bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in transfer ribonucleic acid population of Acanthamoeba castellanii during growth and encystment
Authors: McMahon M E , Katze J R , Jensen T
Published: January 2020

Fifteen aminoacyl-transfer ribonucleic acids (tRNA's) from vegetative cells (trophozoites) and mature cysts of Acanthamoeba castellanii were compared by reversed-phase 5 chromatography. Little or no differences were detected in reversed-phase 5 chromatography elution profiles of alanyl-, arginyl-, isoleucyl-, phenylalanyl-, prolyl-, seryl-, threonyl-, tryptophanyl- and valyl-tRNA's. Significant differences in the relative proportions of isoaccepting species of leucyl-, lysyl-, methionyl-, aspartyl-, histidyl-, and tyrosyl-tRNA's were observed. Based upon the criterion of cyanogen bromide reactivity with the modified nucleoside queuosine, the content of queuosine in aspartyl-tRNA of A, castellanii is significantly greater in mature cysts than in trophozoites. The similarity of change in reversed-phase 5 chromatography elution profiles of aspartyl-, histidyl-, and tyrosyl-tRNA suggests that a common mechanism is responsible for alterations in the chromatographic patterns.
Bacillus subtilis deoxyribonucleic acid gyrase
Authors: Sugino A , Bott K F
Published: January 2020

Bacillus subtilis 168 was shown to contain a deoxyribonucleic acid (DNA) gyrase activity which closely resembled those of the enzymes isolated from Escherichia coli and Micrococcus luteus in its enzymatic requirements, substrate specificity, and sensitivity to several antibiotics. The enzyme was purified from the wild type and nalidixic acid-resistant and novobiocin-resistant mutants of B. subtilis and was functionally characterized in vitro. The genetic loci nalA and novA but not novB were shown to code for portions of the functional gyrase. Enzyme from the antibiotic-resistant mutants was resistant to the drug in vitro. The most striking observation was the remarkable similarity between the B. subtilis enzyme and other DNA gyrases, especially with respect to the oxolinic acid-induced DNA cleavage in the presence of sodium dodecyl sulfate. All of the enzymes appeared to possess the same specificity of cutting sites regardless of the source or type of DNA used. This result implies that gyrase binding to DNA is highly specific.
Development of Stigmatella aurantiaca: effects of light and gene expression
Authors: Inouye S , White D , Inouye M
Published: January 2020

Stigmatella aurantiaca, a gliding, gram-negative bacterium, exhibits complex developmental changes upon starvation. In the light the cells aggregate and develop multicellular fruiting bodies with stalks and sporangia within 20 h. Between 23 and 27 h, sonication-resistant myxospores are synchronously formed inside the sporangia. On the other hand, in the dark, the cells aggregate and differentiate into myxospores between 13 and 27 h without forming stalks and sporangia. The pattern of protein synthesis during development in the light as well as in the dark was investigated. Three periods of synthesis, characterized by sharp increases and decreases in the rate of isotope incorporation into certain proteins, were distinguished. In the light these periods corresponded approximately to an early stage before the formation of aggregates, a middle period during which aggregates appeared and developed into fruiting bodies, and a late stage that corresponded to the appearance of myxospores. The pattern of protein synthesis in the dark could also be divided into three stages, but the middle stage was considerably shorter than in the light and showed diminished synthesis of certain proteins that were actively synthesized in the light. In particular, the synthesis of one protein was detected only in samples that developed in the light.
Ultrastructure of a magnetotactic spirillum
Authors: Balkwill D L , Maratea D , Blakemore R P
Published: January 2020

The ultrastructure of a magnetotactic bacterium (strain MS-1) was examined by transmission, scanning, and scanning-transmission electron microscopy. The organism resembled other spirilla in general cell morphology, although some differences were detected at the ultrastructural level. Electron-dense particles within magnetotactic cells were shown by energy-dispersive X-ray analysis to be localizations containing iron. A non-magnetotactic variant of strain MS-1 lacked these novel bacterial inclusion bodies. A chain of these particles traversed each magnetotactic cell in a specific arrangement that was consistent from cell to cell, seemingly associated with the inner surface of the cytoplasmic membrane. Each particle was surrounded by an electron-dense layer separated from the particle surface by an electron-transparent region. The term "magnetosome" is proposed for the electron-dense particles with their enveloping layer(s) as found in this and other magnetotactic bacteria.
Cysteine synthesis by Desulfovibrio vulgaris extracts
Authors: Gevertz D , Amelunxen R , Akagi J M
Published: January 2020

Extracts of Desulfovibrio vulgaris were found to contain serine transacetylase and cysteine synthase activities. When extracts were incubated with bisulfite and o-acetylserine, or acetyl coenzyme A plus L-serine, under a hydrogen atmosphere, cysteine was formed. Pyruvate served as a reductant for bisulfite reduction to sulfide and concomitantly provided the acetyl moiety for acetyl coenzyme A formation. Consequently, when extracts were incubated with pyruvate, bisulfite, and L-serine, cysteine synthesis resulted.
Physiological function of periplasmic hexose phosphatase in Salmonella typhimurium
Authors: Rephaeli A W , Artenstein I R , Saier M H
Published: January 2020

Hydrolysis of sugar phosphates by crude and purified preparations of periplasmic hexose phosphatase from Salmonella typhimurium followed Michaelis-Menten kinetics. The enzyme bound glucose 1-phosphate with high affinity (Km = 10 microM) but bound glucose 6-phosphate with low affinity (Km = 2,000 microM). The order of substrate affinities was glucose 1-phosphate greater than mannose 1-phosphate = galactose 1-phosphate greater than fructose 1-phosphate greater than glucose 6-phosphate. These results and others suggest that the physiological function of the enzyme is the periplasmic hydrolysis of hexose 1-phosphates.
Gene expression in Escherichia coli after amino acid, purine, or pyrimidine exhaustion
Authors: Blumenthal R M , Dennis P P
Published: January 2020

Three strains of Escherichia coli B auxotrophic for leucine, guanine, or uracil were analyzed after exhaustion of the respective required nutrient from the growth medium. The pattern of transcription was analyzed by ribonucleic acid-deoxyribonucleic acid filter hybridization to specific deoxyribonucleic acid probes, and the pattern of translation was analyzed by autoradiography after the resolution of proteins on sodium dodecyl sulfate-polyacrylamide gels. The results obtained suggest the following conclusions. (i) Specific regulation of rpoBC transcription occurs at both the promoter (PL10) and the putative attenuator between rplL and rpoB. (ii) The stringent response of ribosomal protein gene expression to amino acid insufficiency is only partially mimicked by purine or pyrimidine insufficiency. (iii) Transcription initiation at PL10 decreases in response to guanine exhaustion, but in contrast increases significantly in response to uracil exhaustion. (iv) The expression of the induced lac operon is severely depressed during any of these exhaustions. These conclusions argue against simple models for regulation of ribonucleic acid polymerase production or promoter choice by the intracellular levels of its substrate nucleotides.
Structure of the regular surface layer of Sporosarcina ureae
Authors: Stewart M , Beveridge T J
Published: January 2020

Optical diffraction and computer image processing of electron micrographs were employed to analyze the structure of the regular surface layer of Sporosarcina ureae at high resolution. Negatively stained preparations of regular surface layer fragments showed two types of tetragonal pattern, each having p4 symmetry in projection with a = 12.8 nm. Although the two patterns differed greatly in overall appearance, both had a common pattern of areas of high stain density which we interpret as arising from gaps or holes in the structure. We speculate that these holes may be related to a protective role of the regular surface layer, whereby hostile environmental agents (such as muramidases) larger than about 2 nm would be screened from the underlying layers of the bacterial surface, while the free passage of nutrients and waste products into and out of the cell would still be allowed.
Nitrous acid damage to duplex deoxyribonucleic acid: distinction between deamination of cytosine residues and a novel mutational lesion
Authors: Frankel A D , Duncan B K , Hartman P E
Published: January 2020

The rate of nitrous acid deamination of labeled cytosine residues in native Escherichia coli deoxyribonucleic acid was monitored in vitro by release of acid-soluble counts after treatment with uracil deoxyribonucleic acid glycosylase. The reaction exhibited a lag and was not stimulate by several agents previously shown to enhance base substitution mutagenesis during nitrous acid treatment of duplex deoxyribonucleic acid. We conclude that a significant proportion of nitrous acid induced mutagenic lesions are novel lesions and not cytosine deaminations.
Polarity of Tn5 insertion mutations in Escherichia coli
Authors: Berg D E , Weiss A , Crossland L
Published: January 2020

We assessed the effect of insertions of the kanamycin resistance transposon Tn5 in the lac operon of Escherichia coli on the expression of distal genes lacY and lacA (melibiose fermentation at 41 degrees C and thiogalactoside transacetylase synthesis, respectively). Every insertion mutation tested (41 in lacZ and 23 in lacY) was strongly polar. However, approximately one-third of the insertion mutants expressed distal genes at low levels due to a promoter associated with Tn5. To localize this promoter, we (i) reversed the orientation of Tn5 at several sites and (ii) replaced wild-type Tn5 with several substitution derivatives which lack Tn5's central region. Neither alteration changed the expression of distal genes. Thus, in contrast to transposons IS2 and TnA. Tn5's ability to turn on distal gene expression is not due to a promoter in its central region and therefore is not dependent on the overall orientation of Tn5 in the operon. Our results suggest that the promoter is within 186 base pairs of the ends of Tn5. It is possible that the promoter is detected in only a fraction of insertions because it overlaps Tn5-target sequence boundary.
Location of the multivalent control site for the ilvEDA operon of Escherichia coli
Authors: Gayda D J , Leathers T D , Noti J D , Smith F J , Smith J M , Subrahmanyam C S , Umbarger H E
Published: January 2020

A strain of Escherichia coli K-12 containing a deletion extending from early in the ilvE gene toward the ilvG gene was shown to exhibit a higher expression of the downstream genes, ilvD and ilvA, than did an ilv+ strain. The elevated expression was under apparently normal ilv-specific control, however. The deletion was transferred to the ilv region of lamba h80dilv and shown by restriction endonuclease and heteroduplex analysis to extend through the deoxyribonucleic acid (DNA) shown, in the preceding paper (C. S. Subrahmanyam, G. M. McCorkle, and H. E. Umbarget, J. Bacteriol 142:547--555, 1980), to contain the ilvO determinant. The deletion was also transferred to an ilv-lac fusion strain and shown to cause an increase in beta-galactosidase formation while allowing retention of ilv-specific control. Transducing phages excised from these fusion strains with and without the ilvO determinant were compared. The phage carrying the ilvO+ determinant contained ilv DNA extending only into but not through the ilvG gene. It did not exhibit an ilv-specific control of beta-galactosidase formation. The phage carrying the deletion of ilvO but containing ilv DNA extending beyond the ilvG gene exhibited ilv-specific control of beta-galactosidase formation. It was concluded that the multivalently controlled ilv-specific promoter affecting ilv operon expression lies upstream from ilvG and that the ilvO region in the wild-type K-12 strain is a region of polarity preventing ilvG expression and reducing ilvEDA expression.
Transposon-mediated conjugational transmission of nonconjugative plasmids
Authors: Crisona N J , Nowak J A , Nagaishi H , Clark A J
Published: January 2020

When coresident with conjugative plasmid pNC21, the nonconjugative deletion F-prime pJC59, which retains the F transfer origin oriT, was transmitted to transconjugants at a frequency comparable to that of pNC21. In addition, pJC59 was transmitted as an independent plasmid, physically separate from pNC21, an example of plasmid donation. In contrast, two plasmids that are derived from F and deleted for the oriT site, pJC61 and pML31, were transmitted at frequencies 10(4) lower than that of pNC21. This low-frequency transmission was associated with the appearance of a new plasmid in the transconjugants. In the case of pML31, we determined that this new plasmid was a recombinant composed of pNC21 and pML31, the latter flanked by two copies of transposable element Tn3. We believe that this recombinant plasmid was formed as an intermediate in the transposition of Tn3 from pNC21 to pML31 and was the vehicle for conjugational transmission of pML31 genes by a process known as plasmid conduction.
Interspecies hybrid tryptophan synthase-modified beta 2 protein formed from separate folding regions of the beta monomer
Authors: Rocha V , Brennan E F
Published: January 2020

Escherichia coli and Serratia marcescens tryptophan synthase beta 2 protein (EC 4.2.1.20) was subjected to mild trypsin proteolysis. Two separate folding regions (domains) of the E. coli (EF1 and EF2) and the S. marcescens (SF1 and SF2) enzyme were shown to form interspecies hybrid reconstituted molecules [(EF1-SF2)2 and (SF1-EF2)2] and intraspecies reconstituted molecules [(EF1-EF2)2 and (SF1-SF2)2] with equal efficiency. The data suggest that structural regions, associated with beta monomer assembly, exist somewhere on the domain fragments and that these regions are conserved.
Terminal branching of the respiratory electron transport chain in Neisseria meningitidis
Authors: Yu E K , DeVoe I W
Published: January 2020

The respiratory components of the envelope membrane preparation of Neisseria meningitidis were investigated. Oxidase activities were demonstrated in this fraction in the presence of succinic acid, reduced nicotinamide adenine dinucleotide, and ascorbate-N,N,N',N'-tetramethyl-p-phenylene-diamine (TMPD). Differences in the kinetics of inhibition by terminal oxidase inhibitors on the three oxidase activities indicated that ascorbate-TMPD oxidation involved only an azide-sensitive oxidase, whereas oxidation of the physiological substrates involved two oxidases, one of which was relatively azide resistant. Spectrophotometric studies revealed that ascorbate-TMPD donated its electrons exclusively to cytochrome o, whereas the physiological substrates were oxidized via both cytochromes o and a. The effects of class II inhibitors on the oxidases suggest terminal branching of the electron transport chain at the cytochrome b level. A model of the respiratory system in N. meningitidis is proposed.
Control of protein synthesis in Escherichia coli: strain differences in control of translational initiation after energy source shift-down
Authors: Jacobson L A , Jen-Jacobson L
Published: January 2020

We have studied the parameters of protein synthesis in a number of Escherichia coli strains after a shift-down from glucose-minimal to succinate-minimal medium. One group of strains, including K-12(lambda) (ATCC 10798) and NF162, showed a postshift translational yield of 50 to 65% and a 2- to 2.5-fold increase in the functional lifetime of general messenger ribonucleic acid. There was no change in the lag time for beta-galactosidase induction in these strains after the shift-down. A second group, including W1 and W2, showed no reduction in translational yield, no change in the functional lifetime of messenger ribonucleic acid, and a 50% increase in the lag time for beta-galactosidase induction. Evidence is presented which indicates that this increased lag time is not the result of a decreased rate of polypeptide chain propagation. A third group of strains, including NF161, CP78, and NF859, showed an intermediate pattern: translational yield was reduced to about 75% of normal, and the messenger ribonucleic acid functional lifetime was increased by about 50%. Calculation of the relative postshift rates of translational initiation gave about 0.2, 1.0, and 0.5, respectively, for the three groups. There was no apparent correlation between the ability to control translation and the genotypes of these strains at the relA, relX, or spoT loci. Measurements of the induction lag for beta-galactosidase during short-term glucose starvation or after a down-shift induced by alpha-methylglucoside indicated that these regimens elicit responses that are physiologically distinct from those elicited by a glucose-to-succinate shift-down.
Membrane Deenergization by Colicin K Affects Fluorescence of Exogenously Added but Not Biosynthetically Esterified Parinaric Acid Probes in
Escherichia coli
Authors: Tecoma Evelyn S. , Wu David
Published: January 2020

Fluorescence of the conjugated polyene fatty acid, parinaric acid (PnA), was studied in membranes of
Escherichia coli
during deenergization by colicin K. The free fatty acid and biosynthetically esterified forms of
cis
-PnA (9,11,13,15-
cis,trans,trans,cis
-octadecatetraenoic acid), both of which are sensitive to
E. coli
lipid-phase transitions, were compared. When free
cis
-PnA was added exogenously to respiring bacteria, dissipation of the energized state of the membrane resulted in a dramatic increase in
cis
-PnA fluorescence;
all-trans
-PnA was much less sensitive. Neither spectral shifts nor a change in
cis
-PnA fluorescence polarization were observed. Analysis of the PnA content of extracellular fractions of deenergized and control cells revealed a difference in probe distribution: the membranes of energy-poisoned
E. coli
bound about 77% of exogenously added
cis
-PnA, whereas membranes of actively respiring controls bound only about 44%. No fluorescence enhancement was observed in cells centrifuged to remove unbound
cis
-PnA before colicin treatment. When
cis
-PnA was biosynthetically esterified to phospholipids of an unsaturated fatty acid auxotroph of
E. coli
, the fluorescence did not change during membrane deenergization. In double-probe experiments, membrane deenergization resulted in fluorescence enhancement of exogenously added
N
-phenyl-1-naphthylamine, without change in esterified PnA fluorescence. We conclude that deenergization of
E. coli
membranes leads to increased binding and fluorescence of exogenously added PnA and cannot be detected from within the inner and outer membranes by PnA esterified in vivo.
Novel Mutations Affecting a Signaling Component for Chemotaxis of
Escherichia coli
Authors: Parkinson John S.
Published: January 2020

The genetic relationship between
tsr
and
cheD
mutations, which affect chemotactic ability and map at approximately 99 min on the
Escherichia coli
chromosome, was investigated. Mutants defective in
tsr
function typically exhibited wild-type swimming patterns, but were unable to carry out chemotactic responses to a number of attractant and repellent chemicals. In contrast,
cheD
mutants swam smoothly, with few spontaneous directional changes, and were generally nonchemotactic. In complementation tests,
cheD
mutations, unlike
tsr
, proved to be dominant to wild type, suggesting that the
cheD
defect might be due to an active inhibitor of chemotaxis. Mutations that inactivated the putative inhibitor were obtained by selecting for restoration of chemotactic ability or for loss of
cheD
dominance. The resultant double mutants were shown to carry the original
cheD
mutation and a second tightly linked mutation, some of which exhibited nonsense or temperature-sensitive phenotypes, implying that they had occurred in a structural gene for a protein. All such double mutants behaved like typical
tsr
mutants in all other respects, including complementation pattern, swimming behavior, and chemotactic ability. These findings implied that either overproduction of
tsr
product or synthesis of an aberrant
tsr
product was responsible for the chemotaxis defect of
cheD
strains. Such mutants should be useful in analyzing the role of the
tsr
product in chemotactic responses.
Membrane-wall interrelationship in Gaffkya homari: sulfhydryl sensitivity and heat lability of nascent peptidoglycan incorporation into walls
Authors: Neuhaus F C , Tobin C E , Ahlgren J A
Published: January 2020

Membrane-walls from Gaffkya homari require a specific interrelationship between membrane and wall that functions in the incorporation of nascent peptidoglycan into the preexisting peptidoglycan of the wall. Two different methods were used to inhibit selectively this incorporation process: (i) sensitivity to sulfhydryl reagents and (ii) heat inactivation. Of the sulfhydryl reagents tested, 2.2 mM iodoacetamide inhibited the synthesis of wall peptidoglycan 50%, whereas greater than 100 mM was required to inhibit the synthesis of sodium dodecyl sulfate (SDS)-soluble peptidoglycan. Heat treatment at 37 degrees C (t 1/2 = 5.7 min) inhibited wall peptidoglycan synthesis without affecting SDS-soluble peptidoglycan synthesis. Inhibition of LD-carboxypeptidase by iodoacetamide and heat gave 50% inhibition and t 1/2 values similar to those observed for the incorporation process. Thus, it is suggested that the LD-carboxypeptidase may be one of the enzymes responsible for the sulfhydryl sensitivity and heat lability and that this enzyme may play a role in the relationship between membrane and wall in G. homari.
Molecular Comparison of Plasmids Encoding Heat-Labile Enterotoxin Isolated from
Escherichia coli
Strains of Human Origin
Authors: Willshaw Geraldine A. , Barclay Elizabeth A. , Smith Henry R. , McConnell Moyra M. , Rowe Bernard
Published: January 2020

The molecular properties of enterotoxin (Ent) plasmids from 12
Escherichia coli
strains of human origin were examined. Ten strains belonged to the O78 serogroup, and the remainder were of serogroup O7 or O159. Eleven plasmids coded for heat-labile enterotoxin (LT), and one coded for heat-stable enterotoxin (ST) and LT. The results of restriction enzyme digests and deoxyribonucleic acid reassociation experiments showed that all of the Ent plasmids were related, and supported the subdivision of the LT plasmids into three groups based on their genetic properties (M. M. McConnell et al., J. Bacteriol.
143:
158–167, 1980). Within group 1, two plasmids from South African strains were indistinguishable but differed in
Eco
RI and
Hin
dIII digests from the LT plasmid that originated from an Ethiopian strain. The three plasmids had >70% homology. The two non-autotransferring group 2 plasmids identified in O78.H11 strains from Bangladesh were indistinguishable. The group 3 plasmids were from strains belonging to serogroups O7 and O78 isolated in Bangladesh, India, and Thailand. They shared >95% homology but showed slight differences in fragment patterns when treated with
Eco
RI and
Hin
dIII. There was 60 to 70% homology between the plasmids of groups 1 and 3, and the group 2 plasmid had 40 to 50% homology with members of these two groups. The autotransferring Ent plasmids had up to 40% homology with R factors of incompatibility groups FI, FII, and FIV.
Plasmid Control of 6-Aminohexanoic Acid Cyclic Dimer Degradation Enzymes of
Flavobacterium
sp. K172
Authors: Negoro Seiji , Shinagawa Hideo , Nakata Atsuo , Kinoshita Shinichi , Hatozaki Tomoya , Okada Hirosuke
Published: January 2020

Flavobacterium
sp. K172, which is able to grow on 6-aminohexanoic acid cyclic dimer as the sole source of carbon and nitrogen, and plasmid control of the responsible enzymes, 6-aminohexanoic acid cyclic dimer hydrolase and 6-aminohexanoic acid linear oligomer hydrolase, were studied. The wild strain of K172 harbors three kinds of plasmid, pOAD1 (26.2 megadaltons), pOAD2 (28.8 megadaltons), and pOAD3 (37.2 megadaltons). The wild strain K172 was readily cured of its ability to grow on the cyclic dimer by mitomycin C, and the cyclic dimer hydrolase could not be detected either as catalytic activity or by antibody precipitation. No reversion of the cured strains was detected. pOAD2 was not detected in every cured strain tested but was restored in a transformant. The transformant recovered both of the enzyme activities, and the cyclic dimer hydrolase of the transformant was immunologically identical with that of the wild strain. All of the strains tested, including the wild, cured, and transformant ones, possessed identical pOAD3 irrespective of the metabolizing activity. Some of the cured strains possessed pOAD1 identical with the wild strain, but the others harbored plasmids with partially altered structures which were likely to be derived from pOAD1 by genetic rearrangements such as deletion, insertion, or substitution. These results suggested that the genes of the enzymes were borne on pOAD2.
Genetic Control of Hydroxamate-Mediated Iron Uptake in
Escherichia coli
Authors: Kadner Robert J. , Heller Knut , Coulton James W. , Braun Volkmar
Published: January 2020

Cells of
Escherichia coli
can derive iron from a variety of chelators (siderophores) in addition to enterochelin, the catechol derivative excreted by many enteric bacteria. The genetic control of hydroxamate siderophore utilization was investigated in mutants of
E. coli
K-12 selected for resistance to lethal agents which adsorb to the
tonA
protein of the outer membrane (albomycin, colicin M, and phages T5 and φ80). Many of the mutants were unable to utilize hydroxamate siderophores as an iron source. This phenotype was termed Fhu, for ferric hydroxamate uptake. Mutants carrying lesions in the
tonA
region of the chromosome were studied and fell into several types. Members of one class had lost some or all of the
tonA
receptor protein's functions in that they were resistant to the lethal agents and unable to utilize ferrichrome and its analogs, although able to respond to the hydroxamate rhodotorulic acid (FhuA phenotype). Other mutants were unable to utilize any of the hydroxamate siderophores tested and were resistant to albomycin, althogh many were sensitive to the other lethal agents (FhuB phenotype). Members of these classes lacked ferrichrome-mediated iron uptake. Strains carrying transposon Tn
10
insertions in
fhuA
(previously termed
tonA
) lacked the 78,000-molecular-weight outer membrane protein previously described; insertions in
fhuB
retained this protein and had no detectable change in outer membrane composition. Three-point transduction crosses revealed the gene order to be
pan-fhuA-fhuB-metD
in the min 3.5 region of the chromosome map. Complementation analyses with F′ merodiploid strains showed that
fhuA
and
fhuB
comprise separate transcription units which are both required for utilization of ferrichrome. Response of diploid strains to rhodotorulic acid suggested the existence of a third gene,
fhuC
, required for utilization of this siderophore, but not ferrichrome. It is suggested that
fhuB
encodes a transport component in the cytoplasmic membrane that is necessary for the uptake of all hydroxamate siderophores following their receptor-mediated passage across the outer membrane.
Heterotrophic bacteria from cultures of autotrophic Thiobacillus ferrooxidans: relationships as studied by means of deoxyribonucleic acid homology
Authors: Harrison A P , Jarvis B W , Johnson J L
Published: January 2020

From several presumably pure cultures of Thiobacillus ferrooxidans, we isolated a pair of stable phenotypes. One was a strict autotroph utilizing sulfur or ferrous iron as the energy source and unable to utilize glucose; the other phenotype was an acidophilic obligate heterotroph capable of utilizing glucose but not sulfur or ferrous iron. The acidophilic obligate heterotroph not only was encountered in cultures of T. ferrooxidans, but also was isolated with glucose-mineral salts medium, pH 2.0, directly from coal refuse. By means of deoxyribonucleic acid homology, we have demonstrated that the acidophilic heterotrophs are of a different genotype from T. ferrooxidans, not closely related to this species; we have shown also that the acidophilic obligate heterotrophs, regardless of their source of isolation, are related to each other. Therefore, cultures of T. ferrooxidans reported capable of utilizing organic compounds should be carefully examined for contamination. The acidophilic heterotrophs isolated by us are different from T. acidophilis, which is also associated with T. ferrooxidans but is facultative, utilizing both glucose and elemental sulfur as energy sources. Since they are so common and tenacious in T. ferrooxidans cultures, the heterotrophs must be associated with T. ferrooxidans in the natural habitat.
Involvement of ribosomal ribonucleic acid operons in Salmonella typhimurium chromosomal rearrangements
Authors: Lehner A F , Hill C W
Published: January 2020

As part of our efforts to understand factors influencing chromosomal organization and rearrangements, we studied a family of Salmonella typhimurium tandum duplication mutants. We found that the duplications were originally generated by unequal recombination between pairs of similarly oriented ribosomal ribonucleic acid operons (rrn). This demonstration involved the physical isolation of the duplicated material as circular deoxyribonucleic acid excised from the duplication. The four rrn operons involved embraced the ilv pur D segment of the chromosome and occurred at positions closely analogous to those previously observed for Escherichia coli. The interval between rrnC and rrnA of S. typhimurium was similar in size to that of E. coli (43 versus 39 kilobases), as was the interval between rrnB and rrnE (94 versus 91 kilobases). The rrnA-to-rrnB interval of S. typhimurium, however, was 155 kilobases, substantially greater than the 126 kilobases observed for E. coli.
Regulation of aspartokinase III synthesis in Escherichia coli: isolation of mutants containing lysC-lac fusions
Authors: Richaud F , Phuc N H , Cassan M , Patte J C
Published: January 2020

Mutants containing fusions of the lac gene to the lysC gene were isolated. In these, the expression of beta-galactosidase was regulated by lysine (and arginine), as previously described for aspartokinase III.
Inducible repair system in Haemophilus influenzae unaccompanied by mutation
Authors: Notani N K , Setlow J K
Published: January 2020

Weigle reactivation of ultraviolet-irradiated HPlc1 phage was observed after ultraviolet or mitomycin C treatment of Haemophilus influenzae cells. The amount of reactivation was considerably increased when the treated cells were incubated in growth medium before infection. The presence of chloramphenicol during this incubation abolished the reactivation. No mutation of this phage accompanied the reactivation. When cells were treated so as to produce a maximal reactivation of phage, neither reactivation or mutation of cells was observed. It is concluded that H. influenzae has an inducible repair system that is not accompanied by mutation.
A mutant of Escherichia coli defective in penicillin-binding protein 5 and lacking D-alanine carboxypeptidase IA
Authors: Nishimura Y , Suzuki H , Hirota Y , Park J T
Published: January 2020

A mutant of Escherichia coli defective in penicillin-binding protein 5 activity was isolated. The mutation (pfv) was shown to be located at 14.0 min on the E. coli chromosome map. Loss of penicillin-binding protein 5 in the pfv mutant was associated with the loss of D-alanine carboxypeptidase IA activity and increased sensitivity to beta-lactam antibiotics. We conclude that penicillin-binding protein 5 catalyzes the major D-alanine carboxypeptidase IA activity and that the enzyme activity, in vivo, protects E. coli cells from killing by low inhibitory concentrations of beta-lactam antibiotics.
Adenosine 5'-triphosphate leakage does not cause abortive infection of bacteriophage T7 in male Escherichia coli
Authors: Remes B , Elseviers D
Published: January 2020

galU and rpsL mutations restore plating efficiency of bacteriophage T7 in male Escherichia coli without suppressing leakage of adenosine 5'-triphosphate pools.
p-Cymene pathway in Pseudomonas putida: selective enrichment of defective mutants by using halogenated substrate analogs
Authors: Wigmore G J , Ribbons D W
Published: January 2020

Several classes of mutants of Pseudomonas putida (JT810) defective in the utilization of p-cymene as sole carbon source have been isolated. Selective enrichment of the mutants and for strains putatively cured of a degradative plasmid was achieved by incubation of cells in minimal growth media containing p-cymene (or p-cumate) and various halogenated analogs of the growth substrates or pathway intermediates. Analogs which led to successful enrichments included: p-chlorotoluene, p-bromotoluene, alpha-chloro-p-xylene, and p-iodobenzoate. A mutant strain, PpJT811, constitutive for the p-cymene pathway gave significantly greater enrichments of defective mutants than the wild-type parent PpJT810 after incubation with the halogenated analogs. It is suggested that the defective mutants are enriched because of the genetic alterations they possess, which confer immunity to a lethal synthesis performed by transformation of the analogs in clones possessing an intact p-cymene pathway. A nomenclature for the genetic organization of p-cymene pathway is described.
Involvement of plasmid deoxyribonucleic acid in indoleacetic acid synthesis in Pseudomonas savastanoi
Authors: Comai L , Kosuge T
Published: January 2020

Olive (or oleander) knot is a plant disease incited by Pseudomonas savastanoi. Disease symptoms consist of tumorous outgrowths induced in the plant by bacterial production of indole-3-acetic acid (IAA). Synthesis of IAA occurs by the following reactions: L-tryptophan leads to indoleacetamide leads to indoleacetic acid, catalyzed by tryptophan 2-monooxygenase and indoleacetamide hydrolase, respectively. Whereas the enzymology of IAA synthesis is well characterized, nothing is known about the genetics of the system. We devised a positive selection for the presence of tryptophan 2-monooxygenase based on its capacity to use as a substrate the toxic tryptophan analogue 5-methyltryptophan. Efficient curing of the bacterium of tryptophan 2-monoxygenase, indoleacetamide hydrolase, and IAA production was obtained by acridine orange treatment. Further, loss of capacity to produce IAA by curing was correlated with loss of a plasmid of 34 X 10(6) molecular weight. This plasmid, here called pIAA1, when reintroduced into Iaa- mutants by transformation, restored tryptophan 2-monooxygenase and indoleacetamide hydrolase activities and production of IAA.
Intermediatry steps in Acetobacter xylinum cellulose synthesis: studies with whole cells and cell-free preparations of the wild type and a celluloseless mutant
Authors: Swissa M , Aloni Y , Weinhouse H , Benizman M
Published: January 2020

Intermediatry steps in cellulose synthesis in Acetobacter xylinum were studied with resting cells and particulate-membranous preparations of the wild-type strain and of a celluloseless mutant. Exogenously supplied [1-14C]glucose was rapidly converted by resting cells of both types into glucose 6-phosphate, glucose 1-phosphate, and uridine glucose 5'-diphosphate (UDP)-glucose and incorporated into lipid-, water-, and alkali-soluble cellular fractions. The decrease in the level of labeled hexose-phosphates and UDP-glucose upon depletion of the exogenous substrate was accounted for by a continuous incorporation of [14C]glucose into cellulose in the wild type and into the above-mentioned cellular components in the mutant. [14C]glucose retained in the alkali- and water-soluble fractions of pulse-labeled wild-type cells was quantitatively chased into cellulose. Sonic extracts of both strains catalyzed the transfer of glucose from UDP-glucose into lipid-, water-, and alkali-soluble materials, as well as into an alkali-insoluble cellulosic beta-1,4-glucan. The results strongly support the sequence glucose leads to glucose 6-phosphate leads to glucose 1-phosphate leads to UDP-glucose leads to cellulose and indicate that lipid- and protein-linked cellodextrins may function as intermediates between UDP-glucose and cellulose in A. xylinum.
Analysis of caulobacter crescentus lipids
Authors: De Siervo A J , Homola A D
Published: January 2020

The lipids of Caulobacter crescentus, a procaryotic species which differentiates into stalked and swarmer cell types, were analyzed. Major lipid classes were purified by chromatography and identified by both chromatographic and chemical methods. Approximately half of the total lipid fraction of this organism consisted of glycolipis, which were primarily monoglucosyldiglyceride and an acylated glucuronic acid. Two of the phospholipids of C. crescentus were identified as phopshatidylglycerol and acylphosphatidylglycerol. Commonly occurring bacterial phospholipids, such as phosphatidylethanolamine and cardiolipin (diphosphatidylglycerol), were not detected. Monoglyceride and diglyceride were found in the neutral lipid fraction, which made up 10% of the total lipid. Quantitative lipid compositional studies, performed by the incorporation of [14C]acetate and [32P]orthophosphate into growing cultures, revealed that separated swarmer and stalked cells had similar lipid compositions. However, stationary-phase cultures, compared with logaritmic cultures, had decreased amounts of phosphatidylglycerol and diglyceride and increased amounts of acylphosphatidylglycerol and a glucuronic acid-containing glycolipid, glycolipid X. In addition, two glycolipids were only detected in stationary-phase cultures. These studies indicate that C. crescentus has a distinctive lipid composition compared with those of other procaryotic species which have been analyzed.
Growth of Streptococcus mutans protoplasts is not inhibited by penicillin
Authors: Parks L C , Shockman G D , Higgins M L
Published: January 2020

A method is described in which cells of Streptococcus mutans BHT can be converted to spherical, osmotically fragile protoplasts. Exponential-phase cells were suspended in a solution containing 0.5 M melezitose, and their cell walls were hydrolyzed with mutanolysin (M-1 enzyme). When the resultant protoplasts were incubated in a chemically defined growth medium containing 0.5 M NH4Cl, the protoplast suspensions increased in turbidity, protein, ribonucleic acid, and deoxyribonucleic acid in a balanced fashion. In the presence of benzylpenicillin (5 microgram/ml), balanced growth of protoplasts was indistinguishable from untreated controls. This absence of inhibition of protoplast growth in the presence of benzylpenicillin was apparently not due to inactivation of the antibiotic. When exponential-phase cells of S. mutans BHT were first exposed to 5 microgram of benzyl-penicillin per ml for 1 h and then converted to protoplasts, these protoplasts were also able to grow in chemically defined, osmotically stabilized medium. The ability of wall-free protoplasts to grow and to synthesize ribonucleic acid and protein in the presence of a relatively high concentration of benzylpenicillin contrasts with the previously reported rapid inhibition of ribonucleic acid and protein synthesis in intact streptococci. These data suggest that this secondary inhibition of ribonucleic acid and protein synthesis in whole cells is due to factors involved with the continued assembly of an intact, insoluble cell wall rather than with earlier stages of peptidoglycan synthesis.
Isolation and properties of an antisuppressor in Saccharomyces cerevisiae specific for an omnipotent suppressor
Authors: Liebman S W , Cavenagh M M , Bennett L N
Published: January 2020

A new Mendelian antisuppressor, ASU10, was isolated and shown to reduce the efficiency of the omnipotent yeast suppressor, sup35. ASU10 had no effect on the other omnipotent suppressor, sup45, or on several amber suppressors.
Biochemical characterization of a fructokinase mutant of Rhizobium meliloti
Authors: Gardiol A , Arias A , Cerveñansky C , Gaggero C , Martínez-Drets G
Published: January 2020

A double mutant strain (UR3) of Rhizobium meliloti L5-30 was isolated from a phosphoglucose isomerase mutant (UR1) on the basis of its resistance to fructose inhibition when grown on fructose-rich medium. UR3 lacked both phosphoglucose isomerase and fructokinase activity. A mutant strain (UR4) lacking only the fructokinase activity was derived from UR3; it grew on the same carbon sources as the parent strain, but not on fructose, mannitol, or sorbitol. A spontaneous revertant (UR5) of normal growth phenotype contained fructokinase activity. A fructose transport system was found in L5-30, UR4, and UR5 grown in arabinose-fructose minimal medium. No fructose uptake activity was detected when L5-30 and UR5 were grown on arabinose minimal medium, but this activity was present in strain UR4. Free fructose was concentrated intracellularly by UR4 > 200-fold above the external level. A partial transformation of fructose into mannitol and sorbitol was detected by enzymatic analysis of the uptake products. Polyol dehydrogenase activity was detected in UR4 grown in arabinose-fructose minimal medium. The induction pattern of polyol dehydrogenase activities in this strain might be due to slight intracellular fructose accumulation.
Effect of sterol side chains on growth and membrane fatty acid composition of Saccharomyces cerevisiae
Authors: Buttke T M , Jones S D , Bloch K
Published: January 2020

Saccharomyces cerevisiae GL7 cells require exogenous sterol and unsaturated fatty acid for growth. When grown in the presence of cholesterol or 7-dehydrocholesterol, the cells incorporated less saturated fatty acid into phospholipids than cells grown with ergosterol, stigmasterol, or beta-sitosterol as the sterol source. This lower saturated fatty acid content was most pronounced in phosphatidylethanolamine, slightly less so in phosphatidylcholine, and least evident in phosphatidylserine and phosphatidylinositol. Growing the cells with the various sterols did not affect the ratios of individual phospholipids. The ability of strain GL7 to use 7-dehydrocholesterol as the only sterol supplement for growth was dependent upon the nature of the unsaturated fatty acids added to the growth medium. In the presence of linoleic, linolenic, or a mixture of palmitoleic and oleic acids, excellent growth was observed with either ergosterol, cholesterol, or 7-dehydrocholesterol. However, when the medium was supplemented with either oleic or petroselenic acid, the cells grew more slowly (oleic) or much more poorly (petroselenic) with 7-dehydrocholesterol than with ergosterol. A specific relationship between sterol structure and membrane fatty acid composition in yeast cells is implied.
Substrate specificity and transport properties of the glycerol facilitator of Escherichia coli
Authors: Heller K B , Lin E C , Wilson T H
Published: January 2020

The specificity of the glycerol facilitator (glpF) of Escherichia coli was studied with an osmotic method. This transport system allowed the entry of polyols (glycerol and erythritol), pentitols, and hexitols. The analogous sugars were not transported. However, urea, glycine, and DL-glyceraldehyde could use this pathway to enter the cell. The glpF protein allowed the rapid efflux of preequilibrated xylitol. Glycerol surprisingly did not inhibit the uptake of xylitol, and xylitol only slightly reduced the uptake of glycerol. The observation and the insensitivity of the xylitol transport to low temperature suggest that the facilitator behaves as a membrane channel.
Composition and immunochemical properties of outer membrane proteins of Vibrio cholerae
Authors: Kabir S
Published: January 2020

The protein compositions of the outer membranes of various Vibrio cholerae strains, belonging to both biotypes (El Tor and classical) and both serotypes (Ogawa and Inaba), were analyzed by electrophoresis on polyacrylamide slab gels in the presence of sodium dodecyl sulfate. All these strains contained a major protein band of molecular weight 48,000. But they differed in the composition and proportions of minor proteins. The outer membrane protein profile was influenced by the growth medium. A protein band of molecular weight 15,000 was observed in the outer membrane when V. cholerae Ogawa 395 (classical) was grown in peptone-water, whereas a protein of molecular weight 68,000 appeared when it was grown in the synthetic medium. Under anaerobic growth conditions the proportion of the 13,000-molecular-weight protein was greatly enhanced. The outer membrane contained heat-modifiable proteins, as the protein bands with molecular weights 41,000 and 37,000 disappeared when membrane proteins were disaggregated in sodium dodecyl sulfate at or above 60 degrees C. The antisera to the outer membrane proteins of V. cholerae Ogawa 395 (classical) produced immunoprecipitation to the outer membrane proteins of both biotypes and both serotypes. Also, the antisera agglutinated bacteria of both biotypes and both serotypes, suggesting the presence of a common protein antigen in the outer membrane of V. cholerae.
Effects of specific cations on aggregation and fruiting body morphology in the myxobacterium Stigmatella aurantiaca
Authors: White D , Johnson J A , Stephens K
Published: January 2020

The cation requirements for fruiting body formation in the myxobacterium Stigmatella aurantiaca on agarose were determined. Calcium alone caused the cells to aggregate into interconnecting ridges. Under these conditions, stalk formation was severely depressed but sporangia frequently formed. The combination of magnesium and manganese was necessary for optimal formation of discrete aggregates (rather than ridges) and stalks. Manganese inhibited sporangium development. The inclusion of calcium into the magnesium-manganese medium overcame the inhibition by manganese and stimulated the production of multiple sporangia.
Partial purification and characterization of an exonuclease from Xanthomonas oryzae
Authors: Farber M B , Ehrlich M
Published: January 2020

An exonuclease with a strong preference for single-stranded deoxyribonucleic acid over double-stranded deoxyribonucleic acid has been purified 500-fold from Xanthomonas oryzae. This enzyme liberates 5'-mononucleotides in a reaction which requires Mg2+.
Influence of amino acid starvation on guanosine 5'-diphosphate 3'-diphosphate basal-level synthesis in Escherichia coli
Authors: Lagosky P A , Chang F N
Published: January 2020

We observed that the synthesis of basal-level guanosine 5'-diphosphate 3'-diphosphate (ppGpp) in both relA mutants and relA+ relC strains of Escherichia coli decreased in response to amino acid limitation and that this was accompanied by an increase in ribonucleic acid (RNA) synthesis. Addition of the required amino acid to starved cultures of relaxed bacteria resulted in the resumption of ppGpp synthesis and a concomitant decrease in RNA production. Our results indicate that relA mutants retain a stringent factor-independent ribosomal mechanism for basal-level ppGpp synthesis. They also suggest that in relA+ bacteria, stringent factor-mediated ppGpp synthesis and the production of basal-level ppGpp are mutually exclusive. These findings substantiate the hypothesis that there are two functionally discrete mechanisms for ppGpp synthesis in E. coli. Through these studies we have also obtained new evidence which indicates that ppGpp serves as a modulator of RNA synthesis during balanced growth as well as under conditions of nutritional downshift and starvation.