bluuebunny/crossref_metadata_2025 huggingface dataset:
New tool for studying interactions of components of ribonucleic acid polymerase: rifampin-dependent mutants
Authors: Dabbs E R
Published: January 2020

Mutants of Escherichia coli showing a rifampin-dependent phenotype were isolated from cells of strain CP78 mutagenized with ethyl methane sulfonate or nitrosoguanidine when an antibiotic underlay technique was used. The mutants varied greatly in their rifampin requirement. The minimum necessary concentration ranged from 1 to 50 micrograms/ml. The mutants could be divided into four phenotypic classes. These dependent mutants and their revertants should be a useful tool for probing interactions between the component polypeptides of ribonucleic acid polymerase and for studying the linkage of transcription with other cellular processes.
Isolation from soil and properties of the extreme thermophile Clostridium thermohydrosulfuricum
Authors: Wiegel J , Ljungdahl L G , Rawson J R
Published: January 2020

Thirteen strains of a strict anaerobic, extreme thermophilic bacterium were isolated from soil samples of moderate temperature, from a sewage plant in Georgia, and from hot springs in Utah and Wyoming. They were identified as strains of Clostridium thermohydrosulfuricum. The guanosine + cytosine content (moles percent) was 37.6 (determined by buoyant density) and 34.1 (determined by melting temperature). All strains required a factor present in yeast extract or tryptone growth. Growth characteristics were as follows: a pH range of 5 to 9, with the optimum between 6.9 to 7.5, in a temperature range of 40 to 78 degrees C, with the optimum at 68 degrees C. The doubling time, when grown on glucose at temperature and pH optima, was 1.2 h. The main products of glucose fermentation were ethanol, lactate, acetate, CO2, and H2. The fermentation was inhibited by H2. Formation of spores occurred easily on glucose-agar medium or when cultures growing at temperatures above 65 degrees C were allowed to cool to temperature below 55 degrees C. C. thermohydrosulfuricum occurs widely distributed in the natural environment.
Genetic mapping of toxin regulatory mutations in Vibrio cholerae
Authors: Mekalanos J J , Sublett R D , Romig W R
Published: January 2020

We have mapped a regulatory site mediating the hyperproduction of cholera toxin in mutants of Vibrio cholerae strain 569B. Mutations in this locus, called htx, result in the hypertoxinogenic phenotype, as measured by the ganglioside filter assay and immunoradial diffusion. Transposon-facilitated recombination was used to construct improved genetic donors in 569B parental and hypertoxinogenic mutant strains. Subsequent mapping by conjugation indicated that the htx locus was closely linked to the rif, str, and ilv loci of V. cholerae. Analysis of recombinants from these crosses suggested the following gene order: thy str htx rif ilv arg. The close genetic linkage of htx to rif (as high as 98%) resulted in a high comutation frequency of these two loci by nitrosoguanidine mutagenesis. Transfer of the htx mutant locus from a hypertoxinogenic donor to several unrelated Tox+ strains of V. cholerae caused a detectable elevation of toxin production in the recipients. These results suggest that toxin production in diverse strains of V. cholerae is controlled by a common regulatory mechanism in which the htx gene product plays a significant role.
Effect of repair deficiency and R plasmids on spontaneous and radiation-induced mutability in Pseudomonas aeruginosa
Authors: Lehrbach P R , Lee B T , Dirckze C D
Published: January 2020

The effect of R plasmids on spontaneous and radiation (ultraviolet and gamma)-induced mutability in Pseudomonas aeruginosa was studied in strains containing the radiation-sensitive markers polA3 or rec-2 and the revertable auxotrophic markers hisO27 and trpB1. In the absence of an R plasmid, the radiation-induced mutability was dependent on the recA+ genotype and independent of the polA+ genotype, whereas spontaneous mutability was similar in all genetic backgrounds. R plasmids pPL1, R2, and pMG15 increased the ultraviolet radiation survival and ultraviolet-induced mutability of wild-type and polA host cells but did not alter either effect in a recA mutant. These R plasmids also increased the gamma radiation survival and gamma-induced mutability of wild-type host cells bud pMG15 also enhanced the level of spontaneous mutagenesis in wild-type host cells but not in a polA or recA mutant. These data suggested that a common plasmid gene product(s) may participate in various recA-dependent, error-prone deoxyribonucleic acid repair pathways of P. aeruginosa. The properties of a mutant R plasmid, pPL2, originally selected because it lacked enhanced ultraviolet-induced mutability, supported this conclusion.
Isolation and characterization of mutations in the structural gene for protease III (ptr)
Authors: Cheng Y S , Zipser D , Cheng C Y , Rolseth S J
Published: January 2020

Escherichia coli mutants defective in protease III were isolated by enzyme assays of heavily mutagenized colones. One mutant produced thermolabile enzyme, and it is presumed to have a mutation in the structural gene of protease III. Two other mutants mapping at the same site had less than 5% of the wild-type protease III level. The genetic locus of these mutations, designated ptr, was located at approximately 60 min on the E. coli linkage map based on its high frequency (70%) of contransduction by P1 with argA. Strains with less than 5% of the wild-type protease III activity grew normally and degraded nonsense fragments of beta-galactosidase at wild-type rates.
Mutant single-strand binding protein of Escherichia coli: genetic and physiological characterization
Authors: Glassberg J , Meyer R R , Kornberg A
Published: January 2020

A mutation in the Escherichia coli gene for single-strand binding protein results in temperature-sensitive deoxyribonucleic acid replication (R. R. Meyer, J. Glassberg, and A. Kornberg, Proc. Natl. Acad. Sci. U.S.A. 76:1702-1705, 1979). The mutant (ssb-1) is also more sensitive to ultraviolet irradiation and about one-fifth as active in recombination. Single-strand binding protein is thus implicated in repair and recombination as well as in replication. The mutation in ssb is located between uvrA and melA at 90.8 min on the genetic map. The ssb gene appears to be allelic with lexC, a gene with a proposed role in regulating inducible deoxyribonucleic acid repair.
Regulation of O-acetylserine sulfhydrylase B by L-cysteine in Salmonella typhimurium
Authors: Hulanicka M D , Hallquist S G , Kredich N M , Mojica-A T
Published: January 2020

A technique based on resistance to azaserine was used to isolate mutants lacking O-acetylserine sulfhydrylase B, one of two enzymes in Salmonella typhimurium capable of synthesizing L-cysteine from O-acetyl-L-serine and sulfide. The mutant locus responsible for this defect has been designated cysM, and genetic mapping suggests that cysM is very close to and perhaps contiguous with cysA. Strains lacking either O-acetylserine sulfhydrylase B or the second sulfhydrylase, O-acetylserine sulfhydrylase A (coded for by cysK), are cysteine prototrophs, but cysK cysM double mutants were found to require cysteine for growth. O-Acetylserine sulfhydrylase B was depressed by growth on a poor sulfur source, and depression was dependent upon both a functional cysB regulatory gene product and the internal inducer of the cysteine biosynthetic pathway, O-acetyl-L-serine. Furthermore, a cysBc strain, in which other cysteine biosynthetic enzymes cannot be fully repressed by growth on L-cystine, was found to be constitutive for O-acetylserine sulfhydrylase B as well. Thus O-acetylserine sulfhydrylase B is regulated by the same factors that control the expression of O-acetylserine sulfhydrylase A and other activities of the cysteine regulon. It is not clear why S. typhimurium has two enzymes whose physiological function appears to be to catalyze the same step of L-cysteine biosynthesis.
Characterization of the Bacillus subtilis motile system driven by an artificially created proton motive force
Authors: Matsuura S , Shioi J I , Imae Y , Iida S
Published: January 2020

Transient swimming was induced in energy-depleted cells of Bacillus subtilis by an artificial proton motive force, which was created by valinomycin addition and a pH reduction. This system did not require any ions except protons in the medium. The size of the induced motility was strongly influenced by changes in the size of either the K+ diffusion potential or the pH gradient. A rough estimation indicated that a proton motive force higher than -100 mV was required for induction of translational swimming of the cell. Corresponding with the transient appearance of swimming, a rapid but transient efflux of K+ and influx of H+ were observed. With decreases in the rate of H+ influx, the amount of motility decreased. A rate of H+ influx higher than 0.2 mumol/s per ml of cell water gave translational swimming. These results suggest direct coupling of H+ influx to rotation of bacterial flagella.
Deletions in the r-determinant mer region of plasmid R100-1 selected for loss of mercury hypersensitivy
Authors: Foster T J , Nakahara H
Published: January 2020

A mutant of plasmid R100-1, which conferred cellular hypersensitivity to Hg2+ because of the insertion of Tn801 (TnA) into the gene determining synthesis of mercuric reductase enzyme, allowed further mutational events to be selected which resulted in either reversion to Hg2+ resistance (characteristic plasmid R100-1) or sensitivity at a level characteristic of plasmidless strains. Restriction endonuclease EcoRI and BamHI analysis showed that reversion to resistance resulted from loss of TnA from the R100-mer:Tn801 plasmid, whereas the change from hypersensitivity to sensitivity to Hg2+ usually resulted from deletion of part or all of Tn801 plus plasmid deoxyribonucleic acid sequences corresponding to the operator-proximal end of the mer operon.
Organization of transfer and ribosomal ribonucleic acid genes in Bacillus subtilis
Authors: Moran C P , Bott K F
Published: January 2020

The structural relationship between the transfer ribonucleic acid (tRNA) and the ribosomal RNA (rRNA) genes of Bacillus subtilis has been studied by restriction endonuclease analysis of total chromosomal deoxyribonucleic acid (DNA) and characterization of DNA fragments cloned in Escherichia coli. The DNA sequences encoding rRNA and tRNA were assayed by hybridization to radioactive RNA. The results support the conclusion that the tRNA genes are interspersed between and closely linked to the rRNA genes of B. subtilis. They probably do not appear between the 16S and 23S rRNA genes as in E. coli.
Effect of intracellular carbohydrates on heat resistance of Dictyostelium discoideum spores
Authors: Emyanitoff R G , Wright B E
Published: January 2020

The effect of intracellular trehalose and glycogen on the survival of spores of Dictyostelium discoideum ATCC 25697 after exposure to supraoptimal temperatures was examined. Cells metabolically perturbed by incubation in glucose and inorganic phosphate have intracellular trehalose and glycogen concentrations fivefold and twofold higher, respectively, than those of the controls. These cells were more resistant to the lethal effects of wet heat (45 degrees to 55 degrees C) than were control cells. The presence of 40 mM trehalose in the buffer during heat stress increased the survival of nonperturbed cells to approximately the level of the perturbed cells. No protection was observed when cells were heated in the presence of exogenous glycogen. Glucose or disaccharides other than trehalose when present during heat stress, had no effect on heat resistance. Nonperturbed cells preincubated in 40 mM trehalose and washed before heat stress were more resistant to killing than were controls. Cells perturbed with inorganic phosphate, which has been shown to increase trehalose concentrations but decrease glycogen concentrations, were also more resistant to the lethal effects of wet heat than were controls. The data suggest that trehalose has an effect on the wet-heat resistance of D. discoideum. Some possible mechanisms are suggested.
Requirement for peptidoglycan synthesis during sporulation of Bacillus subtilis
Authors: Dancer B N
Published: January 2020

Cultures of Bacillus subtilis were treated during sporulation with antibiotics (bacitracin and vancomycin) that affect peptidoglycan synthesis. The cells were resistant to the effects of the antibiotics only when the drugs were added about 2 h after the beginning of sporulation. This was about 1 h later than the escape time of a temperature-sensitive sporulation mutant that is unable to complete prespore septation. Similar experiments were done with a mutant temperature sensitive for peptidoglycan synthesis. This showed an escape curve similar to that shown by the antibiotics. When sporulating cells were treated with antibiotics, they produced alkaline phosphatase earlier than normal. Enzyme production was unaffected by inhibition of deoxyribonucleic acid synthesis but was inhibited by chloramphenicol. Sporulation mutants that are unable to make alkaline phosphatase under normal conditions were able to make it in the presence of bacitracin. The alkaline phosphatase made under these conditions was under "sporulation-type" control since its synthesis was repressible by casein hydrolysate and unaffected by inorganic phosphate. When cells were treated with bacitracin in the growth medium as well as in the sporulation medium, alkaline phosphatase synthesis was at the same level as in an untreated control. A number of other antibiotics and surfactants were tested for the ability to cause premature production of the phosphatase of those tested, only taurodeoxycholate whowed this behavior. Moreover, incubation of cells with taurodeoxycholate in the growth medium as well as in the sporulation medium prevented premature enzyme production.
Biosynthesis of phospholipids in Bacillus megaterium
Authors: Langley K E , Yaffe M P , Kennedy E P
Published: January 2020

Information on the biosynthesis of phospholipids in bacteria has been derived principally from the study of Escherichia coli and other gram-negative organisms. We have now carried out a detailed study of the pathways of phospholipid biosynthesis in the gram-positive organism Bacillus megarterium KM in relation to investigations on the biogenesis of lipid asymmetry in membranes. Radioactive precursors such as 32Pi and [3H]palmitate initially label phosphatidylethanolamine much more than phosphatidylglycerol. This raised the possibility that phosphatidylglycerol may be the precursor of phosphatidylethanolamine in a pathway different from that in E. coli. Phosphatidylglycerol is known to be highly reactive metabolically, since it functions as a donor of phosphatidyl residues in the synthesis of cardiolipin and as a donor of glycerophosphate residues in the synthesis of teichoic acids and of membrane-derived oligosaccharides. The large pool of phosphatidylglycerol would dilute the radioactive isotope, slowing the initial rate of incorporation of label into phosphatidylethanolamine. However, assays of cell-free extracts revealed no evidence for such a novel pathway. Instead, phosphatidylserine synthase (cytidine 5'-diphosphate-diglyceride:L-serine phosphatidyl transferase) and phosphatidylserine decarboxylase were detected, although at low levels. These results suggest that the pathway in B. megaterium is the same as that in E. coli in which phosphatidylserine, derived from cytidine 5'-diphosphate-diglyceride, is the precursor of phosphatidylethanolamine. The lag in the appearance of label in phosphatidylethanolamine appears to be the effect of a considerable pool of phosphatidylserine (ca. 5 to 10% of the total phospholipid) in certain strains of B. megaterium. The lag in labeling can be correlated with the size of the pool of phosphatidylserine. Pulse-chase experiments in vivo support the conclusion that in B. megaterium phosphatidylserine is not derived from phosphatidylglycerol. Rates of turnover of the membrane phospholipids of B. megaterium have also been studied.
Transient cell cycle arrest of Saccharomyces cerevisiae by amino acid analog beta-2-DL-thienylalanine
Authors: Bedard D P , Singer R A , Johnston G C
Published: January 2020

When treated with the amino acid analog beta-2-DL-thienylalanine, cells of the yeast Saccharomyces cerevisiae accumulated in the G1 portion of the cell cycle at the "start" event. This G1 arrest was accompanied by a rapid decrease in the rate of labeling of ribonucleic acid (RNA) with little effect on the rate of labeling of protein. When we examined which aspect of RNA metabolism was most affected by beta-2-DL-thienylalanine treatment, we found a dramatic decrease in the production of ribosomal precursor RNA. These results are consistent with previous findings which show a correlation between G1 arrest and reduced ribosomal precursor RNA production. The G1 arrest brought about be beta-2-DL-thienylalanine was transient; cells remain arrested in G1 only for several hours. Release from G1 arrest appeared to be accompanied either by metabolism or sequestration of the analog.
Bioconversion of m-hydroxybenzoate to 2,3-dihydroxybenzoate by mutants of Pseudomonas testosteroni
Authors: Daumy G O , McColl A S , Andrews G C
Published: January 2020

Mutans of Pseudomonas testosteroni were isolated for their inability to grow on m-hydroxybenzoate as sole carbon source. These mutants hydroxylated m-hydroxybenzoate for form 2,3-dihydroxybenzoate in high yeilds. The bioconversion described in this report represents the first reported example of 3-hydroxybenzoate 2-hydroxylase activity.
Guanosine pentaphosphate and guanosine tetraphosphate accumulation and induction of Myxococcus xanthus fruiting body development
Authors: Manoil C , Kaiser D
Published: January 2020

Development of multicellular fruiting bodies of Myxococcus xanthus can be induced by limitation of any of a number of different classes of amino acids. Investigated were amino acids that wild-type strains of M. xanthus are unable to synthesize (isoleucine, leucine, and valine), can synthesize at a low rate (phenylalanine), or can normally synthesize at an adequate rate (tryptophan and serine). In general, gradual rather than abrupt starvation for an essential amino acid was required for the induction of fruiting. Perhaps gradual starvation in general minimizes antagonism between amino acids present in the medium, as was documented for valine starvation. The previously reported induction of fruiting by a high concentration of threonine was shown to be specifically reversed by lysine. Threonine addition may starve cells for lysine by feedback inhibition of aspartokinase activity. Starvation for carbon-energy sources or inorganic phosphate also induced fruiting. As in other bacteria, amino acid starvation of M. xanthus leads to increases in cellular guanosine polyphosphate, usually consisting of large increases in the amount of guanosine pentaphosphate with smaller increases in the level of guanosine tetraphosphate. Guanosine polyphosphate accumulation is thus shown to be correlated with nutritional conditions that induce fruiting, and therefore may serve as an intracellular signal to trigger cells to end vegetative growth and initiate fruiting body development.
Oriented fragmentation of Escherichia coli sacculi by sonication
Authors: Verwer R W , Beachey E H , Keck W , Stoub A M , Poldermans J E
Published: January 2020

Isolated murein sacculi of Escherichia coli PA3092 were physically ruptured by sonication. Electron microscopical analysis showed that the rupturing occurred preferentially prependicular to the long axis of the cell. The fragmentation of the sacculi increased with longer sonication times. It was found that the extent of cross-linkage was more affected by the sonication than was the average glycan chain length. These data confirm earlier observations and indicate that the glycan chains run predominantly perpendicular to the long axis of the cell. By contrast, the peptide cross-links are more dispersely oriented.
Lipid-mediated glycosylation of endogenous proteins in isolated plasma membrane of Saccharomyces cerevisiae
Authors: Welten-Verstegen G W , Boer P , Steyn-Parvé E P
Published: January 2020

A highly purified plasma membrane fraction from Saccharomyces cerevisiae was obtained by centrifugation on discontinuous sucrose and Urografin gradients. This plasma membrane fraction was capable of glycosylating endogenous proteins. It is shown that glycolipids play an intermediate role in these glycosylation reactions; with uridine 5'-diphosphate-N-acetylglucosamine as sugar donor the intermediate lipids possessed stability towards alkali and chromatographic mobilities similar to polyprenyl diphosphate N-acetylglucosamine and polyprenyl diphosphate di-N-acetylchitobiose.
Involvement of periplasmic fibrils in motility of spirochetes
Authors: Paster B J , Canale-Parola E
Published: January 2020

Nonmotile (Mot-) strains of Spirochaeta aurantia and Spirochaeta halophila were isolated with a procedure involving mutagenesis of motile wild-type cells. Electron microscopy showed that a Mot- mutant strain of S. halophia possessed incomplete periplasmic fibrils, inasmuch as most or all of the filamentous portion of the periplasmic fibrils was absent. Some of the cells of this Mot-, fibril-defective mutant strain lacked the filamentous portion of the periplasmic fibrils and formed proximal hooks, whereas other cells appeared to have a very small segment of the filamentous portion of the periplasmic fibrils attached to the proximal hooks. Motile revertants were isolated repeatedly from cultures of the Mot-, fibril-defective mutant and from S. halophila Mot- mutants that completely lacked periplasmic fibrils. The motile revertants possessed periplasmic fibrils ultrastructurally indistinguishable from wild-type periplasmic fibrils. This study indicates that periplasmic fibrils play an essential role in the motility of spirochetes.
A stable plasmid carrying the yeast Leu2 gene and containing only yeast deoxyribonucleic acid
Authors: Toh-e A , Guerry-Kopecko P , Wickner R B
Published: January 2020

The plasmid pSLe1 is a deletion derivative of the yeast-Escherichia coli hybrid plasmid pJDB219, obtained by HindIII digestion, ligation, and transformation directly into Saccharomyces cerevisiae. pSLe1 has only yeast sequences; it contains one of the inverted repeated sequences of plasmid 2muDNA and the LEU2 gene. pSLe1 is stably maintained in yeast cells without selective pressure. pSLe1 is about half as large as 2muDNA, but pSLe1 does not displace the normal 2muDNA.
Cysteine transport and sulfite reductase activity in a germination-defective mutant of Histoplasma capsulatum
Authors: Howard D H , Dabrowa N , Otto V , Rhodes J
Published: January 2020

A mutant of the dimorphic, zoopathogenic fungus Histoplasma capsulatum, defective in the ability of its blastospores to germinate, was used to show that the nutritional requirement for cysteine and the expression of sulfite reductase activity are temperature dependent and not related to the growth form the fungus, whereas the kinetics of cysteine transport depend on both temperature and the form of the fungus.
Direct selection and analysis of mutational events which diminish the level of expression of the trp operon
Authors: Andrews J C , Somerville R L
Published: January 2020

A new procedure was devised for selecting, from lac+ galE strains of Escherichia coli, mutants resistant to galactoside-induced lysis. When applied to trp-lac fusions, our method yields down mutations in the trp promoter.
Growth Rate-Dependent Regulation of Transfer Ribonucleic Acid (5-Methyluridine)Methyltransferase in
Escherichia coli
B/r
Authors: Ny Tor , Björk Glenn R.
Published: January 2020

Enzymes catalyzing the transfer of methyl groups from
S
-adenosyl-
l
-methionine to a precursor transfer ribonucleic acid (tRNA) and forming 5-methyluridine (m
5
U), 1-methylguanine (m
1
G), or 5-methylaminomethyl-2-thio-uridine (mam
5
s
2
U) are denoted tRNA(m
5
U)-(EC 2.1.1.35), tRNA(m
1
G)-(EC 2.1.1.31), and tRNA(mam
5
s
2
U)methyltransferase. We have studied the regulation of these tRNA biosynthetic enzymes in
Escherichia coli
under various physiological conditions and in bacterial mutants known to affect the regulation of components of the translational apparatus. Such studies have revealed that tRNA(m
5
U)-methyltransferase increases with the growth rate in the same fashion as stable RNA, whereas the activity of two other tRNA methyltransferases remains constant in relation to the growth rate. Thus, these tRNA biosynthetic enzymes were not coordinately regulated. Regulation of both tRNA(m
5
U)methyltransferase and stable RNA was similar during shift-up and shift-down experiments. This enzyme showed a stringent regulation in
relA
+
strain (T. Ny and G. R. Björk, J. Bacteriol.
130:
635–641, 1977) but also in two temperature-sensitive mutants,
fusA
and
fusB
, known to influence the accumulation of guanosine 5′-diphosphate 3′-diphosphate and RNA synthesis at nonpermissive temperatures. The tRNA(m
5
U)methyltransferase showed a gene dose effect when its structural gene,
trmA
, was carried on a plasmid or on λ transducing phages. Although the regulation of tRNA-(m
5
U)methyltransferase was surprisingly coupled to that of stable RNA, this enzyme was expressed at a much lower level.
Roles of nifF and nifJ gene products in electron transport to nitrogenase in Klebsiella pneumoniae
Authors: Hill S , Kavanagh E P
Published: January 2020

Crude extracts of the wild-type Klebsiella pneumoniae reduced C2H2 with either pyruvate or formate as reductant (specific activity, 3 nmol min-1 mg of protein-1), whereas crude extracts of nifF mutant were almost inactive (specific activity, 0.05). However, activity in the latter extracts was stimulated by adding Azotobacter chroococcum flavodoxin (specific activity, 10). Thus, nifF mutants may lack an electron transport factor. Crude extracts of nifJ mutants had about 20% of the wild-type level of active MoFe protein, and thus nifJ has a presumptive role in maintaining active MoFe protein. Studies on pyruvate or formate as reductants for nitrogenase in extracts of the nifJ mutants suggest in addition a role in electron input to nitrogenase for the following reasons. (i) Nitrogenase activity with these reductants was very low (specific activity, 0.06) and was not stimulated by extra MoFe protein or the flavodoxin. (ii) Activity was increased by adding a crude extract of a mutant lacking the structural nif genes (specific activity, 1) or a crude extract of the nifF mutant (specific activity, 4).
Chemoautotrophic growth of hydrogen-uptake-positive strains of Rhizobium japonicum
Authors: Lepo J E , Hanus F J , Evans H J
Published: January 2020

Recently reported research from this laboratory has demonstrated the autotrophic growth of certain hydrogen-uptake-positive strains of Rhizobium japonicum and defined minimal conditions for such growth. Ribulose 1,5-bisphosphate carboxylase has been detected in autotrophically growing cells, but at low specific activity. Moreover, growth rates were low, and growth ceased at low cell densities. We report here improved autotrophic growth rates of R. japonicum SR through the use of a modified mineral salts/vitamins medium and a programmed increase in oxygen tension as autotrophic growth proceeds. Under these conditions, ribulose, 1,5-biphosphate carboxylase activity increased greater than 10-fold and crude-extract-uptake-hydrogenase activities were from 20 to 47 times those heretofore reported for free-living R. japonicum. It is likely that previous assays for these enzymes were done on preparations of cells in which their synthesis had been partially repressed. The contribution of CO2 fixation to organic carbon accumulation in autotrophic cells was assessed as sufficient to support observed growth. Enzymological determination of the product of carbon fixation has established a stoichiometric ratio of 1.9 mol of 3-phosphoglycerate per mol of CO2 fixed and unequivocally assigns the role of carbon fixation catalysis to ribulose 1,5-bisphosphate carboxylase. Ammonium served best as a nitrogen source, nitrate was less effective, and gaseous nitrogen would not support autotrophic growth. Ecological, evolutionary, and practical considerations of autotrophy in the rhizobia are briefly discussed in the light of our findings.
Isolation of Klebsiella aerogenes mutants cis-dominant for glutamine synthetase expression
Authors: Rothstein D M , Magasanik B
Published: January 2020

We have isolated three strains of Klebsiella aerogenes that failed to show repression of glutamine synthetase even when grown under the most repressing conditions for the wild-type strain. These mutant strains were selected as glutamine-independent derivatives of a strain that is merodiploid for the glnA region and contains a mutated glnF allele. The mutation responsible for the Gln+ phenotype in each strain was tightly linked to glnA, the structural gene for glutamine synthetase, and was dominant to the wild-type allele. These mutations are probably lesions in the control region of the glnA gene, since each mutation was cis-dominant for constitutive expression of the enzyme in hybrid merodiploid strains. Strains harboring this class of mutations were unable to produce a high level of glutamine synthetase unless they also contained an intact glnF gene, and unless cells were grown in derepressing medium. This study supports the idea that the glnA gene is regulated both positively and negatively, and that the deoxyribonucleic acid sites critical for positive control and negative control are functionally distinct.
Characterization and regulation of galactose transport in Neurospora crassa
Authors: Rand J B , Tatum E L
Published: January 2020

Two galactose uptake systems were found in the mycelia of Neurospora crassa. In glucose-grown mycelia, galactose was transported by a low-affinity (Km = 400 mM) constitutive system which was distinct from the previously described glucose transport system I (R. P. Schneider and W. R. Wiley, J. Bacteriol. 106:479--486, 1971). In carbon-starved mycelia or mycelia incubated with galactose, a second galactose transport activity appeared which required energy, had a high affinity for galactose (Km = 0.7 mM), and was shown to be the same as glucose transport system II. System II also transported mannose, 2-deoxyglucose, xylose, and talose and is therefore a general monosaccharide transport system. System II was derepressed by carbon starvation, completely repressed by glucose, mannose, and 2-deoxyglucose, and partially repressed by fructose and xylose. Incubation with galactose yielded twice as much activity as starvation. This extra induction by galactose required protein synthesis, and represented an increase in activity of system II rather than the induction of another transport system. Glucose, mannose, and 2-deoxyglucose caused rapid degradation of preexisting system II; fructose and xylose caused a slower degradation of activity.
Modifications of the envelope of Chlamydia psittaci during its developmental cycle: freeze-fracture study of complementary replicas
Authors: Louis C , Nicolas G , Eb F , Lefebvre J F , Orfila J
Published: January 2020

Examination of complementary replicas obtained by freeze-fracture of Chlamydia psittaci revealed, at the level of the plasma membrane, a progressive differentiation of "crate-like formations," which likely correspond to transmembranal pores. Recognition of "early" and "late" stages observed in the intermediate bodies permitted detailed study of the developmental cycle of this chlamydia.
Isolation and characterization of outer and inner membranes of Selenomonas ruminantium: lipid compositions
Authors: Kamio Y , Takahashi H
Published: January 2020

The isolation procedure and characterization of the outer and inner membranes from Selenomonas ruminatium cells, a strictly anaerobic bacterium, are described. The metabolic fate of [14C]decanoate incorporated into the outer and inner membranes was examined. The percent distribution of radioactivities in the outer and inner membranes was about 40 and 50% of the total incorporated activity, respectively. Approximately 47% of the radioactivity incorporated into the outer membrane was recovered in the phospholipid fraction, and the remaining radioactivity was found in both aqueous and phenol layers when the outer membrane was treated with phenol-water. In contrast to [14C]decanoate, the percent distribution of [3H]glycerol in the outer and inner membranes was about 25 and 70% of the total incorporated activity, respectively. Most of the assimilated 3H was located in the phospholipid fraction of both membranes. However, no significant label was detected in either the protein or cell wall fraction. The following observations were made concerning lipid compositions in the outer and inner membranes by chemical and isotopic analyses. (i) The outer and inner membranes contained no detectable phosphatidyl glycerol or cardiolipin. (ii) A prominent radioactive compound, designated band III lipid, was found mainly in the outer membrane as a major radioactive spot when cells were grown with [14C]decanoate. This lipid contained phosphorus, 2-keto-3-deoxyoctulosonic acid and 3-OH fatty acid but no detectable glycerol. This lipid was identified tentatively to be 2-keto-3-deoxyoctulosonic acid-lipid A. (iii) Although the ubiquity of phosphatidyl ethanolamine plasmalogen in both outer and inner membranes was confirmed, the occurrence of the molecular species of phosphatidyl ethanolamine plasmalogen was quite different in the outer and inner membranes.
Promoter Sequence for Stringent Control of Bacterial Ribonucleic Acid Synthesis
Authors: Travers Andrew A.
Published: January 2020

In bacterial promoters subject to stringent control the heptanucleotide sequence spanning nucleotide positions −5 to +2 (defining the −10 region [D. Pribnow, J. Mol. Biol.
99:
419–443, 1975] as positions −12 to −6) is highly conserved. This conserved region, for which the best consensus sequence is [Formula: see text] is absent from promoters which are not under stringent control.
Mapping of the
supP
(
Su6
+
) Amber Suppressor Gene in
Escherichia coli
Authors: Arnardóttir Ástrós , Thorbjarnardóttir Sigrídur , Eggertsson Gudmundur
Published: January 2020

The
supP
(
Su6
+
) amber suppressor gene has been mapped on the clockwise side of the
valS
locus near min 95 on the
Escherichia coli
chromosome.
Regulation of a glutamine amidotransferase subunit from Bacillus subtilis by a cloned trpE gene from Bacillus pumilus
Authors: Kane J F , Hill R J
Published: January 2020

The influence of a cloned trpE (trpE+p) gene from Bacillus pumilus on the expression of the gat locus in Bacillus subtilis was examined. The trpE gene was regulated by tryptophan and the mtr locus, which specifies the presumed aporepressor. The specific activity of subunit G varied directly with the level of subunit Ep, and the heterologous EpG complex that was formed was stable to gel filtration.
Extracellular proteases modify cell wall turnover in Bacillus subtilis
Authors: Jolliffe L K , Doyle R J , Streips U N
Published: January 2020

The rate of turnover of peptidoglycan in exponentially growing cultures of Bacillus subtilis was observed to be sensitive to extracellular protease. In protease-deficient mutants the rates of cell wall turnover were greater than that of wild-type strain 168, whereas hyperprotease-producing strains exhibited decreased rates of peptidoglycan turnover. The rate of peptidogylcan turnover in a protease-deficient strain was decreased when the mutant was grown in the presence of a hyperprotease-producing strain. The addition of phenylmethylsulfonyl fluoride, a serine protease inhibitor, to cultures of hyperprotease-producing strains increased their rates of cell wall turnover. Isolated cell walls of all protease mutants contained autolysin levels equal to or greater than that of wild-type strain 168. The presence of filaments, or cells with incomplete septa, was observed in hyperprotease-producing strains or when a protease-deficient strain was grown in the presence of subtilisin. The results suggest that the turnover of cell walls in B. subtilis may be regulated by extracellular proteases.
Intracellular location of catabolite activator protein of Escherichia coli
Authors: Cook D I , Revzin A
Published: January 2020

The catabolite activator protein was assayed in extracts from the minicell-producing Escherichia coli strain P678-54. The level of catabolite activator protein was found to be the same in both parent cells and purified minicells, regardless of whether the bacteria were grown on glucose (which leads to low intracellular cyclic adenosine monophosphate levels) or on glycerol-yeast extract or LB broth (which lead to high cyclic adenosine monophosphate concentrations in the cell). Thus, at any given time most catabolite activator protein molecules are found in the cytoplasm. The implications of this for the mechanism of catabolite activator protein action at catabolite-sensitive operons are discussed.
Acetate Kinase in the Genus
Veillonella
: Effect of Succinate, Serological Cross-Reactivity, and Separation by Electrophoresis
Authors: Yoshimura Fuminobu , Kasai Noriyuki , Sugawara Bin , Suzuki Takeshi
Published: January 2020

Acetate kinases from the genus
Veillonella
were divided into two types: a succinate-stimulated enzyme and a succinate-independent enzyme. Three strains,
V. parvula
ATCC 17743 (antigenic group II),
V. parvula
ATCC 17744 (V), and
V. parvula
ATCC 10790 (VI), contained the succinate-stimulated enzyme. Among four types strains of
V. alcalescens
, three strains, ATCC 17747 (I), ATCC 17746 (III), and ATCC 17748 (VII), contained the succinate-independent enzyme, whereas only one strain, ATCC 17745 (IV), contained the succinate-stimulated enzyme. Small amounts of antiserum to the purified acetate kinase from
V. alcalescens
ATCC 17748 completely inhibited the purified and crude enzyme activity from the strain. Classification of the enzymes on the basis of stimulation by succinate was consistent with classification based on serological reactions using the antiserum as an independent parameter. The succinate-stimulated enzyme could be separated into two classes according to the degree of sensitivity to succinate: (i) enzymes from
V. parvula
ATCC 17744 and
V. alcalescens
ATCC 17745, which could be demonstrated on gel after electrophoresis by a histochemical method to be highly stimulated by the presence of succinate in the reaction mixture, and (ii) enzymes from
V. parvula
ATCC 10790 and
V. parvula
ATCC 17743, which could be easily demonstrated without succinate. Four groups of acetate kinases from the genus
Veillonella
were separated by gel electrophoretic mobility. The results showed that almost all enzymes from the seven type strains were heterogeneous at the molecular level.
Control of phycobiliprotein proteolysis and heterocyst differentiation in Anabaena
Authors: Wood N B , Haselkorn R
Published: January 2020

Phycobiliprotein degradation can be initiated in cultures of the cyanobacterium Anabaena by removal of combined nitrogen from the medium. Certain strains of Anabaena differentiate cells specialized for aerobic nitrogen fixation (heterocysts) under such conditions. We describe here a procedure for the preparation of extracts from heterocysts or vegetative cells that contain an activity capable of degrading only the phycobiliproteins in a mixture of soluble Anabaena proteins in vitro. This activity increased under nitrogen starvation conditions or in ammonia-replete cultures treated with the glutamine synthetase inhibitor methionine sulfoximine. The increase in activity induced by nitrogen starvation was prevented by chloramphenicol or by carbon starvation. Under all these conditions, phycobiliprotein degradative activity assayed in vitro was correlated with the loss of phycobiliprotein absorbance in vivo. Finally, starvation of a met auxotroph of Anabaena for methionine (in the presence of ammonia) did not induce phycobiliprotein degradation in vivo or the increase in proteinase activity. Together with direct measurements of ppGpp, these results indicate that proteolysis in Anabaena is not controlled by compounds associated with the stringent response in Escherichia coli. Since the increase in proteinase activity appears to be regulated by the same variables that control heterocyst differentiation, the activity should provide a useful biochemical marker for the early events of differentiation.
Nitrogen regulation of acid phosphatase in Neurospora crassa
Authors: Grove G , Marzluf G A
Published: January 2020

Neurospora crassa possesses a repressible acid phosphatase with phosphodiesterase activity which appears to permit it to utilize ribonucleic acid as a phosphorus and as a nitrogen source. This acid phosphatase, which is specified by the pho-3 locus, is derepressed approximately eightfold during nitrogen limitation and to an even greater extent during phosphorus limitation, but is unaffected by sulfur limitation. Derepression of the enzyme did not occur when adenosine 5'-monophosphate was the sole phosphorus or nitrogen source. Synthesis of the acid phosphatase is not under the control of the nit-2 locus, which regulates the expression of a large number of other nitrogen catabolic enzymes. The structural gene of the acid phosphatase appears to be a member of both the phosphorus and nitrogen regulatory circuits.
Inititation and termination of chromosome replication in Escherichia coli subjected to amino acid starvation
Authors: Marsh R C , Hepburn M L
Published: January 2020

Initiation and termination of chromosome replication in an Escherichia coli auxotroph subjected to amino acid starvation were examined by following the incorporation of [3H]thymidine into the EcoRI restriction fragments of the chromosome. The pattern of incorporation observed upon restoration of the amino acid showed that starvation blocks the process of initiation prior to deoxyribonucleic acid synthesis within any significant portion of the EcoRI fragment which contains the origin of replication, oriC. In this experiment, no incorporation of [3H]thymidine into EcoRI fragments from the terminus of replication was observed, nor was it found when a dnaC initiation mutant was used to prevent incorporation at the origin which might have obscured labeling of terminus fragments. Thus amino acid starvation does not appear to block replication forks shortly before termination of replication. Attempted synchronization of replication initiation by including a period of thymine starvation subsequent to the amino acid starvation led to simultaneous incorporation of [3H]-thymidine into all EcoRI fragments within the 240-kilobase region that surrounds oriC. It is shown that the thymine starvation step allowed initiation and a variable, but limited, amount of replication to occur.
Deoxyribonucleic acid polymerase from the marine Pseudomonas sp. BAL-31
Authors: Vicuña R , Valdés F , Medina A , Yudelevich A
Published: January 2020

A deoxyribonucleic acid (DNA)-dependent DNA polymerase (DNA nucleotidyltransferase) was purified 3,000-fold from the marine Pseuodomonas sp. BAL-31. The molecular weight of the native enzyme was estimated by glycerol gradient sedimentation to be 110,000. The enzyme migrated in sodium dodecyl sulfate-acrylamide gels as a single polypeptide with a molecular weight of 105,000. An absolute requirement for divalent cation was satisfied by Mg2+ or Mn2+ at concentrations of 1 mM. Monovalent cations at concentrations higher than 50 mM showed an inhibitory effect. The polymerase activity was resistant to N-ethylmaleimide and showed a wide pH optimum.
Wavelength modulation of phycoerythrin synthesis in Synechocystis sp. 6701
Authors: de Marsac N T , Castets A M , Cohen-Bazire G
Published: January 2020

The spectral dependence of phycoerythrin synthesis has been studied in a unicellular photautotrophic cyanobacterium, Synechocystis sp. 6701, in which phycoerythrin synthesis alone is under chromatic control. Cells were partially depleted of their phycobiliprotein pigments through nitrate starvation in the light. Addition of nitrate to the culture medium allowed synthesis of phycobiliproteins in the dark. This synthesis occurred at the expense of the glycogen reserve accumulated during the period of nitrate starvation. Monochromatic irradiations of short duration at lambda less than 590 nm induced increased phycoerythrin synthesis during dark incubation. Monochromatic irradiations of short duration at lambda greater than 590 nm prevented this synthesis. These effects were photoreversible. The spectral distribution showed a maximum at 540 nm for the potentiation of phycoerythrin synthesis, and one at 640 nm for its photoreversal.
The recA+ gene product is more important than catalase and superoxide dismutase in protecting Escherichia coli against hydrogen peroxide toxicity
Authors: Carlsson J , Carpenter V S
Published: January 2020

Various deoxyribonucleic acid repair-deficient strains of Escherichia coli K-12 were exposed to hydrogen peroxide under anaerobic conling of the strains was determined. The level of catalase, peroxidase, and superoxide dismutase in cell-free extracts of the strains as well as the capacity of intact cells to decompose hydrogen peroxide were assayed, recA strains were more rapidly killed than other strains with deoxyribonucleic acid repair deficiencies. There was no correlation between the killing rate of the strains and the capacity of intact cells to decompose hydrogen peroxide or the level of catalase and superoxide dismutase in cell-free extracts. The level of peroxidase in cell-free extract was too low to be determined.
Lyticase: Endoglucanase and Protease Activities That Act Together in Yeast Cell Lysis
Authors: Scott Janet H. , Schekman Randy
Published: January 2020

Yeast lytic activity was purified from the culture supernatant of
Oerskovia xanthineolytica
grown on minimal medium with insoluble yeast glucan as the carbon source. The lytic activity was found to consist of two synergistic enzyme activities which copurified on carboxymethyl cellulose and Sephadex G-150, but were resolved on Bio-Gel P-150. The first component was a β-1,3-glucanase with a molecular weight of 55,000. The

K
m

for yeast glucan was 0.4 mg/ml; that for laminarin was 5.9 mg/ml. Hydrolysis of β-1,3-glucans was endolytic, yielding a mixture of products ranging from glucose to oligomers of 10 or more. The size distribution of products was pH dependent, smaller oligomers predominating at the lower pH. The glucanase was unable to lyse yeast cells without 2-mercaptoethanol or the second lytic component, an alkaline protease. Neither of these agents had any effect on the glucanase activity on polysaccharide substrates. The protease had a molecular weight of 30,000 and hydrolyzed Azocoll and a variety of denatured proteins. The enzyme was unusual in that it had an affinity for Sephadex. Although the activity was insensitive to most protease inhibitors, it was affected by polysaccharides; yeast mannan was a potent inhibitor. The enzyme did not have any mannanase activity, however. Neither pronase nor trypsin could substitute for this protease in promoting yeast cell lysis. A partially purified fraction of the enzymes, easily obtained with a single purification step, had a high lytic specific activity and was superior to commercial preparations in regard to nuclease, protease, and chitinase contamination. Lyticase has been applied in spheroplast, membrane, and nucleic acid isolation, and has proved useful in yeast transformation procedures.
Plasmid-mediated transformation in Bacillus megaterium
Authors: Brown B J , Carlton B C
Published: January 2020

A transformation system was developed for Bacillus megaterium by using antibiotic resistance plasmid deoxyribonucleic acid molecules derived from Staphylococcus aureus and Bacillus cereus. Lysozyme-generated protoplasts of B. megaterium allowed uptake of plasmid deoxyribonucleic acid in the presence of polyethylene glycol. Transformants expressed the antibiotic resistance determinants present on the plasmid deoxyribonucleic acid, and reisolated plasmid deoxyribonucleic acid yielded restriction endonuclease digestion patterns identical to those of the donor deoxyribonucleic acid.