bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen fixation in nitrate reductase-deficient mutants of cultured rhizobia
Authors: Pagan J D , Scowcroft W R , Dudman W F , Gibson A H
Published: January 2020

Forty-eight mutants unable to reduce nitrate were isolated from "cowpea" Rhizobium sp. strain 32Hl and examined for nitrogenase activity in culture. All but two of the mutants had nitrogenase activity comparable with the parental sttain and two nitrogenase-defective strains showed alterations in their symbiotic properties. One strain was unable to nodulate either Macroptilium atropurpureum or Vigna uguiculata and, with the other, nodules appeared promptly, but effective nitrogen fixation was delayed. These results, and the relatively low proportion of nitrate reductase mutants with impaired nitrogenase activity, do not support the proposed commanality between nitrogenase and nitrate reductase in cowpea rhizobia. Inhibition studies of the effect of nitrate and its reduction products on the nitrogenase activity in cultured strains 32Hl and the nitrate reductase-deficient, Nif+ strains, indicated that nitrogenase activity was sensitive to nitrite rather than to nitrate.
Regulation of glnA messinger ribonucleic acid synthesis in Klebsiella aerogenes
Authors: Weglenski P , Tyler B
Published: January 2020

We examined wild-type and mutant strains of Klebsiella aerogenes for the relative amounts of ribonucleic acid (RNA) hybridizing specifically to deoxyribonucleic acid from a transducing phage carrying glnAK, the structural gene for glutamine synthetase. Our data showed a positive correlation between the intracellular level of glutamine synthetase and the level of glnA messenger RNA; we were unable to detect glnA messinger RNA in strains devoid of glutamine synthetase protein. Therefore, it is possible that transcription of glnA is not regulated simply by repression mediated through the glutamine synthetase protein; rather, autogenous control in this system may involve activation of transcription. Our experiments also suggest that the promotor of the glnA gene is located at the rha proximal end of the gene.
Chromosome replication in Caulobacter crescentus growing in a nutrient broth
Authors: Iba H , Fukuda A , Okada Y
Published: January 2020

The pattern of chromosome replication in the Caulobacter crescentus cell cycle was studied by examining the rate of deoxyribonucleic acid (DNA) synthesis during synchronous growth in a fast-growth nutrient broth. As reported previously for the cell cycle in a slow-growth minimal medium (Degnen and Newton, 1972), the Caulobacter cell cycle (at the fastest available growth rate) in nutrient broth consisted of three distinct periods in terms of DNA synthetic activity. The swarmer-cell cycle consisted of a presynthetic period (G1), synthetic period (S), and postsynthetic period (G2) of 30, 50, and 35 min, respectively, whereas the stalked-cell cycle consisted of S and G2 periods of 50 and 35 min, respectively. Synchronously growing cells in the nutrient broth were stained to visualize nuclear bodies. Two nuclear bodies could be discerned in both swarmer and stalked cells, and four could be discerned in predivisional cells. DNA content per cell was determined chemically and found to be about the same in swarmer and stalked cells; it was equivalent to roughly twice the value expected from the kinetic complexity reported previously (Wood et al., 1976) for Caulobacter DNA.
Transitory germinative excision repair in Bacillus subtilis
Authors: Wang T C , Rupert C S
Published: January 2020

Bacillus subtilis strains UVSSP-42-1 (hcr42 ssp1) and UVSSP-1-1 (hcr1 ssp1) are ultraviolet (UV) radiation sensitive both as dormant spores and as vegetative cells. These strains are unable to excise cyclobutane-type dimers from the deoxyribonucleic acid (DNA) of irradiated vegetative cells and fail to remove spore photoproduct from the DNA of irradiated spores either by excision (controlled by gene hcr) or by spore repair (controlled by gene ssp1). When irradiated soon after spore germination, these strains excise dimers, but not spore photoproduct, from their DNA. This process, termed germinative excision repair, functions only transiently in the germination phase and is responsible for the high UV resistance of germinated spores and for their temporary capacity to host cell reactivate irradiated phages infecting them. The recA1 mutation confers higher UV sensitivity to the germinated spores, but does not interfere with dimer removal by germinative excision repair.
Sterol 24(28) methylene reductase in Saccharomyces cerevisiae
Authors: Neal W D , Parks L W
Published: January 2020

Optimal conditions for the 24(28)methylene reductase were obtained. The enzyme assay provided for unusually high activity; the Km was determined to be 10.8 mum. The enzyme activity was increased in cells grown with ethanol as the substrate.
Tn402: a new transposable element determining trimethoprim resistance that inserts in bacteriophage lambda
Authors: Shapiro J A , Sporn P
Published: January 2020

We have found that the trimethoprim resistance determinant of the IncP plasmid R751 (Jacob et al., 1977; Jobanputra and Datta, 1974) transposes to bacteriophage lambda. We call this transposable element Tn402.
Characterization of a glucan from Polyporus circinatus
Authors: Fontana J D , Zancan G T
Published: January 2020

An alpha-D-glucan was isolated from a monokaryon of Polyporus circinatus; it has been characterized as a highly branched glycogn.
Decrease in nitrate reductase activity in extracts of Trichoderma viride Incubated with chlorides
Authors: Balderston W L , Rowe J J , Payne W J
Published: January 2020

Reduced nicotinamide adenine dinucleotide phosphate-dependent nitrate reductase activity in crude extracts of Trichoderma virde was significantly inhibited by physiological concentrations of ammonium chloride, sodium chloride, and potassium chloride, but not by ammonium or sodium sulfate. The chloride inhibition of nitrate reductase activity increased in a linear manner with chloride concentration.
Negative chemotaxis in cellular slime molds
Authors: Keating M T , Bonner J T
Published: January 2020

This study confirms the suggestion of earlier workers that the vegetative amoebae of Dictyostelium repel each other while those of Polysphondylium violaceum do not. When Dictyostelium amoebae were placed in drops on thin and thick agar, the cells moved out faster on the thin agar, presumably because the repellent was more concentrated. This did not occur with Polysphondylium amoebae. Also, if 2 drops of cells were placed side by side, or a single drop was placed near an edge, in Dictyostelium there were fewer cells emerging between the drops (or near an edge) than on the far side. Polysphondylium showed no such difference. However, Polysphondylium amoebae were repelled by Dictyostelium cells (but not vice versa) when drops of each were placed beside one another. Finally, if Dictyostelium discoideum cells were placed in drops over thick and thin agar, but separated from the agar by a dialysis membrane, the cells again spread farther on the thin agar, indicating that the repellent is a dialyzable molecule.
Chemotaxis in Spirochaeta aurantia
Authors: Greenberg E P , Canale-Parola E
Published: January 2020

Cell of Spirochaeta aurantia M1 suspended in isotropic buffer solution swam in nearly straight lines and appeared to spin around their longitudinal axis. Occasionally, cells stopped and flexed, and then resumed translational motility, usually in a different direction. The average cell velocity was 26 micron/s. A quantitative assay for chemotaxis was used to test various chemicals for their ability to attract S. aurantia M1. The cells exhibited a tactic response toward 5 X 10(-2) M D-glucose between 10 and 35degree C; the optimum response was at 25degree C. At 5 degree C motility was not impaired, but D-glucose taxis was abolished. Chemotaxis toward D-glucose was stimulated by L-cysteine (2 X 10(-4) M). D-Glucose, 2-deoxy-D-glucose, alpha-methyl-D-glucoside, D-galactose, D-fucose, D-mannose, D-fructose, D-xylose, maltose, cellobiose, and D-glucosamine were effectve attractants for S. aurantia M1. D-Galactose taxis and D-fucose taxis were induced by the presence of D-galactose in the growth medium. The amino acids tested did not serve as attractants, tgrowing cells of S. aurantia M1 exhibited an aerotactic response.
Initiation and termination of chromosome replication at 45 degree C in a temperature-sensitive deoxyribonucleic acid initiation mutant of Bacillus subtilis 168, TsB134
Authors: Burnett L , Wake R G
Published: January 2020

Deoxyribose nucleic acid transfer experiments showed that upon shifting Bacillus subtilis TsB134 to 45 degree C, initiation of new rounds of replication was effectively blocked and the majority of existing rounds terminated.
Escherichia coli K-12 mutant with alternate requirements for vitamin B6 or branched-chain amino acids and lacking transaminase C activity
Authors: Falkinham J O
Published: January 2020

An Escherichia coli K-12 auxotrophic derivative that grows if supplemented with pyridoxine, isoleucine, leucine, or alanine is described.
Phosphoenolpyruvate and 2-phosphoglycerate: endogenous energy source(s) for sugar accumulation by starved cells of Streptococcus lactis
Authors: Thompson J , Thomas T D
Published: January 2020

In the absence of an exogenous energy source, galactose-grown cells of Streptococcus lactis ML3 rapidly accumulated thiomethyl-beta-D-galactopyranoside (TMG) and 2-deoxyglucose to intracellular concentrations of 40 to 50 mM. Starved cells maintained the capacity for TMG uptake for many hours, and accumulation of the beta-galactoside was insensitive to proton-conducting ionophores (tetrachlorosalicylanilide and carbonylcyanide-m-chlorophenyl hydrazone) and sulfydryl group reagents including iodoacetate and N-ethylmaleimide. Fluorimetric analysis of glycolytic intermediates in extracts prepared from starved cells revealed (a) high intracellular levels of phosphoenolpyruvate (13 mM; PEP) and 2-phosphoglycerate (approximately 39 mM; 2-PG), but an absence of other metabolites including glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-diphosphate, and triosephosphates. The following criteria showed PEP (and 2-PG) to be the endogenous energy source for TMG accumulation by the phosphotransferase system: the intracellular concentrations of PEP and 2-PG decreased with concomitant uptake of TMG, and a close correlation was observed between maximum accumulation of the beta-galactoside and the total available concentration of the two intermediates; TMG accumulated as an anionic derivative, which after extraction and incubation with alkaline phosphatase (EC 3.1.3.1) formed the original analogue; fluoride inhibition of 2-phospho-D-glycerate hydrolyase (EC 4.2.1.11) prevented the conversion of 2-PG to PEP, and uptake of TMG by the starved cells was reduced by 80%; and the stoichiometric ratio [TMG] accumulated/[PEP] consumed was almost unity (0.93). In cells metabolizing glucose, all intermediates listed in (a) and (b) were found. Upon exhaustion of glucose from the medium, the metabolites in (b) were not longer detectable, while the intracellular concentrations of PEP and 2-PG increased to the levels previously observed in starved cells. The glycolytic intermediates in (b) are all in vitro heterotropic effectors of pyruvate kinase (adenosine 5'-triphosphate:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) from S. lactis ML3. It is suggested that the capacity of starved cells to maintain high intracellular concentrations of PEP and 2-PG is a consequence of decreased in vivo activity of this key regulatory enzyme of glycolysis.
Control of beta-glucosidase synthesis in Mucor racemosus
Authors: Borgia P , Sypherd P S
Published: January 2020

The beta-glucosidase of Mucor racemosus was shown to be synthesized when the organism was grown in the presence of such diverse carbon sources as glycerol, lactate, xylose, ribose, alpha-methylglucoside, alpha-phenylglucoside, maltose, and cellobiose. Enzyme synthesis was strongly repressed in the presence of hexoses. In addition, exogenous cyclic adenosine 3',5'-monophosphate (cAMP) resulted in enzyme repression. When cAMP was added exogenously after enzyme activity had accumulated, a reversible enzyme inactivation occurred. Growth on disaccharides (maltose or cellobiose) was severely retarded in the presence of cAMP, whereas that on glucose remained unaffected. The results indicate a probable role for cAMP in control of glucosidase synthesis in Mucor.
Changes in protein synthesis on mitomycin C induction of wild-type and mutant CloDF13 plasmids
Authors: Dougan G , Sherratt D J
Published: January 2020

Mitomycin C treatment of Escherichia coli K-12 cells containing the nonconjugative plasmid CloDF13 resulted in inhibition of host chromosome protein synthesis and a high rate of synthesis of two CloDF13-specified proteins whose molecular weights correspond to cloacin and immunity protein. Five molecules of immunity protein were synthesized for each cloacin DF13 molecule. Mitomycin C-treated cells containing a copy mutant of CloDF13 made three to four times as much of each protein as cells containing wild-type CloDF13. CloDF13 plasmids that contained the transposon Tn1 were isolated. Two did not induce after mitomycin C treatment, failing both to inhibit host cell synthesis and to produce the two new proteins. In minicells, they showed reduced CloDF13-specified protein synthesis and produced three Tn1-specified proteins.
Polysaccharide capsule of Escherichia coli: microscope study of its size, structure, and sites of synthesis
Authors: Bayer M E , Thurow H
Published: January 2020

This report describes the structure, size, and shape of the uncollapsed polysaccharide capsule of Escherichia coli strain Bi 161/42 [O9:K29(A):H-], its ultrastructural preservation as well as the filamentous components of the isolated capsular material. In a temperature-sensitive mutant, sites were localized at which capsular polysaccharide is "exported" to the cell surface. The highly hydrated capsule of the wild-type cells was visible in the uncollapsed state after freeze-etching, whereas dehydration in greater than or equal to 50% acetone or alcohol caused the capsule to collapse into thick bundles. This was prevented by pretreatment of the cell with capsule-specific immunoglobulin G; the capsule appeared as a homogeneous layer of 250- to 300-nm thickness. The structural preservation depended on the concentration of the anti-capsular immunoglobulin G. Temperature-sensitive mutants, unable to produce capsular antigen at elevated temperatures, showed, 10 to 15 min after shift down to permissive temperature, polysaccharide strands with K29 specificity appearing at the cell surface at roughly 20 sites per cell; concomitantly, capsule-directed antibody started to agglutinate the bacteria. The sites at which the new antigen emerged were found in random distribution over the entire surface of the organism. Spreading of purified polysaccharide was achieved on air-water interfaces; after subsequent shadow casting with heavy metal, filamentous elements were observed with a smallest class of filaments measuring 250 nm in length and 3 to 6 nm in width. At one end these fibers revealed a knoblike structure of about 10-nm diameter. The slimelike polysaccharides from mutants produced filamentous bundles of greater than 100-microns length, with antigenic and phage-receptor properties indistinguishable from those of the wild-type K29 capsule antigen.
Gliding motility of Mycoplasma pulmonis
Authors: Bredt W , Radestock U
Published: January 2020

The gliding movements of freshly isolated Mycoplasma pulmonis cells were observed and measured. The motile cells had a characteristic appearance, an average speed of 0.4 to 0.7 micron/s, and a maximum speed of 1 micron/s.
Bacterial mutation affecting plasmid maintenance in Pseudomonas aeruginosa
Authors: Chang B J , Holloway B W
Published: January 2020

A bacterial mutation, risA, in Pseudomonas aeruginosa caused growth inhibition at 43 degrees C of risA strains containing P2 plasmids. Incubation at 43 degrees C resulted in selection for clones that had lost P2 plasmids.
Levels of Small Molecules and Enzymes in the Mother Cell Compartment and the Forespore of Sporulating
Bacillus megaterium
Authors: Singh Ravendra P. , Setlow Barbara , Setlow Peter
Published: January 2020

We have determined the amounts of a number of small molecules and enzymes in the mother cell compartment and the developing forespore during sporulation of
Bacillus megaterium
. Significant amounts of adenosine 5′-triphosphate and reduced nicotinamide adenine dinucleotide were present in the forespore compartment before accumulation of dipicolinic acid (DPA), but these compounds disappeared as DPA was accumulated. 3-Phosphoglyceric acid (3-PGA) accumulated only within the developing forespore, beginning 1 to 2 h before DPA accumulation. Throughout its development the forespore contained constant levels of enzymes of both 3-PGA synthesis (phosphoglycerate kinase and glyceraldehyde-3-phosphate dehydrogenase) and 3-PGA utilization (phosphoglycerate mutase, enolase, and pyruvate kinase) at levels similar to those in the mother cell and the dormant spore. Despite the presence of enzymes for 3-PGA utilization, this compound was stable within isolated forespores. Two acid-soluble proteins (A and B proteins) also accumulated only in the forespore, beginning 1 to 2 h before DPA accumulation. At this time the specific protease involved in degradation of the A and B proteins during germination also appeared, but only in the forespore compartment. Nevertheless, the A and B proteins were stable within isolated forespores. Arginine and glutamic acid accumulated within the forespore in parallel with DPA accumulation. The forespore also contained the enzyme arginase at a level similar to that in the mother cell and a level of glutamic acid decarboxylase 2- to 25-fold higher than that in the mother cell, depending on when in sporulation the forespores were isolated. The specific activities of several other enzymes (protease active on hemoglobin, ornithine transcarbamylase, malate dehydrogenase, aconitase, and isocitrate dehydrogenase) in forespores were about 10% or less of the values in the mother cell. Aminopeptidase was present at similar levels in both compartments; threonine deaminase was not found in either compartment.
6-Phospho-D-gluconate:NAD+ 2-oxidoreductase (decarboxylating) from slow-growing Rhizobia
Authors: Martínez-Drets G , Gardiol A , Arias A
Published: January 2020

6-Phospho-D-gluconate:NAD+ 2-oxidoreductase (decarboxylating) (NAD+-6PGD) was detected in several slow-growing strains of rhizobia, and no activity involving NADP+ was found in the same extracts. By contrast, fast-growing strains of rhizobia had NADP+-6PGD activity; most of them also had NAD+-6PGD activity. NAD+-6PGD was partially purified from the slow-growing strain Rhizobium japonicum 5006. The reaction was shown to be an oxidative decarboxylation.
Unsaturated fatty acid mutants of Neurospora crassa
Authors: Scott W A
Published: January 2020

Unsaturated fatty acid (ufa) auxotrophs of Neurospora crassa were obtained by treatment of conidia with N-methyl-N'-nitro-N-nitrosoguanidine followed by isolation on media containing polyunsaturated fatty acids suspended in Tergitol NP-40. The 24 mutants for which reisolates were obtained from crosses with wild type were assigned to two complementation classes, ufa-1 and ufa-2, located on linkage group V. Unsaturated fatty acids with varying degrees of unsaturation, chain length, and double-bond position as well as different steric configurations were tested for growth requirements.
Genetics of Sensitivity of
Salmonella
Species to Colicin M and Bacteriophages T5, T1, and ES18
Authors: Graham Amy C. , Stocker B. A. D.
Published: January 2020

Nearly all of 62 strains of
Salmonella paratyphi
B were sensitive to colicin M and phage T5 but resistant to phages T1 and ES18 and to colicin B. All tested
S. typhimurium
strains were resistant to colicin M and phage T5, and many were sensitive to phage ES18. A rough
S. typhimurium
LT2 strain given the
tonA
region of
Escherichia coli
or
S. paratyphi
B became sensitive to colicin M and phage T5. We infer that the
tonA
allele of
S. paratyphi
B, like that of
E. coli
, determines an outer membrane protein that adsorbs T5 and colicin M but not phage ES18, whereas the
S. typhimurium
allele determines a protein able to adsorb only ES18. The partial T1 sensitivity of a rough LT2 strain with a
tonA
allele from
E. coli
or
S. paratyphi
B and also the tonB
+
phentotype of an
E. coli
B
trp-tonB
Δ mutant carrying an F′
trp
of LT2 origin showed that
S. typhimurium
LT2 has a
tonB
allele like that of
E. coli
with respect to determination of sensitivity to colicins and phage T1. Rough
S. paratyphi
B, although T5 sensitive, remained resistant to T1 even when given F′
tonB
+
of
E. coli
origin. Classes of
Salmonella
mutants selected as resistant to colicin M included: T5-resistant mutants, probably
tonA
−
; mutants unchanged except for M resistance, perhaps tolerant; and Exb
+
mutants, producing a colicin inhibitor (presumably enterochelin). Some Exb
+
mutants were resistant to a bacteriocin inactive on
E. coli
but active on all tested
S. paratyphi
B and
S. typhimurium
strains (and on nearly all other tested
Salmonella
). A survey showed sensitivity to colicin M in several other species of
Salmonella
.
Properties of an Escherichia coli K-12 mutant defective in the transport of arginine and ornithine
Authors: Celis T F
Published: January 2020

A canavanine-resistant mutant strain, defective in the transport of arginine and ornithine, was isolated and characterized. Experiments presented show that both the kinetics of influx and the steady state of accumulation of arginine and ornithine are affected by the mutation, whereas the activity of other related transport systems remains unchanged. On the basis of competitive studies, it is concluded that L-canavanine can inhibit efficiently the arginine-specific uptake system. D-Arginine appears to be a moderate inhibitor. None of the basic amino acid-binding proteins of the mutant strain showed detectable alterations in terms of quantity, physical properties, or affinity constants. Studies on the relationship between the number of transport carriers and the steady state of accumulation of arginine suggested the presence of a reduced number of membrane carriers in the mutant strain. It is proposed that the mutation affects a regulatory gene concerned with controlling the amount of membrane carriers produced, which are components of the arginine- and ornithine-specific uptake systems. The mutation maps at min 62 on the recalibrated linkage map of Escherichia coli K-12, in a locus closely linked or identical to argP.
Molecular sizes and relationships of TOL plasmids in Pseudomonas
Authors: Duggleby C J , Bayley S A , Worsey M J , Williams P A , Broda P
Published: January 2020

Plasmid deoxyribonucleic acid was isolated from thirteen Pseudomonas strains judged on genetic criteria to carry plasmids coding for the degradation of toluene and m- and p-xylenes (TOL plasmids). Most strains carried a single species, but two strains carried two size classes, and cells of a third strain contained plasmids ranging in size from 25 X 10(6) to 202 X 10(6) daltons. Some plasmids could be transformed into a Pseudomonas putida strain to yield Tol+ progeny. Plasmids from 5 of the 13 strains were indistinguishable on the basis of size and gel pattern of fragments after endonuclease digestion.
Chemotaxis toward amino acids by Bdellovibrio bacteriovorus
Authors: LaMarre A G , Straley S C , Conti S F
Published: January 2020

Chemotaxis toward amino acids by Bdellovibrio bacteriovorous strain UKi2 was studied by the capillary technique of Adler (J. Gen. Microbiol. 74:77-91, 1973). Chemotaxis was shown to be optimal when the capillaries were incubated at between 15 and 40 degrees C for 30 min; the optimal pH was between 7.0 and 8.2. The chemotactic response was proportional to the density of the suspension of bdellovibrios up to a density of 10(8) cells/ml. B. bacteriovorus was attracted to L-asparagine, L-cysteine, L-glutamine, glycine, L-histidine, L-lysine, and L-threonine. The possible roles of chemotaxis in the life of B. bacteriovorus are discussed.
Metabolism of arginine-specific messenger ribonucleic acid in Escherichia coli K-12
Authors: Natter W , Sens D , James E
Published: January 2020

Ribonucleic acid-deoxyribonucleic acid (RNA-DNA) hybridization was employed for the determination of the level of messenger RNA (mRNA) transcribed from seven of the nine genes of the arginine regulon of Escherichia coli K-12. The quantity of RNA complexing with each of the separated DNA strands of the argA, argF, argE, and argCBH operons carried on specialized transducing phages was measured. The derepressed:repressed ratio of mRNA formed in vivo was found to vary between about 3 and 4 when measured by hybridization to DNA isolated from specialized transducing phages carrying the argA, argE, argCBH, argF, and argI operons.
Do cytochromes function as oxygen sensors in the regulation of nitrate reductase biosynthesis?
Authors: MacGregor C H , Bishop C W
Published: January 2020

The observation that oxygen represses nitrate reductase biosynthesis in a hemA mutant grown aerobically with or without delta-aminolevulinic acid indicates that cytochromes are not responsible for nitrate reductase repression in aerobically grown cells.
Transformation of Escherichia coli and Bacillus subtilis with a hybrid plasmid molecule
Authors: Mahler I , Halvorson H O
Published: January 2020

A hybrid molecule constructed from Escherichia coli plasmid pMB9 and a fragment of Bacillus subtilis 168 deoxyribonucleic acid functions in cells of leu-E. coli, converting them to leucine prototrophy, but fails to survive in strains of B. subtilis 168.
Isolation and Characterization of a
Bacillus subtilis
Mutant with a Defective
N
-Glycosidase Activity for Uracil-Containing Deoxyribonucleic Acid
Authors: Makino Fumiko , Munakata Nobuo
Published: January 2020

Crude cell extracts of
Bacillus subtilis
168T exhibit enzyme activity capable of releasing free uracil from phage PBS1 deoxyribonucleic acid (DNA) in the presence of ethylenediaminetetraacetate. By measuring the enzyme activity in 300 clones that emanated from mutagenized cells, we obtained a mutant strain that did not show this
N
-glycosidase activity. The mutant strain, designated as TKJ6901 (
urg-1
) exhibited no physiological abnormalities. We observed the intracellular action of the enzyme by following the fate of uracil-containing DNA in cells from wild-type and mutant cultures. When infection with phage PBS1 was allowed in the presence of chloramphenicol, extensive degradation of phage DNA was observed only in the wild-type cells. When bromouracil residues were converted to uracil residues by ultraviolet light irradiation in the presence of cysteamine, the DNA was extensively fragmented in the wild-type cells. These single-strand breaks were rejoined upon postirradiation incubation. In contrast, such fragmentation of the DNA was not observed in the mutant cells, indicating that the uracil residues were not removed from the DNA. This demonstrated that the
N
-glycosidase activity was involved in the excision of uracil in DNA. A transformation assay with four types of recipient strains with combinations of
N
-glycosidase and DNA polymerase I deficiencies indicated that DNA polymerase I was involved in the later steps of this base excision repair pathway initiated by the action of the
N
-glycosidase.
Characterization of lexB mutations in Escherichia coli K-12
Authors: Morand P , Blanco M , Devoret R
Published: January 2020

Two mutations have been located at the recA locus and phenotypically characterized along with a third one, previously called rec-34. The three mutants behaved similarly to lexA mutants. They were sensitive to ultraviolet (UV) light and X rays, and lambdaFec- phages were able to plate on them. The three mutations were called lexB because they could be distinguished from recA mutations by the last property. lexB mutants were less sensitive to UV and X irradiations than were recA mutants and were, to various degrees, recombination proficient. UV light failed to induce prophage lambda in all three lexB lysogens. In contrast, thymine starvation induced lexB31 and lexB34 lysogens. In lexB34 mutants, but not in lexB30 and lexB31 mutants, UV reactivation occurred at a low level. In Escherichia coli K-12, the recA gene has basic functions in the repair of deoxyribonucleic acid lesions, deoxyribonucleic acid recombination, and prophage induction. The three lexB mutations alter unequally and independently the three functions. This suggests that the recA and lexB mutations affect the same gene.
Sodium ion-stimulated alpha-[1-14C]aminoisobutyric acid uptake in alkalophilic Bacillus species
Authors: Kitada M , Horikoshi K
Published: January 2020

Alkalophilic Bacillus no. 8-1 grows well in alkaline media containing 2.5 to 5% NaCl. The uptake of alpha-aminoisobutyric acid (AIB) into the cells is stimulated by the addition of NaCl (Na+) up to a concentration of 0.2 M, but other monovalent cations such as K+, Li+, or NH4+ cannot substitute for Na+. The kinetic studies reveal that, when the Na+ concentration increases from 0.02 to 0.2 M in alkaline medium, the Km for transport decreases, whereas Vmax remains almost constant. Competition studies indicate that glycine, L-alanine, L-serine, and AIB share common carriers for the transport of the compounds into cells. Other alkalophilic bacteria are also found to require Na+ for the uptake of AIB into the cells.
Ribosomal suppressors and antisuppressors in Podospora anserina: resistance to cycloheximide
Authors: Coppin-Raynal E
Published: January 2020

Informational suppressors and antisuppressors have been previously isolated in Podospora anserina, and a range of exclusively genetic arguments have led to the assumption that they correspond to ribosomal mutations. An in vivo and in vitro comparison of the effect of the ribosomal inhibitor cycloheximide on wildtype and mutant strains described in this paper confirms the ribosomal hypothesis for at least some mutants. Indeed, the four mutants in the AS3 gene were cycloheximide resistant, and their ribosomes were found to be resistant when analyzed by polyuridyl-directed polyphenylalanine systhesis. On the other hand, ribosomes from two su 1 mutants were hypersensitive to the drug.
Origin and direction of replication of the drug resistance plasmid R100.1 and of a resistance transfer factor derivative in synchronized cultures
Authors: Silver L , Chandler M , de la Tour E B , Caro L
Published: January 2020

The origin and direction of replication of the resistance plasmid R100.1 and its resistance transfer factor derivative, pAR132, were studied by electron microscopy autoradiography of partially denatured molecules and partial denaturation mapping of replicative intermediates. Results of these studies indicate the existence of an origin of replication at 8.8 kilobases on the R100 map. Replication from this origin in cultures synchronized for initiation of replication is predominantly unidirectional in a single direction.
Relationship between cell coiling and motility of spirochetes in viscous environments
Authors: Greenberg E P , Canale-Parola E
Published: January 2020

The lowest viscosity that stops translational motility of cells (minimum immobilizing viscosity [MIV] was determined for various spirochetes. The viscous agent used was polyvinylpyrrolidone, The MIV for either Spirochaeta halophila P1 or Spirochaeta aurantia J4T was approximately 1,000 centipoise (cp), and for Leptospira interrogans (biflexa) B16 the MIV was greater than 500 cp. In comparison, the MIV for the flagellated bacteria Escherichia coli and Spirillum serpens was 60 cp. MIV values for two S. halophila mutant strains lacking the characteristic cell coiling (Hel-mutants) were 70 and 120 cp, approximately one-tenth the MIV for the wild-type strain. MIV values for cells of S. aurantia strains with fewer coils than comparably long cells of S. aurantia J4T were 300 to 600 cp. The average velocity of strains of S. aurantia and S. halophila decreased at viscosities higher than 2 to 3 cp. At 2 cp the average velocity of S. halophila P1 was 16 micron/s, whereas the average velocities of Hel-mutant strains were 7 to 9 micron/s. This study indicates that the coiling of spirochetes plays a role in their ability to move through environments of realtively high viscosity. Among the spirochetes we investigated, this ability is greater in the more extensively coiled strains.
Respiratory competence of Dictyostelium discoideum spores
Authors: Kobilinksy L , Beattie D S
Published: January 2020

Analysis of the respiratory chain of spores of Dictyostelium discoideum, which lack a cyanide-sensitive respiration, indicated that cytochromes a-a3, b, and c-c1 are present at levels identical to those found in the vegetative amoebae. The specific activities of enzymes of both the respiratory chain and the citric acid cycle in the 600 x g supernatant fraction of sonically treated spores were at least as high as in similar preparations of amoebae. The activities of glutamic dehydrogenase and oligomycin-sensitive adenosine triphosphatase were reduced in the spores 30 and 56%, respectively. Intact spores appeared to lack a cyanide-sensitive respiration as a result of inadequate quantities of respiratory substrate and, more importantly, as a result of a lack of the cofactor nicotinamide adenine dinucleotide. The emergence phase of spore germination was sensitive to the antibiotic chloramphenicol, which is a specific inhibitor of mitochondrial protein synthesis. It is concluded that germination requires the early synthesis of oxidized nicotinamide adenine dinucleotide and generation of respiratory substrates and one or more mitochondrially synthesized proteins.
Efficient sporulation of yeast in media buffered near pH6
Authors: McCusker J H , Haber J E
Published: January 2020

Diploid cells of Saccharomyces cerevisiae underwent meiosis and sporulation when placed in 1% potassium acetate sporulation medium. In unbuffered sporulation medium the pH rose very rapidly, reaching pH 8.4 after 2 h of sporulation. Under these conditions, the uptake of radioactive adenine and lysine was extremely limited, and ascus formation was insensitive to inhibitors such as 5-fluorouracil and canavanine. By using several different buffers, we showed that an increase in the pH of sporulation media was not necessary for sporulation to occur. Spore viability and the kinetics of ascus and prototroph formation were normal for cells sporulated in several types of media buffered as low as pH 5.5. Incubation of sporulating cells below pH 6.5 did cause separation of small but viable buds from their mother cells. With sporulating cells buffered below pH 6.5, the incorporation of radioactive adenine and lysine was greatly enhanced and cells became sensitive to inhibition by 5-fluorouracil and canavanine.
Use of argA-lac fusions to generate lambda argA-lac bacteriophages and to determine the direction of argA transcription in Escherichia coli
Authors: Eckhardt T
Published: January 2020

Fusions of lac genes to the argA operator were constructed, and lambda phages carrying these fusions were isolated and characterized. With the aid of a lambda phage carrying an argA-lac fusion, the direction of argA transcription on the Escherichia coli chromosome was determined to be clockwise.
Regulation of aromatic amino acid transport systems in Escherichia coli K-12
Authors: Whipp M J , Pittard A J
Published: January 2020

The regulation of the aromatic amino acid transport systems was investigated. The common (general) aromatic transport system and the tyrosine-specific transport system were found to be subject to repression control, thus confirming earlier reports. In addition, tryosine- and tryptophan-specific transport were found to be enhanced by growth of cells with phenylalanine. The repression and enhancement of the transport systems was abolished in a strain carrying an amber mutation in the regulator gene tyrR. This indicates that the tyrR gene product, which was previously shown to be involved in regulation of aromatic biosynthetic enzymes, is also involved in the regulation of the aromatic amino acid transport systems.
Regulation of superoxide dismutase synthesis in Escherichia coli: glucose effect
Authors: Moustafa Hassan H , Fridovich I
Published: January 2020

Growth of Escherichia coli, based upon the fermentation of glucose, is associated with a low intracellular level of superoxide dismutase. Exhaustion of glucose, or depression of the pH due to accumulation of organic acids, causes these organisms to then obtain energy from the oxidative degradation of other substances present in a rich medium. This shift in metabolism is associated with a marked increase in the rate of synthesis of superoxide dismutase. Depression of the synthesis of superoxide dismutase by glucose is not due to catabolite repression since it is not eliminated by cyclic adenosine 3',5'-monophosphate and since alpha-methyl glucoside does not mimic the effect of glucose. Moreover, glucose itself no longer depresses superoxide dismutase synthesis when the pH has fallen low enough to cause a shift to a non-fermentative metabolism. It appears likely that superoxide dismutase is controlled directly or indirectly by the intracellular level of O2- and that glucose depressed the level of this enzyme because glucose metabolism is not associated with as rapid a production of O2- as is the metabolsim of many other substances. In accord with this view is the observation that paraquat, which can increase the rate of production of O2- by redox cycling, caused a rapid and marked increase in superoxide dismutase.
Aspergillus nidulans mutant lacking alpha-(1,3)-glucan, melanin, and cleistothecia
Authors: Polacheck I , Rosenberger R F
Published: January 2020

A mutation in Aspergillus nidulans led to a loss of both melanin and alpha-(1,3)-glucan, a major wall polysaccharide. In addition, the mutation prevented the formation of cleistothecia. Mutant walls contained increased amounts of beta-(1,3)-glucan and galactose polymers, and electron micrographs indicated that they had lost the outermost wall layer. Such walls were more readily digested by lytic enzymes, and this increased susceptibility to hydrolysis was due to the absence of alpha-(1,3)-glucan and not of melanin. The pleiotropic effects of the mutation are discussed, with particular reference to the hypothesis that alpha-(1,3)-glucan acts as the endogenous carbon source for biosynthetic processes in the stationary phase of growth. In this view, glucan synthesis would be the primary target of the mutation, and the absence of glucan would result in the lack of melanin and cleistothecia, formed after nutrients are exhausted. Two other mutations that lowered themycelial alpha-(1,3)-glucan content also inhibited melanin and cleistothecia production.
Distribution and conformation of crystalline nigeran in hyphal walls of Aspergillus niger and Aspergillus awamori
Authors: Bobbitt T F , Nordin J H , Roux M , Revol J F , Marchessault R H
Published: January 2020

Hyphal walls of Aspergillus awamori containing increased amount of the alpha-glucan, nigeran, became correspondingly more opaque when viewed in the electron microscope as shadowed preparations. However, increased polymer deposition was not accompanied by any significant change in wall thickness. The nigeran of both A. awamori and Aspergillus niger occurred in situ in a crystalline conformation identical to that of single crystals prepared with pure polysaccharide. Furthermore, this polymer was the dominant crystalline material in the hyphae whether or not they were enriched in nigeran. Enzymic digestion of nigeran in A. niger and A. awamori revealed that the bulk of the polymer was exposed to the cell's exterior. However, a certain fraction was accessible to enzymic attack only after the wall was treated with boiling water. A third portion, detectable only by x-ray diffraction, was associated with other components and could not be extracted, even with prolonged boiling. It was removed by hot, dilute alkali and was associated in the wall with another glucan fraction. Dry heating of A. niger walls altered their susceptibility to enzymic digestion of nigeran in situ. It is proposed that this treatment introduces interstices in the crystal surface that facilitate attack.
Visualization of ribosomal ribonucleic acid synthesis in a ribonuclease III-Deficient strain of Escherichia coli
Authors: Hofmann S , Miller O L
Published: January 2020

Transmission electron microscopy was used to examine active ribosomal ribonucleic acid (rRNA) genes in two strains of Escherichia coli: N2077, deficient in the enzyme responsible for proper cleavage of the 16S sequence from the elongating nascent rRNA transcript; and N2076, functional in ribonuclease (RNase) III activity, yet otherwise isogenic to N2077. In the strain with wild-type RNase III, double gradients corresponding to a pattern of 16S-cleavage-23S transcription were observed. However, the RNase III-deficient strain exhibited a single ribosomal gradient of approximately the same length as the combined 16S-23S gradients of the wild-type strain. When the rRNA genes were somewhat loosely packed with RNA polymerases, a few of the nascent chains in the ribosomal matrixes of the RNase III-deficient strain were cleaved, but most appeared to be unprocessed. The completed, uncleaved transcripts originating from these gradients are believed to be 30S rRNA molecules recently characterized by biochemical probes.
Effects of a protease inhibitor on biosynthesis of Escherichia coli proteins
Authors: Ito K
Published: January 2020

A protease inhibitor, tosyl-L-lysine chloromethylketone, altered the composition of newly synthesized protein in Escherichia coli; a significant portion of the proteins synthesized sedimented rapidly, presumably forming aggregates of the abnormal proteins. Protein I of the outer membrane was only slightly synthesized under these conditions.
Heat sensitivity of Haemophilus influenzae containing defective prophage
Authors: Setlow J K
Published: January 2020

Strains of Haemophilus influenzae that carry a defective prophage are more sensitive to heat than is a strain that does not, even in the presence of a rec-1 mutation, which normally renders prophage noninducible. The prophage of HP1c1, a nondefective phage, does not affect the heat sensitivity.
Ultrastructural localization of alkaline phosphatase in the blue-green bacterium Plectonema boryanum
Authors: Doonan B B , Jensen T E
Published: January 2020

Histochemical techniques applied at the ultrastructural level have clearly established the periplasmic space as the site of alkaline phosphatase activity in Plectonema boryanum. Considerable enzyme activity is found after the organism is placed in a phosphate-free medium for 5 days. This activity is found only in the cellular fraction of the culture with no activity present in the culture medium. Localization of the site of enzyme activity in cells was investigated by a modification of the method of Costerton. Unfixed cells were reacted with calcium nitrate, which acts as the initial capture reagent. After this deposition, the cells were suspended in 2% lead nitrate to convert the calcium phosphate to more electron-dense lead phosphate. The majority of activity appears associated with layer 3 (periplasmic space) of the cell wall.
Chromosome replication in Myxococcus xanthus
Authors: Zusman D R , Krotoski D M , Cumsky M
Published: January 2020

The rates of DNA synthesis during the cell-division cycle were measured in Myxococcus xanthus growing in three different media permitting a twofold variation in doubling time. In all three media, simple DNA cycles were observed. Synthesis of DNA occurred during 85% of the cell-division cycle, independent of generation time, from 5 to 11 h. Cells were observed to contain one bacterial nucleoid at birth that later divided synchronously midway through the cell cycle. Nucleoid segregation appeared to begin before chromosome replication was completed. The DNA content of exponential-phase bacteria was determined to be about 20 +/- 3 X 10(-9) microgram per cell; newborn bacteria contained about 14 +/- 2 X 10(-9) microgram of DNA per cell. Exponential-phase bacteria showed about a 50% increase in DNA in the presence of chloramphenicol (50 microgram/ml). The number of randomly segregating chromosomes present in exponential-phase bacteria was determined by following the fate of prelabeled DNA during outgrowth in nonradioactive media. The results are consistent with a model in which cells are born with exactly one complete unreplicated chromosome. The molecular weight of such a chromosome is about 8.4 +/- 1.2 X 10(9).
Mycoplasma phosphoenolpyruvate-dependent sugar phosphotransferase system: glucose-negative mutant and regulation of intracellular cyclic AMP
Authors: Mugharbil U , Cirillo V P
Published: January 2020

Glucose-negative mutants of Mycoplasma capricolum were selected for growth on fructose in the presence of the toxic glucose analog alpha-methyl-D-glucopyranoside. The mutants are defective in the phosphoenolpyruvate:sugar phosphotransferase system for glucose. One mutant, pts-4, was studied in detail. It lacks the glucose-specific, membrane-bound enzyme II, IIGlc, as well as the general, low-molecular-weight, phosphocarrier protein, HPr. In place of the latter, however, it has a fructose-specific protein, HPrFru. Consistent with these changes, the mutant lost the ability to grow on glucosamine and maltose but retained its ability to grow on sucrose. In the glucose-negative mutant, glucose did not regulate the intracellular concentration of cyclic AMP. The intracellular concentration of cyclic AMP in M. capricolum is regulated by the presence of metabolizable sugars. In the wild-type, both glucose and fructose reduced the intracellular concentration of cyclic AMP; however, in the glucose-negative mutant, glucose no longer regulated the intracellular level of cyclic AMP.
Structural arrangement of polymers within the wall of Streptococcus faecalis
Authors: Tsien H C , Shockman G D , Higgins M L
Published: January 2020

The structure of the cell wall of Streptococcus faecalis was studied in thin sections and freeze fractures of whole cells and partially purified wall fractions. Also, the structures of wall preparations treated with hot trichloroacetic acid to remove non-peptidoglycan wall polymers were compared with wall preparations that possess a full complement of accessory polymers. The appearance of the wall varied with the degree of hydration of preparations and physical removal of the cell membrane from the wall before study. Seen in freeze fractures of whole cells, the fully hydrated wall seemed to be a thick, largely amorphic layer. Breaking cells with beads caused the cell membrane to separate from the wall and transformed the wall from a predominantly amorphic layer to a structure seemingly made up of two rows of "cobblestones" enclosing a central channel of lower density. Dehydration of walls seemingly caused the cobblestones to be transformed into two bands which continued to be separated by a channel. This channel was also observed in isolated wall preparations treated with hot trichloroacetic acid to remove non-peptidoglycan polymers. These observations are consistent with the interpretation that both peptidogylcan and non-peptidoglycan polymers are concentrated at the outer and inner surfaces of cell walls. These observations are discussed in relation to possible models of wall structure and assembly.
Primary structure of the Escherichia coli serotype K42 capsular polysaccharide and its serological identity with the Klebsiella K63 polysaccharide
Authors: Niemann H , Chakraborty A K , Friebolin H , Stirm S
Published: January 2020

The Escherichia coli K42 capsular polysaccharide consists of leads to 3)-alpha-D-Galp-(1 leads to 3)-alpha-D-GalUAp-(1 leads to 3)-alpha-L-Fucp-(1 leads to repeating units. The E. coli K42 and Klebsiella K63 antigens are serologically identical.