bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutations Affecting the Different Transport Systems for Isoleucine, Leucine, and Valine in
Escherichia coli
K-12
Authors: Guardiola John , De Felice Maurilio , Klopotowski Tadeusz , Iaccarino Maurizio
Published: January 2020

Uptake of isoleucine, leucine, and valine in
Escherichia coli
K-12 is due to several transport processes for which kinetic evidence has been reported elsewhere. A very-high-affinity transport process, a high-affinity transport process, and three different low-affinity transport processes were described. In this paper the existence of these transport processes is confirmed by the isolation and preliminary characterization of mutants altered in one or more of them. The very-high-affinity transport process is missing either in strains carrying the
brnR6
am
mutation or in strains carrying the
brn-8
mutation. This appears to be a pleiotropic effect since other transport systems are also missing. Mutant analysis shows that more than one transport system with high affinity is present. One of them, high-affinity 1, which needs the activity of a protein produced by the
brnQ
gene, transports isoleucine, leucine, and valine and is unaffected by threonine. The other, high-affinity 2, which needs the activity of a protein produced by the
brnS
gene, transports isoleucine, leucine, and valine; this uptake is inhibited by threonine which probably is a substrate. Another protein, produced by the
brnR
gene, is required for uptake through both high-affinity 1 and high-affinity 2 transport systems. The two systems therefore appear to work in parallel,
brnR
being a branching point. The
brnQ
gene is located close to
phoA
at 9.5 min on the chromosome of
E. coli
, the
brnR
gene is located close to
lac
at 9.0 min, and the
brnS
gene is close to
pdxA
at 1 min. A mutant lacking the low-affinity transport system for isoleucine was isolated from a strain in which the high-affinity system was missing because of a
brnR
mutation. This strain also required isoleucine for growth because of an
ilvA
mutation. The mutant lacking the low-affinity transport system was unable to grow on isoleucine but could grow on glycylisoleucine. This mutant had lost the low-affinity transport for isoleucine, whereas those for leucine and valine were unaffected. A pleiotropic consequence of this mutation (
brn-8
) was a complete absence of the very-high-affinity transport system due either to the alteration of a common gene product or to any kind of secondary interference which inhibits it. Mutants altered in isoleucine-leucine-valine transport were isolated by taking advantage of the inhibition that valine exerts on the K-12 strain of
E. coli
. Mutants resistant both to valine inhibition (Val
r
) and to glycylvaline inhibition are regulatory mutants. Val
r
mutants that are sensitive to glycylvaline inhibition are transport mutants. When the very-high-affinity transport process is repressed (for example by methionine) the frequency of transport mutants among Val
r
mutants is higher, and it is even higher if the high-affinity transport process is partially inhibited by leucine.
Phosphate-Mediated Alteration of theMicrosporum gypseumGermination Protease Specificity for Substrate: Enhanced Keratinase Activity
Authors: Page W. J. , Stock J. J.
Published: January 2020

Inorganic phosphate was found to decrease the caseinolytic and ethyl-esterase activities of theMicrosporum gypseumgermination protease. The germination protease possessed exokeratinase (beta-keratinase) activity immediately after release from the fungal spore. After phosphate treatment of the enzyme, the germination protease also possessed endo-keratinase (alpha-keratinase) activity. Phosphate altered the protease's pH optimum from 9.0 to 7.0 and decreased the molecular weight from 33,000 to 16,000. These values were identical to those found for the keratinase. Alpha- and beta-keratinase activities were stimulated in excess of 200-fold by disulfide reducing agents. Natural and suspected keratin degradation products also enhanced keratinase activity. Cell fractionation and in vitro conversion of the alkaline germination protease into a functional keratinase suggested that the subunits comprising the germination protease and the keratinase were of a common origin.
Cyclic Adenosine 3′,5′-Monophosphate and Morphogenesis in
Mucor racemosus
Authors: Larsen Alf D. , Sypherd Paul S.
Published: January 2020

Yeastlike cells of
Mucor racemosus
grown under 100% CO
2
underwent morphogenesis to hyphae after exposure to air. The addition of dibutyryl cyclic adenosine monophosphate (dbcAMP) to yeastlike cultures inhibited this morphogenesis in media containing 2% glucose. The maintenance of uniformly spherical, budding cells required 1 mM dbcAMP in a defined medium containing Casamino Acids, and 3 mM dbcAMP in a medium containing yeast extract and peptone. At these concentrations, dbcAMP also induced yeastlike development in young aerobic hyphae grown in media containing 2% glucose. Removal of dbcAMP resulted in hyphal development. The endogenous cyclic AMP (cAMP) content of yeastlike cultures was measured after a shift from CO
2
to air. A fourfold decrease in intracellular cAMP preceded the appearance of hyphal germ tubes. These results indicate that cAMP plays a role in the control of morphogenesis in
Mucor racemosus
.
l
-Glutamine as a Substrate for
l
-Asparaginase from
Serratia marcescens
Authors: Novak Edward K. , Phillips Arthur W.
Published: January 2020

l
-Asparaginase from
Serratia marcescens
was found to hydrolyze
l
-glutamine at 5% of the rate of
l
-asparagine hydrolysis. The ratio of the two activities did not change through several stages of purification, anionic and cationic polyacrylamide disk gel electrophoresis, and partial thermal inactivation. The two activities had parallel blood clearance rates in mice.
l
-glutamine was found to be a competitive inhibitor of
l
-asparagine hydrolysis. A separate
l
-glutaminase enzyme free of
l
-asparaginase activity was separated by diethylaminoethyl-cellulose chromatography.
Buoyant Density Heterogeneity in Spores of
Bacillus subtilis
: Biochemical and Physiological Basis
Authors: Dean D. H. , Douthit H. A.
Published: January 2020

The biochemical and physiological basis of density heterogeneity in Renografin of
Bacillus subtilis
W23 spores was determined by analysis of metals, macromolecules, and dipicolinic acid in the two density classes of the population. Germination rate and heat resistance were measured in both density classes. Atomic absorption spectrophotometry revealed that heavy spores (density = 1.335 g/ml) have 30% more calcium than light spores (density = 1.290 g/ml). Other metals found in greater amounts in heavy spores were manganese and potassium. However, light spores had more sodium than heavy spores. The amounts of carbohydrates, nucleic acids, and proteins were the same in both types of spores, but light spores contained more lipids, whereas heavy spores had 30% more dipicolinic acid than light spores. Calcium and lipid were excluded as causes of the heterogeneity in density in that alteration of their contents in spores did not detectably affect the density of these spores. Spores of two densities were genetically similar. Furthermore, light density spores arose earlier during sporulation than heavy spores as determined by releasing refractile forespores at various times during sporulation. We concluded that light spores represent an incomplete stage in development because they became heavy when reinoculated into spent sporulation medium. This must involve the additional accretion or synthesis of dipicolinic acid.
Differences in Arginine Requirement for Growth Among Arginine-Utilizing
Mycoplasma
Species
Authors: Hahn Ricardo G. , Kenny George E.
Published: January 2020

The essentiality of arginine for initiation of growth of arginine-utilizing, nonglycolytic
Mycoplasma
species from small populations was studied by growing the organisms in a semisynthetic medium proven to be free from arginine by chemical and biological assays. Initiation of growth of two strains of
M. arginini
did not require arginine, whereas another strain of
M. arginini
required 4 mM arginine, as did
M. gallinarum. M. hominis
grew in 0.4 mM arginine. A species which utilizes both arginine and glucose,
N. fermentans
, did not require arginine but did require glucose for growth. When mycoplasmata were grown in human heteroploid cell cultures employing medium free from arginine but supplemented with citrulline, similar results were obtained: two
M. arginini
strains grew in the absence of arginine, whereas growth of
M. gallinarum
and
M. hominis
and a third
M. arginini
strain was dependent on arginine even though mammalian cells were present. The arginine deiminases were heterogeneous serologically: antisera to
M. hominis
and
M. arginini
showed reciprocal inhibition of their enzymes but did not inhibit arginine deiminase from
M. gallinarum
. Antiserum to
M. gallinarum
inhibited only
M. gallinarum
enzyme.
Molecular Nature of Two Nonconjugative Plasmids Carrying Drug Resistance Genes
Authors: Guerry Patricia , Van Embden Jan , Falkow Stanley
Published: January 2020

Two nonconjugative R-plasmids, N-SuSm and N-Tc, have been characterized. Both were of relatively small size (5 × 10
6
to 6 × 10
6
daltons) and present in multiple copies within their respective bacterial hosts. N-SuSm possessed a guanine plus cytosine content of 55%, whereas N-Tc was 49% guanine plus cytosine. Although these plasmids were inherently nontransmissible they could be mobilized by a large variety of transfer agents including Ent, Hly, and K88. The
fi
−
transfer factors tested were far more likely (about 200×) to mobilize these nonconjugative plasmids than were the
fi
+
transfer factors tested. Although the mobilization phenomenon was not found to be associated with a detectable level of direct stable recombinational union between N-SuSm or N-Tc with a transfer factor, we were able to demonstrate a low level of recombination between these replicons and a transfer factor by P1-mediated transduction. The isolation of recombinants between transfer factors and nonconjugative plasmids presumably represents one means by which unitary molecular types of R-plasmids arise and by which existing R-plasmids may acquire new resistance determinants.
Separate Branches of the
uvr
Gene-Dependent Excision Repair Process in Ultraviolet-Irradiated
Escherichia coli
K-12 Cells; Their Dependence upon Growth Medium and the
polA, recA, recB
, and
exrA
Genes
Authors: Youngs David A. , Van Der Schueren Emmanuel , Smith Kendric C.
Published: January 2020

The extent of repair of single-strand breaks (incision breaks) induced in the deoxyribonucleic acid (DNA) of
Escherichia coli
K-12 cells by the
uvr
gene-dependent excision repair process after ultraviolet (UV) radiation was determined in the wild-type,
polA1, recA56, recB21
, and
exrA
strains. The wild-type strain repaired all incision breaks after incident doses of UV radiation (254 nm) of ∼60 J m
−2
or less when incubated in growth medium, or ∼15 J m
−2
or less when incubated in buffer. The
polA1
strain repaired the incision breaks completely after incident doses of ∼12 J m
−2
or less when incubated in growth medium, or after ∼4 J m
−2
when incubated in buffer. The
recA13, recB21
, and
exrA
strains showed essentially complete repair after incident doses of 10 to 15 J m
−2
whether the cells were incubated in buffer or growth medium. These results suggest that the
uvr
gene-dependent excision repair process may be divided into two branches, one which is dependent on the presence of growth medium and also the
rec
+
exr
+
genotype, and a second which can occur in buffer (growth medium-independent) and is largely dependent on DNA polymerase I. The presence of chloramphenicol in the growth medium resulted in an inhibition of the growth medium-dependent repair occurring in wild-type and
polA1
cells and had little or no effect on the extent of repair observed in
recA56, recB21
, or
exrA
cells. The similarities between the growth medium-dependent and -independent branches of excision repair and two known processes for the repair of X-ray-induced single-strand breaks are discussed.
Plain and Complex Flagella of
Pseudomonas rhodos
: Analysis of Fine Structure and Composition
Authors: Schmitt Rüdiger , Raska Ivan , Mayer Frank
Published: January 2020

Cells of
Pseudomonas rhodos
9-6 produce two morphologically distinct flagella termed plain and complex, respectively. Fine structure analyses by electron microscopy and optical diffraction showed that plain flagellar filaments are cylinders of 13-nm diameter composed of globular subunits like normal bacterial flagella. The structure comprises nine large-scale helical rows of subunits intersecting four small-scale helices of pitch angle 25°. Complex filaments have a conspicuous helical sheath, 18-nm wide, of three close-fitting helical bands, each about 4.7-nm wide, separated by axial intervals, 4.7 nm wide, running at an angle of 27°. The internal core has similar but not identical substructure to plain filaments. Unlike plain flagella, the complex species is fragile and does not aggregate in bundles. Mutants bearing only one of two types of flagellum were isolated. Cells with plain flagella showed normal translational motion, and cells with complex flagella showed rapid spinning. Isolated plain flagella consist of a 37,000-dalton subunit separable into two isoproteins. Complex filaments consist of a 55,000-dalton protein; a second 43,000-dalton protein was assigned to complex flagellar hooks. The results indicate that plain and complex flagella are entirely different in structure and composition and that the complex type represents a novel flagellar species. Its possible mode of action is discussed.
Physiological and Morphological Correlation of
Rhizopus stolonifer
Spore Germination
Authors: Van Etten James L. , Bulla Lee A. , St. Julian Grant
Published: January 2020

Sporangiospores of
Rhizopus stolonifer
were examined at various stages of germination by scanning electron and phase-contrast microscopy. These observations were correlated with changes in spore dry weight, spore volume, respiration, and syntheses of ribonucleic acid, deoxyribonucleic acid, and protein during germination.
Penicillin Binding Components in
Bacillius subtilis
During Sporulation
Authors: Anwar Rashid A. , Blumberg Peter M. , Strominger Jack L.
Published: January 2020

The penicillin binding components of sporulating
Bacillus subtilis
3610 were compared with those of the vegetative organism. No qualitative difference in binding components was observed. The total binding, however, varied with the phase of sporulation.
d
-Alanine Carboxypeptidase and Cell Wall Cross-Linking in
Bacillus subtilis
Authors: Sharpe Arlene , Blumberg Peter M. , Strominger Jack L.
Published: January 2020

Inhibition of
d
-alanine carboxypeptidase in
Bacillus subtilis
by 95% caused no measurable change in the degree of cross-linking of the peptidoglycan.
Isolation and Characterization of Low-Kynureninase Mutants of
Neurospora crassa
Authors: Schlitt Steven C. , Lester Gabriel , Russell Peter J.
Published: January 2020

Two kynureninase activities are known in
Neurospora crassa
, one of which (kynureninase I) is inducible, the other (kynureninase II) being constitutive. A method is described for the isolation of low-kynureninase mutants of
N. crassa
. When grown on an inducer, the mutants show significantly less kynureninase I activity compared with wild type, whereas constitutive kynureninase II activity is unaffected. Since a low level of kynureninase I activity remains in the mutants examined, the mutations may be in a regulatory gene or genes. Other experiments are described concerning the molecular weights of the two enzymes and the intracellular localization and specificity of kynureninase II.
Relation of Macromolecular Synthesis in Streptococci to Efficiency of Transformation by Markers of Homospecific and Heterospecific Origin
Authors: Deddish Peter A. , Ravin Arnold W.
Published: January 2020

In previous studies with
Streptococcus sanguis
and
S. pneumoniae
as recipients and donors of transforming deoxyribonucleic acid (DNA), it was found that heating recipients just prior to exposure to DNA caused an increase in the number of transformants induced by heterospecific DNA relative to that induced by homospecific DNA. In the present studies,
S. sanguis
recipients were found to recover from this effect of heat (48 C, 15 min) when incubated at 37 C before exposure to DNA. Inhibitors of nucleic acid synthesis, such as rifampin, 5-fluorodeoxyuridine, actinomycin, and
p
-hydroxyphenylazo-uracil, but not inhibitors of protein synthesis, such as chloramphenicol and erythromycin, prevented recovery from the effect of heat. Inhibitors of nucleic acid synthesis caused changes in unheated cells similar to those observed with heat treatment; these changes included increased transformability by genetically hybrid DNA and by low-efficiency markers in homospecific DNA. The effect of a combination of heat and inhibitors on transformation by heterospecific DNA was greater than when single treatments were used. The most effective inhibitor used alone was rifampin: in treated recipient cells, the yield of transformants produced by a given amount of irreversibly bound heterospecific DNA was increased without a significant change in the yield of transformants produced by bound homospecific DNA. A cell being doubly transformed by homospecific and heterospecific DNA was enhanced specifically in its transformability with the latter as a consequence of rifampin treatment. Treatment with rifampin also increased co-transformation by linked heterospecific markers. The period during which recipient cells were sensitive to the effects induced by rifampin and fluorodeoxyuridine lasted from 10 to 20 min after DNA uptake.
Magic Spot Metabolism in an
Escherichia coli
Mutant Temperature Sensitive in Elongation Factor Ts
Authors: Glazier Karen , Schlessinger David
Published: January 2020

A temperature-sensitive mutant of
Escherichia coli
HAK88 which has been shown to have a lesion in elongation factor Ts (EFTs) was studied with repsect to its metabolism of guanosine 5′-diphosphate, 2′(3′)-diphosphate (ppGpp) and the associated failure of ribosomal ribonucleic acid (rRNA) accumulation at the nonpermissive temperature. Results reported here show that (i) when EFTs is nonfunctional, a full complement of charged transfer RNA (tRNA) cannot prevent accumulation of ppGpp (magic spot) and the stringent failure of rRNA accumulation; (ii) chloramphenicol prevents magic spot (MS) formation and the stringent response not by increasing the percentage of charged tRNA, but possibly by somehow interfering directly with the synthesis of MS; and (iii) tetracycline can lead to MS disappearance without resumption of RNA synthesis. Thus, the absence of MS and the presence of a functional RNA polymerase and charged tRNA are not sufficient to support rRNA accumulation in vivo. An additional element in the regulatory system is suggested.
Circadian Rhythms of Nucleic Acid Metabolism in
Neurospora crassa
Authors: Martens Christine L. , Sargent Malcolm L.
Published: January 2020

Wild-type, band, and fluffy strains of
Neurospora crassa
exhibit circadian rhythms of ribonucleic acid and deoxyribonucleic acid content in the growth-front hyphae of cultures grown on a solid medium. There is also a rhythm of
3
H-uridine incorporation into the nucleic acids of the band strain. Maximum incorporation precedes the peaks of nucleic acid content which occur during conidiation. As cultures age, ribonucleic acid content decreases rapidly and deoxyribonucleic acid content decreases gradually in standing, shake, and bubble cultures. A reduction of ribonuclease activity with age is also noted in standing and shake cultures. The nucleic acid content, nuclease activity, and changes associated with age vary with the culture conditions.
In Vivo and In Vitro Complementation Between
guaB
and In Vivo Complementation Between
guaA
Auxotrophs of
Salmonella typhimurium
Authors: Schafer Millie P. , Hannon William H. , Levin Alfred P.
Published: January 2020

guaA
and
guaB
mutants of
Salmonella typhimurium
were isolated utilizing the mutagen, nitrous acid. The
guaB
mutants were defective for inosine 5′-monophosphate (IMP) dehydrogenase activity and those mutants classified as
guaA
exhibited no xanthosine 5′-monophosphate aminase activity. In vivo complementation maps were determined for the mutants. The
guaB
map indicated that at least three complementation regions existed whereas five complementation regions were observed for the
guaA
mutants. The demonstration of in vitro complementation was also achieved for the
guaB
mutants by utilizing a process of denaturation and renaturation. All of the
guaB
mutants that exhibited in vivo complementation were found to exhibit in vitro complementation. No correlation was found between the degree of in vivo complementation exhibited by the various pairs of mutants and the specific enzyme activities of the same mutant pair that yielded in vitro complementation. The kinetic parameters for three of the most active
guaB
“complemented” enzymes and a renatured wild-type IMP dehydrogenase were then examined. No apparent differences were found in the

K
m

values between any of the enzymes for substrate, IMP, activator ion, K
+
, and coenzyme, oxidized nicotinamide adenine dinucleotide. Some differences were noted in the apparent
V
max
values; the best “complemented” enzyme yielded only 20% of the velocity exhibited by renatured wild-type enzyme.
Degree of Completion of 3′-Terminus of Transfer Ribonucleic Acids of
Bacillus subtilis
168 at Various Developmental Stages and Asporogenous Mutants
Authors: Vold Barbara
Published: January 2020

Transfer ribonucleic acids from sporulating cells, spores, sporangia, or stationary-phase asporogenous mutants of
Bacillus subtilis
all showed a deficiency in the 3′-terminal adenosine moiety.
Amino-Terminal Sequences of Some
Escherichia coli
30
S
Ribosomal Proteins and Functionally Corresponding
Bacillus stearothermophilus
Ribosomal Proteins
Authors: Higo Ken-Ichi , Loertscher Kenneth
Published: January 2020

Amino-terminal sequences of five purified
Escherichia coli
30
S
ribosomal proteins (S4, S9, S10, S16, and S20) were compared with those of their functionally corresponding
Bacillus stearothermophilus
ribosomal proteins identified previously by the reconstitution technique. An automatic Edman degradation method was used for sequence determinations. The sequence of the first 30 residues is presented, except that only the first 25 residues are shown for the S20 pair. Substantial (40 to 70%) sequence homologies have been observed in every case. The results show that the pairs of functionally equivalent proteins, previously identified by the reconstitution technique, are also chemically related. Thus, the present chemical studies give further support for the previous conclusion that two ribosomes with different properties, 30
S
subunits from
E. coli
and
B. stearothermophilus
, have the same fundamental structural organization.
Nitrate Transport System in
Neurospora crassa
Authors: Schloemer Robert H. , Garrett Reginald H.
Published: January 2020

Nitrate uptake in
Neurospora crassa
has been investigated under various conditions of nitrogen nutrition by measuring the rate of disappearance of nitrate from the medium and by determining mycelial nitrate accumulation. The nitrate transport system is induced by either nitrate or nitrite, but is not present in mycelia grown on ammonia or Casamino Acids. The appearance of nitrate uptake activity is prevented by cycloheximide, puromycin, or 6-methyl purine. The induced nitrate transport system displays a

K
m

for nitrate of 0.25 mM. Nitrate uptake is inhibited by metabolic poisons such as 2,4-dinitrophenol, cyanide, and antimycin A. Furthermore, mycelia can concentrate nitrate 50-fold. Ammonia and nitrite are non-competitive inhibitors with respect to nitrate, with

K
i

values of 0.13 and 0.17 mM, respectively. Ammonia does not repress the formation of the nitrate transport system. In contrast, the nitrate uptake system is repressed by Casamino Acids. All amino acids individually prevent nitrate accumulation, with the exception of methionine, glutamine, and alanine. The influence of nitrate reduction and the nitrate reductase protein on nitrate transport was investigated in wild-type
Neurospora
lacking a functional nitrate reductase and in nitrate non-utilizing mutants,
nit-1, nit-2
, and
nit-3
. These mycelia contain an inducible nitrate transport system which displays the same characteristics as those found in the wild-type mycelia having the functional nitrate reductase. These findings suggest that nitrate transport is not dependent upon nitrate reduction and that these two processes are separate events in the assimilation of nitrate.
Dialysis Culture of T-Strain Mycoplasmas
Authors: Masover Gerald K. , Hayflick Leonard
Published: January 2020

Using dialyzing cultures of T-strain mycoplasmas, it was possible to make some observations relevant to the growth and metabolism of these organisms which would not be possible in nondialyzing cultures due to growth inhibition of the organisms by elevated pH and increased ammonium ion concentration in media containing urea. The rate of ammonia accumulation was found to be related to the initial urea concentration in the medium and could not be accounted for by any change in the multiplication rate of the organisms. More ammonia was generated than could be accounted for by the added urea alone, suggesting that an ammonia-producing activity other than urease may be present in T-strain mycoplasmas. Titers above 10
7
color change units per ml were achieved in dialysis cultures of a T-strain mycoplasma in the presence of urea, and such titers were maintained for approximately 60 h during dialysis culture in the absence of added urea.
Carbohydrate Metabolism During Ascospore Development in Yeast
Authors: Kane Sherwin M. , Roth Robert
Published: January 2020

Carbohydrate metabolism, under sporulation conditions, was compared in sporulating and non-sporulating diploids of
Saccharomyces cerevisiae
. Total carbohydrate was fractionated into trehalose, glycogen, mannan, and an alkali-insoluble fraction composed of glucan and insoluble glycogen. The behavior of three fractions was essentially the same in both sporulating and non-sporulating strains; trehalose, mannan, and the insoluble fraction were all synthesized to about the same extent regardless of a strain's ability to undergo meiosis or sporulation. In contrast, aspects of soluble glycogen metabolism depended on sporulation. Although glycogen synthesis took place in both sporulating and non-sporulating strains, only sporulating strains exhibited a period of glycogen degradation, which coincided with the final maturation of ascospores. We also determined the carbohydrate composition of spores isolated from mature asci. Spores contained all components present in vegetative cells, but in different proportions. In cells, the most abundant carbohydrate was mannan, followed by glycogen, then trehalose, and finally the alkali-insoluble fraction; in spores, trehalose was most abundant, followed by the alkali-insoluble fraction, glycogen, and mannan in that order.
Mutation in
Saccharomyces cerevisiae
Conferring Streptomycin and Cold Sensitivity by Affecting Ribosome Formation and Function
Authors: Bayliss Frank T. , Ingraham John L.
Published: January 2020

A cold-sensitive, streptomycin-sensitive mutant of
Saccharomyces cerevisiae
accumulates a 28
S
ribonucleoprotein particle when grown at low temperature. This particle contains 17
S
ribosomal ribonculeic acid which is degraded when exposed to ribonuclease. The particle does not serve as a precursor to 60 and 40
S
ribosomal subunits nor is it turned over when growth is allowed to resume at the permissive temperature; rather it is only diluted by growth. That streptomycin sensitivity (allelic with cold sensitivity) is ribosomal is evidenced by the inhibition of protein synthesis in vitro by streptomycin and the binding of labeled streptomycin to the mutant but not the parental 40
S
ribosomal subunit.
Novel Ribonucleic Acid Species Accumulated in the Dark in the Blue-Green Alga
Anacystis nidulans
Authors: Singer Richard A. , Doolittle W. Ford
Published: January 2020

In the dark, the obligately photoautotrophic blue-green alga
Anacystis nidulans
accumulates large relative amounts of two novel stable ribonucleic acid species (RNAs). These species are also made in illuminated cells but are unstable in them. When darkened cells are reilluminated, these RNAs are rapidly degraded; degradation is inhibited by chloramphenicol. Upon denaturation with heat or urea, one novel species (0.33 × 10
6
daltons) dissociates into two fragments that comigrate with the second novel species (0.16 × 10
6
daltons) on polyacrylamide gels. Both RNAs are associated with particles sedimenting between 30
S
and 50
S
through sucrose gradients and are removed from these particles at low magnesium concentration. The function(s) of these RNAs remains unknown.
Involvement of
recA
and
exr
Genes in the In Vivo Inhibition of the
recBC
Nuclease
Authors: Marsden Howard S. , Pollard Ernest C. , Ginoza William , Randall Eleanor P.
Published: January 2020

When
Escherichia coli
cells are gamma irradiated they degrade their deoxyribonucleic acid (DNA). The DNA of previously gamma-irradiated T4 phage is also degraded in infected cells. The amount of degradation is not only dependent on the dose but also on the genotype of the cell. The amount of degradation is less in cells carrying a
recB
or a
recC
mutation, suggesting that most of the DNA degradation is due to the
recB
+
and
recC
+
gene product (exonuclease V). In some strains a previous dose of ultraviolet (UV) light followed by incubation renders the cells resistant to DNA degradation after gamma irradiation. We have shown this inhibition to take place for infecting T4 phage also. By using six strains of
E. coli
selected for mutations in the genes
recA, exr
(or
lex
), and
uvrB
, we have been able to show that the preliminary UV treatment produces no change in
recA
and
exr
cells for both endogenous DNA degradation and the degradation of infecting irradiated T4 phage DNA, i.e., inhibition was not detected in these strains. On the other hand, wild-type cells and strains carrying mutations of
uvrB
show inhibition in both types of experiments. Because the
recA
gene product and the
exr
+
(
lex
+
) gene product are necessary for the induction of prophage, it is possible that the phenomenon of inducible inhibition requires
recA
+
and
exr
+
presence. One interpretation of these results is that an inducible inhibitor may be controlled by the
exr
gene.
Isolation and Characterization of Specialized φ80 Transducing Phages Carrying Regions of the
Salmonella typhimurium trp
Operon
Authors: Denney Richard M. , Yanofsky Charles
Published: January 2020

We have isolated a series of nondefective φ80 specialized transducing phage which carry segments of the
Salmonella typhimurium trp
operon. These phage were obtained from a lysogenic derivative of a merozygote constructed by transferring an
S. typhimurium trp
episome into an
Escherichia coli
strain which lacks the normal φ80 attachment site. The deoxyribonucleic acid (DNA) from one such phage was purified and employed in DNA-ribonucleic acid (RNA) hybridization studies. The results obtained show that, under our hybridization conditions, heterologous hybridization is less efficient than homologous hybridization. It was also observed that not all
S. typhimurium trp
messenger RNA can readily anneal to
E. coli trp
operon DNA. Heterologous hybrids consisting of
S. typhimurium trp
messenger RNA and
E. coli trp
operon DNA were estimated to have a dissociation constant 10-fold larger than that of homologous hybrids.
Isolation and Partial Characterization of
Escherichia coli
Mutants with Low Levels of Transfer Ribonucleic Acid Nucleotidyltransferase
Authors: Deutscher Murray P. , Hilderman Richard H.
Published: January 2020

To determine the function of the enzyme transfer ribonucleic acid (tRNA) nucleotidyltransferase in vivo, five mutants of
Escherichia coli
containing low levels of this enzyme were isolated. Since no selection procedure for such mutants existed, these strains were isolated by assay of large numbers of colonies from a heavily mutagenized stock. A procedure employing cells made permeable to tRNA and ATP was used to screen the large number of colonies required for the isolation. All the mutants contained less than 20% of the normal level of the AMP-incorporating activity of tRNA nucleotidyltransferase in extracts prepared by several methods, and the best mutant contained only about 2% of this activity. Three of the mutants also had equally low levels of the cytidine 5′-monophosphate-incorporating activity of the enzyme. Despite these low activities, the mutant strains displayed relatively normal growth characteristics at all temperatures examined. The enzyme in the mutant strains was not temperature sensitive, nor were any other abnormal biochemical properties detected. tRNA isolated from the mutant strains was missing significant amounts of its 3′ terminal adenosine 5′-monophosphate residue, amounting to 10 to 15% in the best mutant. However, only small amounts of the terminal cytidine 5′-monophosphate residue were missing. The results indicate that tRNA nucleotidyltransferase is involved in some aspect of synthesis or repair of the 3′ terminus of tRNA, and that the enzyme is present in large excess over its requirements for this function.
Penetration of
Bdellovibrio bacteriovorus
into Host Cells
Authors: Abram Dinah , e Melo J. Castro , Chou D.
Published: January 2020

Electron microscopy reveals that, in
Bdellovibrio
infection, after the formation of a passage pore in the host cell wall, the differentiated parasite penetration pole is associated with the host protoplast. This firm contact persists throughout the parasite penetration and after this process is completed. In penetrated hosts this contact is also apparent by phase microscopy. The association between the walls of the parasite and the host at the passage pore, on the other hand, is transient.
Bdellovibrio
do not penetrate hosts whose protoplast and cell walls are separated by plasmolysis, or in which the membrane-wall relationship is affected by low turgor pressure. It is concluded, therefore, that for penetration to occur it is essential that the host protoplast be within reach of the parasite, so that a firm contact can be established between them. A penetration mechanism is proposed that is effected by forces generated by fluxes of water and solutes due to structural changes in the infected host envelope. These forces cause a differential expansion of the host protoplast and cell wall and their separation from each other around the entry site, while the parasite remains firmly anchored to the host protoplast. Consequently, the parasite ends up enclosed in the expanded host periplasm. The actual entry, therefore, is a passive act of the parasite.
Purification and Properties of Dextransucrase and Invertase from
Streptococcus mutans
Authors: Fukui Kazuhiro , Fukui Yoshio , Moriyama Takafumi
Published: January 2020

Invertase (β-
d
-fructofuranoside fructohydrolase, EC 3.2.1.26) and dextransucrase (α-1, 6-glucan:
d
-fructose 2-glucosyltransferase, EC 2.4.1.5) were purified from the culture fluids of
Streptococcus mutans
by chromatography on Sepharose 6B and diethylaminoethyl-cellulose followed by treatment with hydroxyapatite. Each of the enzyme preparations gave a single band when analyzed by either polyacrylamide gel electrophoresis or immunodiffusion. The antigenic determinant of invertase was different from that of dextransucrase on immunodiffusion. The pH optima were 5.25 for invertase and 5.75 for dextransucrase, and the

K
m

values were 20 mM for invertase and 2.0 mM for dextransucrase. The molecular weights determined by sodium dodecyl sulfate gel electrophoresis were 160,000 for invertase and 170,000 for dextransucrase. The data obtained suggest that the dextransucrase had dextran-synthesizing activity and invertase-like activity.
Occurrence ofN-Formylkynurenine in Extracts ofNeurospora crassa: Evidence for the Activity of Tryptophan Pyrrolase
Authors: Chen James , Matchett William H.
Published: January 2020

N-formylkynurenine and kynurenine have been detected in extracts of tryptophan-grownNeurospora crassa. When the mycelia were grown in medium supplemented withl-[2-14C]tryptophan, the radioactivity was detected inN-formylkynurenine andN-formylanthranilic acid; withl-[β-14C]tryptophan, radioactivity was detected inN-formylkynurenine, kynurenine, kynurenic acid, and xanthurenic acid. The occurrence ofN-formylkynurenine in extracts of tryptophan-grownNeurosporais interpreted as direct evidence for the activity of tryptophan pyrrolase in this organism. The presence of this enzyme was expected on the basis of several earlier studies, but its activity in vitro has so far escaped detection. The in vivo evidence presented here suggests its presence and contributes importantly to our understanding of the tryptophan-anthranilic acid cycle.
Long-Chain Glycerol Diether and Polyol Dialkyl Glycerol Triether Lipids of
Sulfolobus acidocaldarius
Authors: Langworthy Thomas A. , Mayberry William R. , Smith Paul F.
Published: January 2020

Cells of
Sulfolobus acidocaldarius
contain about 2.5% total lipid on a dry-weight basis. Total lipid was found to contain 10.5% neutral lipid, 67.6% glycolipid, and 21.7% polar lipid. The lipids contained C
40
H
80
isopranol glycerol diethers. Almost no fatty acids were present. The glycolipids were composed of about equal amounts of the glycerol diether analogue of glucosyl galactosyl diglyceride and a glucosyl polyol glycerol diether. The latter compound contained an unidentified polyol attached by an ether bond to the glycerol diether. The polar lipids contained a small amount of sulfolipid, which appeared to be the monosulfate derivative of glucosyl polyol glycerol diether. About 40% of the lipid phosphorus was found in the diether analogue of phosphatidyl inositol. The remaining lipid phosphorus was accounted for by approximately equal amounts of two inositol monophosphate-containing phosphoglycolipids, inositolphosphoryl glucosyl galactosyl glycerol diether and inositolphosphoryl glucosyl polyol glycerol diether.
R62, a Naturally Occurring Hybrid R Plasmid
Authors: Guerry Patricia , Falkow Stanley , Datta Naomi
Published: January 2020

R62, a naturally occurring R factor, was shown to be a single deoxyribonucleic acid molecule composed of polynucleotide sequences typical of I group plasmids and also sequences typical of the N group. It determined I pili and belonged to the Iα compatibility group. Although compatible with plasmids of group N, R62 showed complex genetic reactions with N plasmids which are described and interpreted. It is concluded that R62 was the product of illegitimate recombination between an I group and an N group plasmid.
Extracellular Enzyme Secretion by
Pseudomonas lemoignei
Authors: Stinson M. W. , Merrick J. M.
Published: January 2020

The ability of succinate to repress the secretion of
Pseudomonas lemoignei
poly-β-hydroxybutyrate depolymerase was a function of pH. Repression only occurred when the pH of the medium was 7.0 or less. At a higher pH, lack of sensitivity to succinate concentration may have been due to a limited ability to transport succinate. Actively secreting cultures (at pH 7.4) continued to secrete enzyme for approximately 30 min after the pH was rapidly decreased to pH 6.8, even though sufficient succinate was present to repress enzyme synthesis. Similarly, after the addition of rifampin to secreting cultures, there was a 30-min delay before secretion was inhibited. Evidence is presented which suggests that continued secretion may be the result of depolymerase messenger ribonucleic acid accumulation within the cells. Studies with chloramphenicol indicated that de novo protein synthesis is necessary for the secretion of poly-β-hydroxybutyrate depolymerase and that exoenzyme is not released from a preformed pool. Studies with various inhibitors of protein synthesis indicated that synthesis of exoenzyme is 5 to 10 times more susceptible to inhibition than is the synthesis of cell-associated proteins.
Close Genetic Linkage of the Determinants of the Ribitol and
d
-Arabitol Catabolic Pathways in
Klebsiella aerogenes
Authors: Charnetzky W. T. , Mortlock R. P.
Published: January 2020

Klebsiella aerogenes
strain W70 has separate inducible pathways for the degradation of the pentitols ribitol and
d
-arabitol. These pathways are closely linked genetically as determined by transduction with phage PW52. There are two regulatory sites for the ribitol catabolic pathway as defined by loci for mutations to constitutive synthesis of ribitol dehydrogenase and
d
-ribulokinase,
rbtB
and
rbtC
. The two control sites are separated by a site represented by the
dalB22
mutation. This mutation deprives the cell of the ability to induce synthesis of
d
-arabitol dehydrogenase and
d
-xylulokinase activities. Two additional regulatory mutations for the
d
-arabitol pathway,
dalC31
and
dalC37
, map to the opposite side of
rbtB13
relative to
dalB22
. The order of the genetic sites thus far determined for this region is
dalK-dalD-dalC31, dalC37-rbtB13-dalB22-rbtC14-rbtD-rbtK
, where
dalK
and
dalD
represent structural genes for the kinase and dehydrogenase of the
d
-arabitol pathway, respectively, and
rbtK
and
rbtD
represent the corresponding genes for the ribitol pathway. The two mutations that lead to constitutive synthesis of the
d
-arabitol-induced enzymes,
dalC31
and
dalC37
, have different phenotypes with regard to their response to xylitol. The growth of
dalC31
is inhibited by xylitol, but the toxicity can be reduced by increasing the levels of ribitol dehydrogenase either by induction with ribitol or by selection of a ribitol dehydrogenase-constitutive mutation.
Thymineless Death in
Bacillus subtilis
: Correlation Between Cell Lysis and Deoxyribonucleic Acid Breakdown
Authors: Ephrati-Elizur E. , Yosuv D. , Shmueli E. , Horowitz A.
Published: January 2020

Bacillus subtilis
carrying an inducible defective phage is several times more sensitive to thymineless death than a mutagenized derivative that behaves as a nonlysogen. When the integrity of the deoxyribonucleic acid (DNA) of both strains was examined during thymine starvation by transformation experiments, sedimentation studies, and measurements of acid-soluble DNA degradation products, it was shown that extensive DNA breakdown occurred only in the lysogenic strain. During thymine starvation of this strain, there is a progressive proclivity to lysis, followed by leakage of DNA and DNA degradation products. Such leakage was not observed in the nonlysogen. A correlation between proclivity to lysis and extensive DNA degradation is indicated.
Sensitivity of an Early Step in the Sporulation of
Bacillus subtilis
to Selective Inhibition by Ethidium Bromide
Authors: Rogolsky Marvin , Nakamura Hanh T.
Published: January 2020

When a final concentration of 0.4 μg of ethidium bromide (EB) per ml, which is subinhibitory to vegetative growth, is added to sporulating cells of
Bacillus subtilis
Marburg during either stage 0 or the early part of stage 1, morphogenesis is blocked. If the given concentration of EB is added after the early part of stage 1, sporogenesis is unaffected. The synthesis of the serine protease and antibiotic, which are believed to be associated with sporulation events during the early part of stage 0, are not inhibited by EB. Enhanced binding of [
14
C]benzylpenicillin to sporulating cells during septation (stage 2) is a measure of the presence of terminal enzymes for germ cell wall peptidoglycan synthesis. EB does not interfere with the binding of penicillin to sporulating cells, but penicillin remains more permanently bound to EB-treated postlogarithmic cells than to untreated sporulating cells. The absence of an interval of increased penicillin binding activity during stage 2 by sporulating cells treated with EB indicates that EB blocks sporulation prior to the completion of the germ cell wall.
Adenine Nucleotide Changes Associated with the Initiation of Sporulation in
Bacillus subtilis
Authors: Hutchison Keith W. , Hanson R. S.
Published: January 2020

At the end of the exponential growth phase of
Bacillus subtilis
, there is a decrease in the energy level of the cell, whether expressed as adenosine triphosphate concentration or adenylate energy charge. Phosphate limitation of exponentially growing cells produces a similar decrease in the energy level of the cell, and sporulation is derepressed in the presence of 10 mM glucose. A reduction in the tryptophan concentration of the medium during phosphate limitation of the tryptophan auxotroph
B. subtilis
168 prevented the decrease in energy charge. Cells do not sporulate under these conditions. Energy charge values of 0.30 to 0.35 found during sporulation do not lead to cell death.
A New Episomic Element Controlling Fermentative Metabolism and Excretion of Amino Acids by
Citrobacter intermedium
C3
Authors: Pares R. , Guinea J. , Hernandez S. , Valoix Josefina , Jofre J.
Published: January 2020

Glutamate excretion by colonies of
Citrobacter intermedium
C3 was detected by using the auxotrophic strain
Leuconostoc mesenteroides
P-60. A constant ratio of strain C3 colonies did not excrete glutamate. These colonies were subcultured, and colonial analysis of their descendants established that the change from non-excretor to excretor (Sg
−
→ Sg
+
) is a spontaneous and random process with occurs at a high rate, and that an equilibrium state results from the back-transition Sg
+
→ Sg
−
in large populations. Acridine orange, ethidium bromide, and shaking have a strong influence on Sg
+
-to-Sg
−
interconversion, which suggests that a genetic element like an episome is implicated (S factor). Various auxotrophic mutants of bacterial strain C3 have been cured of the S factor. Strains lacking the S factor (S
−
strains) do not excrete glutamate and lose their fermentative metabolism completely. Consequently, the S factor is different from other extrachromosomal genetic factors whose elimination does not modify central metabolism. The gain of the S factor by infectious transfer has been shown with different C3 auxotrophic mutant strains. Also, the S factor has been transferred to
Paracolobactrum intermedium
ATCC 11606. These findings suggest that phenotypic changes observed are a consequence of elimination or infectious gain of the S factor, with its autonomous or integrated multiplication.
Isolation and Characterization of an
Escherichia coli
Mutant Tolerant to Colicins Ia and Ib
Authors: Cardelli James , Konisky Jordan
Published: January 2020

Two classes of spontaneous colicin I insensitive mutants of
Escherichia coli
have been isolated. The first class (called
cir
) has lost its ability to adsorb either colicin Ia or Ib, maps at 41 min on the
E. coli
genetic map, and retains sensitivity to all other colicins tested. The
cir
phenotype is probably due to an alteration in the colicin I receptor. The second class of mutant (called
tolI
) retains full capacity to adsorb [
125
I]colicin I and, therefore, represents the isolation of a mutant tolerant to colicin I. The
tolI
mutant is sensitive to all other colicins tested and has a map location of 89-1 min. The
tolI
mutant grows with a reduced mass yield when glucose is used as a carbon source and cannot utilize succinate or acetate for growth. The
tolI
mutant shows a reduced sensitivity to sodium azide and phenethylalcohol. It is suggested that
tolI
is deficient in some aspect of aerobic metabolism which must be operative for colicin I sensitivity.