bluuebunny/crossref_metadata_2025 huggingface dataset:
Transcription of the hut operons of Salmonella typhimurium
Authors: Cooper T G , Tyler B
Published: January 2020

We have measured, by ribonucleic acid-deoxyribonucleic acid hybrid formation, the amounts of hut-specific ribonucleic acid contained in extracts of various mutant strains of Salmonella typhimurium. Our data are consistent with a model in which regulation of Hut enzyme production occurs at the level of transcription and support earlier genetic evidence indicating that all of the hut genes are transcribed in the clockwise direction on the S. typhimurium chromosome. These results also suggest that promoter sites of the two hut operons may differ in their ability to initiate transcription.
Effects of carbon dioxide, urea, and ammonia on growth of Ureaplasma urealyticum (T-strain mycoplasma)
Authors: Masover G K , Razin S , Hayflick L
Published: January 2020

By use of a simple device for continuous CO2 gassing of Ureaplasma urealyticum cultures growing in a liquid medium, we have been able to separate some of the effects of urea, CO2, ammonia, and pH on growth. The CO2 acted as a superior buffer in the pH range 5.7 to 6.8, which is optimal for Ureaplasma growth. It was, therefore, possible to observe the effect of repeated additions of urea to the culture without alkalinization of the growth medium. We found that the repeated additions of urea did not enhance Ureaplasma growth, and the resultant accumulation of ammonium ions (greater than 2,000 microng/ml) did not cause more rapid death under these conditions. By abruptly changing the gaseous environment from CO2 to N2, it was possible to cause a rapid pH change in the culture to a value above 8.0. This resulted in a more rapid death of the organisms.
Cell surface topography of Candida and Leucosporidium yeasts as revealed by scanning electron microscopy
Authors: Watson K , Arthur H
Published: January 2020

The cell surface topography of the following yeast strains was examined by scanning electron microscopy: Candida slooffii, C. lipolytica, Leucosporidium frigidum, and L. nivalis. Multipolar and lateral budding were observed in the Candida yeasts in contrast to bipolar budding in the Leucosporidium species. The cell surface topography and the morphology of the bud and birth scars in these yeasts differed markedly. Apart from the bud and birth scars, the cells of C. slooffii showed a relatively smooth topography. The bud scars were seen as a circular ridge of wall material surrounding a markedly convex scar plug. Birth scars were raised, rounded structures, which appeared to distend upon cell growth. In contrast, bud scars of C. lipolytica were platelike, lacked a distinct annulus of wall material, and were much less protuberent than those of C. slooffii. Birth scars were a more permanent feature of these cells. The topography of Leucosporidium yeasts was characterized by the presence of numerous protrusions on the cell surface. In some cases, the entire cell surface was covered by these protrusions. There appeared to be some correlations between the age of the cell and the extent of surface protrusions and degree of surface convolution...
Immunocytological investigation of protein synthesis in Escherichia coli
Authors: MacAlister T J , Irvin R T , Costerton J W
Published: January 2020

Ferritin-conjugated specific antibodies have been used to localize beta-galactosidase and both the monomer and active dimer of alkaline phosphatase in frozen thin sections of cells of Escherichia coli O8 strain F515. The even distribution of the ferritin marker throughout cells that had been induced for beta-galactosidase synthesis, frozen, sectioned, and exposed to ferritin-anti-beta-galactosidase conjugate showed that this enzyme was present throughout the cytoplasm of these cells. Frozen thin sections of cells that had been derepressed for the synthesis of alkaline phosphatase were exposed to both ferritin-anti-alkaline phosphatase monomer and ferritin-anti-alkaline phosphatase dimer conjugates, and the ferritin markers showed a peripheral distribution of both the monomer and the dimer of this enzyme. This indicates that alkaline phosphatase is present only in the peripheral regions of the cell and argues against the existence of a cytoplasmic pool of inactive monomers of this enzyme. This peripheral location of both the monomers and dimers of alkaline phosphatase supports the developing concensus that this enzyme is, like other wall-associated enzymes, synthesized in association with the cytoplasmic membrane and vectorially transported to the periplasmic area, where it assumes its tertiary and quaternary structure and acquires its enzymatic activity.
Third system for neutral amino acid transport in a marine pseudomonad
Authors: Pearce S M , Hildebrandt V A , Lee T
Published: January 2020

Uptake of leucine by the marine pseudomonad B-16 is an energy-dependent, concentrative process. Respiratory inhibitors, uncouplers, and sulfhydryl reagents block transport. The uptake of leucine is Na+ dependent, although the relationship between the rate of leucine uptake and Na+ concentration depends, to some extent, on the ionic strength of the suspending assay medium and the manner in which cells are washed prior to assay. Leucine transport can be separated into at least two systems: a low-affinity system with an apparent Km of 1.3 X 10(-5) M, and a high-affinity system with an apparent Km of 1.9 X 10(-7) M. The high-affinity system shows a specificity unusual for bacterial systems in that both aromatic and aliphatic amino acids inhibit leucine transport, provided that they have hydrophobic side chains of a length greater than that of two carbon atoms. The system exhibits strict stereospecificity for the L form. Phenylalanine inhibition was investigated in more detail. The Ki for inhibition of leucine transport by phenylalanine is about 1.4 X 10(-7) M. Phenylalanine itself is transported by an energy-dependent process whose specificity is the same as the high-affinity leucine transport system, as is expected if both amino acids share the same transport system. Studies with protoplasts indicate that a periplasmic binding protein is not an essential part of this transport system. Fein and MacLeod (J. Bacteriol. 124:1177-1190, 1975) reported two neutral amino acid transport systems in strain B-16: the DAG system, serving glycine, D-alanine, D-serine, and alpha-aminoisobutyric acid; and the LIV system, serving L-leucine, L-isoleucine, L-valine, and L-alanine. The high-affinity system reported here is a third neutral amino acid transport system in this marine pseudomonad. We propose the name "LIV-II" system.
Characterization of the entomocidal parasporal crystal of Bacillus thuringiensis
Authors: Bulla L A , Kramer K J , Davidson L I
Published: January 2020

The parasporal crystalline protoxin of Bacillus thuringiensis contains a single glycoprotein subunit that has a molecular weight of approximately 1.2 X 10(5). The carbohydrate consists of glucose (3.8%) and mannose (1.8%). At alkaline pH, the proendotoxin is apparently solubilized and activated by an autolytic mechanism involving an inherent sulfhydryl protease that renders the protoxin insecticidal. Activation generates protons, degraded polypeptides, sulfhydryl group reactivity, proteolytic activity, and insect toxicity. Chemical modification of the sulfhydryl groups inhibits the proteolytic and insecticidal activities, suggesting that cysteine residues may be present in the active site of the protein.
Energy-dependent incorporation of sphingolipid precursors and fatty acids in Bacteriodes melaninogenicus
Authors: Lev M , Milford A F
Published: January 2020

Washed cells of Bacteroides melaninogenicus are unable to incorporate the sphingolipid precursor 3-ketodihydrosphingosine (3KDS) or dihydrosphingosine into the complete sphingolipids ceramide phosphorylethanolamine (CPE) and ceramide phosphorylglycerol (CPG), whereas growing cultures are able to do so. This result suggested that an energy source was required by washed cells to initiate the incorporation of 3KDS. Investigation of a number of energy sources for B. melaninogenicus showed that glutamine was active in driving the incorporation of 3KDS. This system shows saturation kinetics. Besides glutamine, only asparagine and reduced nicotinamide adenine dinucleotide (NADH) are effective; glutamate and other compounds are inactive. The glutamine-driven system is sensitive to 2,4-dinitrophenol, azide, N,N'- dicyclohexylcarbodiimide, and carbonyl cyanide m-chlorophenylhydrazone. Asparagine plus NADH shows a synergistic effect in stimulating the incorporation of 3KDS into CPE and CPG in washed cells. However, glutamine plus NADH and glutamine plus asparagine show no such synergy. The cytochrome-free mutant of B. melaninogenicus, strain S, incorporates 3KDS in a manner similar to the parent strain when glutamine is used to drive the reaction; NADH or asparagine, however, are ineffective when used with strain S. Vitamin K-depleted cells of B. melaninogenicus are similar to vitamin K-grown cells, when glutamine or NADH is used to drive the 3KDS incorporation. Glutamine and NADH are also effective in stimulating the incorporation of palmitate and acetate by washed cells of B, melaninogenicus. Increased incorporation of these fatty acids into CPE, CPG, 3KDS, and other phospholipids is significantly increased by the presence of glutamine or NADH. Thus, energization of the membrane of B. melaninogenicus by glutamine or the electron transport system by NADH or asparagine is required for sphingolipid and other phospholipid synthesis. The relationship of this energization to possible transport of sphingolipid precursors is discussed.
Genetic complementation analysis of Escherichia coli type 1 somatic pilus mutants
Authors: Swaney L M , Liu Y P , Ippen-Ihler K , Brinton C C
Published: January 2020

A genetic complementation analysis of 75 stable nonpiliated mutants of a type 1 piliated strain of Escherichia coli K-12, AW405, was performed. Strains containing pairs of pil mutations were constructed by the infectious transfer of an F101 plasmid containing one pil mutation into E. coli K-12 AW 405 containing another pil mutation. The presence or absence of type 1 pili on the merodiploid strains was determined by agglutination with type 1 pilus antiserum. All 75 mutants fell into one of four complementation groups. The pattern of complementation defined three cistrons involved in pilus formation, pilA, pilB, and pilC. The fourth complementation group was composed of a large number of mutants defective in both pilA and pilB functions.
Metabolic role of free mycolic acids in Mycobacterium tuberculosis
Authors: Takayama K , Armstrong E L
Published: January 2020

Small amounts of free mycolic acids and trehalose dimycolate that are rapidly formed by Mycobacterium tuberculosis H37Ra are probably derived from mycolyl acetyl trehalose and transferred to the cell wall. However, the transfer of mycolic acids from mycolyl acetyl trehalose to the cell wall still appears to be the more prominent route.
Genetic control of arylsulfatase synthesis in Klebsiella aerogenes
Authors: Murooka Y , Adachi T , Okamura H , Harada T
Published: January 2020

It was shown that at least four genes are specifically responsible for arylsulfatase synthesis in Klebsiella aerogenes. Mutations at chromosome site atsA result in enzymatically inactive arylsulfatase. Mutants showing constitutive synthesis of arylsulfatase (atsR) were isolated by using inorganic sulfate or cysteine as the sulfur source. Another mutation in which repression of arylsulfatase by inorganic sulfate or cysteine could not be relieved by tyramine was determined by genetic analysis to be on the tyramine oxidase gene (tyn). This site was distinguished from the atsC mutation site, which is probably concerned with the action or synthesis of corepressors of arylsulfatase synthesis. Genetic analysis with transducing phage PW52 showed that the order of mutation sites was atsC-atsR-atsA-tynA-tynB. On the basis of these results and previous physiological findings, we propose a new model for regulation of arylsulfatase synthesis.
Occurrence and nature of chromatic adaptation in cyanobacteria
Authors: Tandeau de Marsac N
Published: January 2020

Forty-four axenic strains of cyanobacteria that synthesize phycoerythrin were screened to ascertain the effect of light quality on pigment synthesis. Cellular pigment compositions were determined after photoautotrophic growth with low light fluxes (7.0 X 10(2) ergs/cm2 per s) of green, red, and white light, and in the case of facultative heterotrophs, after dark growth at the expense of sugars. Twelve strains did not adapt chromatically: the cells contained fixed proportions of phycoerythrin, phycocyanin, and allophycocyanin under the growth conditions used. In the remaining strains, the cellular ratio of phycoerythrin to phycocyanin was much higher after growth in green than in red light. Quantitative data on the cellular pigment contents, supplemented by measurements of the differential rates of pigment synthesis on representative strains, show that chromatic adaptation may involve a light-induced modulation either of phycoerythrin synthesis alone (7 strains) or of both phycoerythrin and phycocyanin synthesis (25 strains). Facultative hetrotrophs able to adapt chromatically have a phycobiliprotein composition after dark growth which closely resembles that after growth in red light. Light quality does not affect the differential rate of chlorophyll synthesis. The physiological and taxonomic implications of these findings are discussed.
Pyruvate kinase isozymes of Mucor racemosus: control of synthesis by glucose
Authors: Paznokas J L , Sypherd P S
Published: January 2020

A variety of cultural conditions were examined to determine the relationship between pyruvate kinase isozyme patterns and morphology in Mucor racemosus. The results indicate that M. racemosus has two isozymes of pyruvate kinase, form A and form B, which are clearly separable on ion-exchange columns (diethylaminoethyl-cellulose). Addition of glucose to cultures growing on amino acids in air resulted in the induction of form A and the termination of form B synthesis. Cycloheximide added at the same time as glucose blocked the formation of form A but did not interfere with the termination of form B synthesis. Removal of glucose resulted in termination of form A synthesis and the induction of form B. Cycloheximide blocked the induction of form B and did not interfere with the termination of form A synthesis. The data show that the isozyme type is not directly related to morphology, but depends only on the presence or absence of glucose.
Cell-bound cations of the moderately halophilic bacterium Vibrio costicola
Authors: Shindler D B , Wydro R M , Kushner D J
Published: January 2020

Over most of the range of salt concentrations in which the moderately halophilic bacterium Vibrio costicola could grow, the sum of the cell-associated Na+ + K+ ions was at least as high as in the external medium. This is in contrast to other moderate halophiles, which have substantially lower internal than external salt concentrations for most of their growth range. The relative amounts of Na+ and K+ in V. costicola varied with environmental conditions. The K+/Na+ ratio fell during anaerobic incubation or when cells were poisoned. As Na+ ions left the cells, K+ ions entered. However, movement of these ions was not tightly coupled, since K+ content of cells could increase without a corresponding decrease in Na+ content. The Mg2+ contents of cells varied little with environmental conditions.
Glycine metabolism by Pseudomonas aeruginosa: hydrogen cyanide biosynthesis
Authors: Castric P A
Published: January 2020

Hydrogen cyanide (HCN) production by Pseudomonas aeruginosa in a synthetic medium is stimulated by the presence of glycine. Methionine enhances this stimulation but will not substitute for glycine as a stimulator of cyanogenesis. Threonine and phenylalanine are effective substitutes for glycine in the stimulation of HCN production. Glycine, threonine, and serine are good radioisotope precursors of HCN, but methionine and phenylalanine are not. Cell extracts of P. aeruginosa convert [14C]threonine to [14C]glycine. H14CN is produced with low dilution of label from either [1-14C]glycine or [2-14C]glycine, indicating a randomization of label either in the primary or secondary metabolism of glycine. When whole cells were fed [1,2-14C]glycine, cyanide and bicarbonate were the only radioactive extracellular products observed.
Menaquinone biosynthesis: mutants of Escherichia coli K-12 requiring 2-succinylbenzoate
Authors: Guest J R
Published: January 2020

Two independent mutants of Escherichia coli K-12, selected for their inability to grow anaerobically with fumarate as the terminal electron acceptor, were shown to be deficient in menaquinone biosynthesis. In both cases, exogenously supplied 2-succinylbenzoate promoted normal anaerobic growth on a lactate plus fumarate medium. Anaerobic growth of the mutants on glucose minimal medium was impaired but could be restored to normal by adding either uracil or 2-succinylbenzoate. The addition of 2-succinylbenzoate (but not uracil) permitted the synthesis of menaquinone and demethylmenaquinone by both mutants. The menaquinone content of the parental strain grown on lactate plus fumarate was three times greater than observed after growth on glucose. Transduction studies with phage P1 showed that the two mutations are very closely linked and probably affect the same gene, menC, which is cotransducible with nalA (23%), glpT (51%), and purF (8 to 14%). The gene order nalA-nrdA-glpTA-menC-purF was indicated. The results were consistent with 2-succinylbenzoate being an intermediate in menaquinone biosynthesis and show that the gene designated menC (located at 48.65 min of the E. coli chromosome) is involved in the conversion of chorismate to 2-succinylbenzoate. It was also concluded that menaquinone is essential for electron transport to fumarate in E. coli.
Chloramphenicol-Induced Changes in the Synthesis of Ribosomal, Transfer, and Messenger Ribonucleic Acids in
Escherichia coli
B/r
Authors: Shen V. , Bremer H.
Published: January 2020

The synthesis of ribosomal ribonucleic acid (rRNA), transfer RNA (tRNA) and messenger RNA (mRNA) was measured in
Escherichia coli
B/r after the addition of 100 μg of chloramphenicol (CAM) per ml to cultures growing either in one of three minimal media (succinate, glycerol, or glucose) or in one of the same three media supplemented with 20 amino acids. (i) During CAM treatment, rRNA and tRNA were synthesized in the same relative proportions (85:15) as during exponential growth. The faster accumulation of tRNA relative to rRNA in CAM was due to a decreased stability of rRNA that is synthesized in the presence of or immediately before the addition of CAM. (ii) CAM stimulated the synthesis of rRNA and tRNA two- to eightfold. The results fell into two groups; one group was from studies done in minimal media and the other was from amino acid-supplemented media. In each group the stimulation decreased with increasing growth rate of the culture during exponential growth before the addition of CAM; however, the stimulation in minimal media was lower than that in amino acid-supplemented media. (iii) CAM caused an increase in the proportion of rRNA and tRNA synthesis and a corresponding decrease in the proportion of mRNA synthesis. In minimal media, the residual proportion of mRNA synthesis after CAM treatment was 10 to 15% of total RNA synthesis; in amino acid-supplemented media this proportion was 0 to 10%. In either case, the residual proportion of mRNA synthesis was independent of the proportions observed during exponential growth in these media. (iv) The absolute rate of mRNA synthesis decreased severalfold with the addition of CAM; i.e., the rate of synthesis of rRNA and tRNA was increased at the expense of mRNA synthesis. (v) During exponential growth, the fraction of the instantaneous rate of total RNA synthesis that corresponds to mRNA is a function of both the growth rate and the presence or absence of amino acids in the growth medium: in the absence of amino acids, this fraction decreased with increasing growth rate; in the presence of amino acids, the fraction increased slightly with growth rate. These results are consistent with a regulation of rRNA and tRNA synthesis at the transcriptional level, e.g., with a CAM-induced increase in the affinity of RNA polymerase for the rRNA and tRNA promoters. The results also suggest the occurrence of a regulation of RNA polymerase enzyme activity, i.e., of an activation of RNA polymerase that is inactive during exponential growth. A distinction between these alternatives requires measurements of the rRNA chain growth rates during CAM treatment.
Independent Regulation of Transport and Biosynthesis of Arginine in
Escherichia coli
K-12
Authors: Celis T. F. R.
Published: January 2020

From an arginine auxotrophic strain, a mutant was isolated which is able to utilize
d
-arginine as a source of
l
-arginine and shows a high sensitivity to inhibition of growth by canavanine. Transport studies revealed a four- to five-fold increased uptake of arginine and ornithine in cells from the mutant strain. The kinetics of entry of arginine and ornithine evidenced elevated maximal influx values for the arginine- and ornithine-specific transport systems. A close parallel between arginine transport activity and arginine binding activity with one arginine-specific binding periplasmic protein in the mutant strongly suggests that such binding protein is a component of the arginine-specific permease. The affinity between arginine and the binder, isolated from the mutant cells, as well as the electrophoretic mobility of the protein, remain unchanged. The enhanced transport activity of arginine and ornithine with mutant cells is insensitive to repression by arginine or ornithine, whereas the biosynthesis of arginine-forming enzymes is normally repressible. When transport activity was examined in strains with mutations leading to derepression of arginine biosynthesis, the regulation of arginine transport was found to be normal. These studies support the conclusion that arginine transport and arginine biosynthesis, in
Escherichia coli
K-12, are not regulated in a concerted manner, although both systems may have components in common.
Evidence that specific and "general" control of ornithine carbamoyltransferase production occurs at the level of transcription in Saccharomyces cerevisiae
Authors: Messenguy F , Cooper T G
Published: January 2020

Ornithine carbamoyltransferase synthesis is subject to two major regulatory systems in Saccharomyces cerevisiae. One system is specific for the arginine biosynthetic enzymes, whereas the other appears to be general, acting on a variety of other amino acid pathways as well. We observed that the synthetic capacity for continued ornithine carbamoyltransferase synthesis had the same short half-life (ca. 5 to 7 min) whether repression of enzyme production was brought about by action of the specific or general control system. We present evidence suggesting that both control systems regulate accumulation or ornithine carbamoyltransferase-specific synthetic capacity, rather than modulating its expression.
Biochemical and physiological studies of the yeast virus-like particle
Authors: Oliver S G , McCREADY S J , Holm C , Sutherland P A , McLaughlin C S , Cox B S
Published: January 2020

A study was made of the virus-like particle (VLP) of Saccharomyces cerevisiae S7. This strain contains elevated amounts of P1 double-stranded ribonucleic acid (dsRNA) but no P2 dsRNA. The amount of dsRNA contained in cells grown on a fermentable carbon source (glucose) was compared with that in cells grown on a nonfermentable carbon source (ethanol). It was found that ethanol-grown cells contain higher levels of dsRNA than glucose-grown cells. In the former, the amount of dsRNA increased during the logarithmic phase of growth, whereas in the latter it increased during the transition from the logarithmic to the stationary phase. A method was devised to isolate VLPs from these cells by using CsCl gradients, and the yield was assessed by monitoring the recovery of dsRNA. Three proteins were found to be tightly associated with these particles. They have molecular weights of 75,000, 53,000, and 37,000. Together they account for almost all of the coding capacity of the P1 dsRNA that the VLP contains.
Deoxyribonucleic acid strand breaks during freeze-drying and their repair in Escherichia coli
Authors: Ohnishi T , Tanaka Y , Yoh M , Takeda Y , Miwatani T
Published: January 2020

Freeze-drying of Escherichia coli cells caused strand breaks of deoxyribonucleic acid (DNA) in both radiation-sensitive and -resistant strains. However, in the radiation-resistant strain E. coli B/r the damaged DNA was repaired after rehydration, whereas in the radiation-sensitive strain E. coli Bs-1 the damaged DNA was not repaired and the DNA was degraded. Repeated freeze-drying did not break the damaged DNA into smaller pieces.
Characterization of plasmids in a sucrose-fermenting strain of Escherichia coli
Authors: Palchaudhuri S , Rahn S , Santos D S , Maas W K
Published: January 2020

A multiply drug-resistant strain of Escherichia coli isolated from a patient in Bangladesh was shown to carry four types of plasmids based on size differences. One type carries a gene or genes for sucrose fermentation.
Properties of the relaxation complex of supercoiled deoxyribonucleic acid and protein of R plasmid NR1 in Escherichia coli
Authors: Womble D D , Rownd R H
Published: January 2020

Some properties of the supercoiled deoxyribonucleic acid (DNA)-protein relaxation complex of the R plasmid NR1, which contains more than one origin for DNA replication, were examined. The percentage of complexed NR1 molecules that can be converted to the relaxed (nicked) form appeared to be unaffected by the conditions under which the host cells were cultured. However, the percentage of supercoiled NR1 DNA that can be relaxed was highly dependent on the method used to prepare the DNA and the agents used to induce relaxation. Our data suggest that 100% of NR1 molecules may exist in situ as DNA-protein relaxation complexes. An RTF-Tc segregant of NR1, which has deleted the r-determinants component of the NR1 and therefore does not contain the two origins of replication located in the r-determinants, has indistinguishable relaxation properties in comparison with NR1 itself.
Incompatibility and surface exclusion properties of H1 and H2 plasmids
Authors: Taylor D E , Grant R B
Published: January 2020

Plasmids of the H incompatibility group showed two types of surface exclusion and incompatibility interactions. Strong incompatibility and surface exclusion were evident between plasmids within the same subgroup, and recombination frequently occurred between these plasmids after antibiotic selection for the presence of two plasmids in the same cell. Weaker interactions were seen between plasmids of the different subgroups, H1 and H2, and recombination was not detected. Incompatibility between H1 and H2 plasmids led preferentially to the loss of the H1 plasmid, irrespective of the order of entry of the plasmids. These data are consistent with the hypothesis that incompatibility is negatively controlled.
Morphology and ultrastructure of Crenothrix polyspora Cohn
Authors: Völker H , Schweisfurth R , Hirsch P
Published: January 2020

Naturally grown cell material of Crenothrix polyspora from the well of a waterworks was studied by means of phase-contrast and Nomarski interference microscopy as well as by transmission electron microscopy. The material consisted of clusters of sheathed filaments up to 2 cm long. Propagation forms observed were nonmotile, spherical cells that arose by simple ("macrogonidia") or multiple ("microgonidia") septation of the filamental tips. Ultrastructural analysis revealed Crenothrix to be procaryotic and gram negative, with several layers of sheath material surrounding the filaments. On thin sections, individual cells had elaborate membrane systems in the form of lamellar stacks. They resembled thylakoids of photosynthetic bacteria. Spectrophotometric analysis gave no indication of photosynthetic pigments. The cells also contained large hexagonal bodies, rod-shaped fibrillar elements, and polyphosphate granules.
Expression of R-plasmid functions during anaerobic growth of an Escherichia coli K-12 host
Authors: Burman L G
Published: January 2020

The normal habitat of enteric bacteria is largely anaerobic. Expression of the three characteristic properties of R-plasmids, drug resistance, vegetative replication, and fertility, was therefore studied in Escherichia coli K-12 during anaerobiosis. Replication and drug resistance functions were not altered in the 45 R-plasmids studies, whereas the expression of fertility varied considerably among different R-plasmids during anaerobiosis. The R-plasmids could be divided into three groups, one showing a strong, the second a moderate, and the third little or no reduction of fertility by anaerobiosis. Plasmid-determined sensitivity to F-, N-, and I-specific phage, respectively, was well, although not absolutely, correlated with each of three groups mentioned. Anaerobiosis-aerobiosis appears to change the fertility of type F R-plasmids by influencing the degree of repression of their fertility functions such as the formation of sex pili. Although the minimum inhibitory concentrations of ampicillin, chloramphenicol, streptomycin, and tetracycline were unaltered by anaerobiosis, sulfonamide was found to be four- to eightfold less active under this condition in both resistant and sensitive strains. A surprisingly high frequency and uniformity of minimal inhibitory concentrations was observed for R-plasmid-mediated resistance to streptomycin and chloramphenicol.
Control of Ribosome Synthesis in
Escherichia coli
: Analysis of an Energy Source Shift-Down
Authors: Molin Søren , Meyenburg Kaspar Von , Maaløe Ole , Hansen Mogens T. , Pato Martin L.
Published: January 2020

The rate of ribosome synthesis and accumulation in
Escherichia coli
during the transition after an energy source shift-down was analyzed. The shift was imposed on cultures of stringent and relaxed strains growing in glucose minimal medium by the addition of the glucose analogue α-methylglucoside. In the stringent strain, ribosome synthesis was almost instantaneously reduced after the shift, whereas the relaxed strain exhibited a more gradual response. The rate of messenger ribonucleic acid (mRNA) synthesis was affected similarly, though to a smaller extent. A comparison of the rates of synthesis and accumulation of ribosomal RNA (rRNA) and ribosomal proteins showed that far more ribosomal components were synthesized after the shift than were accumulated, indicating that a substantial part of the rRNA made after the shift was unstable. A new method was used to measure relative rates of rRNA synthesis and to estimate the transcription time for the rRNA operon under different conditions. In steady states of growth with growth rates ranging from 0.75 to 2.3 doublings/h, as well as during the transition after a shift-down, the transcription time of the rRNA operon was constant. The rate of synthesis of rRNA correlated during this transition – in contrast to the rate of accumulation (M. T. Hansen et al., J. Bacteriol. 122: 585-591, 1975) – with the ppGpp pool in the same way as has been observed during partial amino acid starvation.
R-plasmid transfer and its response to nalidixic acid
Authors: Burman L G
Published: January 2020

The conjugational transfer efficiency of 41 wild-type R-plasmids was studied in Escherichia coli K-12. Type I R-plasmids were transferred at comparatively high and rather uniform frequencies, whereas type F R-plasmids showed less uniform and, on average, somewhat lower transfer frequencies. R-plasmids not mediating sensitivity to F-, I-, or N-specific phages showed moderate transfer frequencies, and type N R-plasmids showed very low transfer frequencies. Various lines of evidence suggest that a well-expressed, but functionally inefficient, conjugation apparatus is the cause of the poor transfer of type N R-plasmids in liquid medium. Nalidixic acid efficiently inhibited transfer of type I and particularly type F R-plasmids, whereas the transfer of type N plasmids was resistant to the drug. Type F and type I plasmids appear to depend on at least one host function for their transfer, namely, the nalidixic acid-sensitive reaction in vegetative chromosome replication, whereas type N plasmids are independent of this function.
Suppression of an Escherichia coli dnaA mutation by the integrated R factor R100.1: origin of chromosome replication during exponential growth
Authors: Chandler M , Silver L , Caro L
Published: January 2020

We have investigated the behavior, during exponential growth, of strains of Escherichia coli carrying a dnaA(Ts) mutation that has been suppressed by the integration of the F-like R plasmid R100.1. We present evidence showing that replication in these strains proceeds largely from the normal chromosome origin at 30 degrees C, a permissive temperature for the dnaA(Ts) gene product, whereas, at 42 degrees C, replication proceeds largely from the integrated plasmid. These conclusions are based on measurements made by deoxyribonucleic acid:deoxyribonucleic acid hybridization of the relative frequencies of the prophages Mu-1 and lambdaind- and R100.1 integrated at known locations on the E. coli chromosome in these Hfr strains.
Urease of Klebsiella aerogenes: control of its synthesis by glutamine synthetase
Authors: Friedrich B , Magasanik B
Published: January 2020

Urease was purified 24-fold from extracts of Klebsiella aerogenes. The enzyme has a molecular weight of 230,000 as determined by gel filtration, is highly substrate specific, and has a Km for urea of 0.7 mM. A mutant strain lacking urease was isolated; it failed to grow with urea as the sole source of nitrogen but did grow on media containing other nitrogen sources such as ammonia, histidine, or arginine. Urease was present at a high level when the cells were starved for nitrogen; its synthesis was repressed when the external ammonia concentration was high. Formation of urease did not require induction by urea and was not subject to catabolite repression. Its synthesis was controlled by glutamine synthetase. Mutants lacking glutamine synthetase failed to produce urease, and mutants forming glutamine synthetase at a high constitutive level also formed urease constitutively. Thus, the formation of urease is regulated like that of other enzymes of K. aerogenes capable of supplying the cell with ammonia or glutamate.
Outer membrane phospholipase A from Acinetobacter sp. HO1-N
Authors: Torregrossa R E , Makula R A , Finnerty W R
Published: January 2020

A phospholipase A1 activity that hydrolyzed cardiolipin to triacyl- and diacyl-lysocardiolipin was localized in outer membrane preparations derived from Acinetobacter sp. HO1-N. The specific activity of the enzyme derived from hexadecane-grown cells was 2.5 to 3 times higher than that derived from NBYE-grown cells. An apparent Km of 2.22 mM was determined, although inhibition kinetics resulted at the higher cardiolipin substrate concentrations. Optimal reaction conditions established on metal requirements. Enzyme activity was obligately dependent on Triton X-100 (0.5%) and was inhibited by cationic and anionic detergents. Cardiolipin-specific phospholipase D converted triacyl-lysocardiolipin to lysophosphatidylglycerol and phosphatidic acid. The specific activity of this enzyme was approximately 100 times greater than that reported for other membrane preparations derived from microorganisms.
Restoration of phosphate transport by the phosphate-binding protein in spheroplasts of Escherichia coli
Authors: Gerdes R G , Strickland K P , Rosenberg H
Published: January 2020

Reconstitution of phosphate transport in Escherichia coli was demonstrated. Conversion of E. coli K10 cells to spheroplasts decreased phosphate transport to about 2%. Addition of purified phosphate-binding protein at physiological levels to these spheroplasts caused a mean 14-fold increase in phosphate transport rate. Crude shock fluid fractions were also stimulatory but not if the shock fluid was obtained from mutants lacking phosphate-binding protein. The effect of the binding protein was abolished by its specific antibody. The phosphate was shown to have entered the cell, where it became esterified. Reconstitution was not possible with cold-shocked or osmotically shocked cells.
Permeability of the Cell Envelope and Osmotic Behavior in
Saccharomyces cerevisiae
Authors: Arnold Wilfred N. , Lacy John S.
Published: January 2020

Bakers' yeast (
Saccharomyces cerevisiae
) was equilibrated with distilled water and then packed into standardized pellets by centrifugation. The fractional space (
S
value) that was accessible to passive permeation was probed with a variety of mono- and divalent salts, mono- and disaccharides, polyols, substrates and products of β-fructofuranosidase (EC 3.2.1.26) and acid phosphatase (EC 3.1.3.2), and a cross-linked polymer of sucrose (Ficoll 400). A simple but very reproducible method was developed to measure pellet volume. At the limit of zero osmolality for bathing medium, the interstitial space was 0.223 ml/ml of pellet, and the aqueous volume of cell envelopes was 0.117 ml/ml of pellet. Thus the cell envelope for this yeast, under these conditions, was approximately 15% of the total cell volume. At a finite osmolality, the space in a yeast pellet that was accessible to salt was accounted for by the sum of initial interstitial space, the volume of the cell envelopes, and the volume of water abstracted from the cells by osmosis. Plots of
S
value versus osmolality were linear for uncharged probes and curvilinear for all salts. When Ficoll and potassium thiocyanate were presented to the yeast in admixture, the
S
values for the salt increased continuously over the range of osmolality studied. However, the
S
values for Ficoll 400 (which did not penetrate the cell wall) were lower by an amount equilivalent to the cell envelopes; they increased in parallel with the
S
curve for salt up to 1.15 osmol/kg and then plateaued. The results support the concept of incipient plasmolysis at 1.15 osmol/kg, and the separation of protoplasm from the cell wall is indicated with more concentrated solutions. Such cells were still viable if slowly diluted in distilled water, but they were injured by the shock of rapid dilution. However, shocking the cells did not release β-fructofuranosidase into the medium. The complete accessibility of salts toward killed cells was demonstrated with yeast that had been pretreated with heat, organic solvents, or glutaraldehyde.
Outer membrane proteins of Escherichia coli. VI. Protein alteration in bacteriophage-resistant mutants
Authors: Bassford P J , Diedrich D L , Schnaitman C L , Reeves P
Published: January 2020

Protein 1 was shown to be the receptor for phage PA-2 by the observations that the purified protein inactivates the phage, mutants lacking the protein are resistant to the phage, and mutants selected for PA-2 resistance have altered protein. Protein 1 appears as two bands (1a and 1b) on high-resolution polyacrylamide gels. The most abundant classes of mutants (ParI and ParII) selected for PA-2 resistance were found to lack band 1b. The mutations responsible for the ParI and ParII phenotypes were mapped at a locus termed par, which is near nalA on the Escherichia coli chromosome. The cyanogen bromide peptides of proteins 1a and 1b are similar, suggesting that these bands represent modified forms of the same polypeptide. Strains carrying the tolF mutation produce only band 1b. When a par tolF double mutant was constructed, this strain produced only band 1a. These results suggest that genes at the par and tolF loci are involved in modification of protein 1, or regulation of such modification, and are not structural genes for protein 1.
Propionate-induced synthesis of odd-chain-length fatty acids by Escherichia coli
Authors: Ingram L O , Chevalier L S , Gabba E J , Ley K D , Winters K
Published: January 2020

Exogenous propionate is incorporated in vivo by Escherichia coli as a primer to produce lipids with fatty acids of odd chain lengths. This provides a method for the specific labeling of the three terminal carbons in the fatty acyl chains of phospholipids.
Zeatin ribonucleosides in the transfer ribonucleic acid of Rhizobium leguminosarum, Agrobacterium tumefaciens, Corynebacterium fascians, and Erwinia amylovora
Authors: Cherayil J D , Lipsett M N
Published: January 2020

Until recently, the presence in transfer ribonucleic acid (tRNA) of the hydroxylated cytokinin ribosylzeatin [N6-(4-hydroxy-3-methylbut-2-enyl)adenosine]was thought to be unique to higher plants. This extension of work from several laboratories indicates the presence of 2-methylthioribosylzeatin in the tRNA of the plant-associated bacteria Rhizobium leguminosarum, Agrobacterium tumefaciens, and Corynebacterium fascians, but not in that of Erwinia amylovora. This cytokinin has the cis configuration, as is normally found in the tRNA's of plants. The tRNA thionucleotide patterns in these bacteria are different from those of Escherichia coli, Bacillus subtilis, and Salmonella typhimurium, which contain the unhydroxylated analogs of ribosylzeatin or 2-methylthioribosylzeatin.
Myxospore coat synthesis in Myxococcus xanthus: enzymes associated with uridine 5'-diphosphate-N-acetylgalactosamine formation during myxospore development
Authors: Filer D , Kindler S H , Rosenberg E
Published: January 2020

Activities of the enzymes glutamine synthetase (EC 6.3.1.2.), glucosamine 6-phosphate acetyltransferase (EC 2.3.1.4.), uridine 5'-diphosphate (UDP)-N-acetylglucosamine pyrophosphorylase (EC 2.7.23.), UDP-N-acetylglucosamine 4-epimerase (EC 5.1.3.7.), fructose 1,6-diphosphate phosphatase (EC 3.13.11.), L-glutamine-fructose 6-phosphate transamidase (EC 5.3.1.19.), alkaline phosphatase (EC 3.1.3.1.), and malic dehydrogenase (EC 1.1.1.37) were assayed in partially purified extracts prepared at different stages of myxospore formation and germination in liquid cultures of Myxococcus xanthus. The specific activities of the first six of these enzymes increased 4.5- to 7.5-fold after 2 h of induction with 0.5 M glycerol or 0.2 M dimethyl sulfoxide. The increase in specific activities of these six enzymes was not observed in a mutant unable to be induced with glycerol. During the first 2 to 4 h of induction and during the first hour of germination, the level of these enzymes decreased to the level characteristic of vegetative cells. It is suggested that the six enzymes are responsible for the increased conversion of fructose 1,6-diphosphate to UDP-N-acetylgalactosamine, the major precursor of the myxospore coat.
Genetic characterization of an Escherichia coli mutant altered in the structure of murein lipoprotein
Authors: Yem D W , Wu H C
Published: January 2020

Mutants defective in the structure, biosynthesis, and assembly of murein lipoprotein have been isolated. One of these mutants has been shown to synthesize a structurally altered lipoprotein. The biochemical features of the mutant lipoprotein (lipid deficiency, dimer formation, and a reduced, bound form of lipoprotein) could be attributed to a single mutation (or closely linked mutations) located at 36.4 min of the Escherichia coli map. We propose that this mutant is altered in the structural gene for murein lipoprotein (mlpA). Biochemical studies carried out with a heterogenote, mlpA/F'mlpA+, revealed the biochemical codominance of the wild-type and mutant genes.
Modulation of deoxyribonucleic acid polymerase III level during the life cycle of Bacillus subtilis
Authors: Ciarrocchi G , Attolini C , Cobianchi F , Riva S , Falaschi A
Published: January 2020

Deoxyribonucleic acid (DNA) polymerase III is not detectable in Bacillus subtilis spores; the enzyme activity appears 20 to 30 min after spore activation and rapidly increases just before the onset of the first round of DNA replication (30 min later); the level of polymerase III further increases and reaches its maximum (on a per-genome basis) when the cells enter the vegetative phase of growth; this level is six- to eightfold higher than the one observed during germination. In the stationary phase, the polymerase III drops to levels comparable to those found in germinating spores at the first round of replication. On the contrary, DNA polymerase I is present at appreciable levels in the dormant spore; it increases during vegetative growth by a factor of three and, during the stationary phase, reaches its maximum level which is sixfold higher than that observed in the spores. The block of protein synthesis during vegetative growth does not cause an appreciable reduction of the two enzymes (in absolute terms), showing that the regulation of their levels is probably not due to a balance between synthesis and breakdown. These results indicate that polymerase III is probably one of the factors controlling the initiation of DNA synthesis during spore germination.
Threonyl-Transfer Ribonucleic Acid Synthetase fromEscherichia coli: Subunit Structure and Genetic Analysis of the Structural Gene by Means of a Mutated Enzyme and of a Specialized Transducing Lambda Bacteriophage
Authors: Hennecke H. , Böck A. , Thomale J. , Nass G.
Published: January 2020

Threonyl-transfer ribonucleic acid synthetase (ThrRS) has been purified from a strain ofEscherichia colithat shows a ninefold overproduction of this enzyme. Determination of the molecular weight of the purified, native enzyme by gel chromatography and by polyacrylamide gel electrophoresis at different gel concentrations yielded apparent molecular weight values of 150,000 and 161,000, respectively. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate yields a single protein band of 76,000-dalton size. From these results an α2subunit structure can be inferred. A mutant with a structurally altered ThrRS, which had been obtained by selection for resistance against the antibiotic borrelidin, was used to map the position of the ThrRS structural gene (thrS) by P1 transductions. It was found thatthrSis located in the immediate neighborhood ofpheSandpheT, which are the structural genes for the α and β subunits of phenylalanyl-transfer ribonucleic acid (tRNA) synthetase, the gene order beingaroD-pheT-pheS-thrS. A λ phage that was previously shown to specifically transducepheS, pheT, and also the structural gene for the translation initiation factor IF3 can complement the defect of the altered ThrRS of the borrelidin-resistant strain. This phage also stimulates the synthesis of the 76,000, molecular-weight polypeptide of ThrRS in ultraviolet light-irradiated.E. colicells. These results indicate that the genes for ThrRS, α and β subunits of phenylalanyl-tRNA synthetase, and initiation factor IF3 are immediately adjacent on theE. colichromosome.
Regulatory mutations in the Klebsiella aerogenes structural gene for glutamine synthetase
Authors: Bender R A , Magasanik B
Published: January 2020

Glutamine synthetase could be repressed several hundredfold rather than 6- to 10-fold as previously reported. Ammonia was not the primary repression signal for glutamine synthetase. Repression appeared to be mediated by a high level of glutamine and probably by a high ratio of glutamine to alpha-ketoglutarate. Mutations in glnA (the structural gene for glutamine synthetase) were seen to fall into three phenotypic groups: glutamine auxotrophs that produced no detectable glnA product; glutamine auxotrophs that produced a glnA product lacking enzymatic activity (and hence repressibility by ammonia) but were repressible under appropriate conditions; and glutamine synthetase regulatory mutants, whose glnA product was enzymatically active and not repressible under any conditions.