bluuebunny/crossref_metadata_2025 huggingface dataset:
Conjugative transfer of multiple antibiotic resistance markers in Streptococcus pneumoniae
Authors: Buu-Hoï A , Horodniceanu T
Published: January 2020

Two antibiotic-resistant isolates of Streptococcus pneumoniae were investigated for conjugative transfer of their drug resistance markers into streptococcal (groups B and D) and pneumococcal (encapsulated and non-encapsulataed) recipients. Of these, 7 wild-type donor pneumococci transferred all their resistance markers (except Pc [penicillin], Su [sulfonamide], and Tp [trimethoprim]) into group D Streptococcus and non-encapsulated S. pneumoniae recipients at a low frequency (10(-5) to 10(-6)). The resistance markers transferred were Tc (tetracycline); Tc and Cm (chloramphenicol); Tc and MLS (macrolides, lincosamides, and streptogramin B); Tc, MLS, Km (kanamycin), and Cm. The transconjugants obtained retransferred their resistance markers into appropriate streptococcal or pneumococcal recipients or both. The resistance markers of streptococcal transconjugants could not be cured by chemical agents. All attempts to detect extra-chromosomal deoxyribonucleic acid from pneumococcal or streptococcal transconjugants were unsuccessful. The molecular weight of a streptococcal conjugative R plasmid (pIP501) was investigated after transfer into the non-encapsulated S. pneumoniae recipient and was found to be similar to that of the wild-type group B Streptococcus host (20 x 10(6)).
Glyoxylate cycle in Mucor racemosus
Authors: O'Connell B T , Paznokas J L
Published: January 2020

The dimorphic phycomycete Mucor racemosus was grown in media containing acetate, glutamate, and peptone as carbon sources. The component enzymes of the glyoxylate bypass, isocitrate lyase and malate synthase, were present under these conditions throughout the growth cycles. Highest specific activities for each enzyme were found in media with acetate as the carbon source. In an enriched peptone medium containing glucose, neither activity was detected until glucose was exhausted from the medium. Treatment of acetate-grown cells with glucose resulted in a rapid decline in the specific activities of both enzymes. The importance of this cycle in acetate-grown cells was indicated by the ability of itaconic acid (100 mM) to inhibit the growth of M. racemosus in acetate but not glutamate media. Itaconate was also shown to be a potent inhibitor of isocitrate lyase activity in vitro.
Transformation of Rhodopseudomonas sphaeroides with deoxyribonucleic acid isolated from bacteriophage R phi 6P
Authors: Tucker W T , Pemberton J M
Published: January 2020

The transformation of the photosynthetic bacterium Rhodopseudomonas sphaeroides with the circular genome of the penicillinase-encoding, temperate bacteriophage R phi 6P was demonstrated. The transformation was dependent on the infection of the recipient by another, apparently closely related, temperature bacteriophage, R phi 9. Optimum transformation occurred in the recipient cells already lysogenic for R phi 9 when superinfected with that bacteriophage at multiplicities of infection between 1 and 10 R phi 9 particles per recipient cell.
Microbiology of Methanogenesis in Thermal, Volcanic Environments
Authors: Zeikus J. G. , Ben-Bassat Arie , Hegge P. W.
Published: January 2020

Microbial methanogenesis was examined in thermal waters, muds, and decomposing algal-bacterial mats associated with volcanic activity in Yellowstone National Park. Radioactive tracer studies with [
14
C]glucose, acetate, or carbonate and enrichment culture techniques demonstrated that methanogenesis occurred at temperatures near 70°C but below 80°C and correlated with hydrogen production from either geothermal processes or microbial fermentation. Three
Methanobacterium thermoautotrophicum
strains (YT1, YTA, and YTC) isolated from diverse volcanic habitats differed from the neotype sewage strain ΔH in deoxyribonucleic acid guanosine-plus-cytosine content and immunological properties. Microbial methanogenesis was characterized in more detail at a 65°C site in the Octopus Spring algal-bacterial mat ecosystem. Here methanogenesis was active, was associated with anaerobic microbial decomposition of biomass, occurred concomitantly with detectable microbial hydrogen formation, and displayed a temperature activity optimum near 65°C. Enumeration studies estimated more than 10
9
chemoorganotrophic hydrolytic bacteria and 10
6
chemolithotrophic methanogenic bacteria per g (dry weight) of algal-bacterial mat. Enumeration, enrichment, and isolation studies revealed that the microbial population was predominantly rod shaped and asporogenous. A prevalent chemoorganotrophic organism in the mat that was isolated from an end dilution tube was a taxonomically undescribed gram-negative obligate anaerobe (strain HTB2), whereas a prevalent chemolithotrophic methanogen isolated from an end dilution tube was identified as
M. thermoautotrophicum
(strain YTB). Taxonomically recognizable obligate anaerobes that were isolated from glucose and xylose enrichment cultures included
Thermoanaerobium brockii
strain HTB and
Clostridium thermohydrosulfuricum
strain 39E. The nutritional properties, growth temperature optima, growth rates, and fermentation products of thermophilic bacterial strains 39E, HTB2, and YTB were determined.
Identification of peptide-cross-linked trisdisaccharide peptide trimers in murein of Escherichia coli
Authors: Gmeiner J
Published: January 2020

Purified murein from Escherichia coli K-12 was degraded into disaccharide peptide fragments by endo-N-acetylmuramidase from Chalaropsis. About 5% of the total murein fragments were recovered as peptide-cross-linked trisdisaccharide peptide trimers.
Separation of peptide transport and hydrolysis in trimethionine uptake by Saccharomyces cerevisiae
Authors: Parker D D , Naider F , Becker J M
Published: January 2020

Intact cells of Saccharomyces cerevisiae 139 hydrolyzed amino acid-p-nitroanilide by an activity similar to that of aminopeptidase II, as well-characterized external peptidase in yeast. In contrast, trimethionine, a model peptide used in transport assays, was not hydrolyzed by this aminopeptidase II-like activity, and the peptidase activity toward this substrate was localized in the soluble fraction of the yeast. We conclude that this tripeptide is taken up by S. cerevisiae intact and rapidly hydrolyzed inside the cell.
Deletion of a ribosomal ribonucleic acid operon in Escherichia coli
Authors: Ellwood M , Nomura M
Published: January 2020

One (rrnE) of the seven operons which codes for ribosomal ribonucleic acid in Escherichia coli was deleted. No significant change in phenotype was observed even under maximum laboratory growth conditions.
Proton-coupled calcium transport by intact cells of Azotobacter vinelandii
Authors: Barnes E M
Published: January 2020

Addition of ionophores to resting aerobic cultures of Azotobacter vinelandii OP resulted in 45Ca2+ uptake (Km = 60 microM Ca2+; Vmax 1.1 nmol/min per mg of cell protein) which was inhibited by cations (La3+ greater than Mn2+ greater than Sr2+ greater Ba2+). The rate of Ca2+ entry correlated with the magnitude of a transmembrane proton gradient (inside acid) which developed in the respective order: valinomycin less than tetrachlorosalicylanilide less than nigericin less than gramicidin D less than tetrachlorosalicylanilide plus valinomycin. A process of calcium-proton exchange (antiport) is responsible for calcium accumulation under these conditions.
Spontaneous emergence of an Hfr strain with a cit plasmid from natural isolates of citrate-positive Escherichia coli bovine origin
Authors: Ishiguro N , Oka C , Asagi M , Sato G , Yoshikawa M
Published: January 2020

From citrate-utilizing (Cit+) Escherichia coli strain C53 of bovine origin, strains C53A and C53B were obtained. Upon mating with recA+ but not with recA mutant recipients of K-12, C53A produced chromosomal recombinants at quite high frequencies, leading to the following conclusions: (i) C53A is an Hfr strain; (ii) the site of integration of the Cit plasmid (IncH1) is between metA (89 min) and ara (1 min); (iii) the direction of chromosome transfer is clockwise; and (iv) the plasmid-associated determinants are transferred as the terminal markers. A transductant of a dnaA(Ts) strain, CRT46, which acquired Cit determinants from a recombinant, SG13, was also an Hfr strain similar to SG13, and thermoresistant due to suppressive integration. On the other hand, unstable C53B did not produce recombinants, but the frequency of RecA-independent transfer of the Cit plasmid was high, indicating that the Cit plasmid (IncH1) exists autonomously in C53B. Attempts to isolate an Hfr strain from C53B failed.
Hydroxy fatty acids in Bacteroides species: D-(--)-3-hydroxy-15-methylhexadecanoate and its homologs
Authors: Mayberry W R
Published: January 2020

Acid hydrolysates of 140 strains, representing 11 species of the genus Bacteroides, were analyzed by capillary gas-liquid chromatography for total cellular fatty acid. All samples contained components which appeared to be hydroxy fatty acid. The relative amount and chain length distribution of the hydroxy fatty acids, as well as the nonhydroxy fatty acids, varied according to species. To characterize the presumed hydroxy acids, a composite of some 40 of these samples was analyzed by thin-layer and capillary gas-liquid chromatography, mass spectrometry, infrared spectrophotometry, and polarimetry. The hydroxy acids were shown to be of the D-(--)-3-hydroxy acid family. The predominant component was the iso-branched D-(--)-3-hydroxy-15-methylhexadecanoic acid. Lesser amounts of the iso-branched 15-carbon, straight-chain 16-carbon, and anteiso-branched 17-carbon acids were also found.
Pleiotropic glucose repression-resistant mutation in Saccharomyces carlesbergensis
Authors: Michels C A , Romanowski A
Published: January 2020

We describe the characterization of a mutation of the locus GLR1. This mutation allowed for (i) the glucose repression-insensitive synthesis ot the enzymes maltase, galactokinase, alpha-galactosidase, reduced nicotinamide adenine dinucleotide-cytochrome c reductase, and cytochrome c oxidase and (ii) growth on maltose in the presence of the gratuitous glucose repressor D-glucosamine. The glucosamine resistance cosegregated with the glucose-insensitive synthesis of the enzymes listed above. In addition, crosses between the glucosamine-resistant mutant and isogenic sensitive strains gave only tetrads containing two resistant and two sensitive spores. Thus, a single pleiotropic mutation is responsible for both phenotypes. We call the locus GLR1, for glucose regulation, and the glucose repression-insensitive mutation glr1-1.
Elevated levels of glyoxylate shunt enzymes in Escherichia coli strains constitutive for fatty acid degradation
Authors: Maloy S R , Bohlander M , Nunn W D
Published: January 2020

Mutants of Escherichia coli K-12 constitutive for the synthesis of the enzymes of fatty acid degradation (fadR) have elevated levels of the glyoxylate shunt enzymes, isocitrate lyase and malate synthase. A temperature-sensitive fadR strain has high levels of glyoxylate shunt enzymes when grown at elevated temperatures but has low, inducible levels of glyoxylate shunt enzymes when grown at low temperatures. The increased activity of glyoxylate shunt enzymes did not appear to be due to the degradation of intracellular fatty acids in fadR strains or differences in allosteric effectors in fadR versus fadR+ strains. These studies suggest that the fadR gene product may be involved in the regulation of the glyoxylate operon.
Glutamine-stimulated amino acid and peptide incorporation in Bacteroides melaninogenicus
Authors: Lev M
Published: January 2020

The uptake of a number of amino acids and dipeptides by cells and spheroplasts of Bacteroides melaninogenicus was stimulated by the presence of glutamine; 50 mM glutamine induced maximum uptake of glycine or alanine, and glutamine stimulated the uptake of glycine over a wide concentration range (0.17 to 170 mM). Glutamine stimulated the uptake of the dipeptides glycylleucine and glycylproline at significantly faster rates compared with glycine and leucine. The amino acids whose uptake was stimulated by glutamine were incorporated into trichloroacetic acid-precipitable material, and the inclusion of chloramphenicol or puromycin did not affect this incorporation. The uptake of glutamine by cells was concentration dependent. In contrast, in the absence of chloramphenicol 79% of the glutamine taken up by cells supplied with a high external concentration (4.4 mM) was trichloroacetic acid soluble. Glutamate and alpha-ketoglutarate were identified in the intracellular pool of glutamine-incubated spheroplasts. The amino acids and peptides were incorporated into cell envelope material, and a portion (30 to 50%) of the incorporated amino acids could be removed by trypsinization or treatment with papain. The effect of glutamine was depressed by inhibitors of energy metabolism, suggesting that glutamine-stimulated incorporation is an energy-mediated effect.
Cellular location of enzymes involved in chondroitin sulfate breakdown by Bacteroides thetaiotaomicron
Authors: Salyers A A , O'Brien M
Published: January 2020

Bacteroides thetaiotaomicron, a gram-negative anaerobe found in human colons, could utilize chondroitin sulfate, a tissue mucopolysaccharide, as its sole source of carbohydrate. The enzymes responsible for the breakdown of chondroitin sulfate by B. thetaiotaomicron were similar to those produced by Proteus vulgaris and Flavobacterium heparinum and included a lyase (EC 4.2.2.4), which degraded chondroitin sulfate into sulfated disaccharides, sulfatases (EC 3.1.6.4), which removed the sulfate residues, and a glucuronidase, which broke the unsulfated disaccharides into monosaccharide components. Chondroitin sulfate lyase, the first enzyme in the breakdown sequence, was not extracellular. It appeared to be located in the periplasmic space since lyase activity was released by treatment with ethylenediaminetetraacetate and lysozyme. Moreover, sodium polyanethole sulfonate, a high-molecular-weight inhibitor of chondroitin lyase, did not inhibit breakdown of chondroitin sulfate by intact bacteria. The sulfatase and glucuronidase appeared to be intracellular. None of these enzymes was strongly bound to membranes, and none of the steps in the breakdown of chondroitin sulfate was sensitive to oxygen.
Regulation of nitrogen utilization of hisT mutants of Salmonella typhimurium
Authors: Rosenfeld S A , Brenchley J E
Published: January 2020

Mutations in the hisT gene of Salmonella typhimurium alter pseudouridine synthetase I, the enzyme that modifies two uridines in the anticodon loop of numerous transfer ribonucleic acid species. We have examined two strains carrying different hisT mutations for their ability to grow on a variety of nitrogen sources. The hisT mutants grew more rapidly than did hisT+ strains with either arginine or proline as the nitrogen source and glucose as the carbon source. The hisT mutations were transduced into new strains to show that these growth properties were due to the hisT mutations. The hisT mutations did not influence the growth of mutants having altered glutamine synthetase regulation. Assays of the three primary ammonia-assimilatory enzymes, glutamate dehydrogenase, glutamine synthetase, and glutamate synthase, showed that glutamate synthase activities were lower in hisT mutants than in isogenic hisT+ controls; however, the glutamate dehydrogenase activity was about threefold higher in the hisT strains grown in glucose-arginine medium. The results suggest that the controls for enzyme synthesis for nitrogen utilization respond either directly or indirectly to transfer ribonucleic acid species affected by the hisT mutation.
Positive selection for loss of tetracycline resistance
Authors: Bochner B R , Huang H C , Schieven G L , Ames B N
Published: January 2020

A simple technique has been devised that allows direct plate selection of tetracycline-sensitive clones from a predominantly tetracycline-resistant population. The technique is especially useful in genetic methodologies based on the use of tetracycline resistance transposons, such as Tn10. Potential uses of the method include selection of deletion mutants, fine-structure mapping, generalized mapping, construction of multiply marked strains, elimination of tetracycline resistance transposons and plasmids and cloning. The technique is based on our finding that tetracycline-resistant cells are hypersensitive to lipophilic chelating agents, such as fusaric acid. This finding supports the contention that certain metal ions critically facilitate tetracycline uptake and leads us to suggest possible molecular mechanisms for tetracycline resistance.
In vitro gene fusions that join an enzymatically active beta-galactosidase segment to amino-terminal fragments of exogenous proteins: Escherichia coli plasmid vectors for the detection and cloning of translational initiation signals
Authors: Casadaban M J , Chou J , Cohen S N
Published: January 2020

We report the construction and use of a series of plasmid vectors suitable for the detection and cloning of translational control signals and 5' coding sequences of exogenously derived genes. In these plasmids, the first eight codons of the amino-terminal end of the lactose operon beta-galactosidase gene, lacZ, were removed, and unique BamHI, EcoRI, and SmaI (XmaI) endonuclease cleavage sites were incorporated adjacent to the eighth codon of lacZ. Introduction of deoxyribonucleic acid fragments containing appropriate regulatory signals and 5' coding sequences into such lac fusion plasmids led to the production of hybrid proteins consisting of the carboxyl-terminal segment of a beta-galactosidase remnant plus a peptide fragment that contained the amino-terminal amino acids encoded by the exogenous deoxyribonucleic acid sequence. These hybrid peptides retained beta-galactosidase enzymatic activity and yielded a Lac+ phenotype. Such hybrid proteins are useful for purifying peptide sequences encoded by exogenous deoxyribonucleic acid fragments and for studies relating the structure and function of specific peptide segments.
Correlation between size and age at different events in the cell division cycle of Escherichia coli
Authors: Koppes L J , Meyer M , Oonk H B , de Jong M A , Nanninga N
Published: January 2020

The variability of (i) the B period between birth and initiation of chromosome replication, (ii) the U period between initiation of chromosome replication and initiation of cell constriction, and (iii) the interdivision period (tau) have been estimated for slowly growing Escherichia coli B/r F. Cultures synchronized by the membrane elution technique were pulse-labeled with [3H]thymidine or continuously labeled with [3H]thymine. After fixation, the pattern of deoxyribonucleic acid replication was analyzed by electron microscopic radioautography. Cell length was found to increase exponentially with age at two different slow growth rates. The coefficient of variation of the B period was estimated to be 60%, that of the U period was 29%, and that of the interdivision period was 12%. From these values and the coefficient of variation of length at different cell cycle events were calculated a negative correlation between the B and U period (r = -0.9) and a positive correlation between length at birth and cell separation (r = 0.6). Initiation of chromosome replication and cell constriction were strictly correlated both with respect to age (r = 0.7) and length (r = 0.8). On the other hand, length at initiation of chromosome replication was distantly correlated with age (r = 0.1) or length at birth (r = 0.3). This low correlation excludes a model in which chromosome initiation is controlled by a random event in the B period. It favors a model in which chromosome initiation occurs at a particular distributed size independent of cell division.
Kinetics and regulation of cell-free alkaline phosphatase synthesis
Authors: Pratt C
Published: January 2020

Regulation of alkaline phosphatase (EC 3.1.3.1) synthesis in a cell-free system from Escherichia coli has been observed. Synthesis from transducing phage deoxyribonucleic acid templates carrying phoA+ occurred in S30 fractions from wild-type or alkaline phosphatase-constitutive mutants. It did not occur in S30) fractions from alkaline phosphatase-negative mutants (phoB). The hybrid gene phoA-lacZ was also subject to phoB control, implying that phoA transcription is regulated. The yield of active alkaline phosphatase per phoA+ gene copy from cell-free synthesis was similar to that of beta-galactosidase. Alkaline phosphatase activity took longer to appear than beta-galactosidase activity. Synthesis of alkaline phosphatase subunits was not delayed, suggesting that a minimum number of subunits are synthesized before formation of active alkaline phosphatase occurs.
Reserve carbohydrate metabolism in Saccharomyces cerevisiae: responses to nutrient limitation
Authors: Lillie S H , Pringle J R
Published: January 2020

The amounts of glycogen and trehalose have been measured in cells of a prototrophic diploid yeast strain subjected to a variety of nutrient limitations. Both glycogen and trehalose were accumulated in cells deprived specifically of nirogen, sulfur, or phosphorus, suggesting that reserve carbohydrate accumulation is a general response to nutrient limitation. The patterns of accumulation and utilization of glycogen and trehalose were not identical under these conditions, suggesting that the two carbohydrates may play distinct physiological roles. Glycogen and trehalose were also accumulated by cells undergoing carbon and energy limitation, both during diauxic growth in a relatively poor medium and during the approach to stationary phase in a rich medium. Growth in the rich medium was shown to be carbon or energy limited or both, although the interaction between carbon source limitation and oxygen limitation was complex. In both media, the pattern of glycogen accumulation and utilization was compatible with its serving as a source of energy both during respiratory adaptation and during a subsequent starvation. In contrast, the pattern of trehalose accumulation and utilization seemed compatible only with the latter role. In cultures that were depleting their supplies of exogenous glucose, the accumulation of glycogen began at glucose concentrations well above those sufficient to suppress glycogen accumulation in cultures growing with a constant concentration of exogenous glucose. The mechanism of this effect is not clear, but may involve a response to the rapid rate of change in the glucose concentration.
Novel mutant of Anabaena sp. strain CA which growns on N2 but not on combined nitrogen
Authors: Gotto J W , Tabita F R , Van Baalen C
Published: January 2020

A mutant has been isolated from Anabaena sp. strain CA by treatment with N-methyl-N'-nitro-N-nitrosoguanidine, which has the unusual phenotypic characteristic of growth only under N2-fixing conditions. Growth of the mutant was completely inhibited by NO3- or NH4+ at concentrations routinely used for growth of the wild type, and sensitivity to NH4+ was especially pronounced. The inhibitory effect of NH4+ could not be overcome by glutamine, glutamate, or casein hydrolysate. Ammonia had no immediate inhibitory effect on protein synthesis, CO2 fixation, or O2 evolution, and the gradual inhibition of C2H2 reduction activity by NH4+ resembled a repression phenomenon. The glutamine synthetase activity of N2-fixing cultures appeared normal, yet the mutant was incapable of utilizing exogenous NH4+ for growth. Preliminary evidence suggests a possible alteration of glutamine synthetase, which could result in sensitivity to exogenous NH4+ by progressive inactivation of the enzyme or repression of its synthesis.
tonB-independent ferrichrome-mediated iron transport in Escherichia coli spheroplasts
Authors: Weaver C A , Konisky J
Published: January 2020

Although a functional tonB gene product was required for ferrichrome-mediated iron transport in whole cells of Escherichia coli K-12, such transport did not require the tonB+ function in spheroplasts. We suggest that in spheroplasts ferrichrome has direct access to the cytoplasmic membrane and that this is reflected in tonB-independent accumulation of ferrichrome iron. Therefore, the tonB gene product does not function in the translocation of ferrichrome iron across the inner membrane.
Intermediate location in the assembly of the matrix protein or porin into the outer membrane of Escherichia coli
Authors: Boyd A , Holland I B
Published: January 2020

Evidence from pulse-chase experiments indicates that the outer membrane matrix protein or porin of Escherichia coli B/r passes through a Sarkosyl-soluble membrane pool on the way to its eventual Sarkosyl-insoluble state in the outer membrane.
Cellular distribution and linkage of D-(-)-3-hydroxy fatty acids in Bacteroides species
Authors: Mayberry W R
Published: January 2020

Two strains of Bacteroides asaccharolyticus and two strains of Bacteroides fragilis were analyzed for total fatty acid, total lipid fatty acid, and total bound fatty acid profiles. Extracted lipids and defatted cell residues were subjected to sequential alkaline and acid methanolyses to distinguish ester- and amide-linked fatty acids in each fraction. In the lipid fractions, all the ester-linked fatty acids were nonhydroxylated, whereas all of the amide-linked fatty acids were hydroxylated. In the nonextractable fractions, both hydroxy and nonhydroxy fatty acids were found in both ester and amide linkage, although hydroxy acids predominated. The fatty acid profiles of the bound fractions differed widely from those of the lipid fractions. Bound fatty acid represented approximately 10% of the total cellular fatty acids.
Regulation of cytoplasmic and mitochondrial leucyl-transfer ribonucleic acid synthetases in Neurospora crassa
Authors: Gross S R , Horn E W
Published: January 2020

The production of cytoplasmic leucyl-transfer ribonucleic acid synthetase activity was found to be reciprocally proportional to that of the corresponding mitochondrial enzyme during logarithmic growth of strains of Neurospora crassa with normal mitochondria. In the presence of cni-3 mutant mitochondria, production of mitochondrial enzyme activity was greatly increased whereas cytoplasmic enzyme production remained constant. The effect of cni-3 on the yield of the two enzyme activities indicated that the regulatory mechanism involved is a complicated one that cannot be accounted for by the relatively simple transcription competition model proposed previously.
The positional distribution of fatty acids in Escherichia coli phospholipids is not regulated by sn-glycerol 3-phosphate levels
Authors: Goelz S E , Cronan J E
Published: January 2020

Large changes in the intracellular concentration of sn-glycerol 3-phosphate had no effect on the acyl chain distribution of the phospholipids of Escherichia coli. This result directly contradicts the prediction by other workers based on in vitro experiments.
Genetic analysis of Escherichia coli K-12 chromosomal mutants defective in expression of F-plasmid functions: identification of genes cpxA and cpxB
Authors: McEwen J , Silverman P
Published: January 2020

Two temperature-sensitive, chromosomal mutants of Escherichia coli were selected for their inability to express deoxyribonucleic acid donor activity and other activities associated with the conjugative plasmid F. These mutants were also auxotrophic for isoleucine and valine at 41 degrees C. Each mutant strain contained two altered genes: cpxA, located at 88 min on the E. coli K-12 genetic map, and cpxB, located at 41 min. Mutations in both genes were required for maximal expression of mutant phenotypes. The parent strain of mutants KN401 and KN312 already contained the cpxB mutation that is present in both mutants (cpxB1). This mutation by itself was cryptic. The cpxA mutations represent different mutant alleles since they are of independent origin. A cpxA mutation by itself significantly affected the expression of plasmid functions and growth at 41 degrees C in the absence of isoleucine and valine, but strains containing both a cpxA and cpxB mutation were more severely affected. Along with the observation that both cpxA mutations were revertable, the temperature sensitivity of cpxA cpxB+ cells suggests that both cpxA alleles contain point mutations that do not completely destroy the activity of the cpxA gene product.
Instability in
tyrR
Strains of Plasmids Carrying the Tyrosine Operon: Isolation and Characterization of Plasmid Derivatives with Insertions or Deletions
Authors: Rood Julian I. , Sneddon Margaret K. , Morrison John F.
Published: January 2020

The transformation of
tyrR
strains of
Escherichia coli
with multicopy plasmids which carry the tyrosine operon gave rise to modified plasmids with either insertions or deletions. The effect of each of these insertions or deletions was to decrease the level of expression of this operon. It is proposed that plasmid instability arose as a direct consequence of the metabolic effects of an overproduction of the enzymes coded for by the tyrosine operon. The results have significant implications for the cloning of genes that are repressed by the product of a regulatory gene. Since the predominant plasmid modification observed was the insertion of an IS
1
element near the regulatory region of the tyrosine operon, the results also suggest a role for IS
1
elements in the regulation of gene expression.
dnaA alleles are recessive
Authors: Wechsler J A
Published: January 2020

Dominance tests of several dnaA alleles from Escherichia coli, including two previously reported to be dominant, show that all of the mutant alleles examined are recessive to dnaA+.
Temperature-sensitive glutamate dehydrogenase mutants of Salmonella typhimurium
Authors: Dendinger S M , Brenchley J E
Published: January 2020

Mutants of Salmonella typhimurium defective in glutamate dehydrogenase activity were isolated in parent strains lacking glutamate synthase activity by localizcd mutagenesis or by a general mutagenesis combined with a cycloserine enrichment for glutamate auxotrophs. Two mutants with temperature-sensitive phenotypes had glutamate dehydrogenase activities that were more thermolabile than that of an isogenic control strain. Eight other mutants had less than 10% of the wild-type glutamate dehydrogenase activity. All the mutations were cotransducible with a Tn10 element (zed-2:Tn10) located at approximately 23 U on the S. typhimurium linkage map. These data strongly indicate that this region contains the structural gene (gdhA) for glutamate dehydrogenase.
Histidine starvation and adenosine 5'-triphosphate depletion in chemotaxis of Salmonella typhimurium
Authors: Galloway R J , Taylor B L
Published: January 2020

Starvation for histidine prevented tumbling in Salmonella typhimurium hisF auxotrophs, including constantly tumbling strains with an additional mutation in cheB or cheZ. However, histidine-starved cheZs hisF strains were not defective in flagellar function or the tumbling mechanism since freshly starved auxotrophs tumbled in response to a variety of repellents. Tumbling in histidine-starved S. typhimurium could be restored in 13 s by addition of adenine or in 4 min by addition of histidine. Chloramphenicol did not prevent restoration of tumbling by these substances. Assays of adenosine 5'-triphosphate were performed based upon previous demonstration of adenine depletion in hisF auxotrophs starved for histidine. The adenosine 5'-triphosphate concentration dropped rapidly during the course of starvation, falling to less than 5% of the initial level as the cells ceased tumbling entirely. The change to smooth motility was prevented by 2-thiazolealanine, which inhibits phosphoribosyltransferase, thereby preventing adenine depletion during histidine starvation. These results suggest that an adenosine 5'-triphosphate deficiency was responsible for the change in tumbling frequency.
Enzyme changes during Bacillus subtilis sporulation caused by deprivation of guanine nucleotides
Authors: Vasantha N , Freese E
Published: January 2020

When sporulation is initiated by nutrient limitation, e.g., at the end of growth, certain biochemical processes occur in sequence. To determine which of these processes occur, even when the cells sporulate in the presence of a rapidly metabolizable carbon source, we induced sporulation of Bacillus subtilis by deprivation of guanine nucleotides, in a synthetic medium containing excess glucose, ammonium ions, and phosphate. The deprivation was produced either by decoyinine addition to a standard strain or by guanosin limitation of a guanine auxotroph. At 1 h after the onset of this deprivation, an extensive turnover of proteins began whose appearance was chloramphenicol sensitive. At least one enzyme (aspartate transcarbamylase) lost 70% of its activity within 15 min, indicating its rapid destruction. Whereas the magnitude of the above two changes was similar to that observed during sporulation at the end of growth in nutrient sporulation medium, protease (intracellular and extracellular) increased to less than one-tenth of the specific activity in nutrient sporulation medium, and alkaline phosphatase increased to less than one-half. However, glucose dehydrogenase, an enzyme made only in forespores, increased to the same specific activity under both conditions, presumably because the forespore compartment is protected from media (e.g., glucose) influences by the double membrane (two bilayers with opposite polarity).
Cadaverine is covalently linked to peptidoglycan in Selenomonas ruminantium
Authors: Kamio Y , Itoh Y , Terawaki Y , Kusano T
Published: January 2020

Cadaverine was found to exist as a component of cell wall peptidoglycan of Selenomonas ruminantium, a strictly anaerobic bacterium. [14C]cadaverine added to the growth medium was incorporated into the cells, and about 70% of the total radioactivity incorporated was found in the peptidoglycan fraction. When the [14C]cadaverine-labeled peptidoglycan preparation was acid hydrolyzed, all of the 14C counts were recovered as cadaverine. The [14C]cadaverine-labeled peptidoglycan preparation was digested with lysozyme into three small fragments which were radioactive and were positive in ninhydrin reaction. One major spot, a compound of the fragments, was composed of alanine, glutamic acid, diaminopimelic acid, cadaverine, muramic acid, and glucosamine. One of the two amino groups of cadaverine was covalently linked to the peptidoglycan, and the other was free. The chemical composition of the peptidoglycan preparation of this strain was determined to be as follows: L-alanine-D-alanine-D-glutamic acid-meso-diaminopimelic acid-cadaverine-muramic acid-glucosamine (1.0:1.0:1.0:1.0:1.1:0.9:1.0).
Regulation of nitrogen fixation in Klebsiella pneumoniae: isolation and characterization of strains with nif-lac fusions
Authors: MacNeil D , Zhu J , Brill W J
Published: January 2020

Strains with lac fused to each of the seven nif operons were isolated by two different methods. Repressing conditions prevented expression of all nif operons, whereas derepressing conditions led to the expression of all nif operons. No differences in Nif regulation were observed between Escherichia coli and Klebsiella pneumoniae with the same nif-lac fusions. Most derivatives of nif-lac fusion strains selected on lactose and NH4+ contained nif operator mutations. Some derivative contained deletions, which establishes that the direction of transcription of all seven nif operons is toward his
Genetic analysis of the RecE pathway of genetic recombination in Escherichia coli K-12
Authors: Gillen J R , Willis D K , Clark A J
Published: January 2020

The RecE pathway of genetic recombination in Escherichia coli K-12 was defined to be the pathway that is utilized in deoxyribonucleic acid exonuclease V (ExoV)-defective cells which express constitutively recE+, the structural gene for deoxyribonucleic acid exonuclease VIII. Dependence on ExoVIII was shown by the occurrence in a recB21 sbcA23 strain of recombination deficiency mutations in recE, the structural gene for ExoVIII. Point mutations in recE were found as well as deletion mutations in which the entire Rac prophage, carrying recE, was lost. In addition, strain construction and mutagenesis revealed the dependence of the RecE pathway on recA+ and on recF+. Dependence on a fourth gene was shown by a mutation (rec-77) which does not map near the other genes. The problem of distinguishing the RecE pathway from that previously called RecF is discussed.
Elaboration of cellulose fibrils by Agrobacterium tumefaciens during attachment to carrot cells
Authors: Matthysse A G , Holmes K V , Gurlitz R H
Published: January 2020

The attachment of virulent strains of Agrobacterium tumefaciens to plant cells is the first step in the bacterial induction of tumors. Binding of A. tumefaciens to carrot tissue culture cells occurred as a two-step process. The initial step was the attachment of the bacteria to the plant cell wall. Living plant cells were not required. Bacterial attachment to heat-killed or glutaraldehyde-fixed carrot cells proceeded with only slightly altered kinetics and unaltered bacterial strain specificity. After the bacteria bound to the carrot cell surface, scanning electron microscopy showed that fibrils developed, surrounded the bacteria, and anchored them to the plant cell surface. These fibrils were synthesized by the bacteria and not by the plant cell since they were also made after the attachment of A. tumefaciens to dead carrot cells and since under some conditions the bacteria synthesized fibrils in the absence of plant cells. Calcofluor staining, acid hydrolysis, enzymatic digestion studies, and infrared spectroscopy showed that the fibrils were composed of cellulose. The formation of these cellulose fibrils occurred during the attachment of virulent strains of A. tumefaciens to plant cells in vitro. The fibrils anchored the bacteria to the plant cell surface and entrapped additional bacteria. The multiplication of entrapped and attached bacteria resulted in the formation of large clusters of bacteria held close to the plant cell wall and plasma membrane by cellulose fibrils. This high concentration of bacteria may facilitate transfer of Ti plasmid deoxyribonucleic acid to the plant cell resulting in the formation of tumors.
Pseudomonas aeruginosa outer membrane: peptidoglycan-associated proteins
Authors: Hancock R E , Irvin R T , Costerton J W , Carey A M
Published: January 2020

The Pseudomonas aeruginosa outer membrane was isolated with attached peptidoglycan and fractionated with Triton X-100, ethylenediaminetetraacetate, and lysozyme. The data suggest that major outer membrane proteins F, H2, and I are noncovalently associated with the peptidoglycan.
Globomycin sensitivity of Escherichia coli and Salmonella typhimurium: effects of mutations affecting structures of murein lipoprotein
Authors: Lai J S , Philbrick W M , Hayashi S , Inukai M , Arai M , Hirota Y , Wu H C
Published: January 2020

The sensitivity of strains of Escherichia coli and Salmonella typhimurium to globomycin is increased in mutants defective in the lipopolysaccharide structure. E. coli mutants altered in the structures or biosynthesis of murein lipoprotein are more resistant to globomycin than the parental strains.
Inactivation of transforming Bacillus subtilis deoxyribonucleic acid by monoadducts of 4,5',8-trimethylpsoralen
Authors: te Riele H P , van Sluis P , Venema G
Published: January 2020

4,5',8-Trimethylpsoralen (TMP) monoadducts inactive transforming deoxyribonucleic acid (DNA) in Bacillus subtilis. Contrary to TMP diadducts (TMP cross-links), which severely inhibit entry of donor DNA (G. Venema and U. Canosi, Mol. Gen. Genet. 179:1--11), TMP monoadducts have only a slight effect on entry. Since reextracted TMP-monoadduct-containing transforming DNA is a differentially repaired by Uvr- and Uvr+ recipients and cross-linkable to the recipient strand in the heteroduplex recombinant DNA molecules, the monoadducts can be integrated along with the donor DNA into the recipient chromosome.
Transductional mapping of ksgB and a new Tn5-induced kasugamycin resistance gene, ksgD, in Escherichia coli K-12
Authors: Fouts K E , Barbour S D
Published: January 2020

We have mapped the Escherichia coli ksgB gene to min 36.5, 0.8 min from man and 0.7 min from aroD. A new kasugamycin resistance (Ksgr) gene, ksgD, has been isolated, using a transposon, Tn5. ksgD::TN5 is 44% cotransducible with sbcA, unlinked to trp, and unlinked to man (by P1 transduction). The ksgD::Tn5 has a late time of entry from HfrB7 (PO43). These data place ksgD clockwise from sbcA (which enters early from HfrB7) at min 30.4. The reistance of ksgB ksgD single and double mutant strains has been quantitated. Single mutations, ksgB or ksgD, gave resistance to 600 micrograms of kasugamycin per ml, whereas a ksgB ksgD strain was able to grow in the presence of kasugamycin levels in excess of 3,000 micrograms/ml. This indicates that the mechanisms of resistance coded for by the two genes are independent and synergistic.
Identification and cloning of the genetic determinant that encodes for the K88ac adherence antigen
Authors: Shipley P L , Dougan G , Falkow S
Published: January 2020

Strains of Escherichia coli capable of causing diarrhea in young pigs are often able to proliferate in the upper small intestine of the infected animal due to the presence of a specific surface antigen, K88. The genetic determinants for K88 antigen production and the ability to utilize the trisaccharide raffinose (Raf) are carried on a 50-megadalton plasmid. Recombinant deoxyribonucleic acid techniques were used to insert an 8.2-megadalton HindIII fragment carrying the K88ac gene(s) from the K88/Raf plasmid pPS100 into the vector pBR322. At lease six polypeptides encoded by this fragment were expressed in minicells. These polypeptides ranged in size from 18,000 to 70,000 daltons. The K88ac antigenic subunit, which has an apparent molecular weight of 23,500, was identified by immunoprecipitation with staphylococcal protein A as the coprecipitant.
Cyclic adenosine 3',5'-monophosphate levels in Pseudomonas putida and Pseudomonas aeruginosa during induction and carbon catabolite repression of histidase synthesis
Authors: Phillips A T , Mulfinger L M
Published: January 2020

Inducibility of histidase (histidine ammonia-lyase, EC 4.3.1.3) in Pseudomonas putida and Pseudomonas aeruginosa was observed to be strongly affected by succinate-provoked catabolite repression, but this did not occur as a consequence of reduced intracellular cyclic adenosine 3',5'-monophosphate levels, and repression could not be alleviated by exogenously added cyclic adenosine 3,'5'-monophosphate. Milder repression of histidase by lactate was also not reversed by the addition of cyclic adenosine 3',5'-monophosphate. These results, along with data showing intracellular cyclic adenosine 3',5'-monophosphate levels remained essentially constant during growth on such diverse carbon sources as histidine, acetamide, glucose, and succinate, indicated that catabolite repression of histidase synthesis by efficient carbon sources was not mediated through variations in internal cyclic adenosine 3,'5'-monophosphate.
Influence of corrinoid antagonists on methanogen metabolism
Authors: Kenealy W , Zeikus J G
Published: January 2020

Iodopropane inhibited cell growth and methane production when Methanobacterium thermoautotrophicum, Methanobacterium formicicum, and Methanosarcina barkeri were cultured on H2-CO2. Iodopropane (40 microM) inhibited methanogenesis (30%) and growth (80%) when M. barkeri was cultured mixotrophically on H2-CO2-methanol. The addition of acetate to the medium prevented the observed iodopropane-dependent inhibition of growth. The concentrations of iodopropane that caused 50% inhibition of growth of M. barkeri on either H2-CO2, H2-CO2-methanol, methanol, and acetate were 112 +/- 6, 24 +/- 2, 63 +/- 11, and 4 +/- 1 microM, respectively. Acetate prevented the iodopropane-dependent inhibition of one-carbon metabolism. Cultivation of M. barkeri on H2-CO2-methanol in bright light also inhibited growth and methanogenesis to a greater extent in the absence than in the presence of acetate in the medium. Acetate was the only organic compound examined that prevented iodopropane-dependent inhibition of one-carbon metabolism in M. barkeri. The effect of iodopropane and acetate on the metabolic fates of methanol and carbon dioxide was determined with 14C tracers when M. barkeri was grown mixotrophically on H2-CO2-methanol. The addition of iodopropane decreased the contribution of methanol to methane and cell carbon while increasing the contribution of CO2 to cell carbon. Regardless of iodopropane, acetate addition decreased the contribution of methanol and CO2 to cell carbon without decreasing their contribution to methane. The corrinoid antagonists, light and iodopropane, appeared most specific for methanogen metabolic reactions involved in acetate synthesis from one-carbon compounds and acetate catabolism.
Gene organization around the phenylalanyl-transfer ribonucleic acid synthetase locus in Escherichia coli
Authors: Comer M M
Published: January 2020

The organization of seven genes located at about 38 min on the genetic map of Escherichia coli was examined; these genes included pheS and pheT, which code for the alpha and beta subunits of phenylalanyl-transfer ribonucleic acid synthetase, and thrS, the structural gene for threonyl-transfer ribonucleic acid synthetase. Deletion mutants were isolated from an F-prime-containing merodiploid strain and were characterized genetically. Seventeen different kinds of deletions extending into pheS of pheT were identified. These deletions unambiguously defined the gene order as aroD pps himA pheT pheS thrS pfkB. Mutants with deletions covering either pheS or pheT, but not both, were analyzed further by assay of phenylalanyl-transfer ribonucleic acid synthetase. The phenotype of the mutants with a deletion from pfkB through pheS was anomalous; although the pheT gene was apparently still present, its product, the beta subunit, was much reduced in activity.
Recovery of competence in calcium-limited Azotobacter vinelandii
Authors: Page W J , Doran J L
Published: January 2020

Azotobacter vinelandii cells required 0.5 mM calcium in the iron-limited competence induction medium. This requirement also was fulfilled by strontium, but not by magnesium. Cells pregrown in competence medium lacking calcium rapidly recovered competence with the addition of 0.5 mM calcium, provided they were suspended in the growth supernatant. A 60,000-dalton glycoprotein (pI 5.10) present in competent or incompetent culture supernatants participated in calcium-mediated competence recovery. Cells grown in calcium-limited medium appeared to have leaky cell envelopes and released a diverse array of proteins into the culture supernatant and into distilled water washes of the cells, seven of which appeared to be more dominant in competent cells. Two distilled water washes of cells grown in calcium-limited medium did not prevent calcium-mediated recovery of competence in the culture supernatant. Four to six distilled water washes removed a competence-specific protein (pI 5.19) and prevented calcium-mediated recovery of competence in the culture supernatant.