bluuebunny/crossref_metadata_2025 huggingface dataset:
Length growth of two Escherichia coli B/r substrains
Authors: Meyer M , De Jong M A , Demets R , Nanninga N
Published: January 2020

Length growth of synchronized Escherichia coli B/r substrain A (ATCC 12407) and B/r substrain F26 (Thy his) was followed with an electron microscope. Cells were grown with doubling times (tau) of 60 min (B/rA) and of 82 and 165 min (B/rF26). Different length growth patterns were found for the two substrains. In B/rF, the length growth rate increased about midway in the cell cycle. For tau = 165 min, the rate increase was preceded by a short period of slow growth. For B/r A (r = 60 min), this period seemed to occur at the beginning of the cell cycle. The possibility is raised that the different length growth patterns are related to different deoxyribonucleic acid replication patterns of the respective strains.
Respiration-Linked Proton Transport, Changes in External pH, and Membrane Energization in Cells of
Escherichia coli
Authors: Gould J. Michael
Published: January 2020

The kinetics of respiration-dependent proton efflux and membrane energization have been studied in intact cells of logarithmic-phase
Escherichia coli
. Parallel measurements of the rate and extent of proton efflux into the external medium (half-time, about 10 s; ratio of H
+
to O, about 0.5) and the oxidation of
E. coli
cytochrome
b
(half-time, ≤1 s; about 6% oxidized) after a pulse of 5.5 ng-atoms of O indicate that the rate of proton efflux is at least 10 times slower than expected from the time required for the cells to reduce the oxygen added in the pulse. The kinetics of formation and dissipation of the transmembrane electric potential (δψ) after an O
2
pulse were estimated from changes in the fluorescence properties of the cell envelope-bound probe
N
-phenyl-1-naphthylamine. Under anaerobic conditions, a small pulse of oxygen induced a rapid (half-time, ≤1 s) partial decrease in the fluorescence intensity of the probe, followed by a slower relaxation of the fluorescence change to the original intensity. The extent of the initial rapid decrease was linearly dependent upon the amount of oxygen added in the pulse (0 to 11 ng-atoms of O per pulse), whereas the rate of the subsequent relaxation was accelerated by the uncoupler
p
-trifluoromethoxycarbonylcyanidephenylhydrazone and the K
+
ionophore colicin E1. This suggests that the initial fluorescence decrease after an O
2
pulse reflects the energization of the membrane, whereas the relaxation of the fluorescence decrease reflects the subsequent deenergization of the membrane arising from counterion redistributions. The fact that the efflux of H
+
into the external medium after an O
2
pulse was inefficient and much slower (half-time, about 10 s) than the reduction of the added O
2
(half-time, ≤1 s) and the energization of the membrane (half-time ≤1 s) suggests that some of the protons translocated across the cytoplasmic membrane during a brief pulse of respiratory activity are accumulated in a region of the cell which is not in rapid equilibrium with the external medium.
Fatty acid composition of lipopolysaccharides of Vibrio cholerae 35A3 (Inaba), NIB 90 (Ogawa), and 4715 (Nag)
Authors: Hisatsune K , Kondo S , Kawata T , Kishimoto Y
Published: January 2020

Considerable amounts of odd-numbered fatty acids, such as non-hydroxy C15 and C17 and 3-hydroxy C11 and C13 acids, were found in lipopolysaccharides from Vibrio cholerae 35A3 (Inaba).
Dependency of size of Saccharomyces cerevisiae cells on growth rate
Authors: Tyson C B , Lord P G , Wheals A E
Published: January 2020

The mean size and percentage of budded cells of a wild-type haploid strain of Saccharomyces cerevisiae grown in batch culture over a wide range of doubling times (tau) have been measured using microscopic measurements and a particle size analyzer. Mean size increased over a 2.5-fold range with increasing growth rate (from tau = 450 min to tau = 75 min). Mean size is principally a function of growth rate and not of a particular carbon source. The duration of the budded phase increased at slow growth rates according to the empirical equation, budded phase = 0.5 tau + 27 (all in minutes). Using a recent model of the cell cycle in which division is thought to be asymmetric, equations have been derived for mean cell age and mean cell volume. The data are consistent with the notion that initiation of the cell cycle occurs at "start" after attainment of a critical cell size, and this size is dependent on growth rate, being, at slow growth rates, 63% of the volume of fast growth rates. Previous reports are reanalyzed in the light of the unequal division model and associated population equations.
Specific inhibition of outgrowth of Bacillus subtilis spores by novobiocin
Authors: Gottfried M , Orrego C , Keynan A , Halvorson H O
Published: January 2020

Spores of a Bacillus subtilis mutant temperature sensitive in deoxyribonucleic acid (DNA) replication proceeded through outgrowth at the nonpermissive temperature to the same extent as the wild-type parent spores. In contrast, the DNA synthesis inhibitor novobiocin completely prevented spore outgrowth while displaying a marginal effect on logarithmic growth during one generation time. Inhibition of outgrowth by novobiocin occurred in the absence of DNA replication, as demonstrated in an experiment with spores of the temperature-sensitive DNA synthesis mutant at the restrictive temperature. Novobiocin inhibited the initial rate of ribonucleic acid synthesis to the same extent in germinated spores and in exponentially growing cells. A novobiocin-resistant mutant underwent normal outgrowth in the presence of novobiocin. Therefore, novobiocin inhibition was independent of its effect on chromosome replication per se.
Individual proteins are synthesized continuously throughout the Escherichia coli cell cycle
Authors: Lutkenhaus J F , Moore B A , Masters M , Donachie W D
Published: January 2020

The pattern of synthesis of about 750 individual polypeptides was followed throughout the cell cycle of Escherichia coli B/r. Samples taken at different times in the cell cycle exhibited the same pattern of protein synthesis. No protein could be identified that was synthesized at different rates during different parts of the cell cycle.
Purification and characterization of smooth and rough lipopolysaccharides from Brucella abortus
Authors: Moreno E , Pitt M W , Jones L M , Schurig G G , Berman D T
Published: January 2020

In an attempt to obtain pure and well characterized smooth lipopolysaccharide (S-LPS) and rough lipopolysaccharide (R-LPS), smooth and rough strains of Brucella abortus were extracted by two different modifications of the phenol-water method. S-LPS was obtained in the phenol phase, and R-LPS was obtained in the aqueous phase. Further purification was accomplished by treatment with enzymes, detergents, NaI as a chaotropic agent to separate non-covalently bound contaminants, and by gel filtration. The degree of purity of the molecules was determined by chemical and immunological analysis and by electrophoresis in sodium dodecyl sulfate-polyacrylamide gels. Lipid identification by gas-liquid chromatography showed seven major fatty acids. Palmitic acid accounts for about 50%, stearic acid accounts for about 10%, and hydroxylated fatty acids account for less than 5% of total fatty acids. 2-Keto-3-deoxyoctonate but not heptose was detected in the sugar analysis. Protein was found to be firmly bound to S-LPS but not to R-LPS.
Characterization of a succinate dehydrogenase complex solubilized from the cytoplasmic membrane of Bacillus subtilis with the nonionic detergent Triton X-100
Authors: Hederstedt L , Holmgren E , Rutberg L
Published: January 2020

A succinic dehydrogenase (SDH) complex has been purified from Triton X-100-solubilized membranes from Bacillus subtilis by precipitation with specific antibody. Radioactively labeled precipitated complex was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by autoradiography of the gels. The complex contained equimolar amounts of three polypeptides with approximate molecular weights of 65,000, 28,000, and 19,000. Five succinic dehydrogenase-negative mutants, belonging to the citF group, contained the 65,000-dalton polypeptide in a soluble form in the cytoplasm. Each 65,000-dalton polypeptide had about one molecule of flavin bound. Another citF mutant, citF11, which lacks the 65,000-dalton polypeptide, contained a membrane-bound 28,000-dalton polypeptide. The wild-type succinic dehydrogenase complex contained cytochrome, probably a cytochrome b. The 19,000-dalton polypeptide is suggested to represent the apoprotein of this cytochrome. The 65,000-dalton and the 28,000-dalton polypeptides are thought to constitute succinic dehydrogenase and to correspond to the flavoprotein and the ironprotein, respectively, as described for succinic dehydrogenase isolated from beef heart mitochondria or Rhodospirillum rubrum chromatophores. The results presented suggest that in B. subtilis succinic dehydrogenase is attached to a cytochrome b in the membrane via the 28,000-dalton (ironprotein) polypeptide.
Suppressor of deoxythmidine monophosphate uptake in Saccharomyces cerevisiae
Authors: Remer S , Sherman A , Kraig E , Haber J E
Published: January 2020

Although yeast cannot normally incorporate exogenous deoxythymidine 5'-monophosphate (dTMP) into deoxyribonucleic acid, mutants able to do so have been isolated. We have characterized a recessive suppressor of dTMP uptake (sot1) that prevents strains carrying either tup1, tup2, or tup4 from growing on selective medium. The sot1 mutation maps between rad1 and the centromere of chromosome XVI, and is unlinked to any of the tup mutations. The sot1 mutation does not suppress the other pleiotropic effects of the tup1 mutant, notably the lack of mating of tup1 MATalpha strains. The sot1 mutation specifically blocks the uptake of dTMP into tup strains. After growing a sot1 strain in medium containing [3H]dTMP, we showed that the medium still contained more than 90% of the original [3H]dTMP and that this medium could support the incorporation of [3H]dTMP by a tup2 strain. Therefore, sot1 strains do not degrade dTMP in the medium. The sot1 mutation had no effect on the uptake of other nutrients essential for growth, including several amino acids, adenine, and uracil.
Specific interaction of the tetragonally arrayed protein layer of Bacillus sphaericus with its peptidoglycan sacculus
Authors: Hastie A T , Brinton C C
Published: January 2020

Tetragonal layer protein (T-layer) isolated from Bacillus sphaericus NTCC 9602 (wild type) or 9602 Lmw (variant) bonded specifically to the sacculi (peptidoglycan) of either cell type. Only uncleaved T-layer subunits were capable of specific recognition of the B. sphaericus sacculi; other Bacillus strains and gram-positive bacterial sacculi would not adsorb B. sphaericus strain 9602 T-layer. The peptidogylcan did not function as a template since isolated T-layer subunits self-assembled into characteristic pattern. Upon reassociation with sacculi, T-layer assemblies were randomly oriented patches compared with more continuous strictly oriented pattern on cells or fresh cell walls. T-layer associated with the sacculus was less susceptible to conditions that dissociated in vitro-assembled T-layer. Mild proteolysis of both wild-type and variant T-layer subunits by a variety of enzymes reduced the molecular weight by 18,000 in all cases, indicating that one region of the molecule was particularly susceptible to cleavage. Subunits from which the minor fragment had been cleaved upon aging retained the capacity to assemble in vitro, but would no longer adsorb to sacculi. Thus, the ability of T-layer to form networks was separate from its ability to bind cell walls, and the 18,000-dalton piece of the T-layer polypeptide was necessary for attachment to the cell wall.
Genetic basis for colonial variation in Neisseria gonorrhoeae
Authors: Norlander L , Davies J , Norqvist A , Normark S
Published: January 2020

When the piliated colony types of Neisseria gonorrhoeae, which predominate in recent isolates, were nonselectively subcultured in vitro, they gave rise to large numbers of nonpiliated, avirulent colonial variants. Evidence is presented to show that most of this variation occurs after active growth has ceased and that the variation is sensitive to the action of deoxyribonuclease. We suggest that this variation is a result of transformation. A second variation in colonial morphology involved differing levels of "colony opacity-associated proteins" in the outer membrane. This variation was also inhibited by the presence of deoxyribonuclease, but the genetic basis for it is not as yet clear.
Penicillin selection of Escherichia coli deoxyribonucleic acid repair mutants
Authors: Sancar A , Rupert C S
Published: January 2020

A rapid method has been developed for isolation of ultraviolet-sensitive mutants of Escherichia coli, by inducing delay in the growth and/or division of repair-deficienct cells with low fluences of far-ultraviolet radiation, and killing with penicillin the repair-proficient cells, which continue to grow and divide. With this technique, we have achieved about a 3,000-fold enrichment for photoreactivation less (phr) cells and have isolated and characterized three phr mutants.
Characterization of Azotobacter vinelandii deoxyribonucleic acid and folded chromosomes
Authors: Sadoff H L , Shimel B , Ellis S
Published: January 2020

The properties of Azotobacter vinelandii deoxyribonucleic acid (DNA) and folded chromosomes were studied and compared to those of Escherichia coli as a standard. Based on melting temperature and buoyant density measurements, the guanosine + cytosine content of purified A. vinelandii DNA was 65%, whereas that of E. coli DNA was 50%. The results of renaturation studies showed that the unique DNA sequence lengths of the two organisms were similar with Cot1/2 values of 7.3 +/- 0.4 mol.s/liter and 7.5 +/- 0.3 mol.s/liter, respectively, for A. vinelandii and E. coli. Folded chromosomes of A. vinelandii sedimented in a centrifugal field at a rate identical to those derived from E. coli, 1,600 to 1,700S. Based on the DNA content per cell and the mass of a single genome, A. vinelandii contains at least 40 chromosomes per cell.
Biosynthesis of murein lipoprotein in Escherichia coli: effects of 3,4-dihydroxybutyl-1-phosphonate
Authors: Chattopadhyay P K , Engel R , Tropp B E , Wu H C
Published: January 2020

The effects of 3,4-dihydroxybutyl-1-phosphonate, a four-carbon analog of sn-glycerol 3-phosphate, on the biosynthesis of the glyceryl moiety in murein lipoprotein of Escherichia coli were studied. The compound at a concentration of 55 microM strong inhibits in the incorporation of [2-3H]glycerol radioactivity into lipoprotein by virtue of its inhibition of the synthesis of phosphatidylglycerol. On the other hand, the incorporation of prelabeled [2-3H]glycerol radioactivity into lipoprotein was only partially inhbited by 3,4-dihydroxybutyl-1-phosphonate even at a much higher concentration (1 mM). These data were consistent with the postulated pathway for the biosynthesis of the lipid moiety in lipoportein: cysteine-lipoprotein + phosphatidylglycerol leads to glycerylcystein-lipoprotein + phosphatidic acid.
Partial Purification and Some Properties of the
Staphylococcus aureus
Cytoplasmic Nitrate Reductase
Authors: Burke Kathleen A. , Lascelles June
Published: January 2020

The cytoplasmic nitrate reductase in heme mutant H-14 of
Staphylococcus aureus
was partially purified by steps which included ammonium sulfate fractionation and chromatography on Bio-Gel A 1.5m and ion-exchange columns. The active fractions from the ion-exchange columns showed two forms of the enzyme upon electrophoresis in nondenaturing gels of polyacrylamide; these corresponded to proteins of

R
f

0.16 and 0.28. Each form contained a predominant polypeptide of molecular weight 140,000, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The

R
f

0.16 form contained another major polypeptide of molecular weight 57,000, but the

R
f

0.28 form contained several other polypeptides. The sedimentation properties of the enzyme were examined after partial purification on Bio-Gel A 1.5m. In sucrose gradients containing Triton X-100 the enzyme sedimented as a homogeneous peak with an estimated molecular weight of 225,000; without detergent a heterogeneous profile was observed of molecular weight greater than 250,000. Treatment of the enzyme with trypsin increased the specific activity, and the enzyme sedimented as a homogeneous peak in sucrose gradients without Triton X-100, with an estimated molecular weight of 202,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that trypsin treatment converted the polypeptide of molecular weight 140,000 to a polypeptide of molecular weight 112,000. We conclude that the cytoplasmic nitrate reductase of
S. aureus
has a large subunit of molecular weight 140,000, which can be modified by trypsin to a polypeptide of molecular weight 112,000 without loss of catalytic activity.
Reduction of methionine sulfoxide to methionine by Escherichia coli
Authors: Ejiri S I , Weissbach H , Brot N
Published: January 2020

L-Methionine-dl-sulfoxide can support the growth of an Escherichia coli methionine auxotroph, suggesting the presence of an enzyme(s) capable of reducing the sulfoxide to methionine. This was verified by showing that a cell-free extract of E. coli catalyzes the conversion of methionine sulfoxide to methionine. This reaction required reduced nicotinamide adenine dinucleotide phosphate and a generating system for this compound. The specific activity of the enzyme increased during logarithmic growth and was maximal when the culture attained a density of about 10(9) cells per ml.
Use of gene fusion to study secretion of maltose-binding protein into Escherichia coli periplasm
Authors: Bassford P J , Silhavy T J , Beckwith J R
Published: January 2020

We have employed the technique of gene fusion to fuse the LacZ gene encoding the cytoplasmic enzyme beta-galactosidase with the malE gene encoding the periplasmic maltose binding protein (MBP). Strains were obtained which synthesize malE-lacZ hybrid proteins of various sizes. These proteins have, at their amino terminus, a portion of the MBP and at their carboxyl terminus, enzymatically active beta-galactosidase. When the hybrid protein includes only a small, amino-terminal portion of the MBP, the hybrid protein residues in the cytoplasm. When the hybrid protein contains enough of the MBP to include an intact MBP signal sequence, a significant portion of the hybrid protein is found in the cytoplasmic membrane, suggesting that secretion of the hybrid protein has been initiated. However, in no case is the hybrid protein secreted into the periplasm, even when the hybrid protein includes almost the entire MBP. In the latter case, the synthesis and attempted export of the hybrid protein interferes with the export of at least certain normal envelope proteins, which accumulate in the cell in their precursor forms, and the cell dies. These results suggest that a number of envelope proteins may be exported at a common site, and that there are only a limited number of such sites. Also, these results indicate that it is not sufficient to simply attach an amino-terminal signal sequence to a polypeptide to assure its export.
Specificity of uracil uptake in Neurospora crassa
Authors: Dalke P , Magill J M
Published: January 2020

The specificity of uracil uptake was investigated in germinating wild-type conidia of Neurospora crassa. From comparative inhibition studies, several generalizations concerning the specificity of uracil uptake can be made. (i) The tautomeric forms of uracil analogs is an important determinant of recognition by the uptake system. (ii) Substituents at the 5 position of the pyrimidine ring may impose steric constraints on binding. (iii) The presence of a negative charge results in the loss of recognition. (iv) The double bond between the 5 and 6 carbons appears to be important for recognition. (v) Purine bases do not inhibit uracil uptake. Crude extracts of the transport-deficient mutant strain uc-5 pyr-1 were shown to have uridine 5'-monophosphate pyrophosphorylase activity comparable to that of the wild-type strain, suggesting that uracil uptake in Neurospora does not occur by a group translocation mechanism involving phosphoribosylation. Specificity studies of uridine 5'-monophosphate pyrophosphorylase indicated that phosphoribosylation was not an important determinant of the specificity of uracil uptake.
R-plasmid-mediated chromosomal gene transfer in Agrobacterium tumefaciens
Authors: Hamada S E , Luckey J P , Farrand S K
Published: January 2020

Although several techniques are available for transferring the Ti plasmids from one strain of agrobacterium tumefaciens to another, there are no reproducible methods for analysis of chromosomal markers in this phytopathogen. The R plasmid, R68.45, is known to show chromosomal mobilizing ability in several bacterial genera including the closely related Rhizobia. R68.45 was transferred into the prototrophic A. tumefaciens strain 15955. Ten kanamycin-resistant transconjugant clones were tested for chromosomal mobilizing ability by mating with strain SA10, rifampin- and streptomycin-resistant histidine auxotroph of strain 15955. Of the 10 donor clones, 2 showed high chromosomal mobilizing ability. Between 1,000 and 2,000 His+ colony-forming units per ml were obtained, a value 10 to 20 times greater than can be accounted for by spontaneous reversion. Sequential recloning and matings resulted in the isolation of relatively stable donor cultures. Chromosome gene transfer is dependent upon the presence in the donor of R68.45. Donors lacking an R plasmid or harboring the closely related plasmid RP4 failed to yield His+ transconjugants. With strain SA11, a methionine auxotroph of strain SA10, coinheritance of histidine and methionine independence could be demonstrated. Approximately half of the transconjugants also inherited R68.45. These results indicate that A. tumefaciens 15955 is capable of undergoing host chromosomal genetic exchange.
Isolation and characterization of a mutant ColE1 plasmid that allows constitutive colicin E1 synthesis
Authors: Ohkubo H , Shimada K , Takagi Y
Published: January 2020

It has been possible to isolate a ColE1 mutant which synthesizes colicin E1 constitutively. This result shows that there must be a gene(s) responsible for the regulation of colicin E1 synthesis.
General transduction in Rhizobium meliloti by a thermosensitive mutant of bacteriophage DF2
Authors: Casadesús J , Olivares J
Published: January 2020

A simiplified version of bacteriophage DF2 transduction, using the thermosensitive mutant DF2tsC, is described. The transduction frequencies of Rhizobium meliloti markers by DF1tsC are of about 10(-6) or higher. The development of transductants at 34 degrees C does not require the addition of antiserum for phage neutralization.
Genetic evidence for possible interaction between a ribonucleic acid polymerase subunit and the spo0C gene product of Bacillus subtilis
Authors: Ikeuchi T , Babasaki K , Kurahashi K
Published: January 2020

Spontaneous rifampin-resistant mutants (9V Rifr) were isolated from a mutant strain of Bacillus subtilis, 9V, which has a spo0C mutation. Whereas 90% of the 9V Rifr double mutants maintained the Spo0C phenotype (Spo- Abs +/-), the remaining 10% had the Spo0A phenotype (Spo- Abs-). The latter mutants, termed 9V Rifr Spo- Abs-, were revealed to have other Spo0A characters, such as reduced transformability, higher sensitivity to phage phi 2, and reduced frequency of lysogenization by phage phi 105. The rif mutation of these 9V Rifr Spo- Abs- strains was mapped near the cysA locus. The phenotype of the Rifr transformants of strain 9V by deoxyribonucleic acid derived from these 9V Rifr Spo- Abs- strains was Spo0A, and that of the Rifr transformants of strain 168 was Spo+ Abs+. The ribonucleic acid polymerase of the 9V Rifr Spo- Abs- strains was shown to be resistant to rifampin.
Plasmids and transposable elements in Salmonella wien
Authors: Maimone F , Colonna B , Bazzicalupo P , Oliva B , Nicoletti M , Casalino M
Published: January 2020

The plasmids from six clinical strains of Salmonella wien have been characterized. All the S. wien strains were found to carry three types of plasmids: an IncFI R-Tc Cm Km Ap (resistance to tetracycline, chloramphenicol, kanamycin, and ampicillin) plasmid, either conjugative or nonconjugative, of large size (90 to 100 megadaltons); an R-Ap Su Sm (resistance to ampicillin, sulfonamide, and streptomycin) plasmid of 9 megadaltons; and a very small (1.4 megadaltons) cryptic plasmid. The characteristics of conjugative R plasmids, recombinant between F'lac pro and the FI nonconjugative plasmid, indicated that regions coding for the donor phenotype were present on this plasmid. The molecular and genetic features of the R plasmids were very close to those described for the R plasmids isolated from S. wien strains of different origin. This fact supported the hypothesis of a clonal distribution of this serotype in Algeria and Europe. The analysis used to identify transposable elements showed the presence of only TnA elements, which were located on both the R-Tc Cm Km Ap and R-Ap Su Sm plasmids. They contained the structural gene for a TEM-type beta-lactamase and had translocation properties analogous to those reported for other TnA's.
Regulation of Saccharomyces cerevisiae nicotinamide adenine dinucleotide phosphate-dependent glutamate dehydrogenase by proteolysis during carbon starvation
Authors: Mazón M J , Hemmings B A
Published: January 2020

Inactivation of the nicotinamide adenine dinucleotide phosphate-dependent glutamate dehydrogenase from Saccharomyces cerevisiae during carbon starvation occurs with a simultaneous loss of enzyme protein and enzyme activity.
Nitrogen metabolite repression of nitrate reductase in Neurospora crassa: effect of the gln-1a locus
Authors: Dunn-Coleman N S , Tomsett A B , Garrett R H
Published: January 2020

Nicotinamide adenine dinucleotide phosphate (reduced form)-nitrate reductase was freed from ammonium repression in a Neurospora crassa mutant having drastically lowered glutamine synthetase activity, gln-1a. The general phenomenon of nitrogen metabolite repression required glutamine or some aspect of glutamine metabolism.
Optimal conditions for transformation of Azotobacter vinelandii
Authors: Page W J , von Tigerstrom M
Published: January 2020

Optimal transformation of Azotobacter vinelandii OP required a 20-min incubation of the competent cells with deoxyribonucleic acid at 30 degrees C in buffer (pH 6.0 to 8.0) containing 8 mM magnesium sulfate. Nitrogen-fixing transformants of nitrogen fixation-deficient recipients could be plated immediately on selective medium, but transformants acquiring rifampin and streptomycin resistance required preincubation in nonselective medium. The three phenotypes achieved an approximately equal and stable frequency after 17 h (six generations) of growth in nonselective medium.
Methyl ester of hyaluronate is unable to stimulate exolipase formation by Serratia marcescens
Authors: Jäger K E , Winkler U K
Published: January 2020

Hyaluronate stimulated the formation of exolipase by Serratia marcescens. This ability was abolished when all carboxyl groups of hyaluronate were methyl esterified. Additional studies suggested that the biological inactivity of esterified hyaluronate should be ascribed to the reduced conformational order of the molecules rather than to their electroneutrality.
Transport of C5 dicarboxylate compounds by Pseudomonas putida
Authors: Edwards W V , Sando J J , Hartline R A
Published: January 2020

Induced glutarate and 2-oxoglutarate uptake and transport by Pseudomonas putida were investigated in whole cells and membrane vesicles, respectively. Uptake of 2-oxoglutarate, but not glutarate, was against a concentration gradient to 1.7-fold greater than the initial extracellular concentration. Membrane vesicles transported 2-oxoglutarate and glutarate against gradients to intramembrane concentrations fivefold greater than the initial extravesicle concentrations. The rates of transport of both compounds were greatest in the presence of the artificial electron donor system phenazine methosulfate-ascorbate. Malate and D-lactate were the only naturally occurring compounds that served as electron donors. Uptake and transport were inhibited by KCN, NaN3, and 2,2-dinitrophenol. Kinetic parameters of transport were: glutarate, apparent Km--1.22 mM, Vmax--400 nmol/min per mg of membrane protein; 2-oxoglutarate, apparent Km--131 microM, Vmax--255 nmol/min per mg of membrane protein. Studies of competitive inhibition indicated a common system for transport of five C5 dicarboxylate compounds. The apparent Km and Ki values with 2-oxoglutarate as a substrate placed the substrate affinity for transport in the order 2-oxoglutarate greater than glutarate greater than D-2-hydroxyglutarate and L-2-hydroxyglutarate greater than glutaconate.
Transposable plasmid deoxyribonucleic acid sequence in Pseudomonas aeruginosa which mediates resistance to gentamicin and four other antimicrobial agents
Authors: Rubens C E , McNeill W F , Farrar W E
Published: January 2020

A 9.1 x 10(6)-dalton transposable deoxyribonucleic acid sequence resides within Pseudomonas aeruginosa plasmid R1033 and mediates resistance to gentamicin, streptomycin, sulfamethoxazole, chloramphenicol, and mercuric chloride. Transposability was demonstrated in Escherichia coli when this sequence, designated Tn1696, excised from R1033 and integrated into plasmid pMB8. Excision and insertion of Tn1696 occurred independently of the host Rec phenotype and may involve the 140-base pair, inverted deoxyribonucleic acid repeated region that flanks this sequence. Occurrence of a multiresistance transposon on a transferrable plasmid that has a broad host range may have serious epidemiological and therapeutic consequences.
Membrane enrichment of genetic markers close to the origin and terminus during the deoxyribonucleic acid replication cycle in Bacillus subtilis
Authors: Beeson J , Sueoka N
Published: January 2020

A temperature-sensitive Bacillus subtilis initiation mutant was used to achieve one cycle of synchronized deoxyribonucleic acid (DNA) replication. Markers near the origin of replication and the terminus were assayed for association with the cell membrane at intervals during the DNA replication cycle. DNA near the origin and terminus was found to be enriched in the membrane fraction throughout the DNA replication cycle. The magnitude of membrane enrichment or origin and terminus markers varied coincidentally, possibly as a consequence of incubating the cells at 45 degrees C.
Synthesis of 1,3-β-Glucanases in
Saccharomyces cerevisiae
During the Mitotic Cycle, Mating, and Sporulation
Authors: del Rey Francisco , Santos Tomás , García-Acha Isabel , Nombela César
Published: January 2020

Upon fractionating
Saccharomyces cerevisiae
asynchronous cultures by sucrose density gradient centrifugation in a zonal rotor and examining the exo-1,3-β-glucanase and deoxyribonucleic acid content of the cells, a periodic step increase in the activity of this enzyme was observed, indicating a discontinuous pattern of synthesis or activation of exo-1,3-β-glucanase during the mitotic cycle at the transition from the S to the G
2
phase. Similar results were obtained for endo-1,3-β-glucanase by assaying activity against oxidized laminarin in permeabilized cells, suggesting that the synthesis of endo-1,3-β-glucanase is controlled in the same way. When a and α strains were mated, the specific activity of cell extracts against laminarin, oxidized laminarin, and pustulan remained constant while zygote formation was taking place. However, when growth resumed, active synthesis of 1,3-β-glucanases took place as shown by the occurrence of a significant increase in the specific activity against the three substrates. Specific changes in the level of glucan degradative enzymes, not observed in a haploid parental strain, occurred when the diploid
S. cerevisiae
AP-1 was induced to sporulate. The sporulation process triggered the activation of first the pustulan degradative capacity and then the capacity to hydrolyze oxidized laminarin. The specific activity against this substrate was 10 times higher than that against pustulan.
Comparative Surface Structure of 16S Ribosomal Ribonucleic Acid of 30S Ribosomes of Procaryotic Cells
Authors: Santer Melvin , Chung Shu-Ching , Harmon George , Estner Michael , Hendrick Joseph P. , Hopper James , Brecht Christina , Pandhi Prem
Published: January 2020

Ribonuclease T
1
treatment of 30S ribosomes of
Escherichia coli
converts a large region at the 3′ OH end of 16S ribosomal ribonucleic acid (rRNA) to low-molecular-weight RNA. The final 25 nucleotides at the 3′ terminus of the molecule emerge relatively intact, whereas most of the region “upstream,” for about 150 nucleotides, is converted to oligonucleotides. Identical enzyme treatment generates a fragment of about 60 nucleotides from the middle of 16S rRNA (section D′). To determine whether there are similar sequences in other bacteria, which occupy similar accessible surface locations, we treated 30S ribosomes from
Azotobacter vinelandii
and
Bacillus stearothermophilus
with RNase T
1
. In each case, a fragment of RNA about 25 nucleotides in length containing the 3′ OH end of 16S rRNA and a fragment of about 60 nucleotides in length similar, but not identical, in oligonucleotide composition to section D′ of
E. coli
16S rRNA were obtained from nuclease-treated 30S ribosomes. These data indicate that, although the primary structure at the 3′ end and the middle (section D′) of the various 16S rRNA's is not completely conserved, their respective conformations are conserved. A number of identical oligonucleotides were found in the low-molecular-weight fraction obtained from RNase T
1
-treated
E. coli, A. vinelandii
, and
B. stearothermophilus
30S ribosomes. These results show that identical RNase T
1
-sensitive sequences are present in all three bacteria. Hydrolysis of these regions leads to the production of the fragments 25 and 60 nucleotides in length.
Escherichia coli pleiotropic mutant that reduces amounts of several periplasmic and outer membrane proteins
Authors: Wanner B L , Sarthy A , Beckwith J
Published: January 2020

We have isolated a mutant of Escherichia coli K-12 that is reduced from 6- to 10-fold in the amount of alkaline phosphatase found in the periplasmic space. The reduced synthesis is not due to effects at the level of transcription regulation of the phoA gene, the structural gene for the enzyme. In addition, the mutation (termed perA) responsible for this phenotype results in reduced amounts of possibly six or more other periplasmic proteins and at least three outer membrane proteins. One of the outer membrane proteins affected is protein IA (D. L. Diedrich, A. O. Summers, and C. A. Schnaitman, J. Bacteriol. 131:598-607, 1977). Although other possibilities exist, one explanation for the phenotype of the perA mutation is that it affects the cell's secretory apparatus.
Role of gene flaFV on flagellar hook formation in Salmonella typhimurium
Authors: Kutsukake K , Suzuki T , Yamaguchi S , Iino T
Published: January 2020

Nine temperature-sensitive nonflagellate mutants defective in flaFV were isolated from a strain of Salmonella typhimurium. Among them three mutants were found to produce flagella with abnormally shaped (either straight or irregularly curved) hooks at the permissive temperature. Two mutations that rendered hooks straight were located in one of the eight segments of flaFV defined by deletion mapping. The mutation that rendered hooks irregularly curved was located in a different segment. An flaR mutation was introduced into the latter mutant. At the permissive temperature, the resulting double mutant produced polyhooks whose wavelength and amplitude were both exceedingly reduced. These polyhook structures were more thermolabile than those of the flaFV+ strain. Hook protein of the former strain was shown to have a slightly positive electric charge compared with that of the latter. From these results and other available information, it is inferred that flaFV is the structural gene for the hook protein in Salmonella.
Inversion in the lactose region of Escherichia coli K-12
Authors: Savic D J
Published: January 2020

A spontaneous mutant of Escherichia coli K-12, strain SY99, with an inversion in the lactose region was isolated and partially characterized. The inversion was detected due to inverse chromosomal conjugational transfer after introduction of an F42 (F'lac) episome. The termini of the inversion are between proAB and lac on one side and lac and proC on the other. The inverse conjugational transfer in SY99 did not appear to be absolute but was always accompanied by a residual "normal" counterclockwise mobilization. This residual transfer was further shown to be caused by the intrinsic instability of this region (at least in the line W3110). The possible involvement of IS3 elements flanking the lactose operon is discussed.
Transcriptional regulation of Escherichia coli K-12 major outer membrane protein 1b
Authors: Hall M N , Silhavy T J
Published: January 2020

Eleven independent insertion mutations were isolated that prevented expression of major outer membrane protein 1b. Seven of the mutations were Mucts insertions located at ombP. These ompB::Mucts strains fell into two phenotypic classes with regard to expression of proteins 1a and 1b. The remaining four mutants were comprised of one Tn5 and three Mucts insertions mapping at par. The Mucts insertions at par were used to construct fusions of the lac operon to the par promoter. Expression of beta-galactosidase in these fusion strains reflected known regulatory properties of protein 1b. When an ompB allele was introduced into the par-lac fusion strains, beta-galactosidase activity was reduced 14- to 31-fold. Transcriptional regulation of the par gene and the existence of two functions at ompB are discussed. The results suggest that par is the structural gene for protein 1b and that an ompB gene product is a diffusible, positive regulatory element controlling expression of par.
Sucrose transport by the Escherichia coli lactose carrier
Authors: Heller K B , Wilson T H
Published: January 2020

Several lines of evidence suggest that sucrose is transported by the lactose carrier of Escherichia coli. Entry of sucrose was monitored by an osmotic method which involves exposure of cells to a hyperosmotic solution of disaccharide (250 mM). Such cells shrink (optical density rises), and if the solute enters the cell, there is a return toward initial values (optical density falls). By this technique sucrose was found to enter cells at a rate approximately one third that of lactose. In addition, the entry of [14C]sucrose was followed by direct analysis of cell contents after separation of cells from the medium by centrifugation. Sucrose accumulated within the cell to a concentration 160% of that in the external medium. The addition of sucrose to an anaerobic suspension of cells resulted in a small alkalinization of the external medium. These data are consistent with the view that the lactose carrier can accumulate sucrose by a proton cotransport system. The carrier exhibits a very low affinity for the disaccharide (150 mM) but a moderately rapid Vmax.
Multiple, independent components of ultraviolet radiation mutagenesis in Escherichia coli K-12 uvrB5
Authors: Smith K C , Sargentini N J
Published: January 2020

Reversion systems involving the lacZ53(amber) and leuB19)missense) mutations were developed to study the mutant frequency response of Escherichia coli K-12 uvrB5 (SR250) to ultraviolet radiation (254 nm). A one-hit mutant frequency response was discernible at ultraviolet radiation fluences below approximately 0.5 J m-2. At higher fluences the overall mutant frequency response could be resolved into one-hit and two-hit components. A new interpretation of the published data on E. coli K-12 indicates that SR250 is not unique in this respect. In addition, the Lac reversion system showed enhanced mutagenesis after ultraviolet radiation fluences of approximately 1 to 3 J m-2, whereas the Leu reversion system did not. We conclude that the complex ultraviolet radiation mutant frequency response curves for E. coli K-12 uvrB5 were the result of three independent mutagenic processes for Lac reversion and two for Leu reversion.
Novel microbial and chemical components of a specific black-band region in the cockroach hindgut
Authors: Cruden D L , Gorrell T E , Markovetz A J
Published: January 2020

An area of the hindgut of the cockroach, Eublaberus posticus, is characterized by its black color. This area is the site of accumulation of metal sulfides in the lumen next to the gut wall. In addition to the normal hindgut flora, two unusual procaryotic organisms are seen by both scanning and transmission electron microscopy only in this area of the hindgut. They are (i) a large rod (1.2 by 6 micrometers) with a tuft of polar flagella, many inclusion bodies, and a distinctive complex wall and (ii) an apparently flexible rod with a helically ridged wall. In addition, phagelike particles are described which are apparently infecting gram-positive bacteria attached to the gut wall in the black band area.
Myxococcus xanthus
Mutants with Temperature-Sensitive, Stage-Specific Defects: Evidence for Independent Pathways in Development
Authors: Morrison Cheryl E. , Zusman David R.
Published: January 2020

Fruiting-body formation in the bacterium
Myxococcus xanthus
consists of a temporal sequence of cellular aggregation and sporulation. To examine the developmental stages more closely, we established synchronous and reproducible conditions for fruiting-body formation. Mutants that are temperature sensitive for fruiting-body formation were isolated and analyzed under these conditions. The terminal morphologies of the mutant strains at the nonpermissive temperature were found to resemble intermediate stages of fruiting-body formation and therefore were grouped in the following phenotypic classes: (i) rough mutants, which show no aggregation; (ii) swirl mutants, which show defective aggregation; (iii) flat-mound mutants and translucent-mound mutants, mutants which aggregate but show very low levels of sporulation. The mutants were characterized by temperature-shift experiments and found to exhibit discrete and reproducible temperature-sensitive periods. The ends of the temperature-sensitive periods in the various mutants covered a broad range of the developmental cycle. No correlation was found between the terminal morphologies at the restrictive temperature and the timing of the temperature-sensitive periods. However, the terminal morphologies correlated well with sporulation. The rough and swirl mutants produced normal numbers of myxospores at 34°C even though they failed to aggregate. In contrast, the flat-mound and translucent-mound mutants, which aggregate normally, produced very few spores. The translucent-mound mutants were also temperature sensitive for induction of glycerol spores. The results indicate that both aggregation and sporulation are initiated early in the developmental cycle and that these processes are largely independent of each other.
Rapid screening procedure for detection of plasmids in streptococci
Authors: Leblanc D J , Lee L N
Published: January 2020

An enrichment procedure, yielding plasmid deoxyribonucleic acid preparations normally containing less than 5% chromosomal contamination, has been devised for the isolation of plasmids from virtually all species of streptococci. The procedure is rapid, reproducible, and inexpensive, requiring no radioisotopes or density gradient centrifugation. The procedure can be used for routine screening of several hundred isolates in a short period of time, and plasmids obtained from 10- to 20-ml cultures can readily be visualized in agarose gels.
Isolation of Neurospora crassa bradytrophs
Authors: Kinsey J A
Published: January 2020

A method was developed for the isolation of Neurospora bradytrophs. The bradytrophs (representing lesions in a number of pathways) were resistant to DL-p-fluorophenylalanine when growing in a leaky fashion but were sensitive when grown in the presence of their stimulating supplement.
Conditionally lethal amber mutations in the dnaA region of the Escherichia coli chromosome that affect chromosome replication
Authors: Kimura M , Miki T , Hiraga S , Nagata T , Yura T
Published: January 2020

Three amber mutations, dna-801, dna-803, and dna-806, were isolated by localized mutagenesis of the dnaA-oriC region of the chromosome from an Escherichia coli strain carrying temperature-sensitive amber suppressors. When the mutations were not suppressed at 42 degrees C, the cells did not grow and DNA synthesis was arrested. They were very closely linked to each other and to the dnaA46 mutation. The mutant phenotype of each strain was converted to the wild type by infecting the mutants with specialized transducing phase lambda i21 dnaA-2 but not with lambda i21 tna. Derivatives of lambda i21 dnaA-2, each of which carried the amber mutation dna-801 dna-803, or dna-806, converted the dnaA mutant phenotype to Dna+ but did not convert rhe amber mutants to the wild-type phenotype. E. coli uvrB cells were irradiated with ultraviolet light and infected with each of these phage strains. An analysis of proteins synthesized in the cells revealed that two proteins with molecular weights of 50,000 and 43,000 were specified by lambda i21 dnaA-2 but not by lambda i21 tna. When the ultraviolet-irradiated cells did not carry an amber suppressor, the derivative phage with the amber mutation invariably failed to produce the 43,000-dalton protein, but when the host cell carried supF (tyrT), the protein was produced. The 50,000-dalton protein was unaffected.
Iso-branched 2- and 3-hydroxy fatty acids as characteristic lipid constituents of some gliding bacteria
Authors: Fautz E , Rosenfelder G , Grotjahn L
Published: January 2020

The fatty acids present in the total hydrolysates of several gliding bacteria (Myxococcus fulvus, Stigmatella aurantiaca, Cytophaga johnsonae, Cytophaga sp. strain samoa and Flexibacter elegans) were analyzed by combined gas-liquid chromatography and mass spectrometry. In addition to 13-methyl-tetradecanoic acid, 15-methyl-hexadecanoic acid, hexadecanoic acid, and hexadecenoic acid, 2- and 3-hydroxy fatty acids comprised up to 50% of the total fatty acids. The majority was odd-numbered and iso-branched. Small amounts of even-numbered and unbranched fatty acids were also present. Whereas 2-hydroxy-15-methyl hexadecanoic acid was characteristic for myxobacteria, 2-hydroxy-13-methyl-tetradecanoic acid, 3-hydroxy-13-methyl-tetradecanoic acid, and 3-hydroxy-15-methyl-hexadecanoic acid were dominant in the Cytophaga-Flexibacter group.
Regulation of activity and synthesis of N-acetylglutamate synthase from Saccharomyces cerevisiae
Authors: Wipe B , Leisinger T
Published: January 2020

Feedback inhibition of N-acetylgutamate synthase in a particulate fraction from Saccharomyces cerevisiae by L-arginine was synergistically enhanced by N-actylglutamate, whereas coenzyme A let to an additive enhancement of arginine inhibition. N-acetylglutamate synthase was not inhibited by polyamines, nor was the enzyme inactivated by incubation in the presence of coenzyme A and zinc ions. Evidence was obtained for the involvement of at least three different regulatory mechanisms in the expression of N-acetylglutamate synthase: arginine-specific repression, glucose repression and general amino acid control. The combined action of these control mechanisms led to a 90-fold variation in the specific activity of the enzyme.