normal phenotype is restored when the spores are grown in the presence of 20% sucrose or 2% NaCl. The synthesis of deoxyribonucleic acid and proteins does not seem to be altered in the mutants giving swollen cells. The mutants were grouped into three distinct genetic classes by transformation.
Increased Viability of a Strain of
Neurospora crassa
After Treatment with Ultraviolet Radiation or Other Agents
Authors: Feldhoff Pamela W. , Sullivan Jerome L. , DeBusk A. Gib
Published: January 2020

A strain of
Neurospora crassa
with low viability but near normal germination shows a two- to sixfold increase in the number of colonies formed after treatment with ultraviolet radiation, X radiation, nitrous acid, or heat (50 C). Effective dosages of these agents produce moderate killing of the wild type.
Physiology of
Escherichia coli
K-12 During Conjugation: Altered Recipient Cell Functions Associated with Lethal Zygosis
Authors: Skurray Ronald A. , Reeves Peter
Published: January 2020

The number of viable F
−
cells decreases when
Escherichia coli
recipient cells are mixed with an excess of Hfr cells. Evidence is presented showing that lethal zygosis was accompanied by changes in the physiology of the recipient cells, including (i) inhibition of deoxyribonucleic acid synthesis, (ii) inhibition of β-galactosidase induction, (iii) altered transport and accumulation of galactosides, and (iv) leakage of β-galactosidase into the supernatant fluid. The results are discussed in terms of possible conjugation-associated changes that, at high Hfr to F
−
ratios, lead to lethal zygosis.
Recognition of a Gene Involved in the Regulation of Nicotinamide Adenine Dinucleotide Biosynthesis
Authors: Tritz Gerald J. , Chandler Jerry Lr
Published: January 2020

Mutations affecting the biosynthesis of quinolinic acid, a precursor of nicotinamide adenine dinucleotide (NAD) in
Escherichia coli
K-12, are either near min 17 (
nadA
mutants) or near min 49 on the chromosome. These
nad
mutants all exhibit a phenotypic requirement for NAD or one of its immediate precursors. The mutants with lesions near min 49 can be separated into two groups based on in vitro complementation analysis. One group (
nadB
) exhibits complementation with
nadA
mutants, whereas the other group fails to do so. The latter group is tentatively designated
nadR
based on its regulation of the unlinked
nadA
gene. The
nadR
gene maps adjacent to
nadB
between
purI
and
tyrA
.
Isoleucine and Valine Metabolism in
Escherichia coli
XXII. A Pleiotropic Mutation Affecting Induction of Isomeroreductase Activity
Authors: Pledger W. J. , Umbarger H. E.
Published: January 2020

The
ilvC
gene product, acetohydroxy acid isomeroreductase, an enzyme essential for isoleucine and valine formation, is subject to substrate induction in
Escherichia coli
. We have isolated a mutant of
E. coli
K-12 with a mutation that renders the
ilvC
gene product noninducible by its substrates, the acetohydroxy acids. This mutation,
ilvY466
, has been shown to be in a previously undiscovered locus that lies between
ilvC
and
ilvO
. The
ilvY
product, upsilon, is thought to be a regulatory element involved in the induction of
ilvC
. We postulate the recognition site,
ilvQ
, or upsilon and suggest that it lies between
ilvC
and
ilvB
. A possible model, involving upsilon, in the positive control of isomeroreductase is presented. Pleiotropic effects of the
ilvY466
mutation have been recognized from changes in the end-product inhibition of threonine deaminase and of acetohydroxy acid synthetase. In addition, pleiotropic effects of this lesion on the regulation of threonine deaminase and the physical properties of threonine deaminase and acetohydroxy acid synthetase have been observed.
Cryptic Plasmids in a Minicell-Producing Strain of
Salmonella typhimurium
Authors: Sheehy Ronald J. , Allison David P. , Curtiss Roy
Published: January 2020

A minicell-producing strain of
Salmonella typhimurium
contains two cryptic plasmids. One has a molecular weight of 2.6 × 10
6
to 2.8 × 10
6
, is present in multiple copies per cell, and segregates into minicells. The other has a molecular weight of 130 × 10
6
, is present in few copies per cell, and probably does not segregate into minicells.
Dipicolinic Acid Location in Intact Spores of
Bacillus megaterium
Authors: Leanz Gary , Gilvarg Charles
Published: January 2020

Beta-attenuation analysis of intact spores of
Bacillus megaterium
containing tritium-labeled dipicolinic acid has shown that dipicolinic acid is located in the spore protoplast and not in the cortex.
Insensitivity of Bacteria to Proposed Antimetabolites of
d
-Alanyl-
d
-Alanine
Authors: Gale Glen R. , Smith Alayne B.
Published: January 2020

α-Aminoisobutyryl-
d
-alanine,
d
-alanyl-α-aminoisobutyric acid, and α-amino-isobutyryl-α-aminoisobutyric acid, proposed as antimetabolites of
d
-alanyl-
d
-alanine in bacterial cell wall synthesis, failed to inhibit bacterial growth.
d
-Serine Transport System in
Escherichia coli
K-12
Authors: Cosloy Sharon D.
Published: January 2020

The
d
-serine transport system in
Escherichia coli
K-12 was studied by use of a mutant unable to form
d
-serine deaminase, yet resistant to
d
-serine. The mutant is greatly impaired in its ability to accumulate
d
-serine,
d
-alanine, and glycine. Transport of
l
-alanine is partially affected but transport of
l
-serine is unaffected. The mutant is also resistant to
d
-cycloserine, indicating that
d
-serine is transported by the system responsible for uptake of
d
-cycloserine. The
d
-serine transport system is not inducible, but appears to be formed constitutively, as are the transport systems of most amino acids. The transport mutation appears to be multistep and maps to the right of
malB
on the
E. coli
linkage map.
Metabolism of
d
-Serine in
Escherichia coli
K-12: Mechanism of Growth Inhibition
Authors: Cosloy Sharon D. , McFall Elizabeth
Published: January 2020

Without significant killing,
d
-serine at concentrations greater than 50 μg/ml inhibits growth in minimal media of mutants of
Escherichia coli
K-12 unable to form
d
-serine deaminase. The mutants eventually recover at lower concentrations. There is no evidence of
d
-serine toxicity in rich media. Toxicity is partially reversed by
l
-serine.
d
-Serine does not interfere with
l
-serine activation, one-carbon metabolism, or (Cronan, personal communication) formation of phosphatidylserine. Pizer (personal communication) finds, however, that it is a powerful feedback inhibitor of the first enzyme of
l
-serine biosynthesis. In the presence of
l
-serine, the residual toxicity is largely and noncompetitively over come by pantothenate, indicating that
d
-serine inhibits growth by affecting two targets: pantothenate biosynthesis and
l
-serine biosynthesis.
l
-Serine causes transient growth inhibition in
E. coli
K-12. Contaminating
l
-serine in
d
-serine preparations contributes to the
d
-serine inhibitory response.
Cell Division and Deoxyribonucleic Acid Synthesis after a Nutritional Shift-Up of
Saccharomyces cerevisiae
Authors: Jacobson G. K. , Parks L. W.
Published: January 2020

Rates of cell division and deoxyribonucleic acid synthesis after shift-up with grande and mitchondrial deoxyribonucleic-acid-less petite yeasts were studied. The results indicate that simple eukaryotes behave as prokaryotes.
Influence of Magnesium Ions on Porosity of the
Bacillus megaterium
Cell Wall and Membrane
Authors: Scherrer René , Gerhardt Philipp
Published: January 2020

The presence of magnesium chloride (0.01 M) caused a relatively small but significant reduction in the equivalent porosity of the protoplast membrane, but not in that of the cell wall, in intact
Bacillus megaterium
cells.
Isolation of Deoxyribonucleic Acid Methylase Mutants of
Escherichia coli
K-12
Authors: Marinus M. G. , Morris N. Ronald
Published: January 2020

Fourteen deoxyribonucleic acid (DNA) and 10 ribonucleic acid (RNA) methylation mutants were isolated from
Escherichia coli
K-12 by examining the ability of nucleic acids prepared from clones of unselected mutagenized cells to accept methyl groups from wild-type crude extract. Eleven of the DNA methylation mutants were deficient in 5-methylcytosine (5-MeC) and were designated Dcm. Three DNA methylation mutants were deficient in N
6
-methyladenine (N
6
-MeA) and were designated Dam. Extracts of the mutants were tested for DNA-cytosine:
S
-adenosylmethionine and DNA-adenine:
S
-adenosylmethionine methyltransferase activities. With one exception, all of the mutants had reduced or absent activity. A representative Dcm mutation was located at 36 to 37 min and a representative Dam mutation was located in the 60-to 66-min region on the genetic map. The Dcm mutants had no obvious associated phenotypic abnormality. The Dam mutants were defective in their ability to restrict λ. None of the mutations had the effect of being lethal.
Restriction and Modification of Bacteriophage S2 in
Haemophilus influenzae
Authors: Gromkova Rosa , Bendler John , Goodgal Sol
Published: January 2020

The major conclusion from these studies is that variants of
Haemophilus influenzae
Rd which restrict and modify phage S2 are metastable and capable of giving rise to one another with high frequency. Nonrestrictive RdS cells segregate spontaneously to the restricting, modifying phenotype in about 5% of the progeny of a single clone. The restrictive cells derived from RdS revert to the nonrestrictive phenotype in 15 to 25% of the progeny of a single clone. These frequencies are not appreciably affected by treatment with acriflavine or ethidium bromide, compounds which affect plasmid stability, or by nitrosoguanidine, a powerful mutagen. The genetic locus for restriction and modification of bacteriophage S2 is found to have a chromosomal position between the biotin and proline loci. Restriction-modification of phage S2 has been shown to be a function of its deoxyribonucleic acid (DNA) in that transfection with S2 phage DNA or prophage DNA is subject to host restriction and modification. An enzyme preparation, which contains endodeoxyribonuclease but no appreciable exonuclease activity, from mutant
H. influenzae
com
−10
did not restrict phage S2·RdS DNA or prophage DNA transfecting activity, indicating that this endodeoxyribonuclease is not responsible for phage restriction. A new restriction enzyme isolated from
H. influenzae
Rd was found to be the major enzyme involved in the restriction of bacteriophage S2. The enzyme inactivated the transfecting activity of unmodified phage DNA but did not attack modified phage DNA. Unlike endodeoxyribonuclease R, this enzyme requires adenosine triphosphate and
S
-adenosylmethionine.
Bacterial Metabolism of 3-Hydroxy-3-Methylglutaric Acid
Authors: Ahmad Nafees , Siddiqi Majid
Published: January 2020

An organism belonging toPseudomonadaceaeand capable of utilizing 3-hydroxy-3-methylglutarate as sole carbon source has been isolated from soil. Whole-cell preparations catalyze the oxidation of acetoacetate, acetate, glyoxylate, and citric acid cycle intermediates. Cell-free extracts of 3-hydroxy-3-methylglutarate-grown cells show an adenosine triphosphate, coenzyme A (CoA), and Mg2+-dependent conversion of 3-hydroxy-3-methylglutarate to 3-hydroxy-3-methylglutaryl-CoA. Succinyl-CoA-generating system has no effect on the activation and catabolism of 3-hydroxy-3-methylglutarate.
Demonstration of Ribosomes in Mesosomes Associated with
Bacillus subtilis
Protoplasts
Authors: Matheson Audria , Yang Maria Kwong , Smith Richard P.
Published: January 2020

The physiological differences between
Bacillus subtilis
(ATCC 6633) cells derived from a glucose-salts-yeast extract (GSY) medium and those of cells from tryptose broth permitted the identification of variables in protoplasting environments which noticeably affected the clarity of mesosomal ribosomes. They were the sucrose and magnesium ion concentrations and the type of buffer used. The environment suitable for conversion of GSY cells to the protoplast state was a 0.02 M tris(hydroxymethyl)aminomethane-hydrochloride buffer, pH 7.2, containing 0.6 M sucrose and 0.03 M MgCl
2
. Branched mesosomal tubules and a unique organization of vesicles were detected in thin sections and in negative stains of the specimens. Ribosomes were demonstrable in the extruded structures associated with protoplasts that had been prepared according to four fixation schedules and embedded in either of two epoxy plastics. Adjustments in the fixation schedules improved the clarity of the large bodies of protoplast cytoplasm to a degree equivalent to that of their dangling appendages.
Conservation of
Salmonella typhimurium
Deoxyribonucleic Acid in Partially Diploid Hybrids of
Escherichia coli
Authors: Johnson E. M. , Craig William G. , Wohlhieter J. A. , Lazere Janet R. , Synenki R. M. , Baron L. S.
Published: January 2020

Partially diploid
Escherichia coli
K-12 hybrids recovered from mating with a
Salmonella typhimurium
Hfr strain were found to differ with respect to the manner in which they conserved the added
Salmonella
deoxyribonucleic acid (DNA). Five of the diploid hybrids examined appeared to maintain the
Salmonella
DNA as part of a functional F-merogenote; these hybrids were sensitive to the male-specific phage, R-17, responded as males to the female-specific phage, φII, and transferred their inherited
Salmonella
genetic markers at high frequency in conjugation experiments. Six diploid hybrids were observed which were not sensitive to R-17, and from which the added
Salmonella
DNA was not transmissible in conjugation tests; nevertheless, these hybrids responded as males to φII, and the
Salmonella
chromosomal fragments were conserved in them as parts of supercoiled, circular DNA elements. It was concluded that these circular DNA elements were defective F-merogenotes, unable to direct the synthesis of F-pili. Three diploid hybrids were found which were not sensitive to R-17, and which responded as females to φII; no circular DNA was found in them, and it was concluded that their conservation of the
Salmonella
genetic fragments was accomplished in some manner which did not involve association with F or assumption of the supercoiled circular configuration. Other partially diploid hybrids were observed which appeared similar to these latter three hybrids with regard to their conservation of the
Salmonella
DNA, but which also contained an infecting F-factor; in these hybrids, both genetic and molecular experiments indicated that the unstably conserved
Salmonella
DNA was not associated physically with the F-factor.
Specificity of the Tyrosine-Phenylalanine Transport System in
Bacillus subtilis
Authors: D'Ambrosio Steven M. , Glover George I. , Nelson Stephen O. , Jensen Roy A.
Published: January 2020

l
-Tyrosine and
l
-phenylalanine enter cells of
Bacillus subtilis
via a system of active transport that exhibits complex kinetic behavior. The specificity of the transport system was characterized both at low concentrations of transport substrate (where affinity for
l
-tyrosine or
l
-phenylalanine is high but capacity is low) and at high concentrations (where affinity is low but capacity is high). Specificity was not found to differ significantly as a function of either
l
-tyrosine or
l
-phenylalanine concentration. Kinetic analysis showed that the relationship between the uptake of
l
-phenylalanine and
l
-tyrosine is strictly competitive. Neither
l
-tyrosine nor
l
-phenylalanine uptake was competitively inhibited by other naturally occurring
l
-amino acids, indicating the importance of the phenyl side chain to uptake specificity. Hence, it is concluded that
l
-tyrosine and
l
-phenylalanine are transported by a common system that is specific for these two amino acids. The abilities of analogue derivatives of
l
-tyrosine and
l
-phenylalanine to inhibit the uptake of
l
-[
14
C]tyrosine and
l
-[
14
C]phenylalanine competitively were determined throughout a wide range of substrate and inhibitor concentrations. In this manner, the contributions of the side chain, the α-amino group and the carboxyl group to uptake specificity were established. It is concluded that the positively charged α-amino group contributes more significantly to uptake specificity than does the negatively charged carboxyl group. The recognition of a phenyl ring is an essential feature of specificity; other amino acids with aromatic side chains, such as the indole and imidazole rings of
l
-tryptophan and
l
-histidine, do not compete with
l
-tyrosine and
l
-phenylalanine for uptake. The presence of the
p
-hydroxy substitutent in the side chain (as in
l
-tyrosine) enhances the uptake of the aryl amino acid analogues investigated.
Accumulation of Methylglyoxal in a Mutant of
Escherichia coli
Constitutive for Gluconate Catabolism
Authors: Rekarte U. D. , Zwaig N. , Istúriz T.
Published: January 2020

A culture of a mutant of
Escherichia coli
, derepressed for gluconate catabolism, is killed by the addition of gluconate to the culture. The product responsible for this bactericidal effect was identified as methylglyoxal. Two types of mutants resistant to gluconate were isolated. One of them showed increased activity of glyoxalase I.
Hydroxamate Recognition During Iron Transport from Hydroxamate-Iron Chelates
Authors: Haydon A. H. , Davis W. B. , Arceneaux Jean E. L. , Byers B. R.
Published: January 2020

Kinetics of radioactive iron transport from three structurally different secondary hydroxamate-iron chelates (schizokinen-iron, produced by
Bacillus megaterium
ATCC 19213; Desferal-iron, produced by an actinomycete; and aerobactin-iron, produced by
Aerobacter aerogenes
62-1) revealed that
B. megaterium
SK11 (a mutant which cannot synthesize schizokinen) has a specific transport system for utilization of ferric hydroxamates with a recognition capacity based on the chemical structure of the hydroxamate. Both Desferal and schizokinen enhanced iron uptake in this organism; however, Desferal-iron delivered only one-sixth the level of iron incorporated from the schizokinen-iron chelate. Desferal-iron did not generate the rapid rates of iron transport noted with schizokinen-iron at elevated iron concentrations. Assays containing large excesses of either iron-free Desferal or iron-free schizokinen suggested that the iron-free hydroxamate may compete with the ferric hydroxamate for acceptance by the transport system although the system has greater affinity for the iron chelate. Aerobactin-iron did not stimulate iron uptake in
B. megaterium
SK11 and aerobactin inhibited growth of this organism, indicating that
B. megaterium
SK11 cannot efficiently process the aerobactin-iron chelate.
Studies on β-Galactoside Transport in a
Proteus mirabilis
Merodiploid Carrying an
Escherichia coli
Lactose Operon
Authors: Stubbs John , Horwitz Alan , Moses V.
Published: January 2020

Merodiploid derivatives bearing an F-linked
lac
operon (
i
+
,
o
+
,
z
+
,
y
+
,
a
+
) from
Escherichia coli
were prepared from a
Proteus mirabilis
strain unable to utilize lactose and from a
lac
deletion strain of
E. coli
. A suitable growth medium was found in which the episomal element in the
P. mirabilis
derivative was sufficiently stable to allow induction of the episome-borne
lac
operon and thus to permit a comparison of the activities and properties of
E. coli lac
products in the intracellular environments of
P. mirabilis
and
E. coli
. In both derivatives the episomal
lac
operon was shown to be repressed in the absence of inducer. Kinetics of induction with gratuitous inducer (isopropyl-1-thio-β-
d
-galactoside) were similar for both β-galactosidase activity (β-
d
-galactoside galactohydrolase, EC 3.4.1.23) and β-galactoside transport activity in both derivatives, although the ratio of galactoside transport to β-galactosidase activity was approximately 1.6-fold higher in the
E. coli
derivative. Comparison of β-galactosidase and M-protein (
lac y
gene product)-specific activities indicated coordinate expression of the induced
lac
operon in both derivatives. Quantitatively, the maximal β-galactosidase specific activity was two or three times higher for the
E. coli
derivative. A significant sodium azide inhibition (65% inhibition by 10 mM sodium azide) of lactose permease-mediated transport of
o
-nitrophenyl-β-galactoside from an outside region of high concentration to an inside region of very low concentration (“downhill transport”) was observed for the
P. mirabilis
derivative. Identical conditions for the
E. coli
derivative yielded only about 15% inhibition. Active transport of thiomethyl-β-galactoside was similar for both derivatives, the major difference being that active transport was more sensitive to azide poisoning in the
P. mirabilis
derivative. Preliminary examination of the thiomethyl-β-galactoside derivatives following active transport did not demonstrate the accumulation of a phosphorylated product in either strain but did reveal an unidentified derivative present in the
P. mirabilis
merodiploid extract which was not detectable in the
E. coli
merodiploid.
Methionine Limitation in
Escherichia coli
K-12 by Growth on the Sulfoxides of
d
-Methionine
Authors: Greene Ronald C.
Published: January 2020

The synthesis and resolution of the diastereoisomers of
d
-methionine sulfoxide in high yield is described. Growth of two methionine auxotrophs (strains HfrC and AB1932) on the
d
-methionine sulfoxides is slower than on
l
-methionine, and the resultant cells are markedly derepressed for three enzymes of the methionine regulon (cystathionine synthetase, cystathionase, and
S
-adenosyl-
l
-methionine synthetase). Strain HfrC grows more rapidly on the sulfoxides and shows less derepression than strain AB1932. Although growth on
d
-methionine-
d
-sulfoxide is much slower than on
d
-methionine-
l
-sulfoxide (two- to threefold increase in division times), cells grown on
d
-methionine-
l
-sulfoxide generally have higher enzyme activities. The sulfoxides of
d
-methionine appear to provide a useful supplement to obtain methionine-limited growth in
Escherichia coli
.
Regulation of Phospholipid Synthesis in
Escherichia coli
by Guanosine Tetraphosphate
Authors: Merlie John P. , Pizer Lewis I.
Published: January 2020

Phospholipid synthesis has been reported to be subject to stringent control in
Escherichia coli
. We present evidence that demonstrates a strict correlation between guanosine tetraphosphate accumulation and inhibition of phospholipid synthesis. In vivo experiments designed to examine the pattern of phospholipid labeling with
32
P-inorganic phosphate and
32
P-
sn
-glycerol-3-phosphate suggest that regulation must occur at the glycerol-3-phosphate acyltransferase step. Assay of phospholipid synthesis by cell-free extracts and semipurified preparations revealed that guanosine tetraphosphate inhibits at least two enzymes specific for the biosynthetic pathway,
sn
-glycerol-3-phosphate acyltransferase as well as
sn
-glycerol-3-phosphate phosphatidyl transferase. These findings provide a biochemical basis for the stringent control of lipid synthesis as well as regulation of steady-state levels of phospholipid in growing cells.
First Generation Synchrony of Isolated
Hyphomicrobium
Swarmer Populations
Authors: Moore Richard L. , Hirsch Peter
Published: January 2020

A method is described for obtaining synchronously growing swarmer cell populations of
Hyphomicrobium
sp. strain B-522. This was accomplished by isolating young swarmers from random cultures by centrifugation and filtration. Cell multiplication occurred during 38% of the growth cycle in populations synchronized in this manner. Observations were made of the changes in cellular morphology which occurred during the growth cycle. Of the 14.25 h required for the doubling in cell numbers, an average of 5 h passed before the swarmer cells began to develop their hyphae. This time varied over a range of 10 h. The time interval between the beginning of hyphal development and the beginning of bud formation was 3.5 to 4.5 h. The maturation of the first buds and their separation from the mother cells were completed in 5.5 h. The duration of these steps is compared to those measured previously in agar slide cultures.
Morphogenesis and Ultrastructure of
Geotrichum candidum
Septa
Authors: Hashimoto Tadayo , Morgan J. , Conti S. F.
Published: January 2020

The ultrastructure and mode of formation of septa of
Geotrichum candidum
were investigated by light and electron microscopy. The invaginations of the lateral membrane and wall appear to initiate at multiple points around the circumference of the cell; the immature septum subsequently assumes a cart-wheel shape, with branched spokes radiating from the center of the septum. Each face of the septum is covered with a membrane possessing hitherto undescribed structural differentiation; the membrane substructures are comprised of two central subunits encircled by 12 identical subunits. The diameter of the entire 12 plus 2 structure is 24 to 25 nm, and the diameter of each individual subunit is approximately 4 nm. The maturation of the septum appears to occur by further deposition of material along the branched skeletal regions. Numerous small openings (micropores), formed as a result of incomplete deposition, ultimately give rise to plasmodesmata. During arthrospore formation, the plasmodesmal canals and associated micropores are occluded by electron-dense materials, rendering each segment of the hyphae completely independent of the rest of the hyphae.
Effect of Lysozyme Treatment on Cell Wall Ultrastructure in
Sarcina flava
Authors: Hunter M. I. S. , Muir D. D. M. , Thirkell D.
Published: January 2020

Treatment of
Sarcina flava
NCTC 7503 cells with lysozyme resulted in incomplete removal of the cell wall and imparted a layered appearance to it.
Enzymatic Defects in Three Genetic Classes of Serine-Requiring Mutants of
Bacillus pumilus
Authors: Lovett Paul S. , Pizer Lewis I. , Isom Harriet C.
Published: January 2020

Serine-requiring mutants of
Bacillus pumilus
NRRL B-3275 have been divided into three groups based on the position of the mutant loci on the linkage map of this organism. Representatives of each group were found deficient in enzymatic activities that constitute the phosphorylated pathway for serine biosynthesis. The evidence suggests that the genes coding for the enzymes of the phosphorylated pathway of serine biosynthesis are not clustered in
B. pumilus
.
Distribution of an Inducible Hexose-Phosphate Transport System Among Various Bacteria
Authors: Winkler Herbert H.
Published: January 2020

A transport system for glucose-6-phosphate, which is inducible by glucose-6-phosphate but not glucose or β-glycerophosphate, occurs in a variety of bacterial genera. The correlation of the fosfomycin sensitivity with the presence of the transport system is described.
Participation of Branched-Chain Amino Acid Analogues in Multivalent Repression
Authors: Wasmuth John J. , Umbarger H. E.
Published: January 2020

Two isoleucine analogues and two leucine analogues were examined for their ability to replace the natural amino acid preventing the accumulation of threonine deaminase-forming potential. The procedure used to study repression by the analogues distinguishes between true repression and the formation of inactive enzyme by the analogue in question. The leucine analogue 4-azaleucine was found to replace leucine in multivalent repression of threonine deaminase-forming potential in
Escherichia coli
but not in
Salmonella typhimurium
. Another leucine analogue, trifluoroleucine, was only partially effective in causing repression in either organism. The isoleucine analogue 4-azaisoleucine was ineffective in replacing isoleucine in repression. In contrast, 4-thiaisoleucine effectively replaced isoleucine in the repression of threonine deaminase-forming potential in
S. typhimurium
and
E. coli
.
Enzymes of the Tryptophan Pathway in Three
Bacillus
Species
Authors: Hoch Sallie O'Neil , Crawford Irving P.
Published: January 2020

The tryptophan synthetic pathway was characterized in three species of
Bacillus, B. subtilis, B. pumilus
, and
B. alvei
. They share the common features of a pathway which is subject to tryptophan repression, contains no unexpected complexes among the five enzymes, exhibits dissociable anthranilate synthase enzymes which do not require phosphoribosyl transferase for amidetransfer activity, contains separate indoleglycerol phosphate synthase and phosphoribosylanthranilate isomerase enzymes, and contains similar tryptophan synthetase multimers. In looking at these characteristics in detail however, differences among the three species became apparent, as, for example, in the complementation observed between the α and β
2
components of tryptophan synthetase, and the dissociation patterns of the large and small components of anthranilate synthase. The results demonstrate some pitfalls in attempting to compare multimeric enzymes in crude extracts from different organisms.
Defined Physiological Conditions for the Induction of the L-Form of
Neisseria gonorrhoeae
Authors: Bacigalupi Barbara A. , Lawson John W.
Published: January 2020

Defined conditions are described which allowed luxuriant growth over continuous subculture of strains of
Neisseria gonorrhoeae
in broth and on agar. Growth was equal to or surpassed that observed in Mueller-Hinton broth or on Mueller-Hinton blood agar. The final medium adopted consisted of medium 199 and a supplemental mixture of cysteine, glucose, and various salts. Addition of sodium bicarbonate or CO
2
enrichment was not required. For solidification, only agarose allowed growth of all strains; glutamic acid stimulated growth of two strains but was inhibitory for a third. The addition of 8% polyvinylpyrrolidone (PVP), 2% purified albumin, and penicillin resulted in induction of all three strains to the L-form with frequencies up to 0.3%. At present no induction to the L-form has been achieved in the absence of albumin. Various lots of PVP proved toxic in the defined medium, and extensive dialysis was required for good growth and L-form induction. Substitution of PVP with sucrose indicated a sucrose toxicity for the parental gonococcus even on the addition of albumin. L-form induction did occur on sucrose L-medium but at significantly lower frequencies. The colonies appeared 1 week later than those on PVP L-medium but at significantly lower frequencies. The colonies appeared 1 week later than those on PVP L-medium and remained very small and poorly developed.
Outer Penetration Barrier of
Escherichia coli
K-12: Kinetics of the Uptake of Gentian Violet by Wild Type and Envelope Mutants
Authors: Gustafsson Petter , Nordström Kurt , Normark Staffan
Published: January 2020

Wild-type strains of
Escherichia coli
K-12 adsorb gentian violet to the cell surface, but the dye is not transported into the cytoplasm. However, when some mutants that have an altered outer membrane are exposed to gentian violet, the dye is also found in the ribosomal fraction. The transport into the cytoplasm is inhibited at 0 C and requires that the concentration of gentian violet exceeds a threshold value. The initial rate of uptake as well as the amount of gentian violet found in the cytoplasm increases with the concentration of the dye in the medium. The rate of transport of the dye into the cytoplasm is much lower for stationary mutant cells than for exponentially growing cells. The rate of uptake into the cytoplasm increases with increasing deficiency of carbohydrate in the lipopolysaccharide (carbohydrate content
lpsB
>
lpsA
>
galU
). However, other components are also responsible for the barrier since an
envA
mutant which is not altered in the lipopolysaccharide carbohydrates show an extremely rapid uptake of the dye. The rate of uptake for the
envA
mutant was the highest found and the same as that of spheroplasts. Growth in the presence of agents affecting the murein sacculus, e.g., lysozyme and sublethal concentrations of penicillin, increased the rate of uptake of gentian violet. Brief treatments with tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetic acid drastically impaired the barrier function. Inhibition of protein synthesis by chloramphenicol also opened the barrier to gentian violet. In conclusion, the outer part of the bacterial envelope is a penetration barrier for gentian violet and probably also for other substances. The lipopolysaccharide, the murein and also other components are important for the function of this barrier. Resistance to gentian violet was found to be inversely correlated to the rate of penetration of the dye into the cytoplasm.
Integration Efficiencies of Spontaneous Mutant Alleles of
amiA
Locus in Pneumococcal Transformation
Authors: Tiraby Gérard , Sicard Michel A.
Published: January 2020

The distribution of integration efficiencies of independent mutations spontaneously occurring in the
amiA
locus was determined in two strains of pneumococcus. Strain Cl
3
integrates genetic markers with different efficiencies during transformation, whereas strain 401, isogenic with strain Cl
3
, does not discriminate between markers and integrates all markers with the same high efficiency. The discriminating strain Cl
3
gives rise to spontaneous mutations in the locus
amiA
, which fall into four classes with respect to their individual integration efficiencies. Mutations with a low efficiency of integration are equal in number to mutations with a high efficiency. Mutations from the two other classes corresponding to intermediate and very high efficiencies are about five times less frequent. The same four classes were also found among
amiA
mutants spontaneously occurring in strain 401. However, the two distributions of integration efficiencies of
amiA
mutants arisen either in strain Cl
3
or strain 401 are significantly different. The number of spontaneous
amiA
mutants, estimated by two methods, was found to be higher in strain 401 than in strain Cl
3
. The increase of the mutation rate in strain 401 could be accounted for by the excess of mutations falling in the two less-efficient classes observed in this strain. The discriminating process which acts during transformation presumably also intervenes in the appearance of spontaneous mutations.
Reversibility of the Specific Adsorption of Colicin E2-P9 to Cells of Colicin-Sensitive Strains of
Escherichia coli
Authors: Shannon R. , Hedges A. J.
Published: January 2020

The adsorption of colicin E2-P9 to its specific receptors on cells of sensitive strains of
Escherichia coli
is reversible under normal experimental conditions. At temperatures above 20 C, colicin may desorb from one cell and be readsorbed by a second with potentially lethal consequences. However, desorption of colicin seems unable to rescue a cell once it has received a lethal dose. These findings have implications both for the nature and types of specific receptors, and for the assay of colicin by the survivor count (lethal unit) methods.