bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation-Resistant Mutants of
Salmonella typhimurium
LT2: Development and Characterization
Authors: Davies Roland , Sinskey Anthony J.
Published: January 2020

A series of repeated exposures to gamma irradiation with intervening outgrowth of survivors was used to develop radioresistant cultures of
Salmonella typhimuium
LT2. Stepwise increases in resistance to both ionizing and ultraviolet irradiation were obtained independently of the presence or absence of integrated P22 prophage. Single clonal isolates, representing parent and radioresistant populations, retained the general characteristics of the LT2 parent, including serological properties, phage typing, antibiotic sensitivities, mouse virulence, and most biochemical test reactions. Resistant cells were generally larger and contained 1.8 to 2.1 times more ribonucleic acid and protein than parent cells, but deoxyribonucleic acid (DNA) contents were similar. Heterogeneity in the populations with respect to release of H
2
S, utilization of carbon sources, and growth on minimal medium is considered to be ancillary, rather than causally related, to increased radioresistance. The resistant isolates displayed an increased ability to reactivate gamma-irradiated P22 phage. DNA polymerase I and polynucleotide-joining enzyme activities were elevated in extracts of radioresistant cells relative to parent cells. It is suggested that the observed increases in radioresistance result from a selection of mutations leading to an increased capacity to repair DNA.
Ultraviolet-Sensitive Mutator
mutU4
of
Escherichia coli
Inviable with
polA
Authors: Siegel Eli C.
Published: January 2020

Attempts to transduce the ultraviolet-sensitive mutator lesion
mutU4
into strains deficient in deoxyribonucleic acid polymerase I (
polA
) were unsuccessful. Mutator recombinants were found when the
polA
recipient had first been reverted to Pol
+
by selection for resistance to methyl methanesulfonate. The inviability of the
mutU4 polA
double mutant was demonstrated by a reduction in the absolute number of transductants when the recipient was
polA
as compared with Pol
+
, and selection was made for markers very close to
mutU4
. Double mutants containing
mutU4
and
polA4
, which determines a cold-sensitive polymerase, were unable to grow at 24 C, the nonpermissive temperature.
Modification of Bacteriophage φ25 Adsorption toBacillus subtilisby Concanavalin A
Authors: Birdsell D. C. , Doyle R. J.
Published: January 2020

The phytohemagglutinin, concanavalin A (Con A), interacts specifically and reversibly with the α-d-glucose-substituted polyglycerol phosphate teichoic acids ofBacillus subtilis168. Teichoic acids from nonglucosylated strains (mutants resistant to phage φ25) interact weakly, if at all, with Con A. Prior treatment of glucosylated cell walls with Con A results in a concentration-dependent inhibition of phage φ25 adsorption. The inhibition of adsorption to glucosylated cell walls occurs immediately upon the formation of the Con A-cell wall complex and is reversed upon dissociation of the complex by addition of α-methyl glucose. Examination of the interaction between Con A and whole cells, cell walls, or wall digests from glucosylated (phage-sensitive) and non-glucosylated (phage-resistant) strains further demonstrates the specificity of the reaction. A conditional phage φ25-resistant mutant only forms complexes with Con A when grown under permissive conditions.
Distribution of a Phosphoenolpyruvate-Dependent Sugar Phosphotransferase System in Mycoplasmas
Authors: Cirillo Vincent P. , Razin Shmuel
Published: January 2020

A survey of 10 mycoplasma strains has shown that their capacity to accumulate radioactivity from α-methyl-
d
-glucopyranoside depends on the activity of a phosphoenolpyruvate-dependent phosphotransferase system (PTS), and that this system endows the organisms with a high affinity for glucose as a fermentation substrate. PTS activity was found in
Mycoplasma gallisepticum, M. mycoides
var.
mycoides
, and
M. mycoides
var.
capri
, but in none of the fermentative
Acholeplasma
strains nor in some of the nonfermentative
Mycoplasma
species. Partial characterization of the PTS of
M. mycoides
var.
capri
has shown that, like the PTS of
Escherichia coli
and
Staphylococcus aureus
, it is strictly dependent on phosphoenolpyruvate as a phosphoryl donor and on componenets of both the cytoplasm and the membrane.
Pathways of Carbohydrate Metabolism in
Microcyclus
Species
Authors: Kottel R. H. , Raj H. D.
Published: January 2020

Radiorespirometric and enzymatic studies were conducted to determine primary and secondary pathways of carbohydrate catabolism in
Microcyclus aquaticus
and
M. flavus. M. aquaticus
catabolizes both glucose and gluconate mainly via the Entner-Doudoroff and pentose phosphate pathways with some concurrent participation of the Embden-Meyerhof pathway.
M. flavus
, however, oxidizes glucose mainly via the Embden-Meyerhof pathway and gluconate via the Entner-Doudoroff pathway with some simultaneous operation of the pentose phosphate pathway. Both of the organisms showed evidence of the tricarboxylic acid cycle as a secondary pathway for the oxidation of carbohydrates.
Phycobilisomes in
Anacystis nidulans
Authors: Evans Elisabeth L. , Allen Mary M.
Published: January 2020

Phycobilisomes were demonstrated in
Anacystis nidulans
by chemical and morphological studies on cells grown in red light. These cells showed a marked reduction in the chlorophyll-phycocyanin ratio owing to a decreased chlorophyll content. Granular structures of approximately 35 nm were observed throughout red light-grown cells, but were most distinct in the peripheral region. The presence of phycobilisomes in cells grown in red light as well as in cells grown in white light is supported by experiments in which glutaraldehyde was used to stabilize the attachment between the phycobiliprotein and the thylakoids, allowing the isolation of both in the same fraction by sucrose density gradient centrifugation.
Evidence for the Direct Action of Colicin K on Aerobic
32
P
i
Uptake in
Escherichia coli
In Vivo and In Vitro
Authors: Takagaki Yohtaroh , Kunugita Kiyohiko , Matsuhashi Michio
Published: January 2020

Pentachlorophenol (PCP)-sensitive incorporation of
32
P-labeled orthophosphate (
32
P
i
) into nucleotides and nucleic acids by disrupted spheroplasts of
Escherichia coli
was inhibited by addition of colicin K. Incorporation by intact cells was also inhibited by a similar concentration of colicin K. Various colicin K-resistant mutants were isolated, and their ability to incorporate
32
P
i
was tested. When
T6
r
-
colK
r
mutants (T6 phage-resistant) and
tol I
mutants (T6-sensitive, colicin E-sensitive) were converted to disrupted spheroplasts, their
32
P
i
-incorporation became sensitive to colicin K. On the contrary, incorporation by disrupted spheroplasts from
tol II
mutants (T6-sensitive, colicin E-resistant) was fairly resistant to colicin K like that of intact cells. A modification of the cell surface of
T6
r
-
colK
r
mutants, caused by mutation to novobiocin-permeable, T4 phage-resistant cells, restored the sensitivity of the cells to colicin K. The modified
T6
r
-
colK
r
cells did not adsorb T6 phage or colicin K, indicating that the receptors for T6 phage or colicin K are not reactivated by this modification. Similar treatment of
tol I
mutants did not have this effect. These observations strongly suggest that colicin K can act on its target on the cell membrane if it can penetrate the cell surface to reach this target. The receptor for colicin K on the cell surface, which may be part of the T6 phage-receptor, may have some unknown function in relation to the action of colicin K in normal cells, but tends to become dispensable if the cells become permeable to colicin K.
Ultrastructural Properties of the Extra Membranes of
Escherichia coli
O111a as Revealed by Freeze-Fracturing and Negative-Staining Techniques
Authors: Weigand R. A. , Holt S. C. , Shively J. M. , Decker G. L. , Greenawalt J. W.
Published: January 2020

Escherichia coli
O111a is a thermosensitive strain which, when grown at 40 C, accumulates large quantities of intracellular membranes. The ultrastructure of these membranes in cells which have been chemically fixed, embedded, and examined as thin sections has been compared with that of membranes in cells negatively stained or freeze-fractured. Results indicate that the extra membranes are present in the three types of preparations examined and, therefore, clearly are not artifacts of chemical fixation. Negative staining has proved also to be a valuable tool as a rapid means of monitoring cells for the accumulation of large amounts of extra membranes. Also, examination of thin sections has shown that distinct continuities between the plasma membrane and the extra membranes exist. In general, membrane surfaces in freeze-fractured cells containing extra membranes appear smooth and lack the particles associated with the plasma membranes of many cells.
Electron Microscopy of Colicin I-Producing Cells
Authors: Isaacson Richard E. , Konisky Jordan
Published: January 2020

Electron microscope examination of mitomycin C-induced strains of
Escherichia coli
colicinogenic for colicins Ia or Ib reveals particles of approximately 15 to 20 nm in diameter associated with the cell surface. Such structures are not present on uninduced colicinogenic strains nor on a mitomycin C-treated non-colicinogenic strain. In contrast to wild-type colicinogenic strains, induction of a colicinogenic strain known to be lacking the specific colicin I receptor was shown to result in the release of colicin activity into the cell medium. Examination of such induced mutants by electron microscopy showed their cell surfaces to be free of the particles observed on the wild-type strain. The cell medium of such induced mutant strains contained large numbers of particles of similar size and shape to those found on the surface of induced colicinogenic wild-type strains.
Morphological and Structural Changes During the Yeast-to-Mold Conversion of
Phialophora dermatitidis
Authors: Oujezdsky Karen B. , Grove Stanley N. , Szaniszlo Paul J.
Published: January 2020

The details of the morphological and structural events occurring during yeast-to-mold conversion of the human pathogenic fungus
Phialophora dermatitidis
as seen by phase-contrast microscopy and electron microscopy are described and illustrated. Budding yeasts growing exponentially were observed to have thin walls and a cytoplasm exhibiting the characteristics of rapidly growing cells including numerous mitochondria, abundant ribosomes, few vacuoles, and little accumulation of storage material. In contrast, thick-walled yeasts were characterized by less apparent or significantly fewer mitochondria and ribosomes and the presence of considerable amounts of storage materials. Microscope observations of yeast-to-mold conversion revealed that only thick-walled yeasts having prominent lipid bodies in their cytoplasm converted to hyphal forms. Typically, the thick-walled yeast formed two to a number of moniliform hyphal cells which in turn often produced true hyphae. The results indicated that yeasts of
P. dermatitidis
must acquire spore-like characteristics by becoming thick-walled and by accumulating considerable endogenous substrate reserves before they convert and produce hyphae.
Pseudo-
fi
+
I-Like Sex Factor, R62(I), Selective for Increased Pilus Synthesis
Authors: Meynell Elinor
Published: January 2020

An I-like R factor, R62(I), inhibits F-like pilus synthesis and selects for mutant sex factors with a greatly increased capacity for pilus production.
Characterization of Constitutive Galactose Permease Mutants in
Salmonella typhimurium
Authors: Saier Milton H. , Bromberg Fred G. , Roseman Saul
Published: January 2020

Salmonella typhimurium
strains, lacking both enzyme I and the phosphocarrier protein, HPr, of the phosphoenolpyruvate-sugar phosphotransferase system, cannot transport or metabolize glucose and other sugar substrates of this enzyme system. Mutants which regain the ability to specifically utilize glucose were found to constitutively synthesize a galactose permease by virtue of a mutation in the
galR
gene. This permease, shown to be an active transport system, does not require HPr or enzyme I for activity.
Identification of a Self-Inhibitor from Spores of
Dictyostelium discoideum
Authors: Bacon Charles W. , Sussman Alfred S. , Paul Ara G.
Published: January 2020

A self-inhibitor of spore germination has been isolated from spores of
Dictyostelium discoideum
, a cellular slime mold, and chemically characterized as 2-dimethylamino-6-oxypurineriboside.
Increasing Activity of Germinating
Bacillus subtilis
Spores to Incorporate Thymidine Triphosphate into Deoxyribonucleic Acid After Detergent Treatment
Authors: Fujita Yasutaro , Komano Tohru , Tanooka Hiroshi
Published: January 2020

The incorporation of
3
H-labeled thymidine triphosphate (
3
H-dTTP) into deoxyribonucleic acid (DNA) of germinated and then Brij 58-treated
Bacillus subtilis
spores was measured to study DNA replication activity of cells. The dTTP incorporation rate was very low in dormant spores, gradually increased as germination proceeded, and reached a level of the vegetative cell activity approximately 4 hr after the start of germination. This is in contrast to the DNA polymerase activity in the cell extract which remained at the same level throughout the germination period. The increase of the dTTP incorporation activity was inhibited by chloramphenicol or phenethyl alcohol. When these inhibitors were added after germination had proceeded, the elevated dTTP incorporation activity gradually decreased. Permeability to dTTP of spores germinated in the presence of chloramphenicol and then treated with Brij 58 was confirmed by (i)
3
H-dTTP incorporation into the treated spores following either electron or ultraviolet irradiation and (ii) release of radioactivity from the treated spores containing radioactively labeled DNA after deoxyribonuclease I treatment.
Continuous Culture of
Rhodotorula rubra
: Kinetics of Phosphate-Arsenate Uptake, Inhibition, and Phosphate-Limited Growth
Authors: Button D. K. , Dunker Sally S. , Morse M. L.
Published: January 2020

The pink yeast
Rhodotorula rubra
of marine origin was found to be capable of extended growth at very low phosphate concentrations (
K
0.5
= 10.8 n
m
). Average intracellular phosphate concentrations, based on isotope exchange techniques, were 15 to 200 n
m
, giving concentration gradients across the cell envelope of about 10
6
. Sensitivity to metabolic inhibitors occurred at micromolar concentrations. Inability of the phosphate transport system,
K
s
= 0.5 to 2.8 μ
m
,
V
max
= 55 μmoles per g of cells per min, to discriminate against arsenate transport led to arsenate toxicity at 1 to 10 n
m
, whereas environmental arsenate levels are reportedly much higher. Phosphate competitively prevented arsenate toxicity. The
K
i
for phosphate inhibition of arsenate uptake was 0.7 to 1.2 μ
m
. Phosphate uptake experiments showed that maximal growth rates could be achieved with approximately 4% of the total phosphate-arsenate transport system. Organisms adapted to a range both of concentration of NaCl and of
p
H. Maximal affinity for phosphate occurred at
p
H 4 and at low concentrations of NaCl; however,
V
max
for phosphate transport was little affected. Maximal specific growth rates on minimal medium were consistent in batch culture but gradually increased to the much higher rates found with yeast extract media when the population was subjected to long-term continuous culture with gradually increasing dilution rates. Phosphate initial uptake rates that were in agreement with the steady-state flux in continuous culture were obtained by using organisms and medium directly from continuous culture. This procedure resulted in rates about 500 times greater than one in which harvested batch-grown cells were used. Discrepancies between values found and those reported in the literature for other organisms were even larger. Growth could not be sustained below a threshold phosphate concentration of 3.4 n
m
. Such thresholds are explained in terms of a system where growth rate is set by intracellular nutrient concentrations. Threshold concentrations occur in response to nutrient sinks not related to growth, such as efflux and endogenous metabolism. Equations are presented for evaluation of growth rate-limiting substrate concentrations in the presence of background substrate and for evaluating low inhibitor concentration inhibition mechanisms by substrate prevention of inhibitor flux.
Role of the Translocation Factor G in the Regulation of Ribonucleic Acid Synthesis
Authors: Rabbani Elazar , Srinivasan P. R.
Published: January 2020

In an
Escherichia coli rel
+
arg
strain (ES-2) which carries a temperature-sensitive “G factor,” the synthesis of ribonucleic acid (RNA) continues at the nonpermissive temperature (42 C) even though protein synthesis is terminated. However, at 32 C, the strain exhibits a stringent control of RNA synthesis in the absence of arginine. The stringent control of RNA synthesis imposed by trimethoprim (an inhibitor of initiation of protein synthesis) at 32 C is released at the nonpermissive temperature. Even the diauxie lag in RNA synthesis, which is regulated independently of the allelic state of the
rel
gene, is overcome by inactivation of the G factor. The unusual guanosine nucleotide, guanosine 5′-diphosphate 2′ or 3′-diphosphate (ppGpp), is produced in small amounts during growth in strain ES-2. Withdrawal of arginine results in a greater accumulation of this compound at 32 C. At 42 C, the synthesis of ppGpp is abolished and is considerably lower than the level found in ES-2 under normal growth conditions. These results indicate that the translocation factor G plays an important role in the regulation of RNA synthesis and in the synthesis of ppGpp.
Electric Conductivity and Internal Osmolality of Intact Bacterial Cells
Authors: Marquis Robert E. , Carstensen Edwin L.
Published: January 2020

Intact cells of
Streptococcus faecalis
and
Micrococcus lysodeikticus
were found to have high-frequency electric conductivities of 0.90 and 0.68 mho/m, respectively. These measured values, which reflect movements of ions both within the cytoplasm and within the cell wall space, were only about one-third of those calculated on the basis of determinations of the amounts and types of small ions within the cells. Concentrated suspensions of bacteria with damaged membranes showed similarly large disparities between measured and predicted conductivities, whereas the conductivities of diluted suspensions were about equal to predicted values. Thus, the low mobilities of intracellular ions appeared to be interpretable in terms of the physicochemical behavior of electrolytes in concentrated mixtures of small ions and cell polymers. In contrast to the low measured values for conductivity of intact bacteria, values for intracellular osmolality measured by means of a quantitative plasmolysis technique were higher than expected. For example, the plasmolysis threshold for
S. faecalis
cells indicated an internal osmolality of about 1.0 osmol/kg, compared with a value of only 0.81 osmol/liter of cell water calculated from a knowledge of the cell content and the distribution of small solutes. In all, our results indicate that most of the small ions within vegetative bacterial cells are free to move in an electric field and that they contribute to cytoplasmic osmolality.
Polynucleotide Phosphorylase Has a Role in Growth of
Escherichia coli
Authors: Krishna Rangachar V. , Apirion David
Published: January 2020

Mutants having low levels of polynucleotide phosphorylase activity grow poorly at 45 C. All revertants isolated for their ability to grow better at that temperature also regained higher levels of polynucleotide phosphorylase and the ability to be induced for tryptophanase. Thus, a physiological role is implied for the enzyme polynculeotide phosphorylase.
Control of Arginine Biosynthesis in
Escherichia coli
: Role of Arginyl-Transfer Ribonucleic Acid Synthetase in Repression
Authors: Williams L. S.
Published: January 2020

The physiological role of arginyl-transfer ribonucleic acid (Arg-tRNA) synthetase (E.C. 6.1.1.13, arginine: RNA ligase adenosine monophosphate) in repression of arginine biosynthetic enzymes was examined. Mutants with nonrepressible synthesis of arginine biosynthetic enzymes were isolated from various strains of
Escherichia coli
by resistance to growth inhibition by canavanine, an arginine analogue. These mutants possessed reduced Arg-tRNA synthetase activities which were qualitatively different from the synthetase activity of the wild type. The mutant enzymes exhibited turnover in vivo and were less stable in vitro than the wild type at both 4 C and 40 C; they possessed different affinities for both arginine and canavanine as measured by the three common assay systems for aminoacyl-tRNA synthetases. Furthermore, in one case it was shown that (i) the mutant possesed unaltered uptake of arginine, and (ii) that the mutant possessed diminished ability to incorporate canavanine into proteins and to attach canavanine to tRNA. These observations suggested that the mutation to canavanine resistance involved a structural change in Arg-tRNA synthetase. Likewise, the results of genetic experiments suggested that the mutants differed from the wild-type strain at only one locus, and that this lies in the region of the chromosomes that includes a structural gene for Arg-tRNA synthetase. It appears that Arg-tRNA synthetase may be involved in some way in repression by arginine of its own biosynthetic enzymes.
A Polypeptide Bacteriophage Receptor: Modified Cell Wall Protein Subunits in Bacteriophage-Resistant Mutants of
Bacillus sphaericus
Strain P-1
Authors: Howard Lawrence , Tipper Donald J.
Published: January 2020

Bacillus sphaericus
strain P-1 has previously been shown to have a tetragonally arrayed (T layer) protein which forms the outer layer of the cell wall. The T layer was quantitatively extracted from whole cells by 6 M urea, and the T layer subunits were purified by electrophoresis of the extracts on acrylamide gels containing 0.1% sodium dodecyl sulfate or 6 M urea. Using ethylene diacrylate cross-linked gels, the T layer was found to make up 16% of the total cellular protein. A virulent bacteriophage which is inactivated by purified T layer was isolated from soil. Twenty-four phage-resistant mutants were isolated, of which 17 had T layer subunits of increased mobility on sodium dodecyl sulfate acrylamide gels. No mutants devoid of T layer were found. Mutants were grouped into six classes according to the molecular weight of their T layer subunits. These ranged from that of the wild type, 150,000 down to 86,000. Two mutants from different classes were examined in detail. Cells of the mutant strains did not adsorb phage nor did cell walls isolated from these mutants inactivate phage. The amino acid composition of the T layers from mutants differed little from that of the wild-type T layer.
A
cis/trans
Test of the Effect of the First Enzyme for Histidine Biosynthesis on Regulation of the Histidine Operon
Authors: Kovach John S. , Ballesteros Antonio O. , Meyers Marilyn , Soria Marco , Goldberger Robert F.
Published: January 2020

Previous studies showed that when triazolalanine was added to a derepressed culture of a histidine auxotroph, repression of the histidine operon occurred as though histidine had been added (6). However, when triazolalanine was added to a derepressed culture of a strain with a mutation in the first gene of the histidine operon which rendered the first enzyme for histidine biosynthesis resistant to inhibition by histidine, repression did not occur. The studies reported here represent a
cis/trans
test of this effect of mutations to feedback resistance. Using specially constructed merodiploid strains, we were able to show that the wild-type allele is dominant to the mutant (feedback resistant) allele and that the effect operates in
trans
. We conclude that the enzyme encoded by the first gene of the histidine operon exerts its regulatory effect on the operon not by acting locally at its site of synthesis, but by acting as a freely diffusible protein.
Miniature Cell Formation in
Chlamydia psittaci
Authors: Tanami Yoh , Yamada Yoshitsugu
Published: January 2020

In an electron microscope study on the developmental cycle of the goat pneumonitis strain of
Chlamydia psittaci
in L cells, it was observed that miniature reticulate bodies, measuring approximately 0.2 μm in diameter and surrounded by double unit membranes, were produced infrequently from normal-sized reticulate bodies through a “budding”-like process. As little as 0.1 μg of penicillin per ml greatly increased the frequency of the miniature reticulate body formation.
Mesosomes in
Pseudomonas aeruginosa
Authors: Hoffmann Hans-Peter , Geftic Sam G. , Heymann Hans , Adair Frank W.
Published: January 2020

The use of a combination fixative-staining procedure has allowed a detailed observation of mesosomes in thin sections of
Pseudomonas aeruginosa
.
Purification and Properties of Threonine Deaminase from the X-1 Isolate of the Genus
Thermus
Authors: Higa Edward H. , Ramaley Robert F.
Published: January 2020

Threonine deaminase (
l
-threonine dehydratase EC 4.2.1.16) has been partially purified from a new extreme thermophilic bacterium,
Thermus
X-1, which is similar to
T. aquaticus
YT-1. The threonine deaminase of strain X-1 has a maximal rate of reaction at 85 to 90 C and is more thermostable than the threonine deaminase from mesophilic bacteria. The enzyme has an apparent molecular weight of 100,000 to 115,000, a

K
m

for
l
-threonine of 14 mM, a pH optimum of 8.0, and like other threonine deaminases also catalyzes the deamination of serine. However the
Thermus
X-1 threonine deaminase does not show a strong feedback inhibition by isoleucine. It is suggested that the regulation of the biosynthesis of isoleucine in this extreme theromophile may resemble that reported in
Rodospirillum rubrum
.
Effects of Mutational Loss of Specific Intracellular Proteases on the Sporulation of
Bacillus subtilis
Authors: Hageman James H. , Carlton Bruce C.
Published: January 2020

Two protease-deficient mutants of
Bacillus subtilis
168 (Trp
−
) were isolated and compared with the parental strain with respect to production of intracellular proteases and sporulation. A mutant lacking the metal-requiring “neutral” protease intracellularly sporulated as well as the parental strain. A second mutant, deficient in an as yet uncharacterized intracellular protease, failed to sporulate normally. It is proposed that this new protease is also involved in intracellular protein turnover.
Oxidation of Elemental Sulfur by
Sulfolobus acidocaldarius
Authors: Shivvers Douglas W. , Brock Thomas D.
Published: January 2020

Oxidation of elemental sulfur by
Sulfolobus acidocaldarius
, an autotroph which grows at high temperatures and low pH, was examined by use of
35
S-labeled elemental sulfur. When cultured at pH 3.2 and 70 C,
S. acidocaldarius
oxidized elemental sulfur essentially quantitatively to sulfuric acid. Oxidation rate paralleled growth rate and decrease in pH of the culture medium. Elemental sulfur was not oxidized under these conditions if the culture was poisoned with formaldehyde. During the growth phase, the proportion of cells attached to the sulfur crystals increased progressively, and in the later phases of growth over 10 times more cells were attached to sulfur than were free. Doubling times for eight strains growing on elemental sulfur varied from 37 to 55 h. The organism grows much more rapidly on yeast extract than on sulfur. In a medium containing both sulfur and yeast extract, sulfur oxidation was partially inhibited, although growth was excellent.
Ultrastructure of Lipopolysaccharide Isolated from
Treponema pallidum
Authors: Jackson Sally W. , Zey Pinina N.
Published: January 2020

A lipopolysaccharide (LPS) fraction was extracted from Nichols, nonpathogenic
Treponema pallidum
by the hot, phenol-water procedure. The LPS was freed of nucleic acids and water-soluble proteins by successive exposures to ribonuclease, deoxyribonuclease, and Pronase. Purified LPS responded positively in a colorimetric assay for lipopolysaccharide. Electron microscope examination of the LPS both before and after purification demonstrated a heterogeneous mixture of forms including spheres, doughnuts, and ribbons. The trilaminar nature of the ribbon forms was observed by both negative staining and thin sectioning. Lyophilization of the LPS caused an increase in the number and length of ribbon forms seen. Results suggest that the surface layers of treponemes are similar to those of gram-negative bacteria.
Transcriptional Control of the Galactose Operon by the
capR
(
lon
) and
capT
Genes
Authors: Buchanan Christine E. , Hua Sui-Sheng , Avni Hanna , Markovitz Alvin
Published: January 2020

Mutations in
capR
or
capT
cause derepression of the enzymes of the
gal
operon. The
gal
-specific messenger ribonucleic acid is directly proportional to the
gal
enzyme levels in wild type,
capR
, and
capT
strains. These results indicate that
capR
and
capT
control the
gal
operon at the transcriptional level.
Location of the SPO2 Attachment Site and the Bryamycin Resistance Marker on the
Bacillus subtilis
Chromosome
Authors: Smith Issar , Smith Harriet
Published: January 2020

The attachment site on the
Bacillus subtilis
chromosome for the lysogenic bacteriophage SPO2 has been mapped by PBS1-mediated transduction and was found to be between
spc-2
and
lin-2
, showing 90% linkage to the former and 30% linkage to the latter marker. In the course of these studies the
bry-2
marker was mapped between the
cysA14
and
str-1
loci.
Osmotic Behavior of Bacterial Protoplasts: Temperature Effects
Authors: Eisenberg A. D. , Corner T. R.
Published: January 2020

Among protoplasts released from cells of
Bacillus megaterium
grown at 20, 30, or 37 C, osmotic swelling in NaCl solution at a given external osmotic pressure was greatest for protoplasts from cells grown at 20 C and least for protoplasts from cells grown at 37 C. Protoplasts from cells grown at lower temperaturs were also less stable to osmotic shock and lysed at higher external osmotic pressures than did protoplasts from cells grown at higher temperatures. But for cells grown at any one temperature, osmotic stabilization was itself temperature dependent so that the higher the ambient incubation temperature, the higher the osmotic pressure needed to prevent lysis of a given fraction of the input protoplast population. However, comparison of the osmotic stability of protoplasts from cells grown at different temperatures at various ambient incubation temperatures revealed that, except at 5 C where no differences were discerned, protoplasts from cells grown at lower temperatures still lysed at higher osmotic pressures than did those from cells grown at higher temperatures. The apparent internal osmolality (28 to 31 atm) did not vary significantly among whole cells from the three growth temperatures. Therefore, the observed differences in osmotic behavior could not be attributed to changes in internal osmotic pressure. Rather, it seemed likely that the differences were due to changes in membrane properties.
Nitrate Reduction and the Growth of
Veillonella alcalescens
Authors: Inderlied C. B. , Delwiche E. A.
Published: January 2020

Veillonella alcalescens
, a strict anaerobe, was found to possess a nitrate reductase system which has characteristics of both assimilatory and respiratory nitrate reduction. The nitrate reductase has been identified tentatively as a particulate enzyme which utilizes a variety of electron donors for the reduction of nitrate. By use of
15
N-labeled nitrate, it was shown that under appropriate conditions nitrate nitrogen is incorporated into cell material.
V. alcalescens
grown on pyruvate and nitrate has a greater growth rate than cells grown on pyruvate alone. Growth can occur in a medium with hydrogen and nitrate as the sole energy source. Ammonium chloride decreases the rate of nitrate reduction but does not completely inhibit reduction or incorporation. The results suggest that nitrate assimilation and respiration are not as distinct as in some other organisms.
Comparison of the
resA1
and
polA1
Mutations in Isogenic Strains of
Escherichia coli
K-12
Authors: Glickman Barry W. , Van Sluis Cornelis A. , Van Der Maas Gerda , Rörsch Arthur
Published: January 2020

Strains carrying either the
polA1
or
resA1
mutation are deficient in DNA polymerase I, and the
polA1
and
resA1
mutations do not complement in merozygotes. The effect of these mutations in otherwise identical genetic backgrounds was studied: after ultraviolet irradiation both strains degrade their DNA more rapidly and more extensively than the wild-type strains. However, after X-ray irradiation the
resA1
strain shows little DNA breakdown and repairs its single-strand breaks. In contrast, the
polA1
strain degrades its DNA extensively, and single-strand breaks are not repaired. Moreover, the
resA1
strain is capable of supporting the growth of a
red
−
bacteriophage lambda, whereas the
polA1
strain is not.
Effect of Serine Hydroxamate on Phospholipid Synthesis in
Escherichia coli
Authors: Pizer Lewis I. , Merlie John P.
Published: January 2020

Serine hydroxamate, which inhibits the charging of seryl-transfer ribonucleic acid, reduced the synthesis of phospholipid and nucleic acids in
Escherichia coli
. This effect was analogous to depriving amino acid auxotrophs of their nutritional requirement and appears to be a manifestation of the stringent response shown by
rel
+
strains of
E. coli
. Amino acid starvation (serine or methionine) alone or serine hydroxamate treatment alone results in 60 to 80% inhibition of lipid accumulation, 90% inhibition of ribonucleic acid accumulation, and an increase in guanosine tetraphosphate (ppGpp). These three effects were reversed by addition of chloramphenicol (CM). A combination of serine starvation and serine hydroxamate treatment resulted in inhibition of lipid and RNA accumulation as well as an increase in ppGpp, but the consequences of the double block were not reversed by CM. We conclude that a strong interrelationship exists among these processes and that CM acts to relax a stringent response by mechanisms other than interference with ppGpp formation. All species of phospholipid were affected by a stringent response evoked by amino acid starvation or addition of serine hydroxamate, but in all cases the synthesis of phosphatidylethanolamine was most severely inhibited. Serine hydroxamate was not incorporated into lipid but specifically caused phosphatidylserine accumulation. Serine starvation produced a dramatic alteration of the distribution of isotope incorporated into phospholipid, which resulted from the stringent response compounded with the limitation of a substrate for phosphatidylserine synthesis.
Histidyl-Transfer Ribonucleic Acid Synthetase Mutants Requiring a High Internal Pool of Histidine for Growth
Authors: Straus Daniel S. , Ames Bruce N.
Published: January 2020

Mutants that require histidine due to an altered structural gene for the histidyl-transfer ribonucleic acid synthetase (
hisS
) have been isolated by a general selection for histidine-requiring strains in which the mutation producing histidine auxotrophy is unlinked to the histidine operon. One of the mutants has been shown to require an abnormally high internal histidine pool for growth owing to an altered synthetase that is unstable at low histidine concentrations. It is difficult to determine accurately the

K
m

for histidine of the synthetase enzyme from the mutant because of the instability of the enzyme at limiting histidine concentrations; however, a histidine

K
m

value has been estimated that is approximately 100 times higher than the histidine

K
m

of the wild-type enzyme. For the mutant strains to achieve the high internal pool of histidine required for growth, all the systems that transport histidine from the growth medium must be functioning to capacity. Amino acids that interfere with histidine transport strongly inhibit the growth of the mutants. The mutants have been useful in providing a selective genetic marker for transductional mapping in the
hisS
region. The mutants are discussed as representative of a general class of curable mutants that have an altered enzyme with poor affinity for a substrate or coenzyme.
Aspartokinase of
Myxococcus xanthus
: “Feedback Stimulation” by Required Amino Acids
Authors: Filer David , Rosenberg Eugene , Kindler S. H.
Published: January 2020

The aspartokinase activity found in extracts of the bacterium
Myxococcus xanthus
was subject to feedback inhibition and feedback repression by
l
-threonine and
l
-lysine. Both types of inhibition were essentially additive. The required amino acids,
l
-isoleucine and
l
-methionine, caused considerable increase in the activity of the enzyme. This phenomenon is referred to as “feedback stimulation.” The polyamine, spermidine, exerted strong enhancement of the activity even at 0.1 mM. Meso-diaminopimelate, although not inhibitory by itself, abolished the activation exerted by either
l
-isoleucine or
l
-methionine. The possible physiological significance of interactions between the various effectors is discussed.
Aspartokinase Activity and the Developmental Cycle of
Myxococcus xanthus
Authors: Rosenberg Eugene , Filer David , Zafriti Dina , Kindler S. H.
Published: January 2020

The relationship between aspartokinase activity and fruiting body formation in
Myxococcus xanthus
was investigated. Two required amino acids, methionine and isoleucine, which stimulated the enzyme in vitro also inhibited fruiting body formation when added to 0.1% Casitone agar. Threonine, a potent feedback inhibitor of the aspartokinase, completely reversed the effects of methionine and isoleucine both on enzyme activity and fruiting body formation. A mutant,
M. xanthus
FB-S, which had the unusual property of forming fruiting bodies on 1.0% Casitone agar, also exhibited an altered regulation of aspartokinase activity. Spermidine, which is a strong stimulator of the enzyme in vitro, interfered with the developmental cycle of both
M. xanthus
FB and FS-S. During glycerol induction of myxospores the level of aspartokinase dropped more than 75% during the first hour. These data indicate a strong correlation between aspartokinase activity and the induction of the developmental cycle in
M. xanthus
. It is suggested that the decrease in aspartokinase activity results in diaminopimelic acid starvation, blockage of cell wall growth, and subsequent induction of the developmental cycle.
Cell Surface Protein of
Pseudomonas
(
Hydrogenomonas
)
facilis
Authors: Rittenhouse Harry G. , McFadden Bruce A. , Shumway Lewis K. , Heptinstali John
Published: January 2020

Intact cells of
Pseudomonas facilis
contain one major molecular weight class of protein that is exposed at the cell surface as revealed by lactoperoxidase-catalyzed iodination with
125
I. All molecular weight classes of protein in derived cell envelope preparations are apparently saturated by iodination by lactoperoxidase after prolonged sonic treatment. The molecular weight of the predominantly exposed protein in intact cells is approximately 16,000, which is the minimal molecular weight of a cell envelope protein that precipitates as a complex with phospholipid from extracts of
P. facilis
. The isolation of labeled phospholipoprotein (PLP) after labeling intact cells with
125
I corroborates previous experiments which suggested a surface location for the protein portion of the phospholipoprotein (P
PLP
). Solvent extraction of cells and immunological evidence, including studies with ferritin-coupled antibodies, indicate that P
PLP
is located at the cell surface and may also be within the cell envelope. These experiments suggest that P
PLP
is the major cell surface protein in
P. facilis
.
Occurrence and Ultrastructure of a Variant (
rho
) Form of
Mycoplasma
Authors: Peterson J. E. , Rodwell A. W. , Rodwell E. Shirley
Published: January 2020

The ultrastructure of a variant (ρ) form of
Mycoplasma
is described. The ρ-forms are characterized by dark-ground light microscopy as relatively rigid, unbranched, filamentous organisms with discoidal swellings, and by electron microscopy by the presence of an intracytoplasmic axial fiber extending throughout the length of the cell and associated with a terminal structure of characteristic appearance. In negatively stained preparations the fiber presents a pattern of transverse light and dark major bands, the dark band being divided by a central minor light band. The periodicity of the banding varies from 12.0 to 14.5 nm, and the width of the fiber varies from 40 to 120 nm. The fiber appears to be composed of fibrils aligned parallel to the long axis. The evidence indicates that the fiber contains protein and is devoid of nucleic acid. ρ-Forms were commonly found in
Mycoplasma
strains derived from goats and occasionally in bovine strains. They may have a wider distribution, as the growth medium was shown to be important both for the expression of the ρ-character and for the selection of the ρ-variant. The functional significance, if any, of the fiber and the terminal structure is unknown.
Relationship of Adenosine 3′,5′-Monophosphate to Growth and Metabolism of
Tetrahymena pyriformis
Authors: Voichick Jane , Elson Charles , Granner Daryl , Shrago Earl
Published: January 2020

The concentration of adenosine 3′,5′-monophosphate (cyclic AMP) and the activity of adenylate cyclase were determined for the first time in conjuncation with cyclic 3′,5′-nucleotide phosphodiesterase (phosphodiesterase) during the growth cycle of
Tetrahymena pyriformis
. High levels of cyclic AMP observed during early exponential and late stationary phases were associated with elevated adenylate cyclase and decreased phosphodiesterase activities. Adenylate cyclase and cyclic AMP were decreased and phosphodiesterase was increased in cells grown in glucose-supplemented medium. In contrast to findings in mammalian liver, cyclic AMP was decreased during active gluconeogenesis in
Tetrahymena
. This suggests a different modulation of carbohydrate metabolism in the two species. The results illustrate that both the content of cyclic AMP and its action as a regulatory agent in
Tetrahymena
are uniquely suited to the metabolism of this organism.
Metabolism, Macromolecular Synthesis, and Nuclear Behavior of
Cryptococcus albidus
at 37 C
Authors: Tang S. L. , Howard D. H.
Published: January 2020

The temperature-sensitive events which prevent
Cryptococcus albidus
from growing at 37 C were investigated. Cultures incubated at 37 C immediately after inoculation did not increase in optical density nor in cell numbers, and by 24 h 90% of cells in such cultures were deformed and dead. When cultures in log phase were shifted from 23 to 37 C the optical density increased but the cell numbers did not. Morphological observations revealed that the increase in turbidity at 37 C represented enlargement and distortion of cells without appreciable replication. Uptake and incorporation of
14
C-leucine were similar at 23 and 37 C. There was no difference in
14
CO
2
evolution from cells at either temperature. Uptake and incorporation of adenine-8-
14
C into RNA was slightly lower in cells incubated at 37 C. There was, however, a 60% reduction in incorporation of adenine-8-
14
C into DNA after 3 hr at 37 C. Nuclear staining revealed that nuclear migration did not occur in cells incubated at 37 C. Thus the data indicate that both adenine incorporation into DNA and nuclear migration prior to nuclear division by
C. albidus
are temperature sensitive.
Studies on the Developmental Cycle of
Chlamydia trachomatis
: Selective Inhibition by Hydroxyurea
Authors: Rosenkranz Herbert S. , Gutter Bezalel , Becker Yechiel
Published: January 2020

Hydroxyurea, a potent inhibitor of deoxyribonucleic acid synthesis, inhibits the development of trachoma agent when applied at a concentration of 5 × 10
−2
M. At a lower concentration, 5 × 10
−4
M, hydroxyurea permits the development of the trachoma inclusion bodies and initial bodies, but arrests the formation of elementary bodies, the infectious entity of the agent. The inhibitory effect of 5 × 10
−4
M hydroxyurea is reversible and can be used to synchronize the development of the agent. The synthesis of deoxyribonucleic acid, ribonucleic acid, and proteins takes place in the initial bodies after the removal of the inhibitor.
Synthesis of Unmethylated Deoxyribonucleic Acid in a
dnaB
Temperature-Sensitive Mutant of
Escherichia coli
Starved for Methionine
Authors: Bouché Jean-Pierre C.
Published: January 2020

Strain CRT 266, a polyauxotrophic
dnaB
temperature-sensitive mutant of
Escherichia coli
K, was investigated for residual deoxyribonucleic acid (DNA) synthesis when returned to the permissive temperature in the absence of protein synthesis. In the presence of methionine, a delayed extra-initiation occurs as well as an erratic long-lasting synthesis. In the absence of methionine, there is no evidence for extra-initiation, whereas the long-lasting synthesis is only slightly depressed. A direct role of methionine independent of protein synthesis in the extra-initiation process is postulated. The largest residual syntheses, with or without methionine, are obtained when (i) bacteria are first grown in a rich medium, (ii) bacteria are shifted to the nonpermissive temperature for 2 h in the same medium, and (iii) bacteria are then starved for aminoacid for 20 h at the permissive temperature. Under these conditions, DNA extracted from methionine-starved cells appears to be a mixture of half-methylated and unmethylated products. The possibility of the occurence of a few methyl groups on the so-called unmethylated DNA is discussed.
Ribonucleic Acid Polymerase in
Allomyces arbuscula
Authors: Cain Alice K. , Nester Eugene W.
Published: January 2020

Three distinct species of ribonucleic acid (RNA) polymerase were resolved from
Allomyces arbuscula
by diethylaminoethyl-cellulose chromatography and characterized as to ionic strength and divalent cation preference. α-Amanitin specifically inhibited enzyme II; neither rifampin nor cycloheximide had any effect on the three enzymes. RNA polymerase was isolated from three stages of the diploid life cycle: the hyphal growth stage, mycelia in the process of forming sporangia, and the mitospores. The same three enzyme species could be resolved from each stage. Thus, there is no evidence from this work that RNA polymerase plays a major role in the control of development.
Threonine Synthetase-Catalyzed Conversion of Phosphohomoserine to α-Ketobutyrate in
Bacillus subtilis
Authors: Schildkraut Ira , Greer Sheldon
Published: January 2020

An enzyme activity of
Bacillus subtilis
has been found that catalyzes the dephosphorylation and deamination of phosphohomoserine to α-ketobutyrate, resulting in a bypass of threonine in isoleucine biosynthesis. In crude extracts of a strain deficient in the biosynthetic isoleucine-inhibitable threonine dehydratase, phosphohomoserine was converted to α-ketobutyrate. Phosphohomoserine conversion to α-ketobutyrate was shown not to involve a threonine intermediate. Single mutational events affecting threonine synthetase also affected the phosphohomoserine-deaminating activity, suggesting that the deamination of phosphohomoserine was catalyzed by the threonine synthetase enzyme. It was demonstrated in vivo, in a strain deficient in the biosynthetic threonine dehydratase, that isoleucine was synthesized from homoserine without intermediate formation of threonine.