bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of the Forms of Vitamin B
6
Present in the Culture Media of “Vitamin B
6
Control” Mutants
Authors: Dempsey Walter B. , Arcement Larry J.
Published: January 2020

An
Escherichia coli
mutant resistant to isoniazid (WG497) contained 0.6 μmole of extracellular pyridoxamine and pyridoxamine phosphate in the early stationary phase. A suppressed lysine mutant (AT1024) contained 1.4 μmoles of pyridoxal phosphate under the same conditions. The internal concentration of vitamin B
6
was one-half of normal for AT1024 and increased fivefold for WG497.
Effects of Coumarin, Thiopurines, and Pyronin Y on Amplification of Phleomycin-Induced Death and Deoxyribonucleic Acid Breakdown in
Escherichia coli
Authors: Grigg G. W. , Edwards Merilyn J. , Brown D. J.
Published: January 2020

Phleomycin (≤2 μg/ml) induces neither deoxyribonucleic acid (DNA) breakdown nor cell death in stationary-phase
Escherichia coli
B cells, but the addition of 8 m
m
caffeine immediately initiates these changes in the same way as increasing the phleomycin concentration 10-fold. This phenomenon is termed “amplification” (6). Pyronin Y, a number of nontoxic thio- and mercaptopurines (of which the most active were 6,7- and 6,9-dimethyl-2-methylthiopurine), and coumarin have been found to be considerably more efficient amplifiers of phleomycin activity than caffeine. Thus 2 m
m
6,7- and 6,9-dimethyl-2-methylthiopurine, 0.16 m
m
pyronin, and 4 m
m
coumarin killed 10 to 100 times more phleomycin-treated bacteria within 2 hr than 8 m
m
caffeine. As with caffeine, amplification of cell death by these compounds was accompanied by degradation of DNA to acid-soluble fragments. A number of compounds including 2,6-dichloropurine, 6-hydroxy-2-methylthiopurine, α-naphthol, β-naphthol, naphthionic acid, and α-naphthol-4,8-disulphonic acid inhibited the action of phleomycin, if they were present in the cell suspension during phleomycin treatment, but some caused amplification if added subsequent to the phleomycin. Although no mutants resistant to ≥10 μg of phleomycin per ml were observed among 10
11
E. coli
B cells screened, such mutants occurred with a frequency of 10
−6
to 10
−7
among cultures resistant to 1 to 2 μg of phleomycin per ml. These double mutants were cross-resistant to phleomycin plus caffeine. The amplifying compounds, though structurally dissimilar, shared the common characteristic of binding selectively to denatured DNA as measured by equilibrium dialysis methods. The implications of these observations in supporting a model of phleomycin amplification proposed previously (6) and their utility in providing a logic for developing a new class of antibiotics are discussed.
Biosynthetic Precursors of Some Modified Nucleosides in the Transfer Ribonucleic Acid of
Mycoplasma mycoides
var.
capri
Authors: Walker R. T.
Published: January 2020

The ribosomal and transfer ribonucleic acid (tRNA) from
Mycoplasma mycoides
var.
capri
, grown in a medium containing uridine-(
14
C)-5′-triphosphate and cytidine-(

5-
3
H

)-5′-triphosphate, were isolated and separated. The uridine in both species of RNA was shown to contain
14
C and the cytidine to contain both
3
H and
14
C. Comparison of the labeling of 4-thiouridine and pseudouridine, obtained from an enzymatic digest of the RNA, indicates that their biosynthetic precursor is uridine, not cytidine. It is probable that ribothymidine and dihydrouridine have the same derivation.
Genetic Mapping of Genes Concerned with Glutamyl Polypeptide Production by
Bacillus licheniformis
and a Study of Their Relationship to the Development of Competence for Transformation
Authors: McCuen R. W. , Thorne C. B.
Published: January 2020

By transduction with SP-15, we have mapped some of the genetic sites involved in glutamyl polypeptide (Pep) production by
Bacillus licheniformis
9945A. Eleven peptide mutations were assigned to group 1 which lies between the
gly-42
and
his-6
markers. Three other mutations were assigned to group 2 which lies between the
ade-2
and
str-1
sites. A series of 28 additional Pep
−
mutants did not belong to either group 1 or 2; the chromosomal location of those peptide mutations is unknown. All three mutants of group 2 were highly transformable, but only two of group 1 transformed well under the conditions employed. Knowing the chromosomal markers that were linked to peptide mutations made it possible to investigate the effect peptide mutations might have on the development of competence for transformation. Nontransformable organisms were rendered transformable upon the introduction, by transduction, of Pep
−
mutations from transformable strains. These results supported the conclusion that the ability of cells to develop competence for transformation when grown under appropriate conditions was related to the physiological effects of particular peptide mutations.
Isolation and Characterization of a Phosphatidylethanolamine-Deficient Mutant of
Bacillus subtilis
Authors: Beebe James L.
Published: January 2020

A mutant of
Bacillus subtilis
ATCC 6051 deficient in phosphatidylethanolamine, an important membrane lipid, was isolated by a combination of nitrosoguanidine mutagenesis and penicillin concentration of auxotrophs employing phosphatidylethanolamine as a supplement. The mutant was compared to the parent strain with regard to lipid composition, growth, osmotic fragility, and staining character and differed substantially in each category. In addition to scant amounts of phosphatidylethanolamine, the mutant contained phosphatidylglycerol, cardiolipin, lysyl phosphatidylglycerol, and diglucosyldiglyceride, though in amounts differing from those found in the parent strain. The mutant was unable to grow appreciably on synthetic media, had enhanced osmotic fragility of protoplasts, and resisted decolorization in staining.
Molecular Sieving by theBacillus megateriumCell Wall and Protoplast
Authors: Scherrer Rene , Gerhardt Philipp
Published: January 2020

Passive permeabilities of the cell wall and protoplast ofBacillus megateriumstrain KM were characterized by use of 50 hydrophilic probing molecules (tritiated water, sugars, dextrans, glycols, and polyglycols) which varied widely in size. Weight per cent uptake values (Rw) were measured at diffusional equilibrium under conditions that negated the influences of adsorption or active transport. Plots ofRwfor intact cells as a function of number-average molecular weight (¯Mn) or Einstein-Stokes hydrodynamic radius (¯rES) of the solutes showed three phases: a protoplast uptake phase with a polydisperse exclusion threshold of¯Mn= 0.6 × 103to 1.1 × 103,¯rES= 0.6 to 1.1 nm; a cell wall uptake phase with a polydisperse exclusion threshold of¯Mn= 0.7 × 105to 1.2 × 105,¯rES≅ 8.3 nm; and a total exclusion phase. Isolated cell walls showed only the latter two phases. However, it became evident that the cell wall selectively passed only the smallest molecules in a heterodisperse polymer sample. When the molecular-weight distributions of polyglycol samples (¯Mn= 1,000, 1,450, and 3,350) were determined by analytical gel chromatography before and after uptake by intact cells or isolated cell walls, a quasi-monodisperse exclusion threshold was obtained corresponding toMn= 1,200,rES= 1.1 nm. The permeability of isolated protoplasts was assessed by the relative ability of solutes to effect osmotic stabilization. An indefinite exclusion threshold, evident even with monodisperse sugars, was attributed to lengthwise orientation of the penetrating rod-shaped molecules. Altogether, the best estimate of the limiting equivalent porosity of the protoplast was 0.4 to 0.6 nm in radius and of the cell wall, 1.1 nm.
Biochemical Characterization of a Mutant Isoleucyl-Transfer Ribonucleic Acid Synthetase from
Escherichia coli
K-12
Authors: Treiber Gerda , Iaccarino Maurizio
Published: January 2020

Isoleucyl-transfer ribonucleic acid (tRNA) synthetase [
l
-isoleucine: soluble RNA ligase (adenosine monophosphate), EC 6.1.1.5; IRS] was partially purified from
Escherichia coli
K-12 and from an
ileS
mutant that appears to be altered in IRS. The half-life of wild-type IRS, incubated at 60.5 C, is 69 min, whereas that of mutant IRS is 8 min. Mutant IRS shows about a 100-fold lower affinity than wild-type IRS for isoleucine,
dl
-valine, thiaisoleucine, and O-methyl-
dl
-threonine, both in the pyrophosphate exchange assay and in the assay of isoleucyl-tRNA formation. The affinity of the mutant enzyme for adenosine triphosphate in the assay of isoleucyl-tRNA formation is 15-fold lower than that of the wild-type enzyme. The affinity of mutant IRS for tRNA is not changed as compared with wild-type IRS. These data show that mutant IRS has an altered structure and clearly confirm that
ileS
is the structural gene for IRS.
Induction of Colicin Production by High Temperature or Inhibition of Protein Synthesis
Authors: Kennedy C. K.
Published: January 2020

Escherichia coli
K-12 colicinogenic for ColE1 yielded mutants that appeared to produce colicin at 43 C but not at 30 or 37. These mutants proved to have the mutation
recA
−
Further study revealed that both
recA
−
and
recA
+
bacteria, when carrying ColE1 or ColE2, produce more colicin during growth at higher temperatures or after brief exposure to temperatures beyond the growth range. Counts of lacunae demonstrated that the increase of colicin production is due to an increase in the number of cells that yield colicin. Heat treatment causes lacunae to increase by the same factor in
recA
+
and
recA
−
cells, although
recA
−
bacteria produce 500 times fewer lacunae than
recA
+
. Inhibition of protein synthesis, notably by chloramphenicol, also induces colicin production in as much as 90% of the cells after removal of inhibition (to permit colicin synthesis). Induction of colicin production by chloramphenicol requires that ribonucleic acid synthesis continue during the period of inhibition. These results are discussed in relation to the regulation of colicin production.
Regulation of Synthesis of the Aminoacyl-Transfer Ribonucleic Acid Synthetases for the Branched-Chain Amino Acids of
Escherichia coli
Authors: McGinnis E. , Williams L. S.
Published: January 2020

The regulation of synthesis of valyl-, leucyl-, and isoleucyl-transfer ribonucleic acid (tRNA) synthetases was examined in strains of
Escherichia coli
and
Salmonella typhimurium
. When valine and isoleucine were limiting growth, the rate of formation of valyl-tRNA synthetase was derepressed about sixfold; addition of these amino acids caused repression of synthesis of this enzyme. The rate of synthesis of the isoleucyl- and leucyl-tRNA synthetases was derepressed only during growth restriction by the cognate amino acid. Restoration of the respective amino acid to these derepressed cultures caused repression of synthesis of the aminoacyl-tRNA synthetase, despite the resumption of the wild-type growth rate.
Metabolism of
d
-Arabinose by
Aerobacter aerogenes
: Purification of the Isomerase

a
Authors: Oliver Eugene J. , Mortlock Robert P.
Published: January 2020

In
Aerobacter aerogenes
, the mutational event permitting the utilization of
d
-arabinose as a source of carbon and energy is a regulatory mutation resulting in the constitutive synthesis of certain enzymes of the
l
-fucose catabolic pathway.
l
-Fucose isomerase catalyzes the isomerization of
d
-arabinose to
d
-ribulose. This enzyme was purified to homogeneity as indicated by a single band in disc-gel electrophoretic columns and single peaks with column chromatography and ultracentrifugation from the wild-type PRL-R3 strain, induced with
l
-fucose and two constitutive mutants, 502 and 510. The ratios of the activities of this isomerase on
d
-arabinose and
l
-fucose remained constant throughout all purifications. The apparent
K
m
of the isomerase from the wild-type strain induced with
l
-fucose and from the constitutive mutant strains was 5.0 × 10
−2
m
for
l
-fucose and 1.5 × 10
−1
m
for
d
-arabinose. A strain 531 possessing an apparent alteration in the isomerase was isolated from the strain 502. This altered isomerase exhibited a lowered
K
m
for
d
-arabinose.
Influence of Metal Ions on the Formation of Mycobactin and Salicylic Acid in
Mycobacterium smegmatis
Grown in Static Culture
Authors: Ratledge C. , Hall M. J.
Published: January 2020

Mycobacterium smegmatis
was grown on trace-metal-free medium in static culture. Throughout the growth phase, the concentration of mycobactin increased continuously, reaching a maximum of about 30 to 40 μg of mycobactin/mg of cell dry weight after 6 days; the concentration of salicylic acid remained approximately constant at 1 to 2 μg of salicylic acid/μg of cell dry weight. Fe
2+
(or Fe
3+
), Zn
2+
, Mn
2+
, and Mg
2+
were all essential to a maximum formation of mycobactin. Optimum concentrations required were: Fe
2+
, about 1.8 μ
m
; Mn
2+
and Zn
2+
, about 0.5 μ
m
; and Mg
2+
, at least 0.17 m
m
. Higher levels of Fe
2+
(9 to 90 μ
m
) and Zn
2+
(2 to 7 μ
m
) repressed mycobactin to about half the maximum value. No other cation or anion apparently is required for mycobactin biosynthesis. Salicylic acid concentration increased about fourfold when iron was omitted from the medium, but this is not as great as the increase reported previously for this strain of
M. smegmatis
. Mycobactin formation in another strain of
M. smegmatis
, NCIB 8548, showed similar dependencies on Fe
2+
, Zn
2+
, and Mn
2+
. Maximum accumulation of mycobactin with this strain was 85 μg of mycobactin/mg of dry cell weight, under iron-deficient (1.8 μ
m
Fe
2+
) conditions.
Utilization of Glucose and the Effect of Organic Compounds on the Chemolithotroph
Thiobacillus ferrooxidans
Authors: Tabita Robert , Lundgren D. G.
Published: January 2020

The utilization of glucose by the chemolithotroph
Thiobacillus ferrooxidans
results in a repression of the ability to oxidize iron, the substrate for autotrophic growth. An assay with resting cells was used to measure iron oxidation rates. Concomitant with the decreased iron oxidation rates, the enzyme responsible for carbon dioxide fixation, ribulose diphosphate (RuDP) carboxylase, was also repressed. Maximum iron oxidation rates precede peak RuDP carboxylase levels, consistent with the role of these processes in autotrophic metabolism in nonrepressed cells. The degree of iron oxidation repression depends on the organic substrate supplied, as does the level of RuDP carboxylase. The uptake of glucose parallels an increase in synthesis of glucose-6-phosphate dehydrogenase and the accumulation in cells of poly-β-hydroxybutyrate. The organism is also capable of growing on glucose and other organic supplements in the absence of its inorganic energy source; growth rates depend on the organic substrate supplied.
Glucose-6-Phosphate Dehydrogenase from the Chemolithotroph
Thiobacillus ferrooxidans
Authors: Tabita Robert , Lundgren D. G.
Published: January 2020

Glucose-6-phosphate dehydrogenase was partially purified from both glucose-grown and iron-glucose-grown
Thiobacillus ferrooxidans
. The enzyme possesses a dual nucleotide specificity for either nicotinamide adenine dinucleotide phosphate (NADP) or nicotinamide adenine dinucleotide (NAD) and has a molecular weight of 110,000 as determined by gel electrophoresis. Evidence is presented that
T. ferrooxidans
glucose-6-phosphate dehydrogenase is identical when isolated from cells grown mixotrophically (iron-glucose grown) or cells grown heterotrophically (glucose-grown cells). The enzyme is activated by Mg
2+
, and to a lesser extent by low concentrations of Mn
2+
. Reduced NAD inhibits the enzyme from
T. ferrooxidans
. No deviation from normal Michaelis-Menten kinetics was observed in velocity versus substrate concentration experiments. Adenosine triphosphate exerted a profound inhibition of the enzyme; the effect was 10 times more pronounced in the presence of NAD as compared to NADP. The physiological significance of this inhibition is discussed.
Salmonella typhimurium
Mutants with Alternate Requirements for Vitamin B
6
or Isoleucine
Authors: Guirard Beverly M. , Ames Bruce N. , Snell Esmond E.
Published: January 2020

Several mutants of
Salmonella typhimurium
LT-2, isolated as auxotrophs for vitamin B
6
, grew without the added vitamin when supplied with either isoleucine, α-ketobutyrate, or α-keto-β-methylvalerate, but not with threonine or with other α-keto acids. When grown on minimal medium supplemented with isoleucine, these mutants synthesized vitamin B
6
in amounts comparable to wild-type cells; they thus appeared to contain a modified
l
-threonine dehydratase and to belong to genotype
ilvA
(threonine dehydratase) instead of
pdx
(pyridoxine). Direct assays confirmed this hypothesis. Wild-type cells (toluene-treated) showed approximately the same threonine dehydratase activity whether grown in the presence or absence of added pyridoxal-P; mutant cells approached the activity of wild-type cells only when they were grown with added vitamin B
6
and were assayed in the presence of pyridoxal-P. In cell-free extracts, the threonine dehydratase from mutant cells was cold labile and more labile to oxidative inactivation than the wild-type enzyme; furthermore, activation of the mutant apoenzyme required a 10- to 20-fold higher concentration of pyridoxal-P than was required for the wild-type apoenzyme. These results show that cultures which appear auxotrophic for a given vitamin may synthesize that vitamin in normal amounts, the exogenous requirement arising from impaired binding of the vitamin-derived coenzyme to a genetically altered apoenzyme dependent on that coenzyme. Inadequate nutritional data to support the genetic findings can lead to erroneous genotype classification for such mutants.
Regulation of Tyrosyl-Transfer Ribonucleic Acid Synthetase in
Bacillus subtilis
Authors: Dale Beverly A. , Nester Eugene W.
Published: January 2020

Derepression of tyrosyl-transfer ribonucleic acid synthetase in
Bacillus subtilis
was observed in strains grown with limiting tyrosine, but not in regulatory mutants derepressed in biosynthetic enzyme synthesis.
Extracellular Lipid of
Thiobacillus thiooxidans
Authors: Beebe James L. , Umbreit W. W.
Published: January 2020

The extracellular lipid of
Thiobacillus thiooxidans
is a heterogeneous mixture of phospholipid and neutral lipid, primarily free fatty acids.
Mechanism of Action of Rifampin on
Mycobacterium smegmatis
Authors: White R. J. , Lancini G. C. , Silvestri L. G.
Published: January 2020

Deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase (EC 2.7.7.6) isolated from a rifampin-sensitive strain of
Mycobacterium smegmatis
was 90% inhibited by 1 μg of rifampin per ml; enzyme from a rifampin-resistant mutant was not affected by this concentration of antibiotic. Inhibition of phenylalanine-
1
-
14
C
incorporation by rifampin in growing cultures was complete about 6 min after addition of antibiotic. Under the same conditions, uracil-
2
-
14
c
incorporated was blocked after 1.5 to 2 min. Rifampin kills
M. smegmatis
very slowly. When rifampin-inhibited cultures were transferred to a rifampin-free medium, there was a partial resumption of uracil-
2
-
14
C
incorporation, even in the presence of chloramphenicol. We conclude that a primary event in the inhibition of
M. smegmatis
by rifampin is the block of DNA-dependent RNA polymerase.
Isolation and Partial Characterization of Temperature-Sensitive
Escherichia coli
Mutants with Altered Leucyl- and Seryl-Transfer Ribonucleic Acid Synthetases
Authors: Low B. , Gates F. , Goldstein T. , Söll D.
Published: January 2020

Two temperature-sensitive mutants of
Escherichia coli
have been found in which the conditional growth is a result of a thermosensitive leucyl-transfer ribonucleic acid (tRNA) synthetase and seryl-tRNA synthetase, respectively. The corresponding genetic loci,
leuS
and
serS
, cotransduce with
lip
and
serC
, respectively. As a result of the mutationally altered leucyl-tRNA synthetase, some leucine-, valine-, and isoleucine-forming enzymes were derepressed. Thus, leucyl-tRNA synthetase is involved in the repression of the enzymes needed for the synthesis of branched-chain amino acids.
Structural Changes During Lysis of a Psychrophilic Marine Bacterium
Authors: D'Aoust J. Y. , Kushner D. J.
Published: January 2020

The marine psychrophile, a red, gram-negative motile rod with a single polar flagellum, is stable when suspended in 0.1
m
Mg
2+
plus 0.5
m
NaCl at 0 C and neutral
p
H but lyses if the salt composition of the medium is changed, the temperature raised above 20 C, or the
p
H lowered. Lysis is accompanied by a fall in turbidity, a release of ultraviolet-absorbing substances, and a loss of deoxyribonucleic acid and ribonucleic acid. Ultrastructural changes accompanying lysis were studied. Thin sections of cells fixed while intact showed a triple-layered cell wall and cytoplasmic membrane, each 6.0 to 7.5 nm thick. Mesosomes were also observed. Either Na
+
or Mg
2+
could maintain wall integrity, whereas Mg
2+
was needed for membrane integrity. In distilled water, lysis was very extensive, and much material was released as wall fragments and as vesicles which probably came from the wall and cytoplasmic membrane. Lysis at 37 C resulted in degradation of the wall and liberation of wall fragments. The cell membrane was rarely observed as a triple-layered structure in such temperature-lysed cells. After lysis at
p
H 5.0, the cell wall was distorted, and only a suggestion of the cell membrane remained. Replicas showed that this organism had a matted surface which was distorted under different conditions of lysis.
Evidence That the Majority of Leucine Transfer Ribonucleic Acid Is Not Involved in Repression in
Salmonella typhimurium
Authors: Freundlich Martin , Trela John , Peng Willow
Published: January 2020

Leucine transfer ribonucleic acid (tRNA) was almost fully charged, and the isoleucine-valine and leucine enzymes remained derepressed when trifluoroleucine was added to a leucine auxotroph. High levels of charged leucine tRNA and derepression were also found in a leucyl-tRNA synthetase mutant.
Nucleotide Pools in Growing
Chromatium
Strain D
Authors: Miović Margaret L. , Gibson Jane
Published: January 2020

The growth rate of
Chromatium
at limiting light intensities is not regulated by either the ratio or the concentration of nucleoside phosphates, although transient changes in these parameters may affect the activities of biosynthetic enzymes.
Enzyme Alterations in Tyrosine and Phenylalanine Auxotrophs of
Salmonella typhimurium
Authors: Dayan J. , Sprinson D. B.
Published: January 2020

The enzyme activities specified by the
tyrA
and
pheA
genes were studied in wildtype strain
Salmonella typhimurium
and in phenylalanine and tyrosine auxotrophs. As in
Aerobacter aerogenes
and
Escherichia coli
, the wild-type enzymes of
Salmonella
catalyze two consecutive reactions: chorismate → prephenate → 4-hydroxy-phenylpyruvate (
tyrA
), and chorismate → prephenate → phenylpyruvate (
pheA
). A group of
tyrA
mutants capable of interallelic complementation had altered enzymes which retained chorismate mutase T activity but lacked prephenate dehydrogenase. Similarly,
pheA
mutants (in which interallelic complementation does not occur) had one group with altered enzymes which retained chorismate mutase P but lacked prephenate dehydratase. Tyrosine and phenylalanine auxotrophs outside of these categories showed loss of both activities of their respective bifunctional enzyme.
TyrA
mutants which had mutase T were considerably derepressed in this activity by tyrosine starvation and consequently excreted prephenate. A new and specific procedure was developed for assaying prephenate dehydrogenase activity.
Developmental Regulation of Amylase Activity During Fruiting of
Schizophyllum commune
Authors: Schwalb Marvin N.
Published: January 2020

During the development of fruit bodies of
Schizophyllum commune
there is a minimum 10- to 15-fold increase in amylase activity. There is little or no activity in homokaryons or dikaryons. The activity is found early after the onset of morphogenesis and increases until the fruit bodies are mature. Inhibition studies with CO
2
indicate that the activity is directly associated with fruiting, as a change from fruiting to vegetative growth of the dikaryotic mycelium leads to a loss in activity, whereas the already formed fruit bodies show no loss. The activity is unaffected by the level of glucose in the medium. Evidence is presented, based on the mode of starch degradation and on yield and inhibition studies, that the enzyme is a glucoamylase.
Properties of an R Factor from
Pseudomonas aeruginosa
Authors: Datta Naomi , Hedges R. W. , Shaw Elizabeth J. , Sykes R. B. , Richmond M. H.
Published: January 2020

An R factor from
Pseudomonas aeruginosa
, which confers resistance to penicillins, kanamycin, and tetracycline, was studied in
Escherichia coli
K-12. The R factor could coexist with F-like or I-like plasmids and therefore constituted a novel compatibility group. The R factor was transferable from
E. coli
to bacterial genera outside the
Enterobacteriaceae (Pseudomonas
and members of the
Rhizobiaceae
) to which transfer of F-like and I-like plasmids could not be demonstrated.
Division Mutants of
Bacillus subtilis:
Isolation and PBS1 Transduction of Division-Specific Markers
Authors: Van Alstyne D. , Simon M. I.
Published: January 2020

A procedure for the isolation of
Bacillus subtilis
mutants that appear to be defective in septum synthesis has been described. Fourteen mutants isolated with this technique were found to be located at four distinct loci on the
B. subtilis
chromosome. These have been designated
divA, divB, divC
, and
divD
. The four mutants in the
divA
group synthesize septa; however, they do so with a high frequency of error resulting in minicell production. Mapping data were obtained by scoring cotransduction frequencies using PBS1-transducing lysates. Thus, some of the genes apparently involved in septum synthesis and their order on the genome have been established. The results of a study by electron microscope of some of the mutants is also presented.
Recognition of an
Escherichia
Operator by a
Salmonella
Repressor
Authors: Brandriss Marjorie C. , Calvo J. M.
Published: January 2020

Escherichia coli leu
+
episomes were transferred to
Salmonella typhimurium
. The levels of two leucine-forming enzymes were normal (low) in the resulting merodiploids, suggesting that the putative
Samonella
leucine repressor recognizes the
Escherichia
leucine operator.
Restoration of Deoxycholate-Disrupted Membrane Oxidases of
Micrococcus lysodeikticus
Authors: Eisenberg R. C.
Published: January 2020

Membrane-associated
l
-malate and reduced nicotinamide adenine dinucleotide (NADH) oxidase complexes of
Micrococcus lysodeikticus
were inactivated with deoxycholate. Reactivation of NADH oxidase by addition of Mg
2+
occurred in these detergent-membrane mixtures, but reactivation of
l
-malate oxidase did not occur in the presence of deoxycholate. Removal of detergent by gel filtration allowed Mg
2+
-dependent restoration of both
l
-malate and NADH oxidases. Maximal NADH and
l
-malate oxidase restoration required 10 min and 40 min, respectively, at 30 m
m
MgSO
4
. Maximal restoration of both oxidases required at least 12 m
m
MgSO
4
in an incubation period of 1 hr. Reduced-minus-oxidized difference spectra of Mg
2+
-restored membrane oxidases showed participation of cytochromes
b, c
, and
a
when either
l
-malate or NADH served as reductant; addition of dithionite did not increase the α- and β-region absorbancy maxima of these hemoproteins when restored membranes were first reduced with the physiological substrates
l
-malate or NADH. Not all divalent cations tested were equally effective for reactivation of both oxidases.
l
-Malate oxidase was restored by both Mn
2+
and Ca
2+
. NADH oxidase was not activated by Mn
2+
and only slightly stimulated by Ca
2+
. Separation of deoxycholate-disrupted membranes (detergent removed) into soluble and particulate fractions showed that both fractions were required for Mg
2+
-dependent oxidase activities. Electron micrographs indicated conditions of detergent treatment did not destroy the vesicular nature of protoplast ghost membranes.
Purification and Characterization of Colicin D
Authors: Timmis K.
Published: January 2020

Colicin D-CA23, obtained by sonic treatment of mitomycin C-induced cells ofEscherichia coliK-12 W1485 (colD), was purified by ammonium sulfate precipitation, gel filtration on Sephadex G200, ion-exchange chromatography on diethylaminoethyl cellulose, and isoelectrofocusing. Polyacrylamide-gel electrophoresis, sedimentation velocity analysis, and antigenic analysis indicated that the preparation was homogeneous. Colicin D is composed entirely of amino acids and hence is a simple protein uncomplexed with lipid or lipopolysaccharide. It contains six residues of cysteine per molecule. The molecular weight of colicin D is approximately 92,000, as determined by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis and gel filtration on Sephadex G200. Its sedimentation coefficient is 4.41S. The behavior of colicin D in solutions of sodium dodecyl sulfate and 2-mercaptoethanol indicates that it does not consist of subunits and exists as a single polypeptide chain. Its high molecular weight and presence of six cysteine residues per molecule distinguish colicin D from all colicins previously described. Although colicins D and E3 have similar modes of action, their gross molecular properties are entirely different.
Regulation of Orotidylic Acid Pyrophosphorylase in
Saccharomyces cerevisiae
Authors: Jund R. , Lacroute F.
Published: January 2020

Yeast mutants deficient in orotidine-5′-phosphate (OMP) pyrophosphorylase activity have been obtained. The gene encoding this enzyme is unlinked to the four pyrimidine genes previously described. The specific activity of OMP pyrophosphorylase remains constant under all of the physiological conditions used to repress, to derepress, or to induce pyrimidine biosynthesis. This enzyme appears, therefore, to escape the scheme of regulation by mixed repression and induction controlling the other enzymes of the pyrimidine pathway.
Significance of Altered Carbon Flow in Aromatic Amino Acid Synthesis: an Approach to the Isolation of Regulatory Mutants in
Pseudomonas aeruginosa
Authors: Calhoun Davis H. , Jensen Roy A.
Published: January 2020

Pseudomonas aeruginosa
displays a native resistance to a variety of inhibitory compounds, including many analogues of amino acids, purines, and pyrimidines. Therefore, it has been difficult to isolate analogue-resistant regulatory mutants which have been so valuable in other microbial species for the study of enzyme control mechanisms and for the study of amino acid transport and its regulation. However, we have found that increased sensitivity to growth inhibition by analogues can be demonstrated by manipulation of the nutritional environment. When
P. aeruginosa
is grown with fructose as the nutritional source of carbon and energy, the cells become sensitive to growth inhibition by β-2-thienylalanine and
p
-amino-phenylalanine, analogues of phenylalanine and tyrosine, respectively. Thus, mutants were isolated which are resistant to growth inhibition by β-2-thienylalanine and
p
-amino-phenylalanine when fructose is the carbon source, and many of the β-2-thienylalanine-resistant mutants overproduce phenylalanine. Several lines of evidence suggest that the increased sensitivity to growth inhibition by analogues of phenylalanine and tyrosine reflects a decreased rate of synthesis of aromatic amino acids or their precursors when fructose is the carbon source. This general approach promises to be valuable in the study of regulatory phenomena in microorganisms which, like
P. aeruginosa
, are naturally resistant to many metabolite analogues.
Effect of Monovalent Cations on the Malic Enzyme from the Extreme Halophile,
Halobacterium cutirubrum
Authors: Cazzulo Juan José , Vidal María Cristina
Published: January 2020

The malic enzyme from
Halobacterium cutirubrum
requires monovalent cations for both activation and stabilization. NaCl, the best stabilizer, is ineffective as activator; NH
4
Cl, the best activator, is a poor stabilizer. These results support the idea that the roles of salts in both processes are different.
Similarities Between
Hyphomicrobium
and
Nitrobacter
with Respect to Fatty Acids
Authors: Auran Thomas B. , Schmidt E. L.
Published: January 2020

Vaccenic acid (11-18:1) accounted for 92% of the fatty acids in the extractable lipids of log-phase
Nitrobacter
and
Hyphomicrobium
. During the stationary phase, both genera formed a 19-carbon cyclopropane fatty acid which increased in proportion to a decrease in the amount of vaccenic acid.
Amylolytic Isoenzymes of
Thermoactinomyces vulgaris
Authors: Allen Martin J. , Hartman Paul A.
Published: January 2020

Thermoactinomyces vulgaris
strain 5 produced two electrophoretically different α-amylases. Precipitation with ammonium sulfate and acetone did not alter the electrophoretic mobilities of either amylase isoenzyme. Patterns of the hydrolysis products of amylose by the two amylase isoenzymes were essentially identical.
Genetic and Biochemical Properties of Thymidine-Dependent Mutants of Pneumococcus
Authors: Friedman Linda R. , Ravin Arnold W.
Published: January 2020

Independently isolated thymidine-dependent strains were shown to be defective in thymidylate synthetase and mutated at separable but closely linked sites.
Replication of the R Factor R
ts
1 in
Proteus mirabilis
Authors: Terawaki Yoshiro , Rownd R.
Published: January 2020

The replication of the R factor R
ts
1 in
Proteus mirabilis
was examined by using the technique of CsCl density-gradient centrifugation. The proportion of R
ts
1 deoxyribonucleic acid (DNA) relative to the host chromosomal DNA (% R-DNA) was 7% in both exponential and stationary growth phases in Penassay Broth and supplemented M9 minimal medium at 30 C. The chromosomal DNA content per cell varied over a threefold range in the different growth media. In agreement with previous genetic observations, the replication of R
ts
1 was found to be temperature-sensitive and R
ts
1 DNA was diluted from the cells during exponential growth at 42 C.
14
N-
15
N medium transfer experiments have shown that individual copies of R
ts
1 are selected at random for replication during the duplication of the multicopy episome pool.
Identification of Competence-Repressing Factors During Log-Phase Growth of
Haemophilus influenzae
Authors: Miller Donald H. , Huang P. C.
Published: January 2020

Metabolic factors that suppress development of competence in
Haemophilus influenzae
during growth in the synthetic medium MI
c
have been identified. These include inosine, nicotinamide adenine dinucleotide, glycerol, and uracil. It is also possible to initiate competence in the presence of these substances if the oxygen tension in the culture is temporarily reduced.
Lipids of a T Strain of
Mycoplasma
Authors: Romano Nino , Smith Paul F. , Mayberry William R.
Published: January 2020

Cholesterol, free fatty acids, and phosphatidic acid are the predominant lipids of a T strain of
Mycoplasma
. The remaining neutral lipids are composed of cholesteryl esters, triglycerides, and diglycerides. Three glucose-containing glycolipids are present in trace amounts. In addition to phosphatidic acid, the phospholipids are comprised of phosphatidyl glycerol, diphosphatidyl glycerol, and phosphatidyl ethanolamine. Another polar lipid was found to be ninhydrin-positive and phosphate-free. It appears to be a diamino hydroxy compound containing adjacent fatty acid ester and
N
-acyl groups.
Effect of Glycerol Deprivation on the Phospholipid Metabolism of a Glycerol Auxotroph of
Staphylococcus aureus
Authors: Ray Paul H. , White David C.
Published: January 2020

A study of the effects of glycerol deprivation on the content and metabolism of the phospholipids of a glycerol auxotroph of
Staphylococcus aureus
showed that (i) there was an increase in the proportions of lysylphosphatidylglycerol (LPB) and a concomitant decrease in the proportion of phosphatidylglycerol. The total phospholipid content per sample and the proportion of cardiolipin did not change, but the phosphatidic acid increased transiently and then fell to pretreatment levels. (ii) The loss of
32
P from the lipids during the chase in a pulse-chase experiment was essentially the same in phosphatidylglycerol, cardiolipin, and phosphatidic acid during glycerol deprivation or growth in the presence of glycerol. LPG lost half the radioactivity in slightly more than two doubling times when grown with glycerol. In the absence of glycerol,
32
P accumulated in LPG for about 20 min and then stopped, after which time there was no apparent turnover. (iii) During glycerol deprivation, the initial
32
P incorporation decreased sixfold compared to that of the control with glycerol. The initial incorporation into LPG decreased only 2.5-fold, whereas that of PG decreased 45-fold. (iv) During glycerol deprivation, the free fatty acid content increased from 1.2 to 12.5% of the total extractable fatty acids and then slowly decreased. The increase was largely iso- and anti-iso-branched 21-carbon-atom fatty acids. In glycerol-supplemented cultures, the major fatty acids were branched 14- to 18-carbon fatty acids. The decrease in longer chain free fatty acids after 60 min represented their esterification into lipids. (v) During glycerol deprivation ribonucleic acid synthesis and cell growth continued for 40 min and protein synthesis continued for 90 min. Then synthesis and growth stopped. (vi) After the addition of glycerol to glycerol-deprived cells,
32
P and
14
C-glycerol were incorporated into the phospholipids without lag; ribonucleic acid, protein synthesis, and cell growth began after a 5- to 10-min lag at the pretreatment rate. The initial rate of lipid synthesis after the addition of glycerol was three times greater than the growth rate. This rapid rate continued for about 25 min until the lipid content and proportions of LPG and phosphatidylglycerol were restored.
Alternate Pathway for Isoleucine Biosynthesis in
Escherichia coli
Authors: Phillips A. T. , Nuss J. I. , Moosic J. , Foshay C.
Published: January 2020

A threonine dehydrataseless mutant of
Escherichia coli
, Crookes strain, was observed to grow on an acetate minimal medium without the usual requirement for isoleucine supplementation. Both the wild-type Crookes strain and a threonine auxotroph metabolized
l
-glutamate-
1
-
14
C
to
l
-isoleucine-
1
-
14
C
with no appreciable randomization, suggesting that a pathway for isoleucine formation from glutamate via β-methylaspartate, β-methyloxaloacetate, and α-ketobutyrate was possible in addition to the pathway from threonine and α-ketobutyrate. Crude cell-free extracts formed
14
C-β-methylaspartate from
14
C-glutamate, and the conversion of β-methylaspartate to α-ketobutyrate was also demonstrated, thus supporting the conclusion that glutamate can serve as a precursor of α-ketobutyrate (and isoleucine) without the necessary involvement of threonine as an intermediate.
Transformation of Chromosomal and Plasmid Characters in
Staphylococcus aureus
Authors: Lindberg Martin , Sjöström Jan-Eric , Johansson Thomas
Published: January 2020

Plasmid and probably also chromosomal characters have been genetically transformed in
Staphylococcus aureus
. Recipient cells show competence throughout the exponential growth phase with a maximum at early times.
Fine Structure of
Haemophilus vaginalis
Authors: Criswell B. Sue , Stenback Wayne A. , Black S. H. , Gardner Herman L.
Published: January 2020

Haemophilus vaginalis
594 has a trilaminar cell wall, ribosomes, a fibrillar nucleoid, and both convoluted and simple mesosome-like bodies. Polar bulbous enlargements of the cell and multiple cross wall formations may explain its pleomorphism.
Cell Wall Composition and Deoxyribonucleic Acid Similarities Among the Anaerobic Coryneforms, Classical Propionibacteria, and Strains ofArachnia propionica
Authors: Johnson J. L. , Cummins C. S.
Published: January 2020

Eighty strains of anaerobic coryneforms were compared with 29 strains of classical propionibacteria and 8 strains ofArachnia propionicaby cell wall analysis, deoxyribonucleic acid (DNA) base compositions, and nucleotide sequence similarities. The anaerobic coryneforms have DNA base compositions in the range of 58 to 64% guanine + cytosine (GC) and show at least three homology groups. The largest group corresponds to organisms identified asPropionibacterium acnesand shows about 50% homology to strains in theP. avidumhomology group. The third group,P. granulosum, shows low levels of similarities to the other two. All strains of anaerobic coryneforms have some combination of galactose, glucose, or mannose as cell wall sugars, and most have alanine (ala), glutamic acid (glu), glycine (gly), andl-α-ε-diaminopimelic acid (l-DAP) as amino acids of peptidoglycan. However, a few strains in theP. acnesandP. avidumhomology groups havemeso-DAP and minimal amounts of glycine. Two serological types, based on cell wall antigens, were found in theP. acneshomology group. One type had galactose, glucose, and mannose as cell wall sugars, the other glucose and mannose only. The classical propionibacteria have DNA base compositions in the range of 65 to 68% GC and show four homology groups which correspond closely to van Niel's classification as given in the 7th edition ofBergey's Manual. TheP. jenseniigroup showed about 50% homology to theP. thoeniigroup and about 30 to 35% to theP. acidi-propionicigroup. TheP. freudenreichiistrains showed a rather lower level of similarity (8 to 25%) to the other homology groups. Most of the strains of classical propionibacteria also have some combination of galactose, glucose, or mannose as cell wall sugars and ala, glu, gly, andl-DAP as peptidoglycan amino acids, butP. shermaniiandP. freudenreichiistrains, which form a single homology group, have galactose, mannose, and rhamnose as cell wall sugars and ala, glu, andmeso-DAP in their peptidoglycan. There is a rather low level of DNA homology (10 to 20%) between the anaerobic coryneforms and classical propionibacteria. However, the strains ofA. propionicawhich have a GC content of 64 to 65% and form a single homology group, show no homology to either of the other two major groups.
Induction of Cycloheximide-Resistant Mutants in
Saccharomyces cerevisiae
with
N
-Methyl-
N
′-Nitro-
N
-Nitrosoguanidine and ICR-170
Authors: Brusick David J.
Published: January 2020

N
-Methyl-
N
′-nitro-
N
-nitrosoguanidine (MNNG) induces cycloheximide-resistant mutations in
Saccharomyces cerevisiae
, but few, if any, resistant mutants are induced by the acridine mustard ICR-170. Cycloheximide sensitivity in yeast is associated with the ribosome, and treatment with the antibiotic at concentrations of 2 μg/ml results in complete inhibition of protein synthesis. Missense mutations induced by MNNG probably lead to the loss of cycloheximide binding sites on the ribosome, resulting in resistance to the antibiotic without altering the activity of the organelle in protein synthesis. ICR-170, however, induced primarily frameshift mutations that would alter ribosome structural integrity, resulting in cell death rather than resistance. ICR-170 and MNNG are both mutagenic in a system in which base-pair substitution and frameshift mutations can be detected. These results indicate that cycloheximide resistance in
S. cerevisiae
, like streptomycin and spectinomycin resistance in
Escherichia coli
, can be induced by base-pair substitution mutagens but not by frameshift mutagens such as ICR-170.
Ultrastructure of the Exosporium and Underlying Inclusions in Spores of
Bacillus megaterium
Strains
Authors: Beaman T. Cabrera , Pankratz H. Stuart , Gerhardt Philipp
Published: January 2020

Spores of selected strains of
Bacillus megaterium
were prepared by various methods and examined with the electron microscope. An exosporium like that of
B. cereus
, with a nap and basal layer, was found in spores of a
B. megaterium
strain that reportedly contains a capsule-like exosporium. The exosporium occasionally appeared to be doubled or have an apical opening. Pili-like filaments were discerned on the surface. Beneath the exosporium were found large deposits of planar inclusions, which in cross section appeared laminated and in surface views consisted of a patchwork of striated packets with a periodicity of ∼5 nm. The inclusions were usually attached to the exosporium, but in ultrastructure they differed from both the exosporium and coat. In two other strains of
B. megaterium
, one or two coats occurred but a typical exosporium was not present.
“Compartmentalization” of
Escherichia coli
Ribosomes and Ribonucleic Acid
Authors: Varricchio Frederick
Published: January 2020

Escherichia coli
spheroplasts lysed by Brij 58 and deoxycholate were separated into supernatant (S) and membrane fractions by low-speed centrifugation. The membrane fraction was further divided into that which was releasable by deoxyribonuclease (fraction D) and that which was not (M). In the presence of 10
−2
m
Mg
2+
, the S, D, and M fractions contained, respectively, 60, 20, and 20% of the total cellular ribonucleic acid (RNA). Ribosomal and transfer RNA (rRNA, tRNA) were found in each fraction. The M + D fraction RNA was labeled more by a pulse label. Incorporation of uracil into the D fraction continued only as long as the uptake of exogenous uracil, suggesting that this was a major primary site of RNA synthesis. From pulse-labeled cells, each fraction contained precursor rRNA, and there was a 10
S
RNA in the M fraction. Ninety per cent of the ribosomal subunits and the ribosomal precursor particles, 26 and 43
S
, were in the S fraction. Precursor RNA (17
S
) was found in the 26
S
precursor particles. The D fraction contained 38% of the polysomes (this does not consider polysomes, if any, of the M fraction) which were labeled four times as much as the supernatant polysomes by a 1-min pulse of uracil. These results are interpreted to mean that new RNA is associated with a cytoplasmic membrane-RNA polymerase-DNA complex.
Recombination of
Escherichia coli
Chromosomal Segments in
Salmonella typhosa
Authors: Johnson E. M. , Alexeichik J. A. , Baron L. S.
Published: January 2020

Approximately half of
Salmonella typhosa
hybrids resulting from mating with
Escherichia coli
Hfr donors inherit the selected donor marker by recombination, and the length of the
E. coli
chromosomal segment most frequently incorporated in these recombinants is between 1 and 2 min.
Synchronization of Cell Division in
Escherichia coli
by Elevated Temperatures:
a
Reinterpretation
Authors: Lomnitzer Ruth , Ron Eliora Z.
Published: January 2020

Synchronization of cell division resulting from exposure of
Escherichia coli
to elevated temperatures can be prevented by the presence of methionine. It is suggested that limitation of endogenous methionine at the elevated temperature might be the cause for the subsequent synchronization of cell division.
Ferredoxin-Dependent Conversion of Acetaldehyde to Acetate and H
2
in Extracts of S Organism
Authors: Reddy C. Adinarayana , Bryant M. P. , Wolin M. J.
Published: January 2020

S organism, an anaerobic gram-negative rod, which is one of two bacterial species isolated from the culture known as “Methanobacillus omelianskii,” ferments ethanol to acetate and H
2
. The present study shows that extracts of this organism contain ferredoxin and produce acetate from acetaldehyde via aldehyde: ferredoxin oxidoreductase activity. Electrons generated in the reaction are given off as H
2
by a previously demonstrated ferredoxin-linked hydrogenase system. Extracts were shown to contain good phosphotransacetylase and acetokinase activities, but no mechanism of adenosine triphosphate generation during acetaldehyde conversion to acetate could be detected. No evidence could be obtained for coenzyme A (CoASH) or phosphate requirement or for formation of acetyl CoA or acetyl phosphate.