bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolic Regulation in Glucose-Limited Chemostat Cultures of
Escherichia coli
Authors: Harvey R. J.
Published: January 2020

Glucose-limited chemostat cultures of
Escherichia coli
, growing at dilution rates above 0.3/hr, continue to grow at the restricted rate after removal of glucose restriction. In a glycogenless strain, the specific rates of increase of mass, protein, and ribonucleic acid (RNA) were equal before and after supplementation with 0.05% glucose and did not increase detectably until after 30 to 60 min. The unrestricted specific growth rate was reached after two to three doublings of cell mass. Supplementation with glucose plus 20 amino acids, but not with glucose plus vitamins or ribosides, produced an immediate increase in the specific rates of mass and RNA synthesis followed by an increase in the specific rate of protein synthesis. In a wild-type strain, synthesis of protein and RNA continued at the restricted rate after glucose supplementation, but the specific rate of increase of mass immediately increased due to rapid synthesis of glycogen. At dilution rates less than 0.3/hr, the specific rates of increase of mass, protein, and RNA increased immediately after supplementation with glucose, but did not immediately attain the unrestricted growth. The results at dilution rates greater than 0.3/hr are interpreted to mean that the regulation of a number of enzymatic reactions is entirely through control of enzyme synthesis, without modulation of enzyme function. The levels of such enzymes are controlled so that operation with zero-order kinetics precisely meets the demands for balanced growth. It was shown that glutamic dehydrogenase and glutamic-oxalacetic transaminase are regulated in this manner.
Partial Purification and Properties of
d
-Desthiobiotin Synthetase from
Escherichia coli
Authors: Cheeseman P. , Pai C. H.
Published: January 2020

d
-Desthiobiotin synthetase, an enzyme that catalyzes the synthesis of
d
-desthiobiotin from
dl
-7,8-diaminopelargonic acid and HCO
3
−
, was purified 100-fold from cells of a biotin mutant strain of
Escherichia coli
. Adenosine triphosphate and Mg
2+
were shown, especially in purified extracts, to be obligatory for enzyme activity, although concentrations higher than 5 m
m
caused severe inhibition of the reaction with unpurified cell-free extracts. Adenosine diphosphate and adenosine monophosphate were shown to inhibit the reaction, but fluoride (up to 50 m
m
) had no detectable effect. The product of the enzyme reaction was identical to
d
-desthiobiotin on the basis of biological activity and chromatography. Furthermore, when H
14
CO
3
−
was used as a substrate, the radioactive product was shown to be
14
C-desthiobiotin labeled exclusively in the ureido carbon.
Altered Fatty Acid Distribution in Mutants of
Neurospora crassa
Authors: Brody Stuart , Nyc Joseph F.
Published: January 2020

Morphological mutants of
Neurospora
with decreased levels of reduced nicotinamide adenine dinucleotide phosphate (NADPH) and reduced nicotinamide ad enine dinucleotide (NADH) contained only 20% as much of a polyunsaturated fatty acid (linolenic acid) as the wild type in both the phospholipid and neutral lipid fractions. There was an excellent correlation between linolenic acid levels and morphological appearance as a function of total NADPH content, but no correlation with NADH content. The linolenic acid deficiency was balanced by a relative increase in the amounts of the less unsaturated fatty acids (oleic and linoleic acids), but the level of three other fatty acids did not appear to be changed. This accumulation of these two precursors suggests that the NADPH deficiency preferentially affected the final desaturation step, i.e., the conversion of linoleic to linolenic acid. The NADPH needed for this reaction in vivo was probably generated by the pentose phosphate shunt, since mutations affecting the shunt lead to the decreased levels of linolenic acid. It is not clear whether the changes in fatty acid distribution affect the morphogenesis of
Neurospora
, or if these changes are just part of the NADPH-deficiency syndrome.
Inhibition of Colicin E2 Activity by Bacterial Lipopolysaccharide
Authors: Chang Ying-Ying , Hager Lowell P.
Published: January 2020

Lipopolysaccharide isolated from colicin E2-sensitive
Escherichia coli
and from “receptor-minus” mutants inhibits the activity of colicin E2. Lipid A and the polysaccharide fraction obtained by mild acid hydrolysis of lipopolysaccharide are inactive either alone or when tested in combination. Periodate oxidation of lipopolysaccharide destroys over 85% of its inhibition activity.
Isolation and Characterization of an Extracellular Polysaccharide from
Physarum polycephalum
Authors: McCormick J. Justin , Blomquist Judith C. , Rusch Harold P.
Published: January 2020

The myxomycetes are called slime molds because of the synthesis of copious amounts of extracellular material (slime) during parts of the life cycle. In
Physarum polycephalum
, small amounts of slime are produced during exponential growth of microplasmodia in shake flasks, but the amount of this slime increased 10- to 20-fold at 16 to 34 hr after microplasmodia were induced to form spherules by transferring them to salt solution. The slime obtained during both periods is the same; an acidic polysaccharide consisting of galactose, sulfate, and trace amounts of rhamnose. Analysis of the galactose-to-sulfate ratio gave a value of about 4 to 1. Infrared spectroscopy showed increased absorbance at 820 cm
−1
characteristic of C-O-S vibrations. Electrophoresis on polyacrylamide gel revealed that the material moved as a single band which stained with Alcian Blue and periodic acid Shiff reagent. However, fractionation of identical material on Dowex columns and electrophoresis on cellulose acetate showed the slime to be made up of three major fractions. The polysaccharide appeared as an extracellular capsule closely adhering to the walls of the spherules. It could be separated from the wall by vigorous shaking. The increased synthesis of slime during spherulation was not blocked by cycloheximide, suggesting that new enzyme synthesis was not necessary for its formation.
Glucose Metabolism of L Cells Before and After Infection withChlamydia psittaci
Authors: Moulder James W.
Published: January 2020

Glucose was not utilized at significantly different rates in suspensions of multiplying and nonmultiplying adult mouse fibroblasts (L cells). Infection of L cells withChlamydia psittaci(strain meningopneumonitis) increased the rates of glucose utilization and lactate accumulation during the first 24 hr after infection without changing the rates of glucose utilization by the pentose or tricarboxylic acid cycles. It was concluded that the increased aerobic glycolysis represented a host response to infection and not a parasite activity. The 6BC strain ofC. psittaciand the mouse pneumonitis strain ofC. trachomatisproduced similar changes in the glucose metabolism of L-cells. These results are discussed in relation to the hypothesis that chlamydiae generate to metabolic energy of their own and live by exploiting the energy-rich compounds produced by their hosts.
Location of Aryl Sulfatase in Conidia and Young Mycelia of
Neurospora crassa
Authors: Scott Walter A. , Metzenberg Robert L.
Published: January 2020

Aryl sulfatase (arylsulfate sulfohydrolase, EC 3.1.6.1) was found to have multiple locations in
Neurospora
conidia. Some enzyme activity remained in the supernatant when a spore suspension was centrifuged or filtered. Part of the cell-bound activity could be detected by adding the assay ingredients to a suspension of intact spores (patent enzyme), and additional activity was only detectable when the spores were first treated to destroy their permeability barriers (cryptic enzyme). Such treatments include: disruption with an X-press, brief rinsing with chloroform or acetone, incubation at 60 C for 5 min, and incubation with phenethyl alcohol, nystatin, or ascosin. Part of the patent aryl sulfatase was inactivated by briefly acid treating the intact spores (no loss of conidial viability). This enzyme was considered to have a cell surface location. Some enzyme was acid-resistant in intact spores, but all of the enzyme was acid-sensitive in spores whose permeability barriers had been disrupted. The
p
H dependence, kinetic properties, and
p
-nitrophenyl sulfate uptake were investigated in acid-treated conidia. No aryl sulfatase was detected in ascospores. Young mycelia contained more aryl sulfatase than did conidia, but little, if any, was secreted into the growth medium. Cryptic activity was demonstrated in young mycelia by brief chloroform treatment or by rinsing the cells with 0.1
m
acetate buffer. Enzyme activity in young mycelia was completely labile to acid treatment, as was cell viability.
Dissimilation of Methionine by
Achromobacter starkeyi
Authors: Ruiz-Herrera José , Starkey Robert L.
Published: January 2020

Methionine was decomposed by some bacteria which were isolated from soil. The sulfur of the methionine was liberated as methanethiol, and part of this became oxidized to dimethyl disulfide. Detailed studies with one of these cultures,
Achromobacter starkeyi
, indicated that the first step in methionine decomposition was its oxidadative deamination to α-keto-γ-methyl mercaptobutyrate by a constitutive amino acid oxidase. The following steps were carried out by inducible enzymes, the synthesis of which was inhibited by chloramphenicol. α-Keto-γ-methyl mercaptobutyrate was split producing methanethiol and α-keto butyrate which was oxidized to propionate. The metabolism of propionate was similar to that described for animal tissues; the propionate was carboxylated to succinate via methyl malonyl coenzyme A, and the succinate was metabolized through the Krebs cycle.
Physiological Streptomycin Resistance in a Multiauxotroph of
Escherichia coli
Strain 15 T
−
Authors: Carlson Karen , Bockrath R. C.
Published: January 2020

Escherichia coli
strain WWU was found to be moderately resistant to streptomycin when grown in a minimal medium, although the strain was sensitive if grown in nutrient broth. Transfer experiments showed that cells grown in minimal medium retain the resistant state for a period of time after dilution into nutrient broth; and conversely, sensitive cells grown in nutrient broth were sensitive after dilution into minimal medium for a period of time. The kinetics of transition from resistant to sensitive and from sensitive to resistant were observed, and kinetics of
3
H-dihydrostreptomycin accumulation by resistant and sensitive cells were compared. The data suggested that cells grown in minimal medium were physiologically resistant because they accumulated streptomycin poorly. Inactivation per incorporated antibiotic molecule was the same in resistant and sensitive cells.
Effects of Essential Amino Acid Starvation in
Streptococcus faecalis:
Structural Change in the 50
S
Ribosomal Subunit
Authors: Ziegler R. J. , Daneo-Moore L.
Published: January 2020

The 50
S
ribosomal subunits obtained from exponential-phase and valine-limited cultures of
Streptococcus faecalis
9790 differed in protein content. Approximately 35% of the valine-limited subunits showed protein losses when analyzed by CsCl density centrifugation after formaldehyde fixation. Results of density gradient analysis and of acrylamide gel electrophoresis localized the protein to a “split” subunit fraction. No differences could be detected in the protein contents of 30
S
subunits from exponential-phase and valine-limited cultures.
Catabolite Repression in the
d
-Serine Deaminase System of
Escherichia coli
K-12
Authors: McFall Elizabeth , Bloom Frederic R.
Published: January 2020

The induced synthesis of
d
-serine deaminase in
Escherichia coli
is subject to three catabolic effects: inhibition on inducer uptake, transient repression, and catabolite repression. Inhibition on
d
-serine uptake is not significant at the
d
-serine concentration normally used for induction. Transient repression and catabolite repression of
d
-serine deaminase synthesis are abolished by mutations in
dsdCy
, which appears to be an operator locus. The decline in the rate of constitutive synthesis observed in
dsdCx
mutants growing with glycerol as carbon source at temperatures above 37 C is due to catabolite repression. The low level of constitutivity at 37 C and the partial
cis
dominance of
dsdCx
mutants are not artifacts of catabolite repression. It is suggested that a product of one of the genes of the
dsd
operon may regulate the expression of the operon.
Filterability of Streptococcal L-Forms
Authors: Wyrick Priscilla B. , Gooder Harry
Published: January 2020

The filterability of the broth-grown stable L-form derived from
Streptococcus faecium
F24 was tested by filtration under the influence of varying amounts of applied pressure. A decrease in the pore size of the filter resulted in a corresponding decrease in viable count, but no major effect was noted due to the different pressures applied. Serial filtration of a deoxyribonuclease-treated L-form culture in the mid-logarithmic phase of growth resulted in recovery of viable L-forms from the 0.45-μm filtrate but not from the 0.22-μm filtrate. It is possible that disruption of the L-form bodies with release of small viable elements had occurred. Protoplasts, diluted in an osmotic stabilizer, were filtered similarly; L-forms could be grown from the filtrate passing through the filters of 0.45 μm or greater. Filtration of the parent streptococci gave rise to streptococcal colonies from the 1.2-μm filtrate only.
Inhibition of Polyuridylic Acid-Directed Protein Synthesis by Aurintricarboxylate in Extracts of
Escherichia coli
Authors: Siegelman Frederic L. , Apirion David
Published: January 2020

Aurintricarboxylic acid (ATA) inhibits protein synthesis directed by polyuridylic acid. All steps tested are inhibited by ATA. We conclude that inhibition of polyphenylalanine formation is an additive effect of inhibition of various steps in the protein synthetic machinery.
Reduction of Activity of Reduced Nicotinamide Adenine Dinucleotide Oxidase by Divalent Cations in Cell-Free Extracts of
Bacillus cereus
T
Authors: Thompson E. D. , Nakata H. M.
Published: January 2020

A rapid and effective method was devised for the reduction of activity of reduced nicotinamide adenine dinucleotide (NADH) oxidase in crude extracts of
Bacillus cereus
T. The addition of 25 μmoles of MnCl
2
per mg of extract protein in tris(hydroxymethyl)aminomethane-hydrochloride buffer reduced NADH oxidase activity by 90% within 1 min, and this reduction was independent of
p
H between
p
H 7.0 and 8.5. Other divalent cations such as Mg
2+
, Ba
2+
, Ca
2+
, and Co
2+
also reduced NADH oxidase activity, but monovalent cations such as Na
+
and K
+
were ineffective. The reduction of NADH oxidase activity by divalent cations was presumably due to the removal of an essential flavine cofactor, since the addition of riboflavine and flavine mononucleotide to treated extracts was shown to completely restore NADH oxidase activity. The specificity, convenience, and efficiency of the procedure were shown to be applicable to crude extracts of
B. megaterium
and
B. subtilis
and should facilitate spectrophotometric measurements of nicotinamide adenine dinucleotide-dependent dehydrogenases in these and other microorganisms.
Pressure Sensitivity of Streptococcal Growth in Relation to Catabolism
Authors: Marquis Robert E. , Brown William P. , Fenn Wallace O.
Published: January 2020

The sensitivity of
Streptococcus faecalis
growth to hydrostatic pressures ranging up to 550 atm was found to depend on the source of adenosine triphosphate for growth. Barotolerance of cultures growing in a complex medium with ribose as major catabolite appeared to be determined primarily by the pressure sensitivity of ribose-degrading enzymes. Apparent activation volumes for growth were nearly identical to those for lactate production from ribose, and yield coefficients per mole of ribose degraded were relatively independent of pressure. In contrast, cultures with glucose as main catabolite were less sensitive to pressure; glycolysis was less severely restricted under high pressure than was growth, and yield coefficients declined with pressure, especially above 400 atm. Thus, two distinct types of barotolerance could be defined—one dominated by catabolic reactions and one dominated by noncatabolic reactions. The results of experiments with a series of other catabolites further supported the view that catabolic reactions can determine streptococcal barotolerance. We also found that growing, glucose-degrading cultures increased in volume under pressure in the same manner that they do at 1 atm. Thus, it appeared that the bacterium has no alternative means of carrying out glycolysis under pressure without dilatation. Also, the observation that cultures grown under pressure did not contain abnormally large or morphologically deformed cells suggested that pressure did not inhibit cell division more than cell growth.
Isoleucine Auxotrophy as a Consequence of a Mutationally Altered Isoleucyl-Transfer Ribonucleic Acid Synthetase
Authors: Iaccarino Maurizio , Berg Paul
Published: January 2020

Among mutants which require isoleucine, but not valine, for growth, we have found two distinguishable classes. One is defective in the biosynthetic enzyme threonine deaminase (
l
-threonine hydro-lyase, deaminating, EC 4.2.1.16) and the other has an altered isoleucyl transfer ribonucleic acid (tRNA) synthetase [
l
-isoleucine: soluble RNA ligase (adenosine monophosphate), EC 6.1.1.5]. The mutation which affects
ileS
, the structural gene for isoleucyl-tRNA synthetase, is located between
thr
and
pyrA
at 0 min on the map of the
Escherichia coli
chromosome. This mutationally altered isoleucyl-tRNA synthetase has an apparent
K
m
for isoleucine (∼1 m
m
) 300-fold higher than that of the enzyme from wild type; on the other hand, the apparent
V
max
is altered only slightly. When the mutationally altered
ileS
allele was introduced into a strain which overproduces isoleucine, the resulting strain could grow without addition of isoleucine. We conclude that the normal intracellular isoleucine level is not high enough to allow efficient charging to tRNA
Ile
by the mutant enzyme because of the
K
m
defect. A consequence of the alteration in isoleucyl-tRNA synthetase was a fourfold derepression of the enzymes responsible for isoleucine biosynthesis. Thus, a functional isoleucyl-tRNA synthetase is needed for isoleucine to act as a regulator of its own biosynthesis.
Determination of the Minimal Temperature for Growth of
Escherichia coli
Authors: Shaw Maxwell K. , Marr Allen G. , Ingraham John L.
Published: January 2020

The minimal temperature for growth of
Escherichia coli
ML30 in glucose minimal medium is between 7.5 and 7.8 C. After transfer to subminimal temperature, growth occurs but is not sustained.
Formation of Protoplasts from Resting Spores
Authors: Fitz-James Philip C.
Published: January 2020

Coat-stripped spores suspended in hypertonic solutions and supplied with two essential cations can be converted into viable protoplasts by lysozyme digestion of both cortex and germ cell wall. Calcium ions are necessary to prevent membrane rupture, and magnesium ions are necessary for changes indicative of hydration of the core, particularily the nuclear mass. Since remnant spore coat covered such protoplasts of
Bacillus subtilis
and the germ cell wall of
B. cereus
spores is not lysozyme digestible, coatless spores of
B. megaterium
KM were more useful for these studies. Lysozyme digestion in cation-free environment produced a peculiar semi-refractile spore core free of a cortex but prone to rapid hydration and lytic changes on the addition of cations. Strontium could replace Ca
2+
but Mn
2+
could not replace Mg
2+
in these digestions. When added to the spores, dipicolinic acid and other chelates appeared to compete with the membrane for the calcium needed for stabilization during lysozyme conversion to protoplasts. It is argued that calcium could function to stabilize the inner membrane anionic groups over the anhydrous dipicolinic acid-containing core of resting spores.
Reinitiation of Cell Wall Growth After Threonine Starvation
of Streptococcus faecalis
Authors: Higgins Michael L. , Pooley Harold M. , Shockman Gerald D.
Published: January 2020

Cultures of
Streptococcus faecalis
ATCC 9790 were starved of threonine for 10 hr and then allowed to reinitiate growth in a fresh complete medium. On regrowth, culture turbidity began to increase within 10 min, but the ability of cells to autolyze did not begin to increase until after 30 min. Ultrastructural studies of regrowth of the initially thick-walled cells showed, at about 30 min, centripetal linear extension of new thin cross wall. This was followed, at about 40 min, by a notching, splitting, and peeling apart of the base of the cross wall. After this, extension of new thin peripheral wall from the nascent cross wall appeared to push old thick wall toward the poles. After the first cell division, asymmetric cells with one initial generation thick-walled pole and one second generation thin-walled pole were seen. After two divisions, thick-walled hemispheres were still seen, suggesting conservation of old wall during this time. A small fraction of the initial cell population exhibited aberrations and difficulties in reinitiating linear wall extension and were useful in the establishment of a model for the reinitiation of linear wall extension.
Dissociation and Reassembly of
Escherichia coli
Outer Membrane and of Lipopolysaccharide, and Their Reassembly onto Flagellar Basal Bodies
Authors: DePamphilis M. L.
Published: January 2020

Purified lipopolysaccharide vesicles dissociate when treated with ethylenediaminetetraacetic acid (EDTA) and then reassemble when dialyzed against Mg
2+
. Purified outer, lipopolysaccharide membrane (L membrane) is partially dissociated by treatment with EDTA and fully dissociated upon further treatment with Triton X-100. Both the partially and fully dissociated L membrane can be reassembled by dialysis against Mg
2+
. Reassembly of lipopolysaccharide or L membrane in the presence of intact flagella results in specific attachment of flagellar basal bodies to vesicles via the L and sometimes the M ring. Lipopolysaccharide and L membrane appear to be composed of substructures bound together by both Mg
2+
(divalent cation)-mediated and hydrophobic bonds.
Occurrence of Glucomuramic Acid in Gram-Positive Bacteria
Authors: Wheat R. W. , Ghuysen J. M.
Published: January 2020

Analyses of 48 gram-positive bacteria indicate only glucomuramic acid and no galactomuramic acid in cell walls.
Deficiencies of Chromatophore Proteins in Some Mutants of
Rhodopseudomonas spheroides
with Altered Carotenoids
Authors: Segen Barbara J. , Gibson Kenneth D.
Published: January 2020

Chromatophore proteins of a wild type and three mutant strains of
Rhodopseudomonas spheroides
were examined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The mutants consisted of a green and a blue-green one, whose phenotypes were essentially the same as those of known mutants, and a brown one, which may be a double mutant and represents a new phenotype. Wild-type chromatophores contained at least six major and seven minor protein bands, with molecular weights ranging from 10,000 to 65,000. The green mutant contained the same protein bands in the same relative quantities. The brown mutant had one protein completely missing and no other alterations. The blue-green mutant was deficient in a different protein, and had reduced quantities of all proteins with molecular weights less than 25,000. Chromatophores were separated into a fraction containing the reaction centers and a fraction containing the light-harvesting bacteriochlorophyll by treatment with sodium dodecyl sulfate. Eight of the proteins were found only in the reaction center fraction, one was only in the light-harvesting fraction, and the remainder were present in both fractions. The protein missing from the brown mutant was found to be a component of the reaction center fraction, whereas the proteins which were missing from the blue-green mutant were all components of the light-harvesting fraction. Some implications for the structure and biogenesis of chromatophores are discussed.
Characterization and Genetic Analysis of Mutant Strains of
Escherichia coli
K-12 Accumulating the Ubiquinone Precursors 2-Octaprenyl-6-Methoxy-1,4-Benzoquinone and 2-Octaprenyl-3-Methyl-6-Methoxy-1,4-Benzoquinone
Authors: Young I. G. , McCann L. M. , Stroobant P. , Gibson F.
Published: January 2020

The ubiquinone precursors, 2-octaprenyl-6-methoxy-1,4-benzoquinone and 2-octaprenyl-3-methyl-6-methoxy-1,4-benzoquinone, were isolated from ubiquinone-deficient mutants of
Escherichia coli
and identified by nuclear magnetic resonance and mass spectrometry. Mutants accumulating 2-octaprenyl-6-methoxy-1,4-benzoquinone and 2-octaprenyl-3-methyl-6-methoxy-1,4-benzoquinone were shown to carry mutations in genes designated
ubiE
and
ubiF
, respectively. The
ubiE
gene was shown to be cotransducible with
metE
(minute 75) and close to two other genes concerned with ubiquinone biosynthesis. The
ubiF
gene was located close to minute 16 by cotransduction with the
lip, gltA
, and
entA
genes.
Regulation of Thymidine Metabolism in
Escherichia coli
K-12: Evidence That at Least Two Operons Control the Degradation of Thymidine
Authors: Bonney Robert J. , Weinfeld Herbert
Published: January 2020

In
Escherichia coli
K-12, the rise in activity of thymidine phosphorylase, phosphodeoxyribomutase, and deoxyribose-5-phosphate aldolase caused by exogenous thymidine is dependent on the synthesis of new enzyme protein. Phosphodeoxyribomutase is induced by the purine ribonucleosides adenosine and guanosine, whereas the other two enzymes are not. The mutase activity induced by thymidine and by the purine ribonucleosides has been shown to be the same enzyme by four different criteria. This independent induction of phosphodeoxyribomutase suggests that the gene for this enzyme is in an operon different from the one that may contain the genes for thymidine phosphorylase and deoxyribose-5-phosphate aldolase.
Properties of F′ Factor Deoxyribonucleic Acid Transferred from Ultraviolet-Irradiated Donors: Photoreactivation in the Recipient and the Influence of
recA, recB, recC
, and
uvr
Genes
Authors: Cole Ronald S.
Published: January 2020

Ultraviolet (UV)-irradiated
Escherichia coli
K-12 F
lac
+
donors transfer damaged F′ factors when mated with female cells. Exposure of the zygotes to white light after mating can cause the photoreactivation of the damaged transferred F′ factors. In so far as the photoreactivation is specific for pyrimidine dimers, these experiments indicate the presence of UV-induced dimers in the transferred F′ factor deoxyribonucleic acid (DNA). These damaged F′ factors are remarkably stable in
recA
recipients, having a half-life for susceptibility to photoreactivation of 1.5 to 2 hr. This is judged by the formation of Lac
+
colonies, all of which are male secondary donors. In crosses with wild type and
uvrA, recB
, or
recC
mutant recipients, however, the Lac
+
colonies are predominantly recombinants and photoreactivation is not detected. The extent of DNA synthesis resulting from transfer of F′ episomes from irradiated donors suggests that a complementary strand is formed on the damaged template. Photoreactivation behavior and sedimentation properties are used to deduce properties of such damaged episomes. We conclude that the complementary strand is discontinuous directly opposite dimers in the transferred strand. This structure may be an intermediate in the recombinational event sequence in Rec
+
recipients.
Mutants of
Salmonella typhimurium
with an Altered Leucyl-Transfer Ribonucleic Acid Synthetase
Authors: Alexander Renee R. , Calvo J. M. , Freundlich M.
Published: January 2020

Two trifluoroleucine-resistant mutants of
Salmonella typhimurium
, strains CV69 and CV117, had an altered leucyl-transfer ribonucleic acid (tRNA) synthetase. The mutant enzymes had higher apparent
K
m
values for leucine (ca. 10-fold) and lower specific activities (ca. twofold) than the parent enzyme when tested in crude extracts. Preparations of synthetase purified ca. 60-fold from the parent and strain CV117 differed sixfold in their leucine
K
m
values. In addition, the mutant enzyme was inactivated faster than the parent enzyme at 50 C. The growth rates of strains CV69 and CV117 at 37 C were not significantly different from that of the parent, whereas at 42 C strain CV69 grew more slowly than the parent. Leucine-, valine-, and isoleucine-forming enzymes were partially derepressed when the mutants were grown in minimal medium; the addition of leucine repressed these enzymes to wild-type levels. During growth in minimal medium, the proportion of leucine tRNA that was charged in the mutants was about 75% of that in the parent. The properties of strain CV117 were shown to result from a single mutation located near
gal
at minute 18 on the genetic map. These studies suggest that leucyl-tRNA synthetase is involved in repression of the enzymes required for the synthesis of branched-chain amino acids.
Isolation and Characterization of Supercoiled Circular Deoxyribonucleic Acid from Beta-Hemolytic Strains of
Escherichia coli
Authors: Goebel Werner , Schrempf Hildgund
Published: January 2020

Covalently closed circular deoxyribonucleic acid (DNA) molecules were isolated by cesium chloride centrifugation in the presence of ethidium bromide from a naturally occurring beta-hemolytic
Escherichia coli
strain (SC52). The open circular forms have contour lengths of 2.25 ± 0.1 μm, 24.0 ± 0.3 μm, and 29.5 ± 0.5 μm. The beta-hemolytic character of
E. coli
SC52 can be transferred by conjugation to a nonhemolytic recipient strain. Analysis of the supercoiled DNA of the hemolytic recipient demonstrated that the two large supercoiled DNA molecules of
E. coli
SC52 are transferred during this event, too. A beta-hemolytic laboratory
E. coli
strain and several of its derivatives have been shown to contain at least one circular DNA molecule, slightly larger in size than those isolated from
E. coli
SC52 and its conjugant. The possible significance of these DNA molecules for hemolysin production and transfer is discussed.
Sulfate-Reducing Bacterium with Unusual Morphology and Pigment Content
Authors: Jones H. E.
Published: January 2020

A dissimilatory sulfate-reducing bacterium was isolated which differed in morphology and pigment content from previously described species. The organism was mesophilic, obligately anaerobic, gram-negative, nonsporulating, long, and slender with one polar flagellum. Whole cells fluoresced red at neutral
p
H when excited with light at 365 nm owing to the presence of a pink pigment. Desulfoviridin was present. Reduced
minus
oxidized spectra of whole cells showed peaks in the position of a
c
-type cytochrome characteristic of
Desulfovibrio
species and peaks at about 629 and 603 nm. CO difference spectra showed the presence of a CO-binding pigment with a peak at 593 nm. Lactate and pyruvate supported growth in the presence of sulfate but not in its absence. Sulfate, sulfite, and thiosulfate served as electron acceptors for growth. Hydrogenase was present. The deoxyribonucleic acid had a buoyant density of 1.722 g/cm
3
and a guanosine plus cystosine molar percentage of total bases calculated by two different methods of 61.2 or 63.2.
Efflux and the Steady State in α-Methylglucoside Transport in
Escherichia coli
Authors: Winkler Herbert H.
Published: January 2020

Efflux and the steady state in a group translocation system, the α-methylglucoside (αMG) transport system, were investigated. The maximum intracellular level of α-methylglucoside is a function of a steady state. There is no inhibition of αMG influx as the intracellular pool of αMG, and α-methylglucoside-6-phosphate (αMGP) rises. This steady state has three components: αMG influx, action of an αMGP phosphatase, and αMG efflux. The phosphatase is the rate-limiting step (half-time = 5.0 min); thus, the true efflux rate (half-time = 2.0 min) cannot be simply measured from the kinetics of αMG loss from the cell. Under our steady-state conditions the percentage of intracellular radioactivity present as αMGP was 71%. Under conditions of zero influx, after an efflux of 12 min the percentage present as αMGP fell to 55%. However, when fluoride was present during the efflux period, the percentage of the sugar as αMGP increased to about 85%. Fluoride greatly inhibits both influx and phosphatase activity (half-time = 50 min). The efflux of αMG from the cell is apparently also fluoride-sensitive but to a lesser extent (half-time = 4.1 min). These data are summarized in a model describing the three components of the steady-state and effect of fluoride.
Induction of Pigmentation in Nonproliferating Cells of
Serratia marcescens
by Addition of Single Amino Acids
Authors: Williams Robert P. , Gott Cora L. , Qadri S. M. Hussain
Published: January 2020

Addition of casein hydrolysate to suspensions of washed, nonpigmented, nonproliferating
Serratia marcescens
incubating at 27 C induced biosynthesis of prodigiosin. Four amino acids of casein hydrolysate,
dl
-aspartic acid,
l
-glutamic acid,
l
-proline, and
l
-alanine caused formation of pigment when added individually.
dl
-Ornithine also was effective. Optimal concentrations for maximal pigmentation were 5 to 10 mg/ml; at these high concentrations,
d
-serine also induced biosynthesis of some prodigiosin.
dl
-Alanine and -ornithine were as effective as the
l
-iosomers, but
l
-glutamic acid and
l
-proline gave better responses than their racemic mixtures. Kinetics of prodigiosin biosynthesis after addition of
dl
-alanine (20 mg/ml) were similar to those of cells suspended in 0.2% casein hydrolysate. The other amino acids were less effective. Addition of 5 mg of
dl
-alanine or casein hydrolysate per ml to minimal medium increased by 30% the amount of prodigiosin formed by growing cells after incubation for 7 days at 27 C. Cultures grown for 7 days at 27 C in 0.2% casein hydrolsate formed more prodigiosin than did suspensions of nonproliferating cells containing individual amino acids or casein hydrolysate. However, more pigment was produced by cells suspended in
l
-alanine (5 mg/ml) or
l
-proline (10 mg/ml) than when suspended in 0.4% natural or synthetic casein hydrolysate. Filtrates from suspensions of nonproliferating cells forming pigment in
l
-proline induced more rapid formation of prodigiosin, but filtrates from suspensions in
dl
-alanine did not. The data supported the hypothesis that pyrrole groups of prodigiosin may be synthesized from 5-carbon amino acids such as proline, ornithine, aspartic, and glutamic acids, but the role of alanine is unknown.
Induction of Citrate Transport inBacillus subtilisDuring the Absence of Phospholipid Synthesis
Authors: Willecke Klaus , Mindich Leonard
Published: January 2020

Citrate transport can be induced in a glycerol-requiring mutant ofBacillus subtiliseven after deprival of glycerol. Under these conditions de novo phospholipid synthesis is stopped although ribonucleic acid, deoxyribonucleic acid, and protein syntheses continue. It is concluded that the inducibility of bacterial transport systems must not necessarily require de novo phospholipid synthesis.
Effect of Gene Induction on the Rate of Mutagenesis by ICR-191 in
Escherichia coli
Authors: Herman Robert K. , Dworkin Nomi B.
Published: January 2020

ICR-191, an acridine half-mustard known to cause frameshift mutations in bacteria, was used to induce Lac
−
mutations revertible by ICR-191. The reversion rates of several of these mutations were stimulated approximately twofold by the presence of
lac
inducer. The stimulatory effect of inducer was attributable to gene induction rather than some other effect of inducer, since inducer did not stimulate reversion in a regulator constitutive strain. The stimulatory effect was not observed unless the gene to be reverted was induced during the period of exposure to ICR-191. The presence of a strong polar (nonsense) mutation on the operator side of a frameshift mutation abolished the stimulatory effect of inducer on reversion of the frameshift mutation by ICR-191. (As expected, a nonpolar mutation on the operator side of the frameshift mutation did not affect inducer-stimulated reversion.) It was concluded that some aspect of transcription or translation, or both, in the neighborhood of the ICR-191-induced mutation stimulated reversion by ICR-191. A
recA
mutation had no effect on reversion by ICR-191 in the presence or absence of inducer. In one mutant, gene induction depressed reversion by ICR-191 about sevenfold. The difference between this exceptional strain and other mutants was not attributable to different genetic backgrounds but seemed to be an inherent difference in the original Lac
−
mutations.
Demonstration by Freeze-Etching of a Single Cleavage Plane in the Cell Wall of a Gram-Negative Bacterium
Authors: DeVoe I. W. , Costerton J. W. , MacLeod Robert A.
Published: January 2020

In the examination of protoplasts of a gram-negative bacterium classified as a
Pseudomonas
sp. by freeze-etching, we found a smooth external surface which is not seen if the preparations are not “etched.” This external structure is seen as a sleeve surrounding and connecting the cells in unetched preparations, and we present evidence that it is a eutectic formed during the freezing of the specimen. In the system used in this study, the four layers of the cell wall of a gram-negative bacterium can be removed from the cell. The single cell wall cleavage plane is not affected by the removal of the loosely bound outer layer or of the peptidoglycan layer, but it is lost when the outer double track layer and the underlying soluble layer are simultaneously removed. Thus, we conclude that it is one of these two layers which is responsible for the cleavage plane which exposes variable areas of a smooth surface in the cell wall. This cell wall cleavage plane is more likely to deflect the actual cleavage of the frozen cell when cells are relatively old or when they are suspended in sucrose.
Transport of Vitamin B
12
in
Escherichia coli
Authors: Di Girolamo Paula M. , Bradbeer Clive
Published: January 2020

The uptake of
60
Co-labeled cyanocobalamin (vitamin B
12
) by cells of
Escherichia coli
K-12λ was shown to consist of an initial rapid phase (complete in <1 min), followed by a slower secondary phase. Methods enabling the measurement of
60
Co-B
12
uptake after incubation times of 1 to 2 sec were used in studies on the initial rate of B
12
uptake. This initial process showed saturation kinetics, with a
V
max
of 56 molecules per sec per cell and a
K
m
of 5 nm, and was essentially independent of cellular energy metabolism. No inhibition was obtained with cyanide, fluoride, arsenite, or 2, 4-dinitrophenol, and an energy of activation of 3.8 kcal/mole for this initial phase of uptake was calculated from its response to temperature changes between 15 and 35 C. The inhibition by HgCl
2
(50% at 0.1 m
m
) but not by 1 m
m
N
-ethylmaleimide or 1 m
m
p
-chloromercuribenzoate was consistent with a role for a relatively inaccessible sulfhydryl residue at the initial B
12
binding site. The secondary phase of B
12
uptake was clearly dependent on the energy metabolism of the cell, and, from its response to temperature, an energy of activation of about 17 kcal/mole was calculated. Cyanide (10 m
m
), arsenite (10 m
m
), and 2, 4-dinitrophenol (0.1 m
m
) gave at least 70% inhibition of the rate of the secondary phase. The formation of other cobalamins, such as 5′-deoxyadenosyl cobalamin, was not an obligate part of B
12
transport. The cells were also able to take up
60
Co-labeled cobinamide cyanide.
Auxotroph Accumulation in Deoxyribonucleic Acid Polymeraseless Strains of
Escherichia coli
K-12
Authors: Berg Claire M.
Published: January 2020

Spontaneous auxotrophs are found with high frequency in several strains of
Escherichia coli
K-12 deficient in Kornberg deoxyribonucleic acid polymerase. These include amino acid-, vitamin-, purine-, and pyrimidine-requiring strains. Although this was suggestive evidence that these strains might be mutators, reconstruction experiments demonstrate that auxotrophs possess a selective advantage over prototrophs in the same culture. Thus, despite the high frequency of auxotrophs in polymerase-deficient strains, it is not yet clear whether they have elevated mutation rates.
Effects of
p
H on Transformation of
Bacillus subtilis
with Single-Stranded Deoxyribonucleic Acid
Authors: Tevethia Mary J. , Mandel M.
Published: January 2020

Variation in frequencies of transformation mediated by native and single-stranded DNA and its dependence on
p
H of the medium were investigated. The results indicate that the biological activity of deoxyribonucleic acid (DNA) of both configurations assayed in the presence of ethylenediaminetetraacetic acid (EDTA) increases as the
p
H of the transformation mixture is lowered from 7.7 to a maximum transformation frequency near
p
H 6.1. At this lower
p
H, native DNA transforms equally in medium with and without EDTA, and single-stranded DNA is 0.4 to 0.6 as active as native DNA in transforming
Bacillus subtilis
. A high efficiency of transformation with single-stranded DNA was observed for five markers in three recipient strains. The increased efficiency of native DNA appears to be caused by a lesser capacity of EDTA to bind magnesium at the lower
p
H. The increased efficiency of single-stranded DNA at
p
H below 7.0 results from decreased activity of a single-strand specific nuclease present in competent populations.
Relationship Between Competence for Transformation of
Bacillus subtilis
with Native and Single-Stranded Deoxyribonucleic Acid
Authors: Tevethia Mary J. , Caudill Claire P.
Published: January 2020

The response of populations of
Bacillus subtilis
to both native deoxyribonucleic acid (DNA) and denatured DNA was investigated at maximal competence and at various times during the development of compentency. The results indicate that competence for transformation with native and denatured DNA increases and decreases simultaneously. Competition occurs between native and single-stranded DNA during transformation, and the same cells in a population can be doubly transformed by DNA molecules of both configurations.
Fatty Acid Composition of Thermophilic, Mesophilic, and Psychrophilic Clostridia
Authors: Chan May , Himes Richard H. , Akagi J. M.
Published: January 2020

The fatty acid composition of two thermophilic anaerobes was determined, and the results were compared with those from a mesophilic and a psychrophilic anaerobe. Notable differences were that the thermophiles contained a higher content of saturated straight- and branched-chain fatty acids, and, of the latter, iso C15was the predominant type. The mesophile and psychrophile were characterized by having a higher percentage of unsaturated fatty acids. An unidentified fatty acid, present in all of the organisms, was purified from the psychrophile. By physical and chemical analysis the structure of the unknown acid was resolved and found to be the unsaturated cyclopropane fatty acid, 12,13-methylene-9-tetradecenoic acid.
Resistance of
Zygorhynchus
Species to Lysis
Authors: Ballesta J.-P. G. , Alexander M.
Published: January 2020

Zygorhynchus vuilleminii
, a nonmelanin-containing fungus, was not lysed by mycolytic actinomycetes. Several enzymes and
Streptomyces
enzyme preparations digesting walls of other fungi were without appreciable activity on walls of
Zygorhynchus
species. A bacterium able to solubilize a portion of the
Zygorhynchus
wall released little or no reducing sugars from these structures. Fractions of
Z. vuilleminii
walls were resistant to glucanase hydrolysis, but certain fractions were digested by chitinase and microbial enzyme preparations. The walls and several wall fractions were not readily susceptible to degradation by a soil community. Walls of lysis-resistant
Zygorhynchus
species contained glucosamine, fucose, glucuronic acid, and galactose but little or no glucose. Resistant wall fractions were rich in uronic acid and fucose, whereas the readily degradable fractions contained abundant glucosamine. Cultural conditions affected the extent of digestion and composition of the walls. Possible reasons for the resistance of
Zygorhynchus
to lysis in nature are discussed.
Variation in the Primary Structure ofBacillus subtilisFlagellins
Authors: Emerson Suzanne U. , Simon Melvin I.
Published: January 2020

The flagella derived from 18 strainsBacillus subtiliswere tested for their reaction with antiflagellar filament antibody and antiflagellin antibody. On the basis of their reactivity, at least five serologically distinct classes could be identified. Peptide map analysis of tryptic digests of the subunit proteins were consistent with the immunochemical analysis. Large differences in sequence existed among proteins of the different classes; proteins within an antigenic group differed by only a few peptides. Furthermore, 9 of the 27 tryptic peptides resolved were common to flagellin proteins from all the classes examined. The relationship between antigenic specificity, variability in peptide pattern, and the conformation of the flagellin protein are discussed.
Properties of a
Salmonella typhimurium
Mutant with an Incomplete Deficiency of Uridinediphosphogalactose-4-Epimerase
Authors: Krishnapillai V. , MacPhee D. G. , Stocker B. A. D.
Published: January 2020

A galactose-negative mutant, nonleaky in respect to fermentation and utilization, isolated from a smooth
Salmonella typhimurium
strain by phage selection and inferred deficient of uridine diphosphate (UDP)-galactose-epimerase, was used for experiments on relation of somatic lipopolysaccharide (LPS) character to virulence. Extracts of induced mutant cells retained ca. 1% of wild-type epimerase activity and had only ca. 5% of wild-type kinase and uridyl transferase activities; also, some cultural properties of the mutant differed from those of mutants with complete defects of epimerase only. The mutant was not galactose sensitive, presumably because of its kinase defect. Although the mutant had the phage pattern (including C21-sensitivity) of an epimerase mutant, it was susceptible to transduction by phage P22 and was O-agglutinable, even when grown on defined medium; its LPS must therefore contain some O polymer, including endogenous galactose, resulting from residual epimerase activity. Growth on galactose-supplemented medium restored smooth phage sensitivity; since the mutant was partly inducible this may result, at least in part, from increased endogenous production of UDP-galactose. The mutant was made galactose positive by introduction of an F′-
gal
+
plasmid. Base-change and frame-shift mutagens did not increase the frequency of reversion above the spontaneous rate. An insertion into the operator-promoter region of the
gal
operon seems the most likely mechanism of the mutation.
Properties of an Extracellular β-Galactosidase Secreted by
Neurospora crassa
Authors: Comp Philip C. , Lester Gabriel
Published: January 2020

An extracellular β-galactosidase with an activity optimum at about
p
H 4 was found to occur in the filtrates of
Neurospora crassa
strain 74A when this mold was grown on certain sugars. This activity accounted for a substantial portion of the β-galactosidase activity in the culture. The β-galactosidase in the medium appeared to be a secreted, extracellular enzyme, not a product of cell lysis. The extracellular activity was found to have physical and kinetic properties similar to those of an intracellular β-galactosidase previously found in
Neurospora
. Some conditions for the production and concentration of the enzyme are described.