bluuebunny/crossref_metadata_2025 huggingface dataset:
L-asparagine uptake in Escherichia coli
Authors: Willis R C , Woolfolk C A
Published: January 2020

The uptake of L-asparagine by Escherichia coli K-12 is characterized by two kinetic components with apparent Km values of 3.5 muM and 80 muM. The 3.5 muM Km system displays a maximum velocity of 1.1 nmol/min per mg of protein, which is a low value when compared with derepressed levels of other amino acid transport systems but is relatively specific for L-asparagine. Compounds providing effective competition for L-asparagine uptake were 4-carbon analogues of the L-isomer with alterations at the beta-amide position, i.e., 5-diazo-4-oxo-L-norvaline (Ki = 4.6 muM), beta-hydroxyamyl-L-aspartic acid (Ki = 10 muM), and L-aspartic acid (Ki = 50 muM). Asparagine uptake is energy dependent and is inhibited by a number of metabolic inhibitors. In a derived strain of E. coli deficient in cytoplasmic asparaginase activity asparagine can be accumulated several-fold above the apparent biosynthetic pool of the amino acid and 100-fold above the external medium. The high affinity system is repressed by culture of cells with L-asparagine supplements in excess of 1 mM and is suggested to be necessary for growth of E. coli asparagine auxotrophs with lower supplement concentrations.
Indirect selection of bacterial plasmids lacking identifiable phenotypic properties
Authors: Kretschmer F J , Chang A C , Cohen S N
Published: January 2020

A procedure is described that uses an indicator plasmid (pSC201) to identify cells in a bacterial population that have been co-transformed with a second plasmid lacking detectable phenotypic properties. Under appropriate conditions of indirect selection, between 50 and 85% of transformants carrying the indicator plasmid also contain the nonselected plasmid. A temperature-sensitive mutation in the replication functions of the indicator plasmid enables its elimination from doubly transformed bacteria. Using this procedure, we have isolated bacteria that carry only the small cryptic plasmid. P15A, of the Escherichia coli strain 15. This genetic element, which contains only 2,300 nucleotide pairs, is thus capable of functioning as a replicon independently of the two larger plasmids normally associated with it in E. coli 15 strains (Ikeda, Inuzuka, and Tomizawa, 1970).
Nature and properties of hexitol transport systems in Escherichia coli
Authors: Lengeler J
Published: January 2020

In Escherichia coli K-12 the naturally occurring hexitols D-mannitol, D-glucitol, and galactitol are taken up and phosphorylated via three distinct transport systems by a mechanism called either group translocation or vectorial phosphorylation. For every system, a membrane-bound enzyme II-complex of the phosphoenolpyruvate-dependent phosphotransferase system has been found, each requiring phosphoenolpyruvate, enzyme I, and HPr or alternatively P-HPr as the phosphate donor. Cells with a constitutive synthesis of all hexitol transport systems but with low P-HPr levels have very low transport and phosphorylating activities in vivo, although 40 to 90% of the enzyme II-complex activities are detected in cell extracts of such mutants. No indications for additional hexitol transport systems, especially for systems able to transport and accumulate free hexitols as in Klebsiella aerogenes, have been found. Substrate Km, and Vmax of the three transport systems for several hexitols and hexitol analogues have been determined by growth rates, transport activities, and in vitro phosphorylating activities. Each system was found to take up several hexitols, but only one hexitol serves as the inducer. This inducer invariably is the substrate with the highest affinity. Since bacterial transport systems, as a general rule, seem to have a relatively broad substrate specificity, in contrast to a more restricted inducer specificity, we propose to name the system inducible by D-mannitol and coded by the gene mtlA the D-mannitol transport system, the system inducible by D-glucitol and coded by gutA the D-glucitol transport system, and the system inducible by galactitol and coded by gatA the galactitol transport system.
Yeast sterol esters and their relationship to the growth of yeast
Authors: Bailey R B , Parks L W
Published: January 2020

Variation in the percentage of sterols esterified to long-chain fatty acids during cellular growth has been examined. Under all conditions, a constant percentage of sterol esters was maintained during exponential growth. This maintenance level was found to vary with different growth conditions. A sharp increase in the rate of esterification was observed upon entry of the culture into the stationary growth phase. The minor cellular sterol components were found to accumulate after this period of rapid sterol ester synthesis, with a relative decrease in the size of the ergosterol pool. Evidence is presented that sterol esters of ergosterol precursors are unable to be metabolized to ergosterol. Once esterified, the fatty acids do not appear to be scavenged during starvation conditions.
Formation of cell wall polymers by reverting protoplasts of Bacillus licheniformis
Authors: Elliott T S , Ward J B , Rogers H J
Published: January 2020

The biosynthesis of peptidoglycan and teichoic acid by reverting protoplasts of Bacillus licheniformis 6346 His-, in cubated at 35 C on medium containing 2.5% agar, is detectable after 40 min. The amount of N-acetyl-[1-14C]glucosamine incorporated into peptidoglycan and teichoic acid on continued incubation doubles at the same rate as the incorporation of [3H]tryptophan into protein. At the early stages of reversion the average glycan chain length, measured by the ratio of free reducing groups of muramic acid and glucosamine to total muramic acid present, is very short. As reversion proceeds, the average chain length increases to a value similar to the found in the wall of the parent bacillus. The extent of cross-linkage found in the peptide side chains of the peptidoglycan also increases as reversion proceeds. At the completion of reversion the wall material synthesized has similar characteristics to those of the walls of the parent bacilli, containing peptidoglycan and teichoic and teichuronic acids in about the same proportions. Soluble peptidoglycan can be isolated from the reversion medium, amounting to 30% of the total formed after 3 h of incubation and 8% after 12 h. This amount was reduced by the presence in the medium of the walls of an autolysin-deficient mutant; they were not formed at all by reverting protoplasts of the autolysin-deficient mutant itself. Analysis of the soluble material provided additional evidence for their being autolytic products rather than small unchanged molecules. When protoplasts were incubated on medium containing only 0.8% agar, 53 to 67% of the peptidoglycan formed after 3 h of incubation was soluble, and 21% after 12 h. Fibers that appeared to be sheared from the protoplasts at intermediate stages of reversion on medium containing 2.5% agar were similar in composition to the bacillary walls.
Inhibition of cell division in Escherichia coli K-12 by the R-factor R1 and copy mutants of R1
Authors: Engberg B , Hjalmarsson K , Nordström K
Published: January 2020

The effect of the copy number of plasmid R1drd-19 on cell division of Escherichia coli K-12 was studied in populations growing as steady-state cultures at different growth rates, the growth rate being varied by use of different carbon sources. The plasmid copy number was also varied by using copy mutants of the R-factor. The mean cell size was larger in populations carrying an R-factor than in R-factorless populations, an effect that was more pronounced at low growth rates and in populations carrying R-factor copy mutants. The increased cell size was due to formation of elongated cells in a fraction of the population and to an increase in the diameter of all cells. The majority of the cells divided at a normal cell length, but the presence of an R-factor caused some cells to elongate, probably by the uncoupling of chromosome replication and cell division. This can be explained as a competition between the chromosome and plasmid replicons for some replication factor(s), presumably acting on both initiation and elongation of replication. The formation of elongated cells was a reversible process, but occasionally some of the elongated cells reached lengths 20 times that of newborn cells. If cell division did not occur at the normal cell size, the septum was not formed until the cell size was four times that of a newborn cell. When an elongated cell divided, it usually formed a polar septum, thus producing a newborn cell of normal cell length. The ability of plasmid-containing cells to omit one cell division but to retain the capacity of dividing one mass doubling later is compatible with a mechanical model for septum formation and cell division.
Relationship between the tonB locus and iron transport in Escherichia coli
Authors: Frost G E , Rosenberg H
Published: January 2020

When a strain (arcB-) of Escherichia coli, unable to synthesize the iron transport compound enterochelin, was transduced to tonB-, it became resistant to phage phi80 and simultaneously lost the growth response to enterochelin and the ability to transport its iron complex. However, enterochelin precursors (shikimate and 2,3-dihydroxybenzoate) still supported growth, via the synthesis of enterochelin. Dihydroxybenzoate was a better growth factor at a low concentration than it was at higher levels. The evidence suggests that tonB- strains lack an outer membrane component necessary both for the uptake of ferric-enterochelin and for the adsorption of phage phi80. Thus, although ferric-enterochelin cannot penetrate the cell surface from outside, the complex that is formed within the envelope is transported normally into the cell. The aroB-, tonB- mutant also lacked growth reponses to citrate and various hydroxamate siderochromes, which supported growth in the tonB+ parent strain via inducible transport systems for their ferric complexes. The aroB-, tonB- mutant was unable to transport iron in the presence of citrate, but the low-affinity uptake of uncomplexed iron and the transport of amino acids and phosphate were unimpaired. The tonB locus, thus, affects all the known active transport systems for iron, possibly indicating that they share some common outer membrane component.
Inheritance of low-level resistance to penicillin, tetracycline, and chloramphenicol in Neisseria gonorrhoeae
Authors: Sparling P F , Sarubbi F A , Blackman E
Published: January 2020

The genetics of low-level resistance to penicillin and other antibiotics in a clinical isolate and a multistep laboratory mutant of Neisseria gonorrhoea was studied by transformation. Mutations at three loci affected sensitivity to penicillin. Mutation at penA resulted in an eightfold increase in resistance to penicillin without affecting response to other antimicrobial agents. Mutation at ery resulted in a two- to fourfold increase in resistance to penicillin and similar increases in resistance to many other antibiotics, dyes, and detergents. Mutation at penB resulted in a fourfold increase in resistance to penicillin and tetracycline, the phenotypic expression of which was dependent on the presence of mutation at ery. The cumulative effect of mutations at penA, ery, and penB was an approximate 128-fold increase in penicillin resistance, to a minimum inhibitory concentration of 1.0 mug/ml. Low-level resistance to tetracycline or chloramphenicol was due to similar additive effects between mutations at the nonspecific ery and penB loci and a locus specific for resistance to each drug (tet and chl, respectively). No evidence was found for penicillinases or other drug-inactivating enzymes.
Altered crystal violet permeability and lytic behavior in antibiotic-resistant and -sensitive mutants of Neisseria gonorrhoeae
Authors: Guymon L F , Sparling P F
Published: January 2020

Wild-type, antibiotic-resistant and hypersensitive isogenic strains of Neisseria gonorrhoeae were studied for uptake of crystal violet, rates of autolysis, and response to lysozyme. Total uptake of crystal violet was similar in all strains at 0 C but varied significantly at 37 C. Mutation at the nonspecific resistance locus ery resulted in relative impermeability to crystal violet at 37 C, as compared to wild type. The penetration barrier to crystal violet at 37 C was overcome by addition of 5 mM ethylenediaminetetraacetic acid. Mutation at ery also resulted in reduced rates of autolysis and reduced sensitivity to high concentrations of lysozyme under conditions of divalent cation (Mg2+) depletion. In contrast, mutation at the nonspecific drug hypersensitivity locus env resulted in increased uptake of crystal violet at 37 C, due to increased binding of dye to crude envelope as well as increased penetration into cytoplasm. The env mutants were also more rapidly autolytic and more sensitive to lysozyme than wild type in the absence of Mg2+. These results suggest that the cell envelopes of ery mutants are more stable and less permeable and those of env mutants are less stable and more permeable than wild-type strains.
Altered hexose transport and salt sensitivity in cyclic adenosine 3',5'-monophosphate-deficient Escherichia coli
Authors: Ezzell J W , Dobrogosz W J
Published: January 2020

A cyclic adenosine 3',5'-monophosphate (cAMP)-deficient mutant strain of Escherichia coli K-12 was studied to determine the effect this cyclic nucleotide has on the overall growth and metabolism of this organism. Deficient cells were found to be more susceptible to growth inhibition by salts than were their cAMP-sufficient counterparts. The deficient cells transported alpha-methylglucoside by passive diffusion, whereas the parental cells or mutant cells grown in the presence of exogenous cAMP were able to take up alpha-methylglucoside by the normal active transport process. When viewed together with earlier studies conducted on cAMP-deficient cells, these findings support the view that cAMP plays a key role in regulating the construction and operation of the E. coli membrane system.
Reduced nicotinamide adenine dinucleotide-activated phosphoenolpyruvate carboxylase in Pseudomonas MA: potential regulation between carbon assimilation and energy production
Authors: Newaz S S , Hersh L B
Published: January 2020

Comparison of enzyme activities in crude extracts of methylamine-grown Pseudomonas MA (ATCC 23319) to those in succinate-grown cells indicates the involvement of an acetyl coenzyme A-independent phosphoenolpyruvate carboxylase in one-carbon metabolism. The purified phosphoenolpyruvate carboxylase is activated specifically by reduced nicotinamide adenine dinucleotide (KA = 0.2 mM). The regulatory properties of this enzyme suggests that phosphoenolpyruvate serves as a focal point for both carbon assimilation and energy metabolism.
Deoxyribonucleic acid-binding proteins in vegetative Bacillus subtilis: alterations caused by stage O sporulation mutations
Authors: Brehm S P , Le Hegarat F , Hoch J A
Published: January 2020

Deoxyribonucleic acid (DNA)-binding proteins have been compared between wild-type Bacillus subtilis and five sporulation mutants blocked at different stage O loci. Extracts from exponentially growing cells have been fractionated for proteins binding to single-stranded calf thymus DNA-cellulose and double-stranded B. subtilis DNA-cellulose. In nutrient broth, stage O mutations cause an accumulation of proteins with affinity for double-stranded DNA. Suppression of the mutation with extragenic suppressors relieves the accumulation. In minimal glucose medium, the stage O mutations also cause accumulation of proteins with affinity for double-stranded DNA, but the species accumulated are different from those of nutrient broth-grown cells. In neither case did stage O mutations affect proteins with affinity for single-stranded DNA. The results suggest that the products of stage O loci are functional and operative during vegetative growth.
Serine transhydroxymethylase isoenzymes from a facultative methylotroph
Authors: O'Connor M L , Hanson R S
Published: January 2020

Two serine transhydroxymethylase activities have been purified from a facultative methylotrophic bacterium. One enzyme predominates when the organism is grown on methane or methanol as the sole carbon and energy source, whereas the second enzyme is the major isoenzyme found when succinate is used as the sole carbon and energy source. The enzyme from methanol-grown cells is activated by glyoxylate, is not stimulated by Mg2+, Mn2+, or Zn2+, and has four subunits of 50,000 molecular weight each. The enzyme from succinate-grown cells is not activated by glyoxylate and is stimulated by Mg2+, Mn2+, and Zn2+, and sodium dodecyl sulfate-acrylamide gel electrophoresis indicates that this enzyme has subunit molecular weight of 100,000, the same as the molecular weight obtained for the active enzyme. Cells grown in the presence of both methanol and succinate incorporate less methanol carbon per unit time than cells grown on methanol and have a lower specific activity of the glyoxylate-activated enzyme than methanol-grown cells. Adenine, glyoxylate, or trimethoprim in the growth medium causes an increased level of serine transhydroxymethylase in both methanol- and succinate-grown cells by stimulating the synthesis of the glyoxylate-activated enzyme.
Glycerol dissimilation in Rhodopseudomonas sphaeroides
Authors: Pike L , Sojka G A
Published: January 2020

Rhodopseudomonas sphaeroides followed a diauxic growth curve when grown on a malate-glycerol medium, the first phase of growth being supported by malate and the second by glycerol. A soluble glycerokinase and a particulate, pyridine nucleotide-independent glycerophosphate dehydrogenase, were induced by the presence of glycerol in the medium, but neither was fully expressed nor functional until all malate had been consumed.
Production of cells without deoxyribonucleic acid during thymidine starvation of lexA- cultures of Escherichia coli K-12
Authors: Howe W E , Mount D W
Published: January 2020

When thymidine-requiring lexA- strains were starved for thymidine, the kinetics of survival were similar to those of a nearly isogenic lexA+ strain. The size distribution of cells in the lexA- and lexA+ cultures were, however, quite different. Whereas most of the cells in the starved lexA+ cultures grew into long filamentous forms (longer than 4.0 mum), many of the lexA- cells were found to have a normal rod shape (4.0 mum or shorter). It was shown that lexA- cells undergo more divisions during thymidine starvation than lexA+ cells. Furthermore, using an autoradiographic method to analyze deoxyribonucleic acid (DNA) distribution in the starved cells, we demonstrated that cells without DNA are produced in both normal and starved lexA- cultures at a much higher frequency than in lexA+ cultures. Some of these cells may be produced by breakdown of DNA, but we favor the hypothesis that they result from an abnormal cell division process. Since lexA mutations are dominant, we conclude that a diffusible product decreases the synthesis or activity of an inhibitor of cell division in lexA- strains when DNA synthesis is blocked by thymidine starvation.
Pyridine nucleotide-linked oxidation of methanol in methanol-assimilating yeasts
Authors: Mehta R J
Published: January 2020

An alcohol dehydrogenase linked to nicotinamide adenine dinucleotide and requiring glutathione has been isolated and partially purified from two methanol-assimilating yeasts. It differs from previously described methanol-oxidizing enzymes in pH optima, electron acceptor specificity, substrate specificity, inhibition pattern, and stability.
Analysis of the cell wall and lipopolysaccharide of Spirillum serpens
Authors: Chester I R , Murray R G
Published: January 2020

Isolated walls of Spirillum serpens VHA contained lipid, lipopolysaccharide, and protein in amounts similar to those of other gram-negative organisms. The loosely bound lipids consisted mainly of phosphatidylethanolamine, lyso-phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. Lipopolysaccharide was tightly bound to the wall and could only be removed in a substantial amount after digestion of the wall with Pronase. The lipopolysaccharide contained L-glycero-D-mannoheptose, rhamnose, glucosamine, ethanolamine, and phosphate in common with many of the lipopolysaccharides isolated from the Enterobacteriaceae. However, 2-keto-3-deoxyoctonic acid was not detected. Several unidentified sugars were present. The fatty acid composition resembled that found in lipopolysaccharides isolated from various pseudomonads. Two major regions were identified in the polysaccharide moiety, one apparently corresponding to the core polysaccharide and the other corresponding to the side-chain polysaccharide as in enterobacterial and pseudomonad lipopolysaccharides. The side chains were obtained as low-molecular-weight material and their structure was partially elucidated by the isolation and partial characterization of N-acetylglucosaminyl-(1 leads to 4)-rhamnose.
Fine-structure genetic map of the cysB locus in Salmonella typhimurium
Authors: Cheney R W , Kredich N M
Published: January 2020

A genetic map of the cysB region of the Salmonella typhimurium chromosome was constructed using bacteriophage P22-mediated transduction. Strains bearing delta (supX cysB) mutations were employed to divide this regulatory locus into 12 segments containing a total of 39 single-site mutations. Twenty-five of these single-site mutations were further ordered by reciprocal three-point crosses. The results do not support the concept of multiple cistrons at cysB and suggest that the abortive transductants previously observed in crosses between certain cysB mutants were due to intracistronic complementation. The prototrophic cys-1352 mutation, which causes the constitutive expression of the cysteine biosynthetic enzymes, was found to lie within the cysB region itself. It is bracketed by mutations, which lead to an inability to derepress for these enzymes and result in auxotrophy for cysteine.
Membrane location of a deoxyribonuclease implicated in the genetic transformation of Diplococcus pneumoniae
Authors: Lacks S , Neuberger M
Published: January 2020

The cellular localization of enzymes in Diplococcus pneumoniae was examined by fractionation of spheroplasts. A deoxyribonuclease implicated in the entry of deoxyribonucleic acid (DNA) into the cell during genetic transformation was located in the cell membrane. This enzyme, the major endonuclease of the cell (endonuclease I), which is necessary for the conversion of donor DNA to single strands inside the cell and oligonucleotides outside, thus could act at the cell surface. Another enzyme, the cell wall lysin (autolysin), was also found in the membrane fraction. Other enzymes, including amylomaltase, two exonucleases, and adenosine triphosphate-dependent deoxyribonuclease, and a restriction type endonuclease, were located in the cytosol within the cell. None of the enzymes examined were predominantly periplasmic in location. Spheroplasts were obtained spontaneously on incubation of pneumococcal cells in concentrated sugar solutions. The autolytic enzyme appears to be involved in this process. Cells that were physiologically competent to take up DNA formed osmotically sensitive spheroplasts two to three times faster than cells that were not in the competent state. Although some genetically incompetent mutants also formed spheroplasts more slowly, other such mutants formed them at the faster rate.
Intrageneric transformation of neisseria gonorrhoeae and neisseria perflava to streptomycin resistance and nutritional independence
Authors: Siddiqui A , Goldberg I D
Published: January 2020

Auxotrophic mutants of Neisseria gonorrhoeae and Neisseria perflava were transformed to prototrophy using homologous and heterologous deoxyribonucleic acid (DNA). Within either species the efficiencies of transformation for nutritional markers were found to be very similar to the values obtained for transformation to streptomycin resistance. The number of transformants in the interspecific N. perflava (donor) - - leads to N. gonorrhoeae (recipient) cross was 100-fold lower than the number obtained in the intraspecific N. gonorrhoeae - - leads to N. gonorrhoeae cross for streptomycin resistance, as well as for several nutritional markers. In the reciprocal experiment the difference in the number of transformants in the interspecific N. gonorrhoeae - - leads to N. perflava cross and the number obtained in the intraspecific N. perflava - - leads to N. perflava cross varied from 600 to 1,000-fold for the streptomycin resistance marker. Of greater interest was the finding that N. perflava auxotrophs, although transformable to prototrophy with wild-type N. perflava DNA, were not transformed to nutritional independence by gnoncoccal DNA. These same mutants were transformable to streptomycin resistance using the heterologous gonococcal DNA. When the DNAs of N. meningitidis, N. flava, and N. lactamicus were used to transform N. gonorrhoeae to prototrophy or streptomycin resistance, the transformation frequencies obtained fell along a gradient that in general reflected taxonomic relationships. On the other hand, with N. perflava as the recipient for these same DNAs, only N. flava DNA could transform auxotrophs to prototrophy, although transformation to streptomycin resistance occurred in all cases. DNA from N. perflava - - leads to N. gonorrheae streptomycin-resistant or Ade+ intergenotic transformants transformed N. gonorrhoeae cells at a 100-fold-higher efficiency than did DNA from N. perflava. Our findings suggest that (i) N. gonorrhoeae and N. perflava are more closely related than hitherto suspected and (ii) N. perflava is more selective with respect to heterologous DNA than is N. gonorrhoeae.
Heterologous deoxyribonucleic acid uptake and complexing with cellular constituents in competent Bacillus subtilis
Authors: Soltyk A , Shugar D , Piechowska M
Published: January 2020

With competent cultures of Bacillus subtilis the uptake of Escherichia coli deoxyribonucleic acid (DNA) is about 50% that for homologous DNA. Uptake of phage T6 DNA, if any, is of the order of 7%, while nonglucosylated phage T6 (T6) DNA is taken up almost as effectively as homologous DNA. Both T6 and T4 DNA interfere only minimally with uptake of homologous DNA; by contrast, T6 DNA competes with homologous DNA as effectively as the latter itself. These results indicate that the glucose residues in the T-even phage DNA, located in the large groove of the DNA helix, reduce affinity for cellular receptors, leading to low binding of T6 DNA. The latter DNA is considerably less degraded by extracellular nucleases than homologous DNA, thus excluding enzymatic hydrolysis as the source of poor uptake. Affinity of DNA for competent cells was also evaluated by the formation, and detection in a CsCl density gradient, of complexes of DNA with cellular constituent(s). Such comlexes, similar to those previously observed with transforming DNA, are formed by E. coli DNA and T6 DNA; in reconstruction experiments the denatured forms of these same DNA samples form complexes when added to the cells before lysis. T6 DNA, on the other hand, does not form such a complex. The possible role of such complexes in transport of DNA to the cell interior is discussed.
Transfectability of rough strains of Salmonella typhimurium
Authors: Bursztyn H , Sgaramella V , Ciferri O , Lederberg J
Published: January 2020

Cells of rough (but not smooth) strains of Salmonella typhimurium become competent for transfection by phage P22 deoxyribonucleic acid after treatment with 0.1 M CaCl2. The yield of infectious centers is about 10(-8) per genome equivalent of deoxyribonucleic acid. However, different sorts of rough strains vary in their ability to become competent in a fashion that can be correlated with the level of the genetic block in cell wall lipopolysaccharide synthesis. The most amenable strains are blocked by defects in the addition of galactose units I and II of the lipopolysaccharide by the inability to synthesize uridine 5'-diphosphate-galactose (galE point mutants and gal deletion mutants). Strains blocked only in the addition of galactose I, glucose I, or heptose II have low levels of transfectability, whereas strains with either more complete or more deficient lipopolysaccharide core are not competent for transfection. When normal lipopolysaccharide synthesis is restored either genetically or by furnishing exogenous galactose (galE point mutants that can still use it), the cells are not longer competent for transfection.
Purification and properties of beta-N-acetylglucosaminidase from Escherichia coli
Authors: Yem D W , Wu H C
Published: January 2020

beta-N-acetylglucosaminidase (EC 3.2.1.30) has been purified from Escherichia coli K-12 to near homogeneity based on polyacrylamide gel electrophoresis in both 0.5% sodium dodecyl sulfate and in 6 M urea at pH 8.5. The purified enzyme shows a pH optimum of 7.7 and the Km for p-nitrophenyl-beta-D-2-acetamido-2-deoxyglucopyranoside is 0.43 mM. The molecular weight of this enzyme, determined by both Sephadex gel filtration and by sodium dodecyl sulfate gel electrophoresis, is equivalent to 36,000. It is shown to be a soluble cytoplasmic enzyme. Studies on the substrate specificites of the purified enzyme indicate that this enzyme is an exo-beta-N-acetylglucosaminidase.
Spore membrane(s) as the site of damage within heated Clostridium perfringens spores
Authors: Flowers R S , Adams D M
Published: January 2020

Clostridium perfringens spores were injured by ultrahigh-temperature treatment at 105 C for 5 min. Injury was manifested as an increased sensitivity to polymyxin and neomycin. Since many of the survivors could not germinate normally the ultrahigh-temperature-treated spores were sensitized to and germinated by lysozyme. Polymyxin reportedly acts upon the cell membrane. Neomycin may inhibit protein synthesis and has surface-active properties. Injured spores were increasingly sensitive to known surface-active agents, sodium lauryl sulfate, sodium deoxycholate, and Roccal, a quaternary ammonium compound. Injured spores sensitive to polymyxin and neomycin also were osmotically fragile and died during outgrowth in a liquid medium unless the medium was supplemented with 20% sucrose, 10% dextran, or 10% polyvinylpyrrolidone. The results suggested that a spore structure destined to become cell membrane or cell wall was the site of injury. Repair of injury during outgrowth in the presence of protein, deoxyribonucleic acid, ribonucleic acid and cell wall synthesis inhibitors was consistent with this hypothesis.
Properties of adenyl cyclase and cyclic adenosine 3',5'-monophosphate receptor protein-deficient mutants of Escherichia coli
Authors: Kumar S
Published: January 2020

Several spontaneous cya and crp mutants of Escherichia coli have been selected as clones simultaneously resistant to phage lambda and nalidixic acid and characterized. Both cya and crp mutants have been found to grow as cocci with increased doubling times. They have increased resistance to some mutagens (methylmethanesulfonate, ultraviolet light, gamma rays), antibiotics (nalidixic acid, ampicillin), phages (lambda, T6), sublethal heat and hypotonic shock, and decreased resistance to neutral detergents (sodium dodecyl sulfate, sodium deoxycholate), a protein synthesis inhibitor (streptomycin), and a respiratory inhibitor (sodium azide). The nature of changes in cell parameters indicate fundamental alterations in the envelope structure of the cya and crp mutant cells. The new cya and crp mutants have been found to be multiply carbohydrate negative and nonmotile in conformity with similar previously isolated mutants. Studies of revertants and phi80 cya+ and phi80 cya transductants indicated that the pleiotropic phenotype is related to a single mutational event at the cya or the crp locus in the mutants.
Lethal effect of mitomycin C on Haemophilus influenzae
Authors: Small G D , Setlow J K , Kooistra J , Shapanka R
Published: January 2020

The sensitivity of ultraviolet-sensitive strains to inactivation by mitomycin C (MC) is at the most only a factor of two greater than that of the wild type. The presence of inducible prophage has very little effect on the sensitivity. Genes which control excision of ultraviolet-induced pyrimidine dimers also control repair of MC-induced cross-links, as measured by resistance of denatured deoxyribonucleic acid (DNA) from treated cells to S1 nuclease digestion. However, endonucleolytic breaks in MC-damaged DNA, as judged by decreased single-strand molecular weight upon incubation of treated cells, are independent of these genes and probably are caused by monoadducts. After long periods of incubation there is a return to the molecular weight of untreated DNA. DNA degradation after MC treatment of various strains is not correlated with sensitivity to inactivation. Stationary-phase cells of all strains are more than twice as sensitive to MC as exponentially growing cells, and the sensitivity difference agrees with the measured difference in the number of cross-links after MC treatment of cells in the two growth stages. Evidence has been obtained that these phenomena result from differences in uptake of MC, which can be influenced by cyclic adenosine monophosphate. Small deviations in MC sensitivity from that of the wild type observed in mutants lacking the adenosine 5'-triphosphate-dependent nuclease are postulated to result from differences in MC uptake. These mutants, although no more ultraviolet sensitive than the wild type, are more sensitive to streptomycin, which also must be taken up by the cell to be effective.
Uric acid degradation by Bacillus fastidiosus strains
Authors: Bongaerts G P , Vogels G D
Published: January 2020

Seven Bacillus strains including one of the original Bacillus fastidiosus strains of Den Dooren de Jong could grow on urate, allantoin, and, except one, on allantoate. No growth could be detected on adenine, guanine, hypoxanthine, xanthine, and on degradation products of allantoate. Some strains grew very slowly in complex media. The metabolic pathway from urate to glyoxylate involved uricase, S(+)-allantoinase, allantoate amidohydrolase, S(-)-ureidoglycolase, and, in some strains, urease.
Control of differentiation in streptomycetes: involvement of extrachromosomal deoxyribonucleic acid and glucose repression in aerial mycelia development
Authors: Redshaw P A , McCann P A , Sankaran L , Pogell B M
Published: January 2020

When Streptomyces alboniger spores were grown in Hickey-Tresner broth containing 5 muM ethidium bromide, a high frequency of permanently cured aerial mycelia-negative (am-) colonies was recovered. The appearance an am- colonies was time dependent: a very low frequency (0.3%) at zero time, a maximum (9 to 21%) after 2 to 5 days of growth, and a decline again to low frequencies later in the growth cycle. On agar, cured am- colonies of S. alboniger still produced puromycin. The development of aerial mycelia in S. alboniger, S. scabies, and S. coelicolor was also sensitive to glucose repression. Colonies grown on Hickey-Tresner agar containing 2% glucose remained phenotypically am- throughout the observation period. Adenine (2.5 mM or greater), and to a lesser extent adenosine and guanosine, specifically reversed the repression. The accumulation of undissociated organic acids appears to be involved in glucose repression of aerial mycelia formation. However, this does not appear to be the case with puromycin production in S. alboniger; glucose repression was observed over the pH range 5.0 to 7.5.
Utilization of exogenous thymidine by Chlamydia psittaci growing in the thymidine kinase-containing and thymidine kinase-deficient L cells
Authors: Hatch T P
Published: January 2020

The incorporation of [3H]thymidine into the deoxyribonucleic acid (DNA) of Chlamydia psittaci (strain 6BC) growing in thymidine kinase (adenosine 5'-triphosphate-thymidine 5'-phosphotransferase, EC 1.7.1.21)-containing L cells, L(TK+), and thymidine kinase-deficient L cells, LM(TK-), was examined by autoradiography. Label was detected over C. psittaci inclusions in L(TK+) but not LM(TK-) cells. No evidence for a chlamydia-specific thymidine kinase activity in either L(TK+) or LM(TK-) cells was obtained. Entry of [3H]thymidine into the DNA of C. psittaci growing in L(TK+) cells was quantitated by measuring label in purified C. psittaci. It was 265 times less efficient than entry into infected host cell DNA. It is concluded that low levels of exogenous thymidine are incorporated into the DNA of C. psittaci and that this incorporation is dependent on a fully competent host thymidine kinase activity. Evidence also is presented that L cells possess at least two thymidine kinase activities, both of which are capable of supplying thymidylate precursors for nuclear DNA synthesis.
Transformation of Escherichia coli by chromosomal deoxyribonucleic acid from Salmonella typhi
Authors: Sánchez F , Bolívar F , Martuscelli J
Published: January 2020

The genetic transformation of Escherichia coli K-12 with chromosomal deoxyribonucleic acid purified from Salmonella typhi is described.
Escherichia coli mutants with altered ribosomal ribonucleic acid metabolism
Authors: Jackson J M , Chaney S G
Published: January 2020

This paper reports the partial characterization of two temperature-sensitive mutants of Escherichia coli with alterations in ribosomal ribonucleic acid (rRNA) metabolism at the restrictive temperature. Both mutants continue to synthesize deoxyribonucleic acid and protein at 42 C but showed little or no accumulation of RNA. Both strains are inducible for beta-galactosidase at the restrictive temperature, showing that messenger RNA synthesis continues and that the messenger RNA is translated into functional protein. One of the strains, 2S474, shows a rather severe depression (sevenfold) in the synthesis of all classes of RNA at 42 C. In addition, the synthesis of rRNA is selectively depressed, with the percentage of rRNA synthesis. However, there appears to be a selective depression in the rate of rRNA synthesis and, possibly, in the conversion of p16S rRNA to m16S rRNA.
Turnover and spreading of old wall during surface growth of Bacillus subtilis
Authors: Pooley H M
Published: January 2020

The steady-state concentration of cell wall turnover products in the medium of Bacillus subtilis 168 growing exponentially on a casein hydrolysate-supplemented medium is equivalent to an overall rate of turnover of less than 10% per generation. After transfer of a steady-labeled culture to nonradioactive medium, the rate of release of labeled turnover products increased exponentially for up to two generations. The rate of turnover finally attained by this culture reached an apparently first-order rate of about 50% per generation. The addition of soluble autolytic activity to growing cultures of a mutant possessing a reduced rate of wall turnover resulted in a marked stimulation in the rate of solubilization of the cell wall fraction. The increased rate of solubilization produced was proportional to the concentration of added enzyme and remained constant until less than 20% of the wall originally present was left. Autolytic activity added under these conditions was bound entirely to wall at least one generation old. The results are interpreted in terms of a model for cell wall growth in which wall two or more generations old covers a total surface area at least four times larger than that occupied at the time of synthesis, forming a shallow outer layer (overlying newer wall) from which all turnover takes place. The model is discussed in relation to previous attempts to determine the pattern of surface expansion in bacilli.
Layered distribution, according to age, within the cell wall of bacillus subtilis
Authors: Pooley H M
Published: January 2020

When soluble autolytic activity was added to growing cultures of a mutant possessing a reduced rate of cell wall turnover, there was a delay of more than one generation before solubilization of new cell wall began, in contrast to the immediate increase in the rate of solubilization of old cell wall. A similar delay was found before turnover of new cell wall occurred in the parent, in agreement with a previous report (Mauck et al., 1971). When sodium lauryl sulfate-inactivated cell walls were prepared, the great bulk of the wall formed a uniformly susceptible substrate to added autolytic activity. The immediate solubilization of new wall eliminates insusceptibility to autolytic enzyme as an explanation for the failure to be turned over. There were, however, major differences in the rate of solubilization of wall of different ages. During solubilization of the initial 30% of the cell wall preparation, wall two generations old was solubilized at least seven times faster than wall one-half a generation old. This result is interpreted in terms of differences in accessibility. The cell wall is seen as consisting of a series of layers, the age of which increases with the distance from the membrane, such that wall newly synthesized on the membrane passes out through the thickness of the cell wall layer during subsequent growth and only becomes susceptible to turnover as it reaches the outer surface, largely in the form of a layer, more than one generation after incorporation.
Identification of coreplicating chromosomal sectors in Bacillus subtilis by nitrosoguanidine-induced comutation
Authors: Siccardi A G , Ferrari F A , Mazza G , Galizzi A
Published: January 2020

The simultaneous replication of four regions of dichotomously replicating chromosomes of Bacillus subtilis has been detected by means of nitrosoguanidine-induced comutation. The map distance between successive rounds of replication has been measured as one-half a replicative arm in cells growing exponentially in rich medium.
Excision repair of ultraviolet-irradiated deoxyribonucleic acid in plasmolyzed cells of Escherichia coli
Authors: Seeberg E , Strike P
Published: January 2020

A system of cells made permeable by treatment with high concentrations of surcrose (plasmolysis) has been exploited to study the excision repair of ultraviolet-irradiated deoxyribonucleic acid in Escherichia coli. It is demonstrated that adenosine 5'-triphosphate is required for incision breaks to be made in the bacterial chromosome as well as in covalently closed bacteriophage lambda deoxyribonucleic acid. After plasmolysis, uvrC mutant strains appear as defective in the incision step as the uvrA-mutated strains. This is in contrast to the situation in intact cells where uvrC mutants accumulate single-strand breaks during postirradiation incubation. These observations have led to the proposal of a model for excision repair, in which the ultraviolet-specific endonuclease, coded for by the uvrA and uvrB genes, exists in a complex with the uvrC gene product. The complex is responsible for the incision and possibly also the excision steps of repair. The dark-repair inhibitors acriflavine and caffeine are both shown to interfere with the action of the adenosine 5'-triphosphate-dependent enzyme.
Kinetics of labeling of the S-adenosylmethionine pool of Saccharomyces cerevisiae
Authors: Warner J R , Morgan S A , Shulman R W
Published: January 2020

A method has been developed for studying the specific activity of the pool of S-adenosylmethionine in yeast. The pool reaches half-maximal specific activity within 30 s after the addition of [methyl-3H]methionine. After addition of an excess of nonradioactive methionine, the specific activity of S-adenosylmethionine is reduced by half within 20 s. During that period there is a substantial expansion of the pool. A logarithmically growing cell in synthetic medium contains about 2 X 10(6) molecules of S-adenosylmethionine, of which only 10% is used for the methylation of ribonucleic acid molecules.
Metabolism of resorcinylic compounds by bacteria: orcinol pathway in Pseudomonas putida
Authors: Chapman P J , Ribbons D W
Published: January 2020

Enrichment cultures yielded two strains of Pseudomonas putida capable of growth with orcinol (3,5-dihydroxytoluene) as the sole source of carbon. Experiments with cell suspensions and cell extracts indicate that orcinol is metabolized by hydroxylation of the benzene ring followed successively by ring cleavage and hydrolyses to give 2 mol of acetate and 1 mol of pyruvate per mol of orcinol as shown: orcinol leads to 2,3,5-trihydroxytoluene leads to 2,4,6-trioxoheptanoate leads to acetate + acetylpyruvate leads to acetate + pyruvate. Evidence for this pathway is based on: (i) high respiratory activities of orcinol-grown cells towards 2,3,5-trihydroxytoluene; (ii) transient accumulation of a quinone, probably 2-hydroxy-6-methyl-1,4-benzoquinone, during grouth with orcinol; (iii) formation of pyruvate and acetate from orcinol, 2,3,5-trihydroxytoluene, and acetylpyruvate catalyzed by extracts of orcinol, but not by succinate-grown cells; (iv) characterization of the product of oxidation of 3-methylcatechol (an analogue of 2,3,5-trihydroxytoluene) showing that oxygenative cleavage occurs between carbons bearing methyl and hydroxyl substituents; (v) transient appearance of a compound having spectral properties similar to those of acetylpyruvate during 2,3,5-trihydroxytoluene oxidation by extracts of orcinol-grown cells. Orcinol hydroxylase exhibits catalytic activity when resorcinol or m-cresol is substituted for orcinol; hydroxyquinol and 3-methylcatechol are substrates for the ring cleavage enzyme 2,3,5-trihydroxytoluene-1,2-oxygenase. The enzymes of this pathway are induced by growth with orcinol but not with glucose or succinate.
Biosynthesis of membrane-bound nitrate reductase in Escherichia coli: evidence for a soluble precursor
Authors: MacGregor C H
Published: January 2020

Membrane-bound nitrate reductase of Escherichia coli consists of three subunits designated as A, B, and C, with subunit C being the apoprotein of cytochrome b, A hemA mutant that cannot synthesize delta-aminolevulinic acid (ALA) produces a normal, stable, membrane-bound enzyme when grown with ALA. When grown without ALA, this mutant makes a reduced amount of membrane-bound enzyme that is unstable and contains no C subunit. Under the same growth conditions, this mutant accumulates a large amount of a soluble form of the enzyme in the cytoplasm. Accumulation of this cytoplasmic form begins immediately upon induction of the enzyme with nitrate. The cytoplasmic form is very similar to the soluble form of the enzyme obtained by alkaline heat extraction. It is a high-molecular-weight complex with a Strokes radius of 8.0 nm and consists of intact A and B subunits. When ALA is added to a culture growing without ALA, the cytoplasmic form of the enzyme is incorporated into the membrane in a stable form, coincident with the formation of functional cytochrome b. Reconstitution experiments indicate that subunit C is present in cultures grown without ALA but is reduced in amount or unstable. These results indicate that membrane-bound nitrate reductase is synthesized via a soluble precursor containing subunits A and B, which then binds to the membrane upon interaction with the third subunit, cytochrome b.