bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of Na+-dependent K+ ion transport in a marine pseudomonad
Authors: Hassan H M , MacLeod R A
Published: January 2020

The effect of external Na plus concentration on the transport of K plus was studied using K plus-depleted cells of a marine pseudomonad. K plus transport was found to be a saturable process and requires Na plus. The initial rates for K plus transport over a range of external K plus concentrations were measured in suspensions containing various fixed concentrations of Na plus. Reciprocals of the initial rates for K plus transport were plotted against reciprocals of the external concentration of K plus or Na plus to yield two primary Lineweaver-Burk plots. The experimental data were found to fit bisubstrate enzyme kinetics, with a sequential type mechanism. However, the initial rate data did not allow distinction between ordered or random mechanisms. The results suggest that Na plus and K plus form a ternary complex with a specific K plus carrier molecule on the outer surface of the membrane prior to translocation and the release of K plus inside the cell.
Control of lysine biosynthesis in Bacillus subtilis: inhibition of diaminopimelate decarboxylase by lysine
Authors: Rosner A
Published: January 2020

Diaminopimelate decarboxylase has been characterized in extracts of Bacillus subtilis and resolved from aspartokinases I and II. Under certain conditions, the enzyme is specifically inhibited by physiological concentrations of L-lysine, but less specificity and altered kinetics of inhibition are observed if lower ionic strengths are employed in the assay procedure. Diaminopimelate decarboxylase can be desensitized to lysine inhibition by either lowering the pH or diluting the enzyme in Tris buffer in the absence of pyridoxal phosphate. Evidence is presented to incidate that, under proper conditions, lysine inhibition involves an interaction of the amino acid with the enzyme rather than competition for available pyridoxal phosphate in the assay. Lysine, by affecting the level of meso-diaminopimelate, may thus regulate its biosynthesis through sequential feedback inhibition. Analysis of the diaminopimelate decarboxylase of 15 revertants of mutants that had originally lacked diaminopimelate decarboxylase activity indicates that as little as 5% of the specific activity of enzyme observed in the wild-type strain is sufficient to permit normal growth rates. In the growing cell, diaminopimelate decarboxylase may therefore exist largely in an inhibited state.
Reinitiation of deoxyribonucleic acid synthesis by deoxyribonucleic acid initiation mutants of Escherichia coli: role of ribonucleic acid synthesis, protein synthesis, and cell division
Authors: Hanna M H , Carl P L
Published: January 2020

The dnaA and dnaC genes are thought to code for two proteins required for the initiation of chromosomal deoxyribonucleic acid replication in Escherichia coli. When a strain carrying a mutation in either of these genes is shifted from a permissive to a restrictive temperature, chromosome replication ceases after a period of residual synthesis. When the strains are reincubated at the permissive temperature, replication again resumes after a short lag. This reinitiation does not require either protein synthesis (as measured by resistance to chloramphenicol) or ribonucleic acid synthesis (as measured by resistance to rifampin). Thus, if there is a requirement for the synthesis of a specific ribonucleic acid to initiate deoxyribonucleic acid replication, this ribonucleic acid can be synthesized prior to the time of initiation and is relatively stable. Furthermore, the synthesis of this hypothetical ribonucleic acid does not require either the dnaA of dnaC gene products. The buildup at the restrictive temperature of the potential to reinitiate deoxyribonucleic acid synthesis at the permissive temperature shows rather complex kinetics the buildup roughly parallels the rate of mass increase of the culture for at least the first mass doubling at the restrictive temperature. At later times there appears to be a gradual loss of initiation potential despite a continued increase in mass. Under optimal conditions the increase in initiation potential can equal, but not exceed, the increase in cell division at the restrictive temperature. These results are most easily interpreted according to models that postulate a relationship between the initiation of deoxyribonucleic acid synthesis and the processes leading to cell division.
Tryptophan biosynthetic pathway in the Enterobacteriaceae: some physical properties of the enzymes
Authors: Largen M , Belser W L
Published: January 2020

Several physical properties of the first four enzymatic activities of the tryptophan pathway were examined using gel filtration and ion exchange chromatography. Five different patterns were noted. Differences in the anthranilate synthetase (AS) and phosphoribosylanthranilate transferase (PRT) defined these patterns. In all the organisms studied phosphoribosylanthranilate isomerase and indoleglycerol phosphate synthetase co-eluted from both diethylaminoethyl-cellulose and G-200 and thus probably are contained in a single polypeptide of 50,000 daltons. An AS-PRT complex was found in Citrobacter species, Enterobacter cloacae, and Erwinia dissolvens. In all the other bacteria examined AS and PTR were separate molecules. In Serratia marcescens, S. marinorubra, and Enterobacter liquefaciens, AS was 140,000 daltons and PRT was 45,000 daltons. In Erwinia carotavora and Enterobacter hafniae the AS was the same size as the Serratia species but the PRT was larger at 67,000 daltons. Two Proteus species had an AS and PRT of the same size as E. carotavora and E. halfniae but the Proteus AS was different in that it partially dissociated upon gel filtration. Aeromonas formicans was unique in its possession of an AS with a molecular weight of 220,000. The PRT of A. formicans was found to elute at 67,000 daltons. Possible paths of evolution of the tryptophan enzymes are discussed in terms of the results of this study. The results presented here are also considered with respect to existing taxonomic schemes of the enteric bacteria.
Fine structure of mesosomal involvement during Bacillus macerans sporulation
Authors: Decker S , Maier S
Published: January 2020

The ultrastructure of endospore formation in Bacillus macerans ATCC 8244 is characterized by the examination of thin sections of cells grown synchronously in a defined medium. For the most part, sporulation in this organism proceeds as described in other Bacillus species. However, unusually extensive mesosomal involvement occurs during the early stages of sporulation, through the completion of engulfment. A large mesosome is associated with spore septum formation and a portion of this mesosome is included in the developing forespore. As engulfment continues, the forespore mesosome moves to the apex of the cell and participates in the completion of the double forespore membrane. This participation is morphologically similar to mesosome involvement in division and spore septation and seems to comprise a second sporal septation process. Based on this study, it is suggested that the mesosome functions to facilitate the "fusion" of membranes thought to occur during cell division and sporulation.
Reversion of Bacillus megaterium protoplasts to the bacillary form
Authors: Fodor K , Hadlaczky G , Alföldi L
Published: January 2020

Photomicrographic evidence of reversion of Bacillus megaterium protoplasts to the bacillary form on soft agar plates hypertonic medium is demonstrated.
Cellular content of ribonucleic acid and protein in Saccharomyces cerevisiae as a function of exponential growth rate: calculation of the apparent peptide chain elongation rate
Authors: Boehlke K W , Friesen J D
Published: January 2020

The average cellular content of ribonucleic acid and protein was determined in cultures of Saccharomyces cerevisiae growing exponentially at different rates in a variety of media. Estimations of the proportion of total cellular ribonucleic acid that is made up of ribosomal ribonucleic acid were used to calculate the average number of ribosomes per cell at the different growth rates. The fraction of ribosomes actively engaged in translation was estimated by sucrose gradient centrifugation of ribosomes and polysomes. These data were used in a calculation of the apparent time taken for the addition of an amino acid to the growing polypeptide chain; this value was found to vary linearly with growth rate over a fivefold range of doubling times.
Enzymes of deoxythymidine triphosphate biosynthesis in Neurospora crassa mitochondria
Authors: Rossi M , Woodward D O
Published: January 2020

Intact mitochondria of Neurospora crassa incorporate deoxythymidine 5'-monophosphate (dTMP) into deoxyribonucleic acid but not the label from (methyl-3H) deoxythymidine. Mitochondrial homogenates contain deoxythymidylate kinase (EC 2.7.4.9), deoxycytidylate aminohydrolase (dCMP deaminase) (EC 3.5.4.12), and thymidylate synthetase (EC 2.1.1b), but not thymidine kinase (EC 2.7.1.21) activity. dTMP kinase is loosely bound to the mitochondrial membrane and is solubilized by 0.4 M KCl in mitochondrial homogenates, the dCMP aminohydrolase deaminase) is bound to the inner membrane and is not solubilized by 0.4 M KCl. dTMP synthetase activity is found in the 2,000 times g particulate fractions by homogenization of mitochondria in 0.4 M KCl. The dCMP deaminase activity found in the particulate fraction of the inner membrane is efficiently regulated by the products of the pathway: deoxycytidine 5'-triphosphate activates whereas deoxythymidine 5'-triphosphate inhibits, as found for the soluble enzyme from other sources. These data indicate that mitochondria of N. crassa contain specific enzymes for the biosynthesis of deoxythymidine triphosphate.
Role of bacterial ribosomes in barotolerance
Authors: Pope D H , Smith W P , Swartz R W , Landau J V
Published: January 2020

The effects of high hydrostatic pressures on protein synthesis by whole cells and cell free preparations of Escherichia coli, Pseudomonas fluorescens, and Pseudomonas bathycetes were determined. Actively growing cells of P. bathycetes and P. fluorescens were less sensitive than were E. coli cells. Protein synthesis by cell free preparations of E. coli and P. fluorescens showed the same extent of inhibition as their respective whole cell preparations, whereas cell free preparations of P. bathycetes showed a marked increase in pressure sensitivity over whole cells. Protein synthesis by hybrid protein synthesizing cell free preparations (the ribosomes from one organism and the S-100 supernatant fraction from another) demonstrated that response to high pressure is dependent on the source of the ribosome employed. A hybrid system containing E. coli ribosomes and P. fluorescens S-100 shows the same sensitivity to pressure as a homologous E. coli system, whereas a hybrid containing P. fluorescens ribosomes and E. coli S-100 shows the greater pressure tolerance characteristic of the P. fluorescens homologous system.
Growth of bacteriophages MS2 and T7 on streptomycin-resistant mutants of Escherichia coli
Authors: Chakrabarti S , Gorini L
Published: January 2020

Streptomycin-resistant mutants of an Hfr strain of Escherichia coli K were examined for their ability to support the growth of male-specific ribonucleic acid phage MS2 and female-specific deoxyribonucleic acid phage T7. Normally, the Hfr strain allows propagation of MS2 and is lysed by it (efficiency of plating equal to 1), whereas the same strain restricts propagation of T7 and is not lysed by it (efficiency of plating smaller than 10-7). Twenty-four isolates out of 26 independently obtained streptomycin-resistant mutants are partially or completely derestricted for propagation of T7; efficiency of plating of T7 in such strains ranges from 10-3-1. Depending on their response to plating of MS2 and T7, the streptomycin-resistant mutants can be divided into four classes. The mutants in all four classes continue to be "male" in conjugation with F- strains. Genetic analysis is presented to show that restriction of MS2, derestriction of T7, and resistance to streptomycin are the pleiotropic effects of a single mutation at the strA locus.
Ultrastruct of Methylosinus trichosporium as revealed by freeze etching
Authors: Weaver T L , Dugan P R
Published: January 2020

The methane-oxidizing bacterium Methylosinus trichosporium forms extensive intracytoplasmic membranes that lie near the cell periphery and paralled to it. These membranes enclose cavities within the cytoplasm and exist as flattened, balloon-like vesicles. The internal membranes are passed along to both cells during budding. The bacteria accumulate poly-beta-hydroxybutyrate granules that lie in the center of the cells, neither within the internal membrane vesicles nor attached to them. Intercellular bridges result in the formation of chains of bacteria two to four cells in length.
Metabolic control of urea catabolism in Chlamydomonas reinhardi and Chlorella pyrenoidosa
Authors: Hodson R C , Williams S K , Davidson W R
Published: January 2020

In the unicellular green alga Chlamydomonas reinhardi (strain y-1), synthesis of the enzymes required for urea hydrolysis is under substrate induction control by urea and under end product repression control by ammonia. Hydrolysis of urea if effected by the sequential action of the discrete enzymes urea carboxylase and allophanate lyase, collectively called urea amidolyase. The carboxylase converts urea to allophanate in a reaction requiring biotin, adenosine 5'-triphosphate, and Mg2+. The lyase hydrolzyes allophanate to ammonium ions and bicarbonate. Neither activity is present in more than trace amounts when cultures are grown with ammonia or urea plus ammonia, or when they are starved for nitrogen for 8 h. Urea in the absence of ammonia induces both activities 10 to 100 times the basal levels. Addition of ammonia to an induced culture causes complete cessation of carboxylase accumulation and an 80% depression of lyase accumulation. Ammonia does not reduce urea uptake by repressed cells, so it does not prevent induction by the mechanism of inducer exclusion. The unicellular green alga Chlorella pyrenoidosa (strain 3 Emerson) also has discrete carboxylase and lyase enzymes, but only the carboxylase exhibits metabolic control.
Kinetics of induced and repressed enzyme synthesis in Saccharomyces cerevisiae
Authors: Lawther R P , Cooper T G
Published: January 2020

Our previous work has shown that both induction, after addition of inducer, and loss of ability to produce allophanate hydrolase, after removal of inducer, proceed more rapidly than expected from the reported half-life of messenger ribonucleic acid in Saccharomyces cerevisiae. As a basis of rectifying these observations, we have characterized induction and repression of allophanate hydrolase synthesis and find that: (i) induction of the hydrolase begins immediately upon addition of inducer, (ii) once induction has been initiated removal of inducer does not result in immediate loss of synthetic capacity, (iii) induction of the capacity to produce hydrolase can occur in the absence of protein synthesis, (iv) the half-life of hydrolase synthetic capacity increases if protein synthesis is inhibited, (v) allophanate hydrolase itself is not degraded upon removal of inducer, and (vi) induction and repression of allophanate hydrolase synthetic capacity likely occurs at the level of transcription.
Synthesis of nitrate reductase components in chlorate-resistant mutants of Escherichia coli
Authors: MacGregor C H
Published: January 2020

Specific antibody to purified nitrate reductase from Escherichia coli was used to identify enzyme components present in mutants which lack functional nitrate reductase. chlA and B mutants contained all three subunits present in the wild-type enzyme. Different peptides with a broad range of molecular weights could be precipitated from chlCmutants, and chlE mutants contained either slightly degraded enzyme subunits or no precipitable protein. No mutants produced significant amounts of cytoplasmic enzyme. The chlA and B loci are suggested to function in the synthesis and attachment of a molybdenum-containing factor. The chlC locus is suggested to be the structural gene for nitrate reductase subunit A and chlE is suggested to be involved in the synthesis of the cytochrome b1 apoprotein.
Minicell Yield and Cell Division Suppression in
Bacillus subtilis
Mutants
Authors: Mendelson Neil H. , Coyne Sheila I.
Published: January 2020

Minicell yield is determined by the probability of a minicell-producing division and the relationship of growth to division in
Bacillus subtilis
mutants.
Correlation Between Thymineless Elimination and Absence of
hsp
II (
Eco
RII) Specificity in N-Group R Factors
Authors: Birks Jean H. , Pinney R. J.
Published: January 2020

Examination of R factors from 12 different compatibility groups shows that thymineless elimination is apparently confined to N-group plasmids that lack the
hsp
II (
Eco
RII) restriction specificity.
Isolation of a catabolite repression mutant of yeast as a revertant of a strain that is maltose negative in the respiratory-deficient state
Authors: Schamhart D H , Ten Berge A M , Van De Poll K W
Published: January 2020

A character originating from Saccharomyces cerevisiae 1403-7A is described which interferes with maltose growth in the respiratory-deficient state. This character is inherited in an apparently non-Mendelian way, but at present no statement can be made concerning the localization of this character on a plasmid or the involvement of multiple genes. As a revertant of this character, a flaky mutant was isolated, showing a heavy flocculation during growth on liquid medium and resistance to catabolite repression for maltase, alpha-methyl-glucosidase, invertase, and succinate dehydrogenase. In wild-type cells, repression (caused by growth on 2% glucose) and derepression (caused by growth on 2% galactose) can be correlated with a lower and a higher level of cyclic 3',5'-adenosine monophosphate (cAMP), respectively. In cells of flaky mutant, growth on these carbon sources results in the same levels of cAMP as observed for the wild type. Consequently, in this mutant derepression in the presence of 2% glucose is not reflected in a higher level of cAMP.
Accumulation of the capacity of initiation of deoxyribonucleic acid replication in Escherichia coli
Authors: Evans I M , Eberle H
Published: January 2020

Several temperature-sensitive initiation mutants of Escherichia coli were examined for the ability to initiate more than one round of replication after being held at nonpermissive temperature for approximately 1.5 generation equivalents. The capacity for initiation was measured by residual synthesis experiments and rate experiments under conditions where protein synthesis and ribonucleic acid synthesis were inhibited. Results of the rate and density transfer experiments suggest that the cells may initiate more than one round of replication in the absence of protein or ribonucleic acid synthesis. This contrasts with the results of the residual synthesis experiments which suggest that, under these conditions, only one round of synthesis is achieved. These findings suggest that the total amount of residual synthesis achieved in the presence of an inhibitor may be both a function of the number of initiation events which occur and the effect of the inhibitor of protein or ribonucleic acid synthesis on chain elongation.
Dose dependence of the excision of ultraviolet-induced pyrimidine dimers from nuclear deoxyribonucleic acids of haploid and diploid Saccharomyces cerevisiae
Authors: Waters R , Moustacchi E
Published: January 2020

The yield of ultraviolet-induced dimers is similar for a fixed dose in both haploid and diploid Saccharomyces cerevisiae. The excision of these photo-products from the nuclear deoxyribonucleic acids of cells of both ploidies after ultraviolet incident doses of 2 times 10-3 to 4 times 10-3 ergs/mm2 decreased with the corresponding increasing dose. Postirradiation incubation in saline followed by a further incubation in nutrient medium increases the excision as compared to that seen in either nutrient medium or saline alone. Previous data regarding both pyrimidine dimer removal and the survival of haploid and diploid cells after ultraviolet irradiation and either immediate or delayed plating are discussed.
6-Phosphogluconate dehydratase deficiency in pleiotropic carbohydrate-negative mutant strains of Pseudomonas aeruginosa
Authors: Blevins W T , Feary T W , Phibbs P V
Published: January 2020

Mutants of Pseudomonas aeruginosa, strain PAO, have been isolated that are unable to grow on mannitol, glucose, gluconate, or 2-ketogluconate, cut that exhibit wild-type growth on pyruvate, lactate, citrate, succinate, or acetate. Although some of these mutants were also unable to grow on glycerol, the mutations formed a single linkage group by quantitative transductional analysis with phage F116 on glucose minimal agar medium. Cell extracts of all mutant strains were either lacking or severely deficient in 6-phosphogluconate dehydratase activity. Glu+ transductants derived from mutant strains that retained the wild-type ability for growth at the expense of glycerol also regained the ability to grow on all C-6 compounds. Although a role for the pentose phosphate pathway in the catabolism of C6 substrates was not found, a functional Entner-Doudoroff pathway appears to be essential for the catabolism of mannitol, glucose, gluconate, and 2-ketogluconate.
New transfer ribonucleic acid species during sporulation of Bacillus subtilis
Authors: Jeng Y H , Doi R H
Published: January 2020

The transfer ribonucleic acid (tRNA) populations from log-phase cells, sporulating cells (stage III), and dormant spores were compared by tRNA-deoxyribonucleic acid hybridization techniques. New tRNA species not found in log-phase cells were observed in stage III cells. Some of the tRNA made during sporulation were also present in dormant spores. Although the role and function of these new tRNA species cannot be ascribed directly to the sporulation process, their presence indicates that new tRNA genes can be transcribed during sporulation and suggests that translational control may be exerted during sporulation by tRNA.
Maltose chemoreceptor of Escherichia coli
Authors: Hazelbauer G L
Published: January 2020

Strains carrying mutations in the maltose system of Escherichia coli were assayed for maltose taxis, maltose uptake at 1 and 10 muM maltose, and maltose-binding activity released by osmotic shock. An earlier conclusion that the metabolism of maltose is not necessary for chemoreception is extended to include the functioning of maltodextrin phosphorylase, the product of malP, and the genetic control of the maltose receptor by the product of malT is confirmed. Mutants in malF and malK are defective in maltose transport at low concentrations as well as high concentrations, as previously shown, but are essentially normal in maltose taxis. The product of malE has been previously shown to be the maltose-binding protein and was implicated in maltose transport. Most malE mutants are defective in maltose taxis, and all those tested are defective in maltose transport at low concentrations. Thus, as previously suggested, the maltose-binding protein probably serves as the recognition component of the maltose receptor, as well as a component of the transport system. tsome malE mutants release maltose-binding activity and are tactic toward maltose, although defective in maltose transport, implying that the binding protein has separate sites for interaction with the chemotaxis and transport systems. Some mutations in lamB, whose product is the receptor for the bacteriophage lamba, cause defects in maltose taxis, indicating some involvement of that product in maltose reception.
Physiological function of the Pseudomonas putida PpG6 (Pseudomonas oleovorans) alkane hydroxylase: monoterminal oxidation of alkanes and fatty acids
Authors: Nieder M , Shapiro J
Published: January 2020

Pseudomonas putida PpG6 is able to utilize purified n-alkanes of six to ten carbon atoms for growth. It can also grow on the primary terminal oxidation products of these alkanes and on 1-dodecanol but not on the corresponding 2-ketones or 1,6-hexanediol, adipic acid, or pimelic acid. Revertible point mutants can be isolated which have simultaneously lost the ability to grow on all five n-alkane growth substrates but which can still grow on octanol or nonanol. An acetate-negative mutant defective in isocitrate lysase activity is unable to grow on even-numbered alkanes and fatty acids. Analysis of double mutants defective in acetate and propionate or in acetate and glutarate metabolism shows that alkane carbon is assimilated only via acetyl-coenzyme A and propionyl-coenzyme A. These results support the following conclusions: (i) The n-alkane growth specificity of P. putida PpG6 is due to the substrate specificity of whole-cell alkane hydroxylation; (ii) there is a single alkane hydroxylase enzyme complex; (iii) the physiological role of this complex is to initiate the monoterminal oxidation of alkane chains; and (iv) straight-chain fatty acids from butyric through nonanoic are degraded exclusively by beta-oxidation from the carboxyl end of the molecule.
Thermosensitive mutants of Escherichia coli K-12 altered in the catalytic Subunit and in a Regulatory factor of the glutamy-transfer ribonucleic acid synthetase
Authors: Lapointe J , Delcuve G
Published: January 2020

The glutamyl-transfer ribonucleic acid synthetase (GluRS) of a partial revertants (ts plus or minus) of the thermosensitive (ts) mutant strain JP1449 (LOcus gltx) and of a ts mutant strain EM111-ts1 with a lesion in or near the locus gltx have been studied to find the relation between these two genetic loci known to influence the GluRS activity in vitro and the presence of a catalytic subunit and of a regulatory subunit in the GluRS purified from Escherichia coli K-12. The ts character of strain JP1449-18ts plus or minus is co-transduced with the marker dsdA at the same frequency as is the ts character of strain JP1449. Its purified GluRS is very thermolabile and its Km for glutamate is higher than that of a wild-type GluRS. These results indicate that the locus gltX is in the structural gene for the catalytic subunit of this enzyme. The location of the mutation causing the partial ts reversion in strain JP1449-18ts plus or minus is discussed. The GluRS purified from the ts mutant strain EM111-ts1 has the same stability as the wild-type enzyme, but its Km forglutamate increases with the temperature, suggesting that the locus gltE codes for a regulatory factor, possibly for the polypeptide chain that is co-purified with the catalytic subunit.
Alteration of tyrosine isoaccepting transfer ribonucleic acid species in wild-type and asporogenous strains of Bacillus subtilis
Authors: McMillian R A , Arceneaux J L
Published: January 2020

The relative amounts of two isoacceping species of tyrosine transfer ribonucleic acid, tRNATyrI and tRNATyrII, determined from reversed phase 5 profiles of tyrosyl-tRNA, prepared from Bacillus subtilis strain W168, were growth phase and medium dependent. The growth phase-dependent alterations in the relative amounts of tRNATyr species were also demonstrated in 11 asporogenous strains of B. subtilis. The proportion of tRNA-Tyr species and the extent of the alteration in their relative amounts during the transition from the exponential to the stationary phase of growth of these strains was not directly correlated with the formation of spores by strain W168 grown in various media or the stage at which the asporogenous strains are blocked in the process of sporulation.
Characterization of cytosine permeation in Saccharomyces cerevisiae
Authors: Chevallier M R , Jund R , Lacroute F
Published: January 2020

Cytosine permeation in Saccharomyces cerevisiae has been studied. Cytosine uptake is mediated by a permease which is also responsible for purines transport. The Km for the transport of various substrates of this permease have been determined. By means of appropriate selective techniques, mutants with altered Km and mutants lacking the permease have been selected. Cytosine transport is active and is inhibited by 2,4-dinitrophenol, an uncoupler of oxidative phosphorylation, and by N-ethylmaleimide, a reagent of--SH group. Internal labeled cytosine is chased by addition of unlabeled cytosine in the medium. These results support the hypothesis of a carrier-mediated transport, with reduced internal affinity, allowing the release and accumulation of cytosine in the inner compartment. The efflux of cytosine from cytosine permease-less cells has also been studied and shows first order kinetics. A diffusion coefficient of 5.7 per 10- minus 8 cm per S- minus 1 has been evaluated for this efflux.
Cyclic 3', 5'-adenosine monophosphate phosphodiesterase mutants of Salmonella typhimurium
Authors: Alper M D , Ames B N
Published: January 2020

Positive selection procedures for mutants of Salmonella typhimurium lacking cyclic 3', 5'7-adenosine monophosphate (cAMP) phosphodiesterase have been devised. The gene (cpd) coding for this enzyme has been located on the chromosome and shown to be 25% co-transducible with metC using phage P22. The mutants have been used to investigate the role of the enzyme in the control of genes whose expression is known to be dependent on cAMP. Significant alterations in the regulation of some but not others of these genes have been observed in these mutants. Mutants lacking the cAMP phosphodiesterase are more sensitive than their parents to a variety of antibiotics that appear to enter the cell through cAMP-dependent transport systems. They grow faster than the wild type on succinate-ammonia-salts, and glucose-proline-salts media and are inhibited by added cAMP on glucose, citrate, or glycerol-ammonia salts media whereas the wild type is unaffected. Neither the growth of Salmonella typhimurium on glycerol or citrate media nor the level of acid hexose phosphatase in the strain is affected by the loss of cAMP phosphodiesterase. In addition, the mutant strains are extremely sensitive to high levels of cAMP. Loss of the cAMP phosphodiesterase in strains unable to synthesize cAMP (adenyl cyclase negative) reduces by 10-fold the requirement for exogenous cAMP for expression of catabolite-sensitive phenotypes. These results suggest that through its control of cAMP levels in the cell the phosphodiesterase may be involved in the regulation of certain classes of catabolite-sensitive operaons and also in protecting the cell against high levels of cAMP.
Suppression of spectinomycin resistance in a mutant of Escherichia coli K-12
Authors: Berg P E , Kang S S
Published: January 2020

A mutant of Escherichia coli has been isolated which exhibits partial suppression of spectinomycin resistance. The site of mutation is in the streptomycin (strA) region and is closely linked to the spcA gene. However, this gene, which we propose to call mod, is phenotypically distinguishable from both the neomycin-kanamycin (nek) and the ribosomal ambiguity gene (ram). The relative gene order is mod spcA strA. In a cell-free protein synthesizing system, altered ribosomes appear to be responsible for the suppression of spectinomycin resistance caused by mod.
Purification, characterization, and regulation of a nicotinamide adenine dinucleotide-dependent lactate dehydrogenase from Actinomyces viscosus
Authors: Brown A T , Christian C P , Eifert R L
Published: January 2020

A nicotinamide adenine dinucleotide-specific L-(+)-lactate dehydrogenase (LDH) (EC 1.11.27) from Actinomyces viscosus T-6-1600 was purified approximately 110-fold by a combination of diethylaminoethyl-cellulose and 0.5 M Agarose A column chromatography. The ldh was stable at 26 C, but was quite labile at temperatures below 5 C. The enzyme had a molecular weight of 100,000 +/- 10,000 as determined by 0.5 M Agarose molecular exclusion chromatography and showed optimum activity between pH 5.5 and 6.2. The A. viscosus LDH exhibited homotropic interactions with its substrate, pyruvate, and its coenzyme, reduced nicotinamide adenine dinucleotide, indicating multiple binding sites on the enzyme for these ligands with some degree of cooperative interaction between them. The enzyme was under negative control by adenosine 5'-triphosphate, and its kinetic response to the negative effector was sigmoidal in nature. Inorganic phosphate reversed the inhibition exerted on the A. viscosus LDH by adenosine. The 5'-triphosphate thermal stability at 65 C of the LDH from A. viscosus was increased in the presence of its negative effector, adenosine 5'-triphosphate, but was markedly decreased in the presence of its coenzyme, reduced nicotinamide adenine dinucleotide. The glycolytic intermediate, fructose-1,6-diphosphate, had no effect on the catalytic activity of the A. viscosus LDH at saturating pyruvate concentrations. However, fructose-1,6-diphosphate was a potent positive effector at low substrate concentrations. Thus the A. viscosus LDH is under positive control by fructose-1,6-diphosphate and inorganic phosphate, but under negative control by adenosine 5'-triphosphate.
Scanning electron microscopy of surface and internal features of developing perithecia of Neurospora crassa
Authors: Harris J L , Howe H B , Roth I L
Published: January 2020

Stages in the development of perithecia of Neurospora crassa, designated by the time elapsed after crossing, were investigated with the scanning electron microscope, from protoperithecia through perithecia. The usual examination of external features of whole specimens with this instrument was augmented by a freeze-fracture technique which allowed the viewing of development internally as well. Rapid increases in perithecial size soon after crossing were followed by the appearance, in section, of a centrum, at first undifferentiated but subsequently developing ascogenous hyphae. The perithecial beak appeared as a compact mass easily distinguishable in whole specimens from the surrounding hyphae by means of texture as well as shape. Two ascospores were photographed during emergence from an ostiole, but ostioles were found more frequently closed than open.
Purification and properties of glutamate dehydrogenase from a thermophilic bacillus
Authors: Epstein I , Grossowicz N
Published: January 2020

A 250- to 300-fold purification of a nicotinamide adenine denucleotide phosphate (NADP)-dependent glutamate dehydrogenase (GDH, E.C. 1.4.1.4) with a yield of 60% from a thermophilic bacillus is described. More than one NADP-specific GDH was detected by polyacrylamide gel electrophoresis. The enzyme is of high molecular weight (approximately 2 X 10-6), similar to that of the beef and frog liver GDH. The pI of the thermophilic GDH is at pH 5.24. The enzyme is highly thermostable at the pH range of 5.8 to 9.0. The purified GDH, unlike the crude enzyme, was very labile at subzero temperatures. An unidentified factor(s) from the crude cell-free extract prevented the inactivation of the purified GDH at -70 C. Various reactants of the GDH system and D-glutamate also protected, to some extent, the enzyme from inactivation at -70 C. From the Michaelis constants for glutamate (1.1 X 10-2M), NADP (3 X 10-4M), ammonia (2.1 X 10-2M), alpha-ketoglutarate (1.3 X 10-3M), and reduced NADP (5.3 X 10-5M), it is suggested that the enzyme catalyzes in vivo the formation of glutamate from ammonia and alpha-ketoglutarate. The amination of alpha-ketoglutarate and deamination of glutamate by the thermophilic GDH are optimal at the pH values of 7.2 and 8.4, respectively.
Presence of Polyribosomes in Conidiospores of
Botryodiplodia theobromae
Harvested with Nonaqueous Solvents
Authors: Brambl Robert
Published: January 2020

Polyribosomes detected in extracts of spores harvested with water also were found in extracts prepared from spores harvested with nonaqueous fluids.
Anacystis nidulans mutants resistant to aromatic amino acid analogues
Authors: Phares W , Chapman L F
Published: January 2020

Three classes of mutants of Anacystis nidulans were selected on the basis of resistance to fluorophenylalanine and 2-amino-3-phenylbutanoic acid. The most frequent type exhibited DAHP synthetase (7-phospho-2-keto-3-deoxy-D-arabino-heptonate-D-erythrose-4-phosphate-lyase [pyruvate phosphorylating], EC 4.1.2.15) activity identical to that of the parental strain. The second type was characterized by extremely low levels of the activity. The third type had a DAHP synthetase showing decreased sensitivity to inhibition by L-tyrosine. The enzyme was purified 140-fold from wild-type and feedback-insensitive strains, and the kinetics of the reaction was examined. The activity of the wild-type enzyme was inhibited 75% in the presence of 2.0 X 10-3 M tyrosine, and the altered enzyme was inhibited 10%. The following apparent constants were obtained from kinetic studies with partially purified wild-type enzyme: S0.5 for D-erythrose-4-phophate equal to 7.1 X 10-4 M; S0.5 for phosphoenolpyruvate equal to 1.4 X 10-4 M. Inhibition by tyrosine was mixed with respect to binding of both D-erythrose-4-phosphate and phosphoenolpyruvate. In addition, tyrosine promoted cooperative interactions in the binding of phosphoenolpyruvate. For the altered enzyme the following apparent constants were obtained: S0.5 for D-erythrose-4-phosphate equal to 7.1 X 10-4 M; S0.5 for phosphoenolpyruvate equal to 2.9 X 10-4 M. Inhibition by tyrosine was mixed with respect to D-erythrose-4-phosphate and competitive with respect to phosphoenolpyruvate. Tyrosine did not promote cooperative effects in the binding of phosphoenolpyruvate to the altered enzyme.
Utilization of selected leucine peptide amides by Escherichia coli
Authors: Hirshfield I N , Price M B
Published: January 2020

Studies on the utilization of leucine peptide amides as a source of leucine for a leucine auxotroph showed that in general compounds with the structure leu-chi amide (where chi is any amide) are utilized as well as the free peptide, but that compounds with the structure chi-leu amide (where chi is not leucine) are used less effectively than the free peptide. Growth and enzymological experiments indicated that the lower capacity of Escherichia coli to utilize amides of the structure chi-leu amide is not a result of poor transport of these compounds, but rather the inability to rapidly liberate leucine from the amide when it is supplied to the cell in the form of a peptide. Competition studies indicated that the peptide amides enter the cell via the oligopeptide permease system.
Transformation of Bacillus subtilis: transforming ability of deoxyribonucleic acid in lysates of L-forms or protoplasts
Authors: Bettinger G E , Young F E
Published: January 2020

The transformation of Bacillus subtilis by homologous deoxyribonucleic acid (DNA) made available by gently lysing a stable L-form or protoplast suspension was 3 to 10-fold more efficient than DNA isolated by conventional procedures. This increased transformation was not influenced by digestion with pronase, trypsin, or ribonuclease. Preincubation of isolated DNA with L-form lysates did not increase the transformation efficiency above that achieved with untreated, isolated DNA. In addition to displaying a higher efficiency of transformation, the DNA found in these gently prepared lysates was also able to co-transform heretofore unlinked markers at frequencies in excess of those found by congression. Comparison of the frequency of multiple marker transformations to single marker events as a function of DNA dilution conclusively proves that these markers originated from the same continuous strand of DNA.
Restoration of F' superinfection inhibition in a DnaB mutant of Escherichia coli upon construction of heterozygous DnaB merodiploids or P1 lysogens carrying a dnaB analogue
Authors: Bezanson G S , Iyer V N
Published: January 2020

F-prime derivatives of the Escherichia coli strain CR34 bearing the thermosensitivity mutation dnaB43 display low levels of plasmid-determined superinfection inhibition in conjugational crosses at 30 C. Salt-mediated phenotypic suppression of this temperature sensitivity fails to restore normal levels of inhibition, indicating its alteration is not a secondary effect of dnaB43 a-tion on growth or deoxyribonucleic acid syntheiss. Superinfection inhibition is fully restored in mutant cells made merodiploid for the dnaB region by introduction of the F' dnaB-+ plasmid F134-1. dnaB43-bearing strains lysogenized with P1 phage contribution dnaB-analogue protein show eight to nine times more superinfection inhibition than do the same cells carrying P1 prophage repressed dnaB-analogue protein production. Taken together, this evidence suggests a direct causal relationship between dnaB43 and the altered superinfection inhibition phenotype.
Gentic properties of an R factor carrying resistance to aminolgycoside antibiotics
Authors: Hasuda K , Krcméry V , Iyobe S , Mitsuhashi S
Published: January 2020

R factor Rms 151 is an fi+ R factor and belongs to a incompatibility group FII. It carries the genes governing resistance to various aminoglycoside antibiotics, i.e., kanamycin (KM), lividomycin (LV), gentamicin C complex (GM), and 3',4'-dideoxykanamycin B (DKB), in addition to those governing to tetracycline (TC), chloramphenicol (CM), sulfanilamide (SA), and ampicillin (APC). Electron microscopy observation disclosed that the Rms151 deoxyribonucleic acid was a circular form with length of 31.2 mum. A probable circular genetic map of Rms151 was proposed by genetic and biochemical studies, the genes being in the order of -tet-tra-amp-aad-sul-aph-cml-, in which aad and aph confer resistance to KM.GM.DKB by adenylytransferase or resistance to KM.LV by phosphotransferase, respectively.
Effect of pH and biotin on a circadian rhyythm of conidiation in Neurospora crassa
Authors: West D J
Published: January 2020

Expression of a circadian rhythm of conidiation in Neurospora crassa is enhanced in cultures grown on medium that is neutral or deficient in biotin.
Pediococcus cerevisiae mutant with altered transport of folates
Authors: Mandelbaum-Shavit F , Grossowicz N
Published: January 2020

A Pediococcus cerevisiae mutant that actively accumulated folate (PteGlu), in contrast to the wild-type, was also found to exhibit changes in the pattern of uptake of 5-methyl-tetrahydrofolate (5-CH3-H4PteGlu) and amethopterin. Most of the 5-CH3-H4PteGlue accumulated through a glucose- and temperature-dependent process, and a concentrative uptake was also found in gluocse-starved cells and in cells incubated at OC. About 75% of the accumulated 5-CH3-H4PteGlu exchanged with amethopterin. In contrast to the wild type, the mutant accumulated both diastereoisomers of 5-CH3-H4PteGlue by glucose-dependent and glucose-independent processes. Amethopterin and PteGlue competitively inhibited the uptake in both processes, with an apparent lower affinity of the carrier for PteGlu than for the analogue. p-Chloromercuribenzoate strongly inhibited the uptake (75%). The p-chloromercuribenzoate-nonsusceptible and temperature-independent uptake was also competed by amethopterin. Metabolic poisons like sodium azide, potassium fluoride, iodoacetate, and 2,4-dimitrophenol inhibited the glucose-dependent process. Uptake, in the absence of glucose, was enhanced by sodium azide and potassium fluoride.
Germination and peptidoglycan solubilization in Bacillus megaterium spores
Authors: Hsieh L K , Vary J C
Published: January 2020

During initiation of Bacillus megaterium QM B1551 spore germination, trichloroacetic acid-soluble, nondialyzable peptidoglycan fragments with an average molecular weight of 20,000 were excreted. This solubilization of peptidoglycan was measured in vitro as the amount of trichloroacetic acid-soluble hexosamine released from a suspension of broken spores. HgC12, a potent inhibitor of initiation, had no effect on the in vitro solubilization of peptidoglycan. In vivo, HgC12 had no effect on peptidoglycan release from spores that had lost heat resistance, but HgC12 did block complete absorbance loss. These results suggest that mercury inhibits some reactions that normally occur before loss in heat resistance but not the subsequent peptidoglycan release, and mercury inhibits other reactions involved with complete absorbance loss.
Discontinuous replication of colicin E1 plasmid deoxyribonucleic acid
Authors: Inselburg J , Oka A
Published: January 2020

The plasmid pML 21, which was found to contain approximately 49% of the Col E1 genome was used to determine the template origin of single-stranded deoxyribonucleic acid (DNA) fragments (4 to 32% of the Col E1 units length) associated with Col E1 dna replicative intermediates. The results of DNA hybridization competition experiments indicate that the single-stranded fragments derive from the full length of the Col E1 DNA template as expected for Okazaki fragments and the plasmid pML 21 contains the replication origin of Col E1 DNA.
Isolation of a small-cell mutant in the blue-green bacterium Agmenellum quadruplicatum
Authors: Ingram L O , Olson G J , Blackwell M M
Published: January 2020

A new type of high-temperature conditional cell division mutant has been isolated in Agmenellum quadruplicatum strain BG1 in which the process of cell division is uncoupled from that of growth at 39 C. This mutant produces abnormally small cells under conditions of nutrient limitation and forms multinucleoid filaments under normal growth conditions.
Enzymatic and non-enzymatic reduction of nitrite by extracts of Neurospora crassa
Authors: Chang H C , Mulkins G J , Dyer J C , Sorger G J
Published: January 2020

Two activites causing nitrite disappearance are found in extracts of Neurospora; one, inducible by nitrate or nitrite and present only in nitrite-utilizing strains, catalyze the stoichiometric reduction of nitrite to ammonia; the other, present in all strains under all conditions, causes the disappearance of nitrite to something other than ammonia. The latter activity has a molecular weight of about 600 and may contain an oligopeptide, a metal, and an SH group(s). It has no known physiological function.
Amino-terminal sequences of indoleglycerol phosphate synthetase of Escherichia coli and Salmonella typhimurium
Authors: Li S S , Hanlon J , Yanofsky C
Published: January 2020

The partial sequences of the first 40 residues of indoleglycerol phosphate synthetase of Escherichia coli and Salmonella typhimurium were determined, and three amino acid differences were observed among the 38 residues compared.
Soluble and membrane-bound aspartate-binding activities in Salmonella typhimurium
Authors: Aksamit R R , Howlett B J , Koshland D E
Published: January 2020

The specificities of the soluble and membrane aspartate-binding activities were compared with each other and with the specificity of aspartate chemotaxis and were found to be distinct. The soluble aspartate-binding protein was purified to homogeneity and had a molecular weight of 30,000. The dissociation constant was 10(-6) M for aspartate, and the protein bound glutamate, cysteic acid, and 2-amino-3-phosphonopropionate. Aspartate transport was inhibited by cysteic acid.