bluuebunny/crossref_metadata_2025 huggingface dataset:
Tumbling chemotaxis mutants of Escherichia coli: possible gene-dependent effect of methionine starvation
Authors: Kondoh H
Published: January 2020

Some mutants defective in chemotaxis show incessant tumbling behavior and are called tumbling mutants. Previously described tumbling mutations lie in two genes, cheB and cheZ (41.5 min on Escherichia coli map). Genetic analysis of various tumbling mutants, however, revealed that two more genetic loci, cheC (43 min) and cheE (99.2 min), could also mutate to produce tumbling mutants. The genetic map around cheC was revised: his flaP flaQ flaR flbD flaA (= cheC) flaE. flbD is a new gene. When cells were starved for methionine, the tumbling mutants changed their swimming behavior depending on the che gene mutated. cheZ mutants, like wild-type bacteria, ceased tumbling shortly after removal of methionine. The tumbling of cheB or cheE mutants was depressed after prolonged methionine starvation in the presence of a constant level of an attractant. cheC tumbling mutants appeared unique in that they did not cease tumbling even when cells were deprived of methionine. By contrast, arsenate treatment of the tumbling mutants resulted in smooth swimming of the cells in every case. These results suggest that two different processes are involved in regulation of tumbling; one requiring methionine and the other requiring some phosphorylated compound.
Conditional-lethal deoxyribonucleic acid polymerase I mutant of Escherichia coli
Authors: Shizuya H , Millar S
Published: January 2020

A new deoxyribonucleic acid polymerase I mutant of Escherichia coli was isolated among conditional lethal mutants. Deoxyribonucleic acid replication in the mutant ceased in 20 min after the temperature was raised to 43 degrees C, and reinitiated when cells were further incubated at this temperature.
Physiology of dark fermentative growth of Rhodopseudomonas capsulata
Authors: Madigan M T , Cox J C , Gest H
Published: January 2020

The photosynthetic bacterium Rhodopseudomonas capsulata can grow under anaerobic conditions with light as the energy source or, alternatively, in darkness with D-fructose or certain other sugars as the sole source of carbon and energy. Growth in the latter mode requires an "accessory oxidant" such as trimethylamine-N-oxide, and the resulting cells contain the photosynthetic pigments characteristic of R. capsulata (associated with intracytoplasmic membranes) and substantial deposits of poly-beta-hydroxybutyrate. In dark anaerobic batch cultures in fructose plus trimethylamine-N-oxide medium, trimethylamine formation parallels growth, and typical fermentation products accumulate, namely, CO2 and formic, acetic, and lactic acids. These products are also found in dark anaerobic continuous cultures of R. capsulata; acetic acid and CO2 predominate when fructose is limiting, whereas formic and lactic acids are observed at elevated concentrations when trimethylamine-N-oxide is the limiting nutrient. Evidence is presented to support the conclusions that ATP generation during anaerobic dark growth of R. capsulata on fructose plus trimethylamine-N-oxide occurs by substrate level phosphorylations associated with classical glycolysis and pyruvate dissimilation, and that the required accessory oxidant functions as an electron sink to permit the management of fermentative redox balance, rather than as a terminal electron acceptor necessary for electron transport-driven phosphorylation.
Isolation and characterization of an Escherichia coli K-12 mutant defective in tyrosine- and phenylalanine-specific transport systems
Authors: Whipp M J , Halsall D M , Pittard A J
Published: January 2020

A mutant strain of Escherichia coli K-12 that is defective in both the tyrosine-specific and phenylalanine-specific transport systems was isolated. The defects in these systems were shown to be due to mutations in two distinct loci, tyrP and pheP, respectively.
Biosynthesis of bacterial glycogen: purification and properties of Salmonella typhimurium LT-2 adenosine diphosphate glucose pyrophosphorylase
Authors: Lehmann M , Preiss J
Published: January 2020

The adenosine diphosphate glucose pyrophosphorylase from a Salmonella typhimurium LT-2 mutant, JP102, derepressed in the glycogen biosynthetic enzymes was purified to homogeneity. The enzyme was found to be identical with the parent wild-type enzyme with respect to regulatory properties, immunological reactivity, and kinetic constants for the allosteric effectors and for the substrate, adenosine triphosphate. The JP102 enzyme was composed of four identical subunits, each with a molecular weight of about 48,000. This was supported by the findings that (i) gel electrophoresis under denaturing conditions showed only one component; (ii) digestion with carboxypeptidase B released stoichiometric amounts of arginine, and (iii) amino-terminal sequencing showed a single sequence for the first 27 residues. The properties of the purified S. typhimurium enzyme were compared with the properties of the previously purified Escherichia coli B enzyme.
Proton Motive Force During Growth of
Streptococcus lactis
Cells
Authors: Kashket Eva R. , Blanchard Alaina G. , Metzger William C.
Published: January 2020

Experiments with the aerotolerant anaerobe
Streptococcus lactis
provide the opportunity for determining the proton motive force (Δ
p
) in dividing cells. The two components of Δ
p
, ΔΨ (the transmembrane potential) and ΔpH (the chemical gradient of H
+
), were determined by the accumulation of radiolabeled tetraphenylphosphonium (TPP
+
) and benzoate ions. The ΔΨ was calibrated with the K
+
diffusion potential in starved, valinomycin-treated cells. With resting, glycolyzing cells, the Δ
p
was measured also by the accumulation of the non-metabolizable sugar thiomethyl-β-galactoside (TMG). In resting cells the Δ
p
, calculated either by adding ΔΨ and
Z
ΔpH or from the levels of TMG, was relatively constant between pH 5 to 7, decreasing from 160 to 150 mV and decreasing further to 100 mV at pH 8.0. With the TPP
+
probe for ΔΨ, we confirmed our previous finding that the K
+
ions dissipate ΔΨ and increase ΔpH, whereas Na
+
ions have little effect on ΔΨ and no effect on ΔpH. [
3
H]TPP
+
and [
14
C]benzoate were added during exponential phase to
S. lactis
cells growing at pH 5 to 7 at 28°C in a defined medium with glucose as energy source. As with resting cells, the ΔpH and ΔΨ were dependent on the pH of the medium. At pH 5.1, the ΔpH was equivalent to 60 mV (alkaline inside) and decreased to 25 mV at pH 6.8. The ΔΨ increased from 83 mV (negative inside) at pH 5.1 to 108 mV at pH 6.8. The Δ
p
, therefore, was fairly constant between pH 5 and 7, decreasing from 143 to 133 mV. The values for Δ
p
in growing cells, just as in resting cells, are consistent with a system in which the net efflux of H
+
ions is effected by a membrane-bound adenosine triphosphatase and glycolytically generated adenosine triphosphate. The data suggest that in both growing and resting cells the pH of the medium and its K
+
concentration are the two principal factors that determine the relative contribution of ΔpH and ΔΨ to the proton motive force.
Catabolism of 3- and 4-hydroxyphenylacetate by the 3,4-dihydroxyphenylacetate pathway in Escherichia coli
Authors: Cooper R A , Skinner M A
Published: January 2020

Various strains of Escherichia coli (but not strain K-12) were found to grow on 3-hydroxyphenylacetate and 4-hydroxyphenylacetate. Both compounds were catabolized by the same pathway, with 3,4-dihydroxyphenylacetate as a substrate for fission of the benzene nucleus, and with pyruvate and succinate as products. All the necessay enzymes were demonstrated in cell extracts prepared from induced cells but were essentially absent from uninduced cells. Mutants unable to grow on 3- and 4-hydroxyphenylactetate were defective in particular enzymes of the pathway. The characteristics of certain mutants indicated that either uptake or hydroxylation of 3- and 4-hydroxyphenylacetate may involve a common protein component. E. coli also grew on 3,4-hydroxyphenylacetate, with induction of the enzyme necessary for its degradation but not those for the uptake-hydroxylation of 3- and 4-hydroxyphenylacetate.
Nitrogen catabolite repression of asparaginase II in Saccharomyces cerevisiae
Authors: Dunlop P C , Meyer G M , Roon R J
Published: January 2020

The biosynthesis of asparaginase II in Saccharomyces cerevisiae is subject to strong catabolite repression by a variety of nitrogen compounds. In the present study, asparaginase II synthesis was examined in a wild-type yeast strain and in strains carrying gdhA, gdhCR, or gdhCS mutations. The following effects were observed: (i) In the wild-type strain, the biosynthesis of asparaginase II was strongly repressed when either 10 mM ammonium sulfate or various amino acids (10 mM) served as the source of nitrogen. (ii) In a yeast strain carrying the gdhA mutation, asparaginase II was synthesized at fully derepressed levels when 10 mM ammonium sulfate was the source of nitrogen. When amino acids (10 mM) served as the nitrogen source, asparaginase II synthesis was strongly repressed. (iii) In a strain carrying the gdhCR mutation, the synthesis of asparaginase II was partially (30 to 40%) derepressed when either 10 mM ammonium sulfate or amino acids were present in the medium. (iv) In a yeast strain containing both gdhA and gdhCR mutations, asparaginase II synthesis was fully derepressed when 10 mM ammonium sulfate was the nitrogen source and partially derepressed when 10 mM amino acids were present. (v) Yeast strains carrying the gdhCS mutation were indistinguishable from the wild-type strain with respect to asparaginase II synthesis.
Inhibition of leucine transport in Saccharomyces by S-adenosylmethionine
Authors: Law R E , Ferro A J
Published: January 2020

S-Adenoxyl-L-methionine (SAM) inhibited leucine transport in Saccharomyces cerevisiae. By using a mutant defective in the active transport of SAM, we demonstrated that the inhibitory effect was exerted at an extracellular site. Cells preincubated wtih SAM for 120 min became refractory to its inhibitory effect, which was not a result of either the active transport or the metabolism of SAM. The quantitative recovery of labeled SAM from the incubation medium indicated that SAM, and not a metabolite, was the true inhibitory molecule. S-Adenosyl-L-homocysteine and S-adenosyl-L-ethionine also functioned as inhibitors of leucine transport, whereas S-adenosyl-D-methionine, S-adenosyl-D-homocystein, 5'-methylthioadenosine, 5'-dimethylthioadenosine, and adenosine lacked this property. Kinetic studies demonstrated that SAM was a competitive inhibitor of leucine transport.
lac Thiogalactoside transacetylase of Escherichia coli K-12 and ML
Authors: Fried V A
Published: January 2020

The lac thiogalactoside transacetylase was purified from both a wild-type Escherichia coli K-12 strain (H3000) and an E. coli ML strain (ML308). These enzymes are indistinguishable by using several criteria. The subunit molecular weight of the enzyme is 24,800, which is significantly less than the previously reported value of 30,000. Although the function of the thiogalactoside transacetylase is unknown, it is suggested that this enzyme plays an important role in lactose utilization since its structure and enzymatic activity have been conserved.
Role of recBC nuclease in Escherichia coli transformation
Authors: Hoekstra W P , Bergmans J E , Zuidweg E M
Published: January 2020

In Escherichia coli transformation with linear donor deoxyribonucleic acid, the recBC pathway is functional, but genetic analysis shows that the recBC nuclease is deleterious to linear deoxyribonucleic acid.
Construction and characterization of hybrid plasmids containing the Escherichia coli nrd region
Authors: Platz A , Sjöberg B M
Published: January 2020

Recombinant plasmids containing all or part of the genetic region of Escherichia coli coding for the two subunits of ribonucleoside diphosphate reductase (proteins B1 and B2) were constructed with the aid of the multicopy plasmid pBR322. Two of these plasmids (pPS1 and pPS2) appeared to carry both a regulator and the complete structural information for the enzyme and, after transformation of E. coli, directed a 10- to 20-fold overproduction of both proteins B1 and B2. The other plasmids (pPS101 and pPS201) carried structural information for only protein B2. Cells carrying pPS1 and pPS2 showed a 5- to 500-fold increased resistance against the drug hydroxyurea. This establishes that in E. coli the inhibition of deoxyribonucleic acid synthesis by hydroxyurea is fully explained by its action on ribonucleotide reductase.
Naphthalene metabolism by pseudomonads: purification and properties of 1,2-dihydroxynaphthalene oxygenase
Authors: Patel T R , Barnsley E A
Published: January 2020

1,2-Dihydroxynaphthalene oxygenase was purified from Pseudomonas putida NCIB 9816 grown on naphthalene as the sole source of carbon and energy. The enzyme had a subunit molecular weight of 19,000 and in a medium containing phosphate buffer, 1 mM mercaptoethanol, and 10% (vol/vol) ethanol had a native molecular weight greater than 275,000. The enzyme required Fe2+ for activity. It was inactivated slowly on standing, and inactivation was accelerated by dilution with aerated buffers and by H2O2. Bathophenanthroline sulfonate, o-phenanthroline, 8-hydroxyquinoline, and 2,2'-dipyridyl also inhibited the enzyme. The inactive enzyme was reactivated by anaerobic incubation with ferrous sulfate and ferrous ammonium sulfate. Thiol reagents and acetone, ethanol, or glycerol decreased the rate of loss of activity. The enzyme was most active with 1,2-dihydroxynaphthalene, for which the Km was 2.8 X 10(-4) M. 3-Methyl- and 4-methylcatechols were oxidized at 3 and 1.5%, respectively, of the rate of 1,2-dihydroxynaphthalene, and the Km for 3-methylcatechol was 1.5 X 10(-4) M. Purified 1,2-dihydroxynaphthalene oxygenase catalyzed the oxidation of 1,2-dihydroxynaphthalene, leading to the appearance of 2-hydroxychromene-2-carboxylic acid, but 3-methylcatechol was oxidized by this enzyme to 2-hydroxy-6-oxoheptadienoic acid. Thus, a product structurally analogous to 2-hydroxychromene-2-carboxylic acid was not observed when 3-methylcatechol was oxidized. This may indicate that 2-hydroxychromene-2-carboxylic acid results from cyclization of a ring fission product before release from the enzyme.
Recombination-deficient mutant of Streptococcus faecalis
Authors: Yagi Y , Clewell D B
Published: January 2020

An ultraviolet radiation-sensitive derivative of Streptococcus faecalis strain JH2-2 was isolated and found to be deficient in recombination, using a plasmid-plasmid recombination system. The strain was sensitive to chemical agents which interact with deoxyribonucleic acid and also underwent deoxyribonucleic acid degradation after ultraviolet irradiation. Thus, the mutant has properties similar to those of recA strains of Escherichia coli.
Morphological effect of cerulenin treatment on Streptococcus faecalis as studied by ultrastructure reconstruction
Authors: Higgins M L , Carson D D , Daneo-Moore L
Published: January 2020

Exponential-phase cells of Streptococcus faecalis ATCC 9790 were treated with a concentration of cerulenin (5 micrograms/ml) that has been shown to block both lipoteichoic acid and lipid synthesis and cell division within 10 min. The morphological effect of this treatment was studied by making three-dimensional reconstructions of cells based on measurements taken from axial thin sections. This analysis indicated that cerulenin interferes with cell division by inhibiting normal constriction of the division furrow and centripetal growth of the cross wall in envelope growth sites. Rather than dividing, many of the sites in treated cells apparently continue to elongate and produce abnormally large amounts of peripheral wall surface. These observations were interpreted in terms of a previously proposed model in which cerulenin would prevent the synthesis of a lipid-containing inhibitor of autolytic enzyme activity needed for division. In addition, measurements showed that the average number of envelope growth sites per cell increased during treatment, suggesting that although cerulenin treatment blocks division, it does not interfere with the formation of new envelope growth sites. It was also observed that the size and frequency of mesosomes did not decline during the 60-min period of drug treatment. This tends to decrease the likelihood that mesosomes are formed from a pool of intracellular membrane precursors that would be depleted during a period of restricted lipid biosynthesis.
Construction and expression of hybrid plasmids containing Escherichia coli K-12 uxu genes
Authors: Ritzenthaler P , Mata-Gilsinger M , Stoeber F
Published: January 2020

The three genes of the Escherichia coli K-12 uxu region (uxu operon and regulatory gene) were isolated on a ColE1-uxu hybrid plasmid from the bank of Clarke and Carbon, and a restriction map of this region was established. In vitro recombination techniques were used to subclone the uxu restriction fragments into the plasmid vector pBR322 or pBR325. The various chimeric plasmids obtained were analyzed by restriction mapping and characterized genetically by introducing them in uxu mutant or wild-type strains. Differential rates of synthesis of the enzymes coded for by the uxu region were measured in the plasmid-containing strains; amplification of the products of the cloned genes was up to 40-fold the level found in haploid strains. The enzymes coded for by uxuA and uxuB were synthesized in vitro in a coupled transcription-translation system, confirming the results of the cloning experiments. The restriction analysis also suggests that the transcriptional direction of the uxu operon is from uxuA to uxuB and that the order of the loci in this region is: uxuR (regulatory gene), uxuB, uxuA, uxuAp (promoter), uxuAo (operator).
Isolation and properties of membranes from Bacillus megaterium spores
Authors: Racine F M , Vary J C
Published: January 2020

Membranes from dormant and heat-activated spores of Bacillus megaterium QM B1551 were isolated and purified by gentle lysis procedures followed by differential and sucrose density gradient centrifugations. The purified membranes were enriched for inner membranes and were characterized by their density and content of proteins, phospholipids, enzymes, cytochromes, and carotenoids. These purified spore membranes could be used to investigate their role in the triggering of germination.
High-frequency conjugation associated with Streptococcus lactis donor cell aggregation
Authors: Gasson M J , Davies F L
Published: January 2020

Conjugal transfer of the Streptococcus lactis 712 lactose plasmid was found to occur at a low frequency. Variants of this plasmid were selected which had much greater donor abilities and which also exhibited an unusual cell aggregation phenotype.
Synthesis and function of ribonucleic acid polymerase and ribosomes in Escherichia coli B/r after a nutritional shift-up
Authors: Shepherd N , Churchward G , Bremer H
Published: January 2020

The syntheses of stable ribosomal ribonucleic acid (RNA) and transfer RNA in bacteria depend on the concentration and activity of RNA polymerase and on the fraction of active RNA polymerase synthesizing stable RNA. These parameters were measured in Escherichia coli B/r after a nutritional shift-up from succinate-minimal to glucose-amino acids medium and were found to change in complex patterns during a 1- to 2-h period after the shift-up before reaching a final steady-state level characteristic for the postshift growth medium. The combined effect of these changes was an immediate, one-step increase in the exponential rate of stable RNA synthesis and thus of ribosome synthesis. This suggests that the distribution of transcribing RNA polymerase over ribosomal and nonribosomal genes and the polymerase activity are continuously adjusted during postshift growth to some growth-limiting reaction whose rate increases exponentially. It is proposed that this reaction is the production of amino-acylated transfer RNA and that is exponentially increasing rate results in part from a gradually increasing concentration of aminoacyl transfer RNA synthetases after a shift-up. This idea was tested and is supported by a computer simulation of a nutritional shift-up.
Developmental fate of Rhizobium meliloti bacteroids in alfalfa nodules
Authors: Paau A S , Bloch C B , Brill W J
Published: January 2020

Nitrogen-fixing bacteroids are degraded during nodule senescence. This is in contrast to recent implications that viable bacteroids can be released into soil from legume nodules. Rhizobia originating from persistent infection threads in senescing nodule plant cells seem to be the source of viable cells required for perpetuation of the Rhizobium spp. population in the soil. Our conclusions were derived from electron microscopic examination of stages of development and senescence of alfalfa root nodules.
Protein synthesis during germination of Allomyces macrogynus mitospores
Authors: Smith B A , Burke D D
Published: January 2020

Protein synthesis in Allomyces marcogynus mitospores began at the time of encystment and was required for further germination. The rate of protein synthesis in germinating spores decreased in the absence of ribonucleic acid synthesis relative to the uninhibited control. There was a concomitant decrease in polysome content, suggesting that some of the messenger ribonucleic acid synthesized during early germination is translation.
Are growth rates of Escherichia coli in batch cultures limited by respiration?
Authors: Andersen K B , von Meyenburg K
Published: January 2020

Batch cultures of Escherichia coli were grown in minimal media supplemented with various carbon sources which supported growth at specific growth rates from 0.2 to 1.3/h. The respiration rates of the cultures were measured continuously. With few exceptions, the specific rate of oxygen consumption was about 20 mmol of O2/h per g (dry weight), suggesting that the respiratory capacity was limited at this value. The adenosine triphosphate (ATP) required for the production of cell material from the different carbon sources was calculated on the basis of known ATP requirements in the biochemical pathways and routes of macromolecular synthesis. The calculated ATP requirements, together with the measured growth rates and growth yields on the different carbon sources, were used to calculate the rate of ATP synthesis by oxidative phosphorylation. This rate was closely related to the respiration rate. We suggest that aerobic growth of E. coli in batch cultures is limited by the rate of respiration and the concomitant rate of ATP generation through oxidative phosphorylation.
Regulation of enzyme synthesis in the arginine deiminase pathway of Pseudomonas aeruginosa
Authors: Mercenier A , Simon J P , Vander Wauven C , Haas D , Stalon V
Published: January 2020

The three enzymes of the arginine deiminase pathway in Pseudomonas aeruginosa strain PAO were induced strongly (50- to 100-fold) by a shift from aerobic growth conditions to very low oxygen tension. Arginine in the culture medium was not essential for induction, but increased the maximum enzyme levels twofold. The induction of the three enzymes arginine deiminase (EC 3.5.3.6), catabolic ornithine carbamoyltransferase (EC 2.1.3.3), and carbamate kinase (EC 2.7.2.3) appeared to be coordinate. Catabolic ornithine carbamoyltransferase was studied in most detail. Nitrate and nitrite, which can replace oxygen as terminal electron acceptors in P. aeruginosa, partially prevented enzyme induction by low oxygen tension in the wild-type strain, but not in nar (nitrate reductase-negative) mutants. Glucose was found to exert catabolite repression of the deiminase pathway. Generally, conditions of stress, such as depletion of the carbon and energy source or the phosphate source, resulted in induced synthesis of catabolic ornithine carbamoyltransferase. The induction of the deiminase pathway is thought to mobilize intra- and extracellular reserves of arginine, which is used as a source of adenosine 5'-triphosphate in the absence of respiration.
Deoxyribonucleic acid-binding properties and membrane protein composition of a competence-deficient mutant of Haemophilus influenzae
Authors: Kooistra J , van Boxel T , Venema G
Published: January 2020

A mutant of Haemophilus influenzae was isolated which was completely unable to take up double-stranded homologous deoxyribonucleic acid (DNA) at normal physiological conditions but which took up DNA equally as well as the wild type at low pH (pH 4.4). The properties of the mutant provide evidence for the existence of two different mechanisms for DNA entry in the H. influenzae transformation system. With the aid of the mutant the optimal conditions for entry of DNA by these two mechanisms were determined, and the dependence of entry and the specific transforming activity of the entered DNA on competence was examined. The mechanism of entry of DNA at neutral pH, which is not functioning in the mutant, effected entry of homologous DNA only, whereas the mechanism involved in entry of DNA at low pH also effected entry of heterologous DNA. This suggests that the mutant is lacking a protein which recognizes the specific base sequence(s) required for entry. Comparison of the protein composition of the membranes of mutant cells subjected to a growth regimen provoking competence in wild-type cells with that of competent wild-type cells revealed that the mutant is impaired in the synthesis of a protein with a molecular weight of 22,500.
Repression of nitrate reductase activity and loss of antigenically detectable protein in Neurospora crassa
Authors: Amy N K , Garrett R H
Published: January 2020

Experiments were performed to determine whether conditions which cause the rapid loss of nitrate reductase activity in Neurospora crassa mycelia were accompanied by the loss of antigenically detectable nitrate reductase protein. When mycelia with nitrate reductase activity were transferred to ammonia media, there was a rapid loss in the reduced nicotinamide adenine dinucleotide-nitrate reductase activity plus the parallel loss of the reduced nicotinamide adenine dinucleotide-diaphorase and the reduced methyl viologen-nitrate reductase activities associated with the nitrate reductase. In addition, there was the loss of cross-reacting material to anti-nitrate reductase antisera that was concomitant with the loss of nitrate reductase activity. When mycelia were exposed to either ammonia plus cycloheximide, nitrate plus cycloheximide, or nitrogen-free media, or to media which lacked an assimilable carbon source, the amount of cross-reacting material declined in concert with the nitrate reductase activity. The mutant nit-6, which lacks nitrite reductase activity, was exposed to ammonia or nitrate plus cycloheximide media. The nitrate reductase and the amount of cross-reacting material declined together as in the wild-type mycelia. We conclude that the loss of nitrate reductase activity was accompanied by the specific loss of this protein and that no pool of inactivated nitrate reductase molecules existed.
Possible regulation of the Salmonella typhimurium histidine operon by adenosine triphosphate phosphoribosyltransferase: large metabolic effects
Authors: Goitein R K , Parsons S M
Published: January 2020

An effort to find growth conditions leading to conditional regulation of the histidine operon of Salmonella typhimurium by the allosteric first enzyme of the pathway, adenosine triphosphate phosphoribosyltransferase (EC 2.4.2.17), is reported. A strain deleting the enzyme, TR3343, behaved simply and predictably under all growth conditions, whereas histidine auxotrophs containing active enzyme behaved in complicated ways dependent upon the location of the histidine pathway lesion. hisE strains derepressed the operon only one-half as much as TR3343 when grown on limiting histidine and a poor carbon source, but they also grew more slowly, probably as a result of high N1-(5-phospho-beta-D-ribosyl)-adenosine triphosphate levels in the cell. hisC strains exhibited oscillatory growth behavior and oscillatory histidine operon expression when grown on intermediate concentrations of the histidine precursor histidinol. This behavior probably was caused by synergistic in-phase variations in the histidine, purine nucleotide, and ppGpp pools of the cell. All of the growth and histidine operon expression effects associated with the presence of adenosine triphosphate phosphoribosyltransferase could be assigned to metabolic perturbation of the cell caused by unregulated enzymatic activity.
Characterization of two genetically separable inorganic phosphate transport systems in Escherichia coli
Authors: Willsky G R , Malamy M H
Published: January 2020

Inorganic phosphate (Pi) transport by wild-type cells of Escherichia coli grown in excess phosphate-containing media involves two genetically separable transport systems. Cells dependent upon the high affinity-low velocity Pst (phosphate specific transport) system have a Km of 0.43 +/- 0.2 microM Pi and a Vmax of 15.9 +/- 0.3 nmol of Pi (mg [dry weight]-1min-1) and will grow in the presence of arsenate in the medium. However, cells dependent upon the low affinity-high velocity Pit (Pi transport) system have a Km of 38.2 +/- 0.4 microM and a Vmax of 55 +/- 1.9 nmol of Pi (mg [dry weight]-1min-1), and these cells cannot grow in the presence of an arsenate-to-Pi ratio of 10 in the medium. Pi transport by both systems was sensitive to the energy uncoupler 2,4-dinitrophenol and the sulfhydryl reagent N-ethylmaleimide, whereas only the Pst system was very sensitive to sodium cyanide. Evidence is presented that Pi is transported as Pi or a very labile intermediate and that accumulated Pi does not exit through the Pst or Pit systems from glucose-grown cells. Kinetic analysis of Pi transport in the wild-type strain containing both the Pst and Pit transport systems revealed that each system was not operating at full capacity. In addition, Pi transport in the wild-type strain was completely sensitive to sodium cyanide (a characteristic of the Pst system).
Identification of new genes in a cell envelope-cell division gene cluster of Escherichia coli: cell envelope gene murG
Authors: Salmond G P , Lutkenhaus J F , Donachie W D
Published: January 2020

We report the identification, cloning, and mapping of a new cell envelope gene, murG. This lies in a group of five genes of similar phenotype (in the order murE murF murG murC ddl) all concerned with peptidoglycan biosynthesis. This group is in a larger cluster of at least 10 genes, all of which are involved in some way with cell envelope growth.
Improved method for conjugative transfer by filter mating of Streptococcus pneumoniae
Authors: Smith M D , Guild W R
Published: January 2020

The frequency of conjugation during filter mating of pneumococcus was increased 10- to 100-fold when the filter was embedded in agar during incubation instead of being on the surface. The major effect was not due to protection from oxygen. The factor of increase was similar for transfer of plasmids and of chromosomal insertions of drug resistance elements.
Mutations in genes cpxA and cpxB of Escherichia coli K-12 cause a defect in isoleucine and valine syntheses
Authors: McEwen J , Silverman P
Published: January 2020

Mutations in two chromosomal genes of Escherichia coli, cpxA and cpxB, produced a temperature-sensitive growth defect that was remedied specifically by the addition of isoleucine and valine to the minimal medium. This auxotrophy was manifested only when the medium contained exogenous leucine, suggesting that mutant cells fail to elaborate active acetohydroxy acid synthase, isozyme I. In the presence of leucine, this enzyme was required to catalyze the first reaction common to the biosynthesis of isoleucine and valine. Measurements of enzyme activity in crude extracts showed that mutant cells were seven- to eightfold deficient in active isozyme I when the cells were grown in the presence of leucine. When grown in the absence of leucine, mutant cells contained more acetohydroxy acid synthase activity. We attribute this activity to isozyme III, the product of the ilvHI genes, which are derepressed in the absence of exogenous leucine. The cpxA and cpxB mutations appear to affect the production of active isozyme I, rather than its activity, since (i) neither the cpxA nor the cpxB gene mapped near the structural gene for isozyme I (ilvB), (ii) the growth of mutant cells shifted from the permissive (34 degrees C) to the nonpermissive (41 degrees C) temperature did not immediately cease, but declined gradually over a period corresponding to several normal generation times, and (iii) the enzyme from mutant cells grown at 34 degrees C was as stable at 41 degrees C as the enzyme from cpx+ cells.
Fluctuation in polyadenylate size and content in exponential- and stationary-phase cells of Saccharomyces cerevisiae
Authors: Sogin S J , Saunders C A
Published: January 2020

Stationary-phase cells of Saccharomyces cerevisiae were found to have a reduced polyadenylate [poly(A)] content as compared with exponential-phase cells. A sizing procedure for poly(A) was devised to distinguish between alternative hypotheses to explain this reduction. Two major size classes of poly(A) were found. The decreased representation of the larger of the two classes accounted for the majority of the poly(A) loss. The remainder of the loss was accounted for by fewer poly(A)-containing sequences. The smaller of the two poly(A) classes was apparently not of mitochondrial origin and may be added transcriptionally.
Transcription of bacteriocinogenic plasmid CloDF13 in vivo and in vitro: structure of the cloacin immunity operon
Authors: van den Elzen P J , Konings R N , Veltkamp E , Nijkamp H J
Published: January 2020

Escherichia coli minicells harboring plasmid CloDF13 synthesized at least 25 messenger ribonucleic acid (RNA) species; three of these RNAs, a 2,400-, a 2,200-, and a 100-nucleotide RNA, were synthesized in relatively large amounts. Using insertion and deletion mutants of CloDF13 as well as an RNA blotting technique, we could demonstrate that these three RNAs are transcripts from the CloDF13 DNA region from 0 to 40%. This region contains the cloacin and immunity genes and the genetic information involved in plasmid DNA replication. A transcription map of this region is presented and discussed. The data indicate that the cloacin and immunity genes were coordinately transcribed into messenger RNAs of about 2,400 and 2,200 nucleotides, which differ in length at their 3' terminus. RNA polymerase binding studies and in vitro transcription assays indicated that transcription of these genes initiates at a promoter located around 32% on the CloDF13 map. Furthermore, it is shown that a 100-nucleotide RNA is encoded by the CloDF13 DNA region between 7.7 and 8.8% on the plasmid genome; the synthesis of this RNA proceeds in a direction opposite to the transcription of the cloacin and immunity genes.
Structural instability of IncP-1 plasmids in Pseudomonas aeruginosa PAT involves interaction with plasmid pVS1
Authors: Godfrey A J , Morgan A F , Holloway B W
Published: January 2020

The structural instability exhibited by IncP-1 plasmids in Pseudomonas aeruginosa strain PAT was shown to be Rec+ dependent and involved interaction with the resident plasmid pVS1. Structural instability resulted from deletion of plasmid deoxyribonucleic acid at a frequency of ca. 10(-2)/cell per generation. Deletants could be stabilized by transduction into P. aeruginosa strain PAO, but in strain PAT deletants had only a transient existence, as continued deletion led eventually to the loss of the entire plasmid. The patterns of markers lost in PAT were used to demonstrate a marker order for R68 similar to that published elsewhere for RP4 (Barth and Grinter, J. Mol. Biol. 113:455-474, 1977), except that only one Tra region was found. R68 also exhibited Rec+-dependent structural instability in PAO(pVS1) derivatives but, unlike the case in PAT, instability was not accompanied by chromosome mobilization. We isolated deletants of pVS1 which were unable to promote structural instability.
Size heterogeneity of Salmonella typhimurium lipopolysaccharides in outer membranes and culture supernatant membrane fragments
Authors: Munford R S , Hall C L , Rick P D
Published: January 2020

Enterobacteriaceae cells growing in liquid media shed fragments of their outer membranes. These fragments, which may constitute a biologically important form of gram-negative bacterial endotoxin, have been reported to contain proteins, phospholipids, and lipopolysaccharides (LPS). In this study we compared the sizes of LPS molecules in shed membrane fragments and outer membranes from cells growing in broth cultures. Using conditional mutants of Salmonella typhimurium which incorporate specific sugars into LPS, we analyzed radiolabeled LPS by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This technique revealed that S. typhimurium LPS are more heterogeneous than previously known; molecules possessing from 0 to more than 30 O-chain repeat units were identified in outer membranes, supernatant fragments, and purified LPS. The size distributions of LPS molecules in outer membranes and supernatant fragments were similar; supernatant fragments appeared to be slightly enriched in molecules with long O-polysaccharide chains. Our results indicate the LPS molecules of many sizes are synthesized, translocated to outer membranes, and released into culture supernatants. Since the hydrophilic O-polysaccharides extend from bacterial surfaces into the aqueous environment, our findings suggest that the cell surface topography of this bacterium may be very irregular. We also speculate that heterogeneity in the degree of polymerization of O-antigenic side chains may influence the interactions of the toxic moiety of LPS (lipid A) with host constituents.
Mutagenesis by neocarzinostatin in Escherichia coli and Salmonella typhimurium: requirement for umuC+ or plasmid pKM101
Authors: Eisenstadt E , Wolf M , Goldberg I H
Published: January 2020

Neocarzinostatin, a protein with antibiotic activity, is a bacterial mutagen. We have investigated the mutagenicity of neocarzinostatin towards Salmonella typhimurium and discovered that, unlike the situation in Escherichia coli, neocarzinostatin will revert base pair substitution mutations (missense or nonsense). However, when the R46 factor derivative, plasmid pKM101, was introduced, the mutagenicity of neocarzinostatin towards base pair substitution-carrying mutants of S. typhimurium was readily detected. Neocarzinostatin had only modest activity in reverting a frameshift mutation in S. typhimurium, but that activity, too, required the presence of pKM101. Mutant pKM101 plasmids which no longer enhanced mutagenesis also lost their ability to promote neocarzinostatin-induced mutations. Finally, the umuC36 mutation, which renders E. coli nonmutable by ultraviolet light, also rendered the bacteria nonmutable by neocarzinostatin. The effect of the umuC36 mutation was suppressed by plasmid pKM101.
I-like R plasmids promote degradation of stable ribonucleic acid in Escherichia coli
Authors: Ohnishi Y , Akimoto S
Published: January 2020

Some I-like R plasmids, R483, R144, R64drd-11 and R621a, belonging to compatibility groups IncI alpha and I gamma promoted degradation of stable RNA in the srnA1 cells of Escherichia coli after addition of rifampin at 42 degrees C. R16 and R834 plasmids of compatibility group IncB also promoted the degradation of RNA. However, other many kinds of plasmids did not. The promotion of RNA degradation was delayed by the addition of chloramphenicol with rifampin.
Mechanism of Haemophilus influenzae transfection by single and double prophage deoxyribonucleic acid
Authors: Stuy J H
Published: January 2020

Whole phages HP1 and HP3, vegetative-phage deoxyribonucleic acid (DNA), and single and tandem double prophage DNA were exposed to ultraviolet radiation and then assayed on a wild-type (DNA repair-proficient) Haemophilus influenzae Rd strain and on a repair-deficient uvr-1 strain. Host cell reactivation (DNA repair) was observed for whole-phage and vegetative-phage DNA but not for single and double prophage DNA. Competent (phage-resistant) Haemophilus parainfluenzae cells were normally transfected with H. influenzae-grown phage DNA and with tandem double prophage DNA but not at all with single prophage DNA. CaCl2-treated H. influenzae suspensions could be transfected with vegetative phage DNA and with double prophage DNA but not with single prophage DNA. These observations support the hypothesis that transfection with single prophage DNA occurs through prophage DNA single-strand insertion into the recipient chromosome (at the bacterial att site) followed by DNA replication and then prophage induction.
Simplified fluctuation test to distinguish liquid holding recovery from cell multiplication in ultraviolet-irradiated Escherichia coli
Authors: Aragão B R , Araújo A C , Gomes R A
Published: January 2020

Improved plating techniques and a fluctuation test have been used to distinguish between liquid holding recovery of ultraviolet-irradiated cells and cell multiplication in Escherichia coli. Among tested strains, only recA mutants showed true recovery.
Effect of oxygen on Bacteroides fragilis survival after far-ultraviolet irradiation
Authors: Jones D T , Robb F T , Woods D R
Published: January 2020

Bacteroides fragilis cells were more sensitive to far-ultraviolet radiation under aerobic conditions than under anaerobic conditions. The percentage of pyrimidine dimers assayed after irradiation under both conditions was similar.
Cytochrome b reducible by succinate in an isolated succinate dehydrogenase-cytochrome b complex from Bacillus subtilis membranes
Authors: Hederstedt L
Published: January 2020

In previous work with membranes of Bacillus subtilis, the succinate dehydrogenase complex was isolated by immunoprecipitation of Triton X-100-solubilized membranes. The complex included a polypeptide with an apparent molecular weight of 19,000, probably attributable to apocytochrome. This paper reports the further characterization of this cytochrome and its relation to the respiratory chain of B. subtilis. The cytochrome was identified as cytochrome b, and its difference absorption spectra showed maxima at 426, 529, and 558 nm at room temperature. The oxidized cytochrome had an absorption maximum at 413 nm. The cytochrome was reduced by succinate in the isolated succinate dehydrogenase complex and in Triton X-100-solubilized membranes. In whole membranes cytochromes b, c, and a were reduced by succinate. In membranes from a mutant containing normal cytochromes but lacking succinate dehydrogenase no reduction of cytochrome was seen with succinate. It was concluded that the isolated succinate dehydrogenase-cytochrome b complex is a functional unit in the intact B. subtilis membrane. An accompanying paper describes cytochrome b as a structural unit involved in the membrane binding of succinate dehydrogenase.
Regulation of hexuronate system genes in Escherichia coli K-12: multiple regulation of the uxu operon by exuR and uxuR gene products
Authors: Robert-Baudouy J , Portalier R , Stoeber F
Published: January 2020

New regulatory mutants of Escherichia coli K-1 carrying alterations of the uxuR gene were isolated and characterized. In the presence of superrepressed or derepressed uxuR mutations, mannonic hydrolyase (uxuA) and oxidoreductase relationship analyses suggested that the uxuR gene product acted as a repressor in the control of uxuA-uxuB operon expression. uxuR mutations were localized near min 97, and the following gene order was established: (argH)-uxuR-uxuB-uxuA-(thr). Properties of exuR (point and deletion) mutants showed that both exuR and uxuR regulatory gene products were involved in the control of the uxuA uxuB operon. Analysis of exuR uxuR double-derepressed mutants suggested that exuR and uxuR repressors act cooperatively to repress the uxu operon.
Infection of Salmonella typhimurium with coliphage Mu d1 (Apr lac): construction of pyr::lac gene fusions
Authors: Csonka L N , Howe M M , Ingraham J L , Pierson L S , Turnbough C L
Published: January 2020

A procedure was developed for introducing the coliphage Mu d1 (Apr lac) into Salmonella typhimurium in order to construct gene fusions that place the structural genes of the lac operon under the control of the promoter-regulatory region of other genes. To introduce Mu d1 from Escherichia coli K-12 into S. typhimurium, which is normally not a host for Mu, we first constructed an E. coli double lysogen carrying the defective Mu d1 phage and a Mu-P1 hybrid helper phage (MuhP1) that confers the P1 host range. A lysate prepared from this strain was used to infect a P1-sensitive (i.e., galE), restriction-deficient, modification-proficient strain of S. typhimurium, and a double lysogen carrying Mu d1 and MuhP1 was isolated. Induction of the latter strain produced lysates capable of infecting and generating gene fusions in P1-sensitive strains of S. typhimurium. In this paper we describe the construction of pyr::lac fusions by this technique.
Menaquinone biosynthesis in Bacillus subtilis: isolation of men mutants and evidence for clustering of men genes
Authors: Taber H W , Dellers E A , Lombardo L R
Published: January 2020

Menaquinone (vitamin K2)-deficient mutants of Bacillus subtilis were selected by simultaneous resistance to two aminoglycoside antibiotics. These men mutants fell into two groups: group I, in which the nutritional requirement was satisfied either by o-succinylbenzoic acid or by 1,4-dihydroxy-2-naphthoic acid; and group II, comprising those capable of growing only when supplemented with 1,4-dihydroxy-2-naphthoic acid. The latter group could be further subdivided into two classes on the basis of syntrophy experiments, fine-structure genetic mapping, and in vitro complementation by cell-free extracts (Meganathan et al., J. Bacteriol., 145:328-332, 1981). These subclasses of group II defined the menB and menE genes, whereas group I appeared to comprise mutations in the menC and menD genes. All of the men mutations tested, whether occurring in menB, menE, or menC,D, could be placed by genetic mapping with bacteriophage PBS1 between bioB and ald on the B. subtilis genome.
Identity of the B56.5 protein, the A-protein, and the groE gene product of Escherichia coli
Authors: Neidhardt F C , Phillips T A , VanBogelen R A , Smith M W , Georgalis Y , Subramanian A R
Published: January 2020

Protein B56.5 is a major Escherichia coli protein, originally identified on two-dimensional gels as an abundant cellular protein with unique regulation. The groE gene product is a bacterial protein essential for the assembly of many diverse bacteriophages. The ribosomal A-protein is a large, acidic protein of unknown function associated with isolated, washed ribosomes. On the basis of comigration in two-dimensional gels, oligopeptide map patterns, amino acid composition, immunological specificity, physical properties, and genetic analysis, protein B56.5 has now been shown to be the groE gene product and to be identical with the A-protein.
Synthesis of Bacillus cereus spore coat protein
Authors: Aronson A I
Published: January 2020

The major structural protein of Bacillus cereus spore coats was synthesized, commencing 1 to 2 h after the end of exponential growth, as a precursor with a mass of ca. 65,000 daltons. About 40% of this precursor, i.e. 26,000 daltons, was converted to spore coat monomers of 13,000 daltons each, perhaps as disulfide-linked dimers. The rate of conversion varied, being initially slow, most rapid at the time of morphogenesis of the coat layers, and then slow again late in sporulation, coincident with a decrease in intracellular protease activity. There was a second major spore coat polypeptide of about 26,000 daltons that was extractable from mature spores in variable amounts. This protein had a peptide profile and a reactivity with spore coat protein antibody that were very similar to those of the 13,000-dalton monomers. It is probably a disulfide-linked dimer that is not readily dissociated.