bluuebunny/crossref_metadata_2025 huggingface dataset:
Parameters governing bacterial regeneration and genetic recombination after fusion of Bacillus subtilis protoplasts
Authors: Gabor M H , Hotchkiss R D
Published: January 2020

Bacterial protoplast fusion, induced by polyethylene glycol, has been made more regular and convenient by further specification and improvement of various steps in the previously used procedure. These have made it possible to obtain regularly 100% regeneration of Bacillus subtilis cells from protoplasts before treatment with polyethylene glycol and yields of 10 to 75% from polyethylene glycol-treated protoplasts. Genetic recombination frequencies do not increase correspondingly. Also, when regeneration is reduced by various experimental conditions, recombination does not decrease in proportion. It is concluded that regeneration of recombinant-forming cells is independently determined and not closely related to the average regeneration for the population. Kinetic studies with varying individual parental or total protoplast concentrations strongly indicate that protoplast collision and contact is not the limiting factor determining the number of genetic recombinants obtained. Recombination approximates a linear, rather than quadratic, function of the total or of the majority protoplast population present, from which it is concluded that fusion events are always adequate to produce substantially more potential recombinants than are registered. The strong effect of the majority/minority ratio upon the number of minority cells that become recombinant is independent of which parent is in excess. This shows in a direct and physiological way that both parents are equivalent partners in their genetic contributions.
Electron microscope study of the rod-to-coccus shape change in a temperature-sensitive rod- mutant of Bacillus subtilis
Authors: Burdett I D
Published: January 2020

The changes in cell morphology of Bacillus subtilis rodB during a temperature shift from 20 to 42 degrees C, in the absence of added anions, are described. At 20 degrees C the organisms grow as rods but gradually become spherical in shape when placed at 42 degrees C. The shape change is initiated by an increase in diameter at the cell equator, resulting in a bulged morphology, which is further modified to the morphology of a coccus. This change may involve a modification of the pattern of normal cylindrical extension such that incorporation of newly synthesized wall leads only to increase in diameter, perhaps from a growth zone of limited extent. The pattern of surface growth was followed by reconstructing the sequence of cross wall formation and pole construction in rods grown at 20 degrees C and in organisms incubated at 42 degrees C for 75 and 150 min. In thin section, wall forming the septum and nascent poles can be distinguished from the surface distal to the division site by the presence of raised tears, perhaps analogous to the wall bands of streptococci. By using an analog rotation technique involving the three-dimensional reconstruction of cells by mathematical rotation of axial thin sections about their longitudinal axis, it is shown that the proportion of septal wall increases during the shape change. In the coccal forms, all surface growth may arise from septal growth sites.
Repair of ultraviolet light-damaged deoxyribonucleic acid in sbc-A strains of Escherichia coli K-12
Authors: Shlaes D M , Barbour S D
Published: January 2020

An Escherichia coli strain carrying both rec+ and sbcA has been constructed. Repair of ultraviolet light-induced deoxyribonucleic acid damage was examined by measuring survival and thymine-dimer excision in the rec+ sbcA strain as well as rec+ sbcA+ and recB recC sbcA strains. The sbcA mutation restores normal survival in both recB recC uvrB and recB recC uvr+ strains. Excision of thymine-containing dimers does not occur in uvrB mutants, regardless of the rec or sbcA genotype. Survival, after ultraviolet-light damage, of a rec+ sbcA strain is quantitatively similar to rec+ sbcA+ and recB recC sbcA strains.
Regulation of nonspecific acid phosphatase in Salmonella: phoN and phoP genes
Authors: Kier L D , Weppelman R M , Ames B N
Published: January 2020

Mutations in Salmonella typhimurium strains lacking nonspecific acid phosphatase mapped in two unlinked loci. One of these, phoP, was cotransducible by phage P22 with purB, whereas the second, phoN, was cotransducible by phage P1 with purA. Mutants with temperature-sensitive nonspecific acid phosphatase activity (measured in whole cells) were also isolated. A phoN mutant with thermolabile whole-cell activity was isolated directly from wild-type LT-2. Several other mutants with temperature-sensitive enzyme activity were also isolated as revertants of phoN mutants. These data suggest that phoN might be a structural locus for nonspecific acid phosphatase. The observation that a mutation resulting in high level of nonspecific acid phosphatase mapped in phoP suggests a possible regulatory role for this locus.
Rapid methods for generalized transduction of Salmonella typhimurium mutants
Authors: Rosenfeld S A , Brenchley J
Published: January 2020

A procedure has been developed that allows the propagation of generalized transducing phage directly on cells growing on solid media. After the donor cells are killed with chloroform, the phage can be transferred directly to recipient cells and transductants can be selected.
Increased amplification of pBR322 plasmid deoxyribonucleic acid in Escherichia coli K-12 strains RR1 and chi1776 grown in the presence of high concentrations of nucleoside
Authors: Norgard M V , Emigholz K , Monahan J J
Published: January 2020

When pBR322 plasmid-harboring Escherichia coli strains RR1 or chi1776 were grown in the presence of 1 mg of uridine or cytidine per ml and later treated with chloramphenicol, as much as three times more plasmid deoxyribonucleic acid was recovered than would normally be obtained by routine plasmid amplification procedures.
Biochemistry of L-proline-triggered germination of Bacillus megaterium spores
Authors: Rossignol D P , Vary J C
Published: January 2020

The mechanism by which L-proline triggers germination in Bacillus megaterium QM B1551 spores was investigated. First, brief exposure of spores to L-proline, followed by dilution, was sufficient to trigger germination. Once germination was triggered, the spores continued initiation of germination and did not require high concentrations of L-proline. Triggering of germination was pH and temperature dependent. Second, enzymes for L-proline catabolism were absent in spores, and several non-metabolizable analogs of L-proline were effective trigger compounds. Third, triggering of germination occurred in the presence of inhibitors of proton motive force production, oxygen uptake, and metabolism. Fourth, uptake of L-proline occurred after the triggering of germination. These results argue that neither uptake nor metabolism of L-proline was necessary to trigger germination. Instead, L-proline probably causes a biophysical alteration in the spores that triggers the biochemical changes in germination.
Lipid and cell wall changes in an inositol-requiring mutant of Neurospora crassa
Authors: Hanson B , Brody S
Published: January 2020

An inositol deficiency in the inositol-requiring (inl) mutant of Neurospora crassa led to changes in the composition of the inositol-containing lipids and the cell wall. On deficient levels of inositol, phosphatidyl inositol decreased by 23-fold, di(inositolphosphoryl) ceramide decreased by 4-fold, and monoinositolphosphoryl ceramide increased slightly. The inositol deficiency also led to an aberrant hyphal morphology and changes in both the amount of cell wall and the amino sugar content of the cell wall. The glucosamine content of the cell wall decreased by 50%, the galactosamine increased by 50%, but no significant changes were found in the content of the cell wall amino sugar precursors, or in the amino acid, glucose, or total hexose content of the cell wall. Inositol-containing compounds were found associated with purified cell wall material. These compounds were bound tightly to the cell wall but could be removed by treatment with alkali, a treatment which disrupts the cell wall integrity. Possible mechanisms of how changes in lipid composition can affect cell wall biosynthesis are discussed.
Evidence for the presence of messenger ribonucleic acid in Allomyces macrogynus mitospores
Authors: Smith B A , Burke D D
Published: January 2020

Sucrose density gradient analysis was used to show that polysomes were present in the mitospores of Allomyces macrogynus. Fifty percent of the spore monosomes were shown to be resistant to dissociation by 0.8 M KCl, indicating that messenger ribonucleic acid (mRNA) was bound to them. These polysomes and all the spore ribosomes were contained in the nuclear cap. Only 4S RNA could be demonstrated in the extra-cap fraction. Hybridization studies using 3H-labeled polydeoxythymidylic acid indicated that polyadenylate was present to the extent of 0.08% of the total spore RNA. Sixty-eight percent of the polyadenylic acid is found in the nuclear cap, and 32% is found in the extra-cap fraction. It was demonstrated that [3H]uridine was taken up by the spores and converted to uridine triphosphate. Lack of incorporation of 3H into RNA indicated that the spores do not synthesize RNA. Thus, the mRNA found in spores is synthesized prior to spore formation.
Comparative ultrastructure of Mycobacterium leprae and Mycobacterium lepraemurium cell envelopes
Authors: Nguyen H T , Trach D D , Man N V , Ngoan T H , Dunia I , Ludosky-Diawara M A , Benedetti E L
Published: January 2020

The structural properties of the cell envelopes of Mycobacterium leprae and Mycobacterium lepraemurium were investigated by freeze-fracture, freeze-etching, and negative-staining techniques. Freeze-fracture split the cell wall and exposed the internal features of the peptidoglycolipid mycosidic filamentous network. The cell membrane was also split into two asymmetric faces. The external fracture face was characterized by linear arrays of intramembranous particles, whereas the protoplasmic fracture face showed randomly distributed clusters of particulate entities. Comparative analysis of the ultrastructural features observed in M. leprae and M. lepraemurium indicated that the organization of the cell envelope in these two species differed particularly with respect to the amount and complexity of the superficial peptidoglycolipid and mycosidic integument, which is poorly developed in the mycobacterium responsible for human disease.
Respiration in the yeast and mycelial phases of Histoplasma capsulatum
Authors: Maresca B , Lambowitz A M , Kobayashi G S , Medoff G
Published: January 2020

Respiration in the yeast and mycelial phases of Histoplasma capsulatum proceeds via a cytochrome system and an alternate oxidase, both present constitutively. The mycelial cytochrome system is distinguished by an additional partial shunt around the antimycin-sensitive site.
Asymmetric transcription of R plasmid NR1 in Proteus mirabilis
Authors: Appelbaum E R , Rownd R H
Published: January 2020

The composite R plasmid NR1, its resistance transfer factor which specifies resistance to tetracycline (RTF-Tc component), and its r-determinants component were each denatured and centrifuged to equilibrium in CsCl density gradients containing polyuridylic acid-polyguanidylic acid. The complementary deoxyribonucleic acid strands of NR1 and the complementary strands of the RTF-Tc component could be separated by this technique because of a threefold difference in polyuridylic acid-polyguanidylic acid binding to the strands of the RTF-Tc component. The two strands of the r-determinants component bound equal amounts of polyuridylic acid-polyguanidylic acid. Hybridization of single strands of plasmid deoxyribonucleic acid with in vivo-labeled ribonucleic acid from Proteus mirabilis containing NR1 indicated that transcription within the RTF-Tc component is from the NR1 strand which preferentially binds polyuridylic acid-polyguanidylic acid, whereas transcription within the r-determinants component is predominantly from the complementary strand.
Flagellar hook and basal complex of Caulobacter crescentus
Authors: Johnson R C , Walsh M P , Ely B , Shapiro L
Published: January 2020

Intact bacterial flagella possessing a membrane-free hook and basal complex were purified from Caulobacter crescentus CB15, as well as from mutants which synthesize incomplete flagella. The basal body consisted of five rings mounted on a rod. Two rings were in the hook-proximal upper set, and three rings (two narrow and one wide) were in the lower set. The diameters of the two upper rings differed, being 32 and 21 nm, respectively. The lower rings were all approximately 21 nm in diameter, although they varied significantly in width. During the normal course of the C. crescentus cell cycle, the polar flagellum with hook and rod was shed into the culture medium without the basal rings. Similarly, hooks with attached rods were shed from nonflagellate mutants, and these structures also lacked the basal rings. The hook structure was purified from nonflagellated mutants and found to be composed of a 70,000-molecular-weight protein component.
Functional homology of chemotaxis genes in Escherichia coli and Salmonella typhimurium
Authors: DeFranco A L , Parkinson J S , Koshland D E
Published: January 2020

Generally nonchemotactic mutants of Escherichia coli and Salmonella typhimurium were analyzed by interspecies complementation tests to determine the functional correspondence between the che genes of these two organisms. The E. coli che region was introduced into Salmonella recipients by means of a series of F-prime elements. Wild-type che genes of E. coli F'420 complemented all che mutants of Salmonella except cheS, cheV, and a subclass of cheU. A series of tester episomes carrying E. coli che mutations were then used to determine which E. coli che function was responsible for the complementation of each Salmonella che defect. By this method, the following correspondences were determined: cheAE and chePS,cheWE, and cheWS, cheXE and cheRS, cheYE and cheQS, cheCE and cheUS, cheBE and cheXS, and cheZE and cheTS. (The subscripts E and S refer to E. coli and S. typhimurium genes, respectively.) In some tests, especially those involving the last two pairs of genes, poor complementation was observed between noncorresponding genes. A model explaining these observations in terms of subunit interactions is proposed.
Effect of carbamoyl phosphate on nitrogenase in Anabaena cylindrica Lemm
Authors: Lawrie A C
Published: January 2020

Carbamoyl phosphate inhibited acetylene reduction by whole cells and cell-free extracts of Anabaena cylindrica. Higher levels of both endogenous carbamoyl phosphate and carbamoyl phosphate synthase activity were present in NH4+-grown cells (in which acetylene reduction was absent) than in N2-grown cells (in which acetylene reduction was present). However, inhibition of acetylene reduction was observed also with cyanate, the main initial decomposition product under the conditions used. It is concluded that carbamoyl phosphate or one of its metabolites may act as a physiological regulator of both nitrogenase activity and synthesis, but caution must be used in interpreting effects observed several hours after the addition of carbamoyl phosphate, because the effects may be due to cyanate.
Second EcoRI fragment of F capable of self-replication
Authors: Lane D , Gardner R C
Published: January 2020

The cloning of fragments of F' plasmid deoxyribonucleic acid produced by restriction endonuclease EcoRI has revealed that fragment f7, not previously suspected to have replicative properties, is able to replicate autonomously. The ability of f7 to replicate was observed when it was cloned with fragments coding for resistance to either kanamycin or streptomycin and sulfonamide. Such f7 miniplasmids have been obtained from an F'lac+ and two F'gal+ temperature-sensitive mutant plasmids and from the unmutated F plasmid. Plasmids containing both f5 and f7 fragments were also obtained. Expression of resistance to "female-specific" bacteriophages requires that f5 and f7 be present in the same plasmid since cells containing separate f5 and f7 plasmids are not resistant to bacteriophage phi II. f7 plasmids were less stable than miniplasmids containing f5, particularly at fast growth rates. The bearing of these results on the isolation and behavior of temperature-sensitive F mutants is discussed.
5-n-Alkylresorcinols from encysting Azotobacter vinelandii: isolation and characterization
Authors: Reusch R N , Sadoff H L
Published: January 2020

Azotobacter vinelandii was found to form novel lipid compounds when encystment was initiated by 0.2% beta-hydroxybutyrate. An examination of these compounds led to the isolation and characterization of 5-n-heneicosylresorcinol, 5-n-tricosylresorcinol, and their galactoside derivatives.
Inactivation of
Escherichia coli
by Near-Ultraviolet Light and 8-Methoxypsoralen: Different Responses of Strains B/r and K-12
Authors: Bridges B. A. , Mottershead R. P.
Published: January 2020

A series of
Escherichia coli
K-12 AB1157 strains with normal and defective deoxyribonucleic acid repair capacity were more resistant to treatment with 8-methoxypsoralen (8-MOP) and near-ultraviolet light (NUV) than a comparable series of strains from the B/r WP2 family although sensitivities to 254-nm ultraviolet light were closely similar. The difference was most marked with strains deficient in both excision and postreplication repair (
uvrA recA
). The hypothesis that the internal level of 8-MOP was lower in K-12 than B/r
uvrA recA
derivatives was ruled out on the basis of fluorometric determinations of 8-MOP content and the similar inactivation curves for phage T3 treated intracellularly within the two strains. The demonstration of liquid holding recovery with AB2480 but not WP100 (both
recA uvrA
strains) and the somewhat greater resistance of the former strain to inactivation by captan revealed the presence in the K-12 strain of a deoxyribonucleic acid repair system independent of the
recA
+
and
uvrA
+
genes. The presence of this repair system did not, however, affect the survival of T3 phage treated with 8-MOP plus NUV and probably has a relatively small effect on survival of AB2480 under normal conditions. Experiments in which 8-MOP monoadducts were converted to cross-links by a second NUV exposure in the absence of 8-MOP indicated that the level of potentially cross-linkable monoadducts immediately after 8-MOP + NUV is about eightfold lower in K-12-than in B/r-derived strains. It is therefore suggested that the photoproduct yield in the former is well below that in the latter. In agreement with this is the observation that, during the first 10 min after treatment, deoxyribonucleic acid synthesis was just over five times more sensitive to inhibition by 8-MOP plus NUV in WP100 than in AB2480. We assume that 8-MOP in K-12 bacteria is hindered in some way from adsorbing to cellular (though not to phage T3) deoxyribonucleic acid. Consistent with this, 8-MOP has been shown to act as an inhibitor of a component of repair of 254-nm ultraviolet light damage in WP2 but not in AB1157.
Role of lithium ions in proline transport in Escherichia coli
Authors: Kayama-Gonda Y , Kawasaki T
Published: January 2020

Mechanisms of Li+ stimulation of proline transport were studied in cells of Escherichia coli 7 and NR70, a mutant of strain 7 lacking adenosine triphosphatase (EC 3.6.1.3). An electrochemical potential difference of Li+ induced in an inward direction of energy-depleted cells caused a transient uptake of proline depending on the driving force provided. When proline was added to unbuffered cell suspensions under anaerobic conditions, the medium was found to be acidified only in the presence of Li+ but not in the presence of Na+ or K+. This acidification was abolished by the addition of a permeant anion, SCN-, to the medium containing Li+, but this was not demonstrated with cells of a mutant strain deficient in a carrier protein specific for proline. These results support the assumption that proline is taken up by a mechanism of Li+-proline cotransport in E. coli.
Host range conferred by the virulence-specifying plasmid of Agrobacterium tumefaciens
Authors: Loper J E , Kado C I
Published: January 2020

The host range of Agrobacterium tumefaciens 1D1109, known to induce crown gall only on grapevine (Vitis spp.), was extended to include many plant species by transferring a tumor-inducing plasmid (pTi) from strain 1D1, a broad-host-range pathogen. The pTi plasmid was mobilized by the conjugative plasmid pRK2, which was inserted into 1D1 by mating with Escherichia coli J53(pRK2). The resulting transconjugants were screened for their ability to induce crown gall tumors on hosts other than grapevine by inoculation into sunflower. Transconjugants that were virulent on sunflower were then tested on 36 different host plants and compared with host-limited strain 1D1109 and the donor strain. Two transconjugants induced tumors on the same 28 plant species as those of the original plasmid donor 1D1(pRK2) (pTi). These results show that pRK2 promoted transfer of the pTi plasmid and suggest that the pTi plasmid rather than the A. tumefaciens chromosome determined the host range of the pathogen. Insertion of pRK2 alone did not extend the host range of strain 1D1109. Insertion of pS-a into A. tumefaciens 1D1 by mating with E. coli J53-1 (pS-a) resulted in the concomitant loss of pTi and virulence. There appears to be incompatibility between pTi and pS-a.
Conditional-lethal deoxyribonucleic acid ligase mutant of Escherichia coli
Authors: Dermody J J , Robinson G T , Sternglanz R
Published: January 2020

A new Escherichia coli deoxyribonucleic acid (DNA) ligase mutant has been identified among a collection of temperature-sensitive DNA replication mutants isolated recently (Sevastopoulos, Wehr, and Glaser, Proc. Natl. Acad. Sci. U.S.A. 74:3485-3489, 1977). At the nonpermissive temperature DNA synthesis in the mutant stops rapidly, the DNA is degraded to acid-soluble material, and cell death ensures. This suggests that the mutant may be among the most ligase-deficient strains yet characterized.
Surface arrays on the wall of Sporosarcina ureae
Authors: Beveridge T J
Published: January 2020

Thin sections of the cell wall of Sporosarcina ureae revealed two structurally distinct layers: a continuous amorphous zone, approximately 15 nm thick, which was adjacent to the plasma membrane, and an overlying periodic zone, approximately 16 nm thick. Sequential Triton X-100 and lysozyme treatment of isolated walls produced small fragments of the outer regular structure which allowed high-resolution, negatively stained images suitable for optical diffractometric analysis. These data suggested a tetragonal array of complex polygonal units of C-C spacing = 12 nm, with each unit joined to another by two delicate linkers. The array was entirely proteinaceous, consisting of a 150,000-dalton polypeptide which had a high affinity for Mg2+. It proved to be sensitive to chelating agents, 5 mM concentrations of Ca2+, Sr2+, or Ba2+, proteases, heat greater than or equal to 45 degrees C, sodium dodecyl sulfate, and pH greater than or equal to 5.8, but magnesium offered protection against the chelating agents and the deleterious salts.
Small arrays of electron-dense cylinders in Escherichia coli cells
Authors: Bradley D E
Published: January 2020

Electron microscopy of unstained Escherichia coli cells from cultures kept near 0 degrees C after incubation at 37 degrees C revealed small areas of geometrically arranged electron-dense cylinders. Their morphology, organization, and occurrence are described.
Growth-rate-dependent alteration of 6-phosphogluconate dehydrogenase and glucose 6-phosphate dehydrogenase levels in Escherichia coli K-12
Authors: Wolf R E , Prather D M , Shea F M
Published: January 2020

The levels of 6-phosphogluconate dehydrogenase and glucose 6-phosphate dehydrogenase are subject to metabolic regulation; they increased three- to fivefold with increasing growth rate.
Protein K: a new major outer membrane protein found in encapsulated Escherichia coli
Authors: Paakkanen J , Gotschlich E C , Mäkelä P H
Published: January 2020

The protein composition of purified outer membranes of 47 Escherichia coli strains was examined by sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis. Of 33 encapsulated strains, all contained an outer membrane protein distinguishable from previously reported proteins. The 14 non-encapsulated strains with one exception lacked this protein. Because of its apparent association with encapsulation (K antigen) we have named it K protein. The protein was purified nearly to homogeneity by chromatography in the presence of detergents, and its composition was determined. Its amino acid composition does not differ significantly from that reported for protein I, another E. coli major outer membrane protein. Furthermore, the N-terminal amino acid sequence of protein K indicates that it is related to protein I.
Cyanobacterial ribonucleic acid polymerases recognize lambda promoters
Authors: Miller S S , Ausubel F M , Bogorad L
Published: January 2020

We compared the initiation specificities in vitro of deoxyribonucleic acid-dependent ribonucleic acid polymerases purified from two cyanobacteria, Fremyella diplosiphon and Anacystis nidulans, and from Escherichia coli. A restriction fragment made from lambda deoxyribonucleic acid was used as a template. The cyanobacterial and E. coli ribonucleic acid polymerases recognized the same lambda promoters but exhibited different sensitivities to the inhibitor heparin, suggsesting differences in the structure of the initiation complexes.
Chimeric plasmids for cloning of deoxyribonucleic acid sequences in Saccharomyces cerevisiae
Authors: Storms R K , McNeil J B , Khandekar P S , An G , Parker J , Friesen J D
Published: January 2020

Two sets of plasmids, each carrying a Saccharomyces cerevisiae gene and a portion or all of the yeast 2-micron circle linked to the Escherichia coli plasmid pBR322, have been constructed. One of these sets contains a BamHI fragment of S. cerevisiae deoxyribonucleic acid that includes the yeast his3 gene, whereas the other set contains a BamHI fragment of S. cerevisiae that includes the yeast leu2 gene. All plasmids transform S. cerevisiae and E. coli with a high frequency, possess unique restriction endonuclease sites, and are retrievable from both host organisms. Plasmids carrying the 2.4-megadalton EcoRI fragment of the 2-micron circle transform yeast with 2- to 10-fold greater frequency than those carrying the 1.5-megadalton EcoRI fragment of the 2-micron circle. Restriction endonuclease analysis of plasmics retrieved from S. cerevisiae transformed with plasmics carrying the 2.4-megadalton EcoRI fragment showed that in 13 of 96 cases the original plasmic has acquired an additional copy of the 2-mcron circle. These altered plasmids appear to have arisen by means of an interplasmid recombination event while in S. cerevisiae. A clone bank of S. cerevisiae genes based upon one of these composite plasmids has been constructed. By using this bank and selecting directly in S. cerevisiae, the ura3, tyr1, and met2 genes have been cloned.
Fertility properties and regulation of antimicrobial substance production by plasmid SCP2 of Streptomyces coelicolor
Authors: Troost T R , Danilenko V N , Lomovskaya N D
Published: January 2020

Streptomyces coelicolor A3(2) possesses two plasmids (SCP1 and SCP2) that act as sex factors. The plasmid deoxyribonucleic acid isolated from S. coelicolor A3(2) SCP1- strains A617 and A585 had the same molecular weight and endonuclease cleavage pattern as the SCP2 plasmid. The plasmidless strain S18 SCP2- was isolated from the A617 X A585 cross. SCP2 plasmid-containing strains acted as donors of chromosomal markers, whereas the plasmidless strain acted as recipient. The transfer of SCP2+ donor strain markers into the SCP2- recipient occurred at high frequencies (approximately 75%), was unidirectional, was initiated from a fixed region of the chromosome, and had the SCP2 fertility factor transferred first. The introduction of the SCP2 plasmid into a recipient strain greatly reduced the recombination frequency. These fertility properties differed from those previously reported, thereby suggesting that the SCP2 plasmid examined in this investigation may be an additional variant to those described in the literature. The SCP2 plasmid also regulated production of three antibacterial substances and conveyed resistance for S. coelicolor A3(2) strains against growth inhibition by one of them.
Resistance plasmids in Pseudomonas cepacia 4G9
Authors: Williams J A , Yeggy J P , Field C C , Markovetz A J
Published: January 2020

Pseudomonas cepacia 4G9 utilizes 2-tridecanone as its sole carbon source and has been shown to be resistant to a variety of antibiotics. To ascertain whether any of these characteristics were plasmid mediated, Escherichia coli HB101 was transformed with plasmid DNA isolated from Pseudomonas cepacia 4G9. No 2-tridecanone-utilizing transformants were obtained. Tetracycline (Tc)- and ampicillin (Ap)- resistant transformants were obtained at a low frequency. Plasmid deoxyribonucleic acid from antibiotic-resistant E. coli HB101 transformants had molecular weights of 2.9 x 10(6) for pJW2 Tcr and 5.4 x 10(6) for pJW3 Apr as determined by electron microscopy. Electron microscopy of plasmid deoxyribonucleic acid from P. cepacia 4G9 revealed a single plasmid species, pJW1 of 1.78 x 10(6). Tetracycline resistance in both P. cepacia 4G9 and E. coli HB101(pJW2) was inducible, whereas ampicillin resistance in P. cepacia 4G9 was constitutive. The level of ampicillin resistance coded by pJW3 was lower in P. cepacia 4G9 than in the transformant E. coli HB101(pJW3).
Activation of ribulose 1,5-bisphosphate carboxylase from Rhodopseudomonas sphaeroides: probable role of the small subunit
Authors: Gibson J L , Tabita F R
Published: January 2020

The activation properties of the form I and form II ribulose 1,5-bisphosphate carboxylases from Rhodopseudomonas sphaeroides were examined. Both enzymes have a requirement of Mg2+ for optimal activity. Mn2+, Ni2+, and Co2+ can also support activity of the form I enzyme, whereas only Mn2+ can substitute for Mg2+ with the form II enzyme. The effect of different preincubations on the carboxylase reaction was also examined. Both enzymes exhibited a lag when preincubated with other than Mg2+ and CO2 before assay, but the lag was much more pronounced and the rate of the reaction was slower with the form I enzyme under these conditions. Activation of the form I carboxylase By Mg2+ and CO2 occurred more rapidly than that of the form II enzyme. The results obtained with the two distinct forms of carboxylase from R. sphaeroides, as well as studies with the spinach and Rhodospirillum rubrum enzymes, thus indicate that the presence of the small subunit affects the rate of activation by Mg2+ and CO2 as well as the rate of reactivation of ribulose bisphosphate-inactivated enzyme.
Presence and synthesis of cholesterol in stable staphylococcal L-forms
Authors: Hayami M , Okabe A , Sasai K , Hayashi H , Kanemasa Y
Published: January 2020

The sterol which was present in two strains of a stable staphylococcal L-form was analyzed by gas-liquid chromatography and combined gas-liquid chromatography-mass spectrometry. The retention time of the sterol on gas-liquid chromatography was the same as that of authentic cholesterol. Analysis of the sterol by mass spectrometry showed a molecular ion at an m/e of 386 and the same patterns of major ions above an m/e of 145 as those of authentic cholesterol. As a result, the sterol in staphylococcal L-form was identified as cholesterol. A parent strain and its L-forms were cultured in medium containing [14C]acetate, and the synthesis of cholesterol was examined. In the L-forms, 0.52% of the total lipid radioactivity was found in cholesterol fraction, whereas no significant radioactivity was detected in the cholesterol fraction of the parent strain, indicating that staphylococcal L-forms have acquired the capacity to synthesize cholesterol.
Manganese, an Essential Trace Element for N
2
Fixation by
Rhodospirillum rubrum
and
Rhodopseudomonas capsulata
: Role in Nitrogenase Regulation
Authors: Yoch Duane C.
Published: January 2020

Nitrogenase (N
2
ase) from the photosynthetic bacterium
Rhodospirillum rubrum
can exist in two forms, an unregulated form (N
2
ase A) and a regulatory form (N
2
ase R), the latter being identified in vitro by its need for activation by a Mn
2+
-dependent N
2
ase activating system. The physiological significance of this Mn
2+
-dependent N
2
ase activating system was suggested here by observations that growth of
R. rubrum
and
Rhodopseudomonas capsulata
on N
2
gas (a condition that produces active N
2
ase R) required Mn
2+
, but growth on ammonia or glutamate did not. Manganese could not be shown to be required for the biosynthesis of either nitrogenase or glutamine synthetase or for glutamine synthetase turnover, but it was required for the in vitro activation of N
2
ases from N
2
and glutamate-grown
R. rubrum
and
R. capsulata
cells.
Chromatium
N
2
ase, in contrast, was always fully active and did not require Mn
2+
activation, suggesting that only the purple nonsulfur bacteria are capable of controlling their N
2
ase activity by this new type of regulatory system. Although
R. rubrum
could not substitute Fe
2+
for Mn
2+
in the in vivo N
2
fixation process, Fe
2+
and, to a lesser extent, Co
2+
could substitute for Mn
2+
in the in vitro activation of N
2
ase. Electron paramagnetic resonance spectroscopy of buffer-washed
R. rubrum
chromatophores showed lines characteristic of Mn
2+
. Removal of the Mn
2+
-dependent N
2
ase activating factor by a salt wash of the chromatophores removed 90% of the Mn
2+
, which suggested a specific coupling of this metal to the activating factor. The data presented here all indicate that Mn
2+
plays an important physiological role in regulating the N
2
fixation process by these photosynthetic bacteria.
Deoxyribonucleic acid restriction and modification systems in Salmonella: chromosomally located systems of different serotypes
Authors: Bullas L R , Colson C , Neufeld B
Published: January 2020

With the use of four different phages, Salmonella strains representing 85 different serotypes were examined to determine their restriction-modification phenotype. They fell into one of three groups on this basis: group 1, those which lacked the common LT system; group 2, those in which only the LT system could be recognized; and group 3. those which possessed the LT system and at least one other system shown with some serotypes to be closely linked to serB. The specificity of the serB-linked restriction-modification system was unique for each serotype, but different strains of the same serotype expressed the same specificity. Two of the systems were shown to behave in genetic crosses as functional alleles of the S. typhimurium SB system. It is possible that these serB-linked restriction-modification systems constitute a large multiallelic series of genes extending throughout the Salmonella genus and Escherichia coli. We suggest that the division of the Salmonella into the three restriction-modification groups may be significant in defining a "biological grouping" of the different serotypes within the genus which may ultimately be useful in describing the Salmonella species. From the genetic relatedness between the genes of some of the Salmonella restriction-modification systems with those of the E. coli systems, we deduce that the restriction endonuclases produced by the Salmonella serB-linked systems are of type 1. Determination of the nucleotide sequences of the recognition sites of the restriction endonucleases of selected Salmonella systems should further our understanding of specificity with these enzymes.
pryB mutations as suppressors of arginine auxotrophy in Salmonella typhimurium
Authors: Jenness D D , Schachman H K
Published: January 2020

Salmonella typhimurium strains which produce high constitutive levels of aspartate transcarbamoylase due to the pyrH700 mutation were found to grow more slowly in minimal medium than pyrH+ controls. The addition of arginine or citrulline but not ornithine restored normal growth rates. This requirement for arginine was completely suppressed by pyrB mutations and partially suppressed by pyrC and pyrD mutations. No suppression was observed with mutants at the pyrF locus. Introduction of leaky mutation argI2002 resulted in a more extreme arginine requirement and accentuated suppression by pyrB mutations. Suppression by the pyrC and pyrD mutations was reduced as a result of the incorporation of the leaky argI2002 allele. These results indicate that in pyrH700 strains carbamoyl phosphate is preferentially directed toward the formation of intermediates in the pyrimidine biosynthetic pathway. Arginine auxotrophy results from the reduced availability of carbamoyl phosphate for the biosynthesis of arginine. Suppression of this arginine dependence for growth is used as a convenient positive selection technique for pyrB mutations.
Cloning of replication, incompatibility, and stability functions of R plasmid NR1
Authors: Miki T , Easton A M , Rownd R H
Published: January 2020

The region of R plasmid NR1 that is capable of mediating autonomous replication was cloned by using EcoRI, SalI, and PstI restriction endonucleases. The only EcoRI fragment capable of mediating autonomous replication in either a pol+ or a polA host was fragment B. SalI fragment E joined in native orientation with the part of SalI fragment C that overlapped with EcoRI fragment B, and also two contiguous PstI fragments of sizes 1.6 and 1.1 kilobases from EcoRI fragment B-mediated autonomous replication. When these individual SalI fragments were cloned onto plasmid pBR313 or the individual PstI fragments were cloned onto plasmid pBR322, none of these single fragments could rescue the replication of the ColE1-like vectors in a polA host, even in the presence of a compatible "helper" plasmid derived from a copy mutant of NR1. In contrast to the results reported for closely related R plasmid R6, EcoRI fragment A of NR1 could not rescue the replication of ColE1 derivative RSF2124 in a polA(Am) mutant or in a polA(Ts) mutant at the restrictive temperature. Although capable of autonomous replication, EcoRI fragment B of NR1 (or smaller replicator fragments cloned from it by using other restriction enzymes) was not stably inherited in the absence of selection for the recombinant plasmid. When EcoRI fragment B was ligated to EcoRI fragment A of NR1, the recombinant plasmid was stable. Thus, EcoRI fragment A contained a stability (stb) function. The stb function did not act in trans since EcoRI fragment B was not stably inherited when a ColE1 derivative (RSF2124) ligated to EcoRI fragment A was present in the same cell. A cointegrate plasmid consisting of EcoRI fragment B of NR1 ligated to RSF2124 was also not stably inherited, whereas only EcoRI fragment B was unstable when both RSF2124 and EcoRI fragment B coexisted as autonomous plasmids in the same cell. The incompatibility gene of NR1 was shown to be located within the region of overlap between SalI fragment E and the PstI 1.1-kilobase fragment. A copy mutant of NR1 (called pRR12) was found to have greatly reduced incompatibility with NR1; this Inc- phenotype is cis dominant.
Isolation and characterization of cell-associated nucleases related to streptococcal extracellular deoxyribonuclease D
Authors: Citak B P , Gray E D
Published: January 2020

A group of at least four distinct nucleases designated DcI through DcIV were isolated from cellular extracts of group A streptococcal strain S43 and shown to be antigenically similar to streptococcal extracellular deoxyribonuclease (DNase) D. These cellular endonucleases degraded single- and double-stranded deoxyribonucleic acid (DNA) as well as ribonucleic acid (RNA) to acid-soluble oligonucleotides. The products of digestion of DNA bore 5'-terminal phosphates, and in partial digests pdX-pdG linkages were most susceptible and pdA-pdX linkages were most resistant to nuclease action. The enzymes had pH optima of 8.0 to 8.5, were inhibited by NaCl, were unaffected by sulfhydryl modifying reagents, and absolutely required a divalent cation. Nucleases DcIII and DcIV were apparently hydrophobic in nature since they required the presence of detergents for migration on nondenaturing polyacrylamide gels. All four nucleases were electrophoretically distinct on such gels, from each other, and from DNase D. Molecular weights of DcI and DcII were similar to that of DNase D, suggesting that the mobility differences of these enzymes at least are reflections of differing net charges. It is suggested that the cellular nucleases represent a group of processing intermediates in the maturation and excretion of DNase D.
Incorporation and excision of 5-fluorouracil from deoxyribonucleic acid in Escherichia coli
Authors: Warner H R , Rockstroh P A
Published: January 2020

When Escherichia coli are grown in the presence of 5-fluorouracil, the 5-fluorouracil is incorporated almost exclusively into ribonucleic acid as fluorouridylate. In this study, small but detectable amounts were incorporated into ribonucleic acid as fluorocytidylate and into deoxyribonucleic acid as fluorodeoxyuridylate and fluorodeoxycytidylate. The amount of 5-fluorouracil found in deoxyribonucleic acid as fluorodeoxyuridylate increased 50-fold when the cells were deficient in both deoxyuridine triphosphatase and uracil-deoxyribonucleic acid glycosylase activities. Therefore, the same mechanisms which excluded uracil from deoxyribonucleic acid in vivo also excluded 5-fluorouracil. Even though purified uracil-deoxyribonucleic acid glycosylase excised 5-fluorouracil from deoxyribonucleic acid at only 5% the rate with which it excised uracil, most of the 5-fluorouracil excised from deoxyribonucleic acid in vivo was apparently excised directly by uracil-deoxyribonucleic acid glycosylase rather than by repair initiated by excision of uracil.
Genetic and molecular characteristics of Vir plasmids of bovine septicemic Escherichia coli
Authors: Lopez-Alvarez J , Gyles C L , Shipley P L , Falkow S
Published: January 2020

Three wild strains of bovine septicemic Escherichia coli were selected on the basis of their production of a toxin lethal for mice and chickens and their characteristic surface antigen. The transfer of these virulence (Vir) properties from two of the three to recipient E. coli was detected after mating. One Vir plasmid (pJL1) was derepressed for transfer and associated with mobilization of chromosomal markers. The other, pJL2, was repressed. Both plasmids were tagged with transposon Tn5 (kanamycin resistance), and transfer parameters of the tagged plasmids were studied. The Tn5 insertion in pJL2 usually increased transfer efficiency 100-fold. Plasmid pJL1 was classified as a member of the FIV incompatibility group. A pJL1::Tn5 derivative plasmid was incompatible with ColV1. Plasmid pJL2 behaved as an fi+ plasmid. Both plasmids pJL1 and pJL2 had a molecular weight of 92 x 10(6) and were present at about four copies per chromosome; their deoxyribonucleic acid (DNA) structures were not identical on the basis of restriction enzyme analysis. DNA-DNA hybridization revealed a polynucleotide sequence homology of at least 58% between the two plasmids. No plasmids could be detected in one wild or certain laboratory-derived Vir+ E. coli strains.
Germination properties as marker events characterizing later stages of Bacillus subtilis spore formation
Authors: Dion P , Mandelstam J
Published: January 2020

At various stages during spore formation sporangia were shocked by cold treatment or with toluene, and the germination requirements of the prespores were examined. Up to 5 h after induction of sporulation (t5) germination was spontaneous; i.e., it occurred without any added germinants. After t5, during stages V and VI, the capacity for spontaneous germination diminished progressively, and the spores acquired a need for externally added germinants. At t6 this need was satisfied by either L-alanine or a mixture of KCl, glucose, and fructose. By t8, the latter response had disappeared. The spores germinated only with L-alanine, and the response was much slower. Experiments with chloramphenicol showed that the germination properties of the spores appearing between t6 and t8 were the expression of events in protein synthesis that had occurred before t5. Although the germination requirements developed at about the same time as heat resistance, they could be dissociated from heat resistance in wild-type and mutant cells. The germination properties of the developing spores are additional marker events characterizing the later stages of sporulation, as follows: (i) spontaneous germination (up to the end of stage IV); (ii) germination requirements that are satisfied by KCl-glucose-fructose or L-alanine (stage V); and (iii) slow germination response with L-alanine only (stage VI).
Ultrastructure of the Bacteroides nodosus cell envelope layers and surface
Authors: Every D , Skerman T M
Published: January 2020

The surface structure and cell envelope layers of various virulent Bacteroides nodosus strains were examined by light microscopy and by electron microscopy by using negative staining, thin-section, and freeze-fracture-etch techniques. Three surface structures were described: pili and a diffuse material, both of which emerged from one or both poles of the bacteria (depending on the stage of growth and division), and large rodlike structures (usually 30 to 40 nm in diameter) associated with a small proportion of the bacterial population. No capsule was detected. The cell envelope consisted of four layers: a plasma membrane, a peptidoglycan layer, an outer membrane, and an outermost additional layer. The additional layer was composed of subunits, generally hexagonally packed with center-to-center spacing of 6 to 7 nm. The outer membrane and plasma membrane freeze-fractured through their hydrophobic regions revealing four fracture faces with features similar to those of other gram-negative bacteria. However, some unusual features were seen on the fracture faces of the outer membrane: large raised ring structure (11 to 12 nm in diameter) on cw 3 at the poles of the bacteria; complementary pits or ring-shaped depressions on cw 2; and small raised ring structures (7 to 8 nm in diameter) all over cw 2.
Structure of the nucleoid in cells of Streptococcus faecalis
Authors: Daneo-Moore L , Dicker D , Higgins M L
Published: January 2020

The structure of the nucleoid of Streptococcus faecalis (ATCC 9790) was examined and compared in the unfixed and fixed states by immersive refractometry and electron microscopy. It appears from these studies that the nucleoid structure is much more centralized in unfixed chloramphenicol-treated (stationary-phase) cells than it is in cells in the exponential phase of growth. The more dispersed configuration of the exponential-phase nucleoid could be preserved by fixation in glutaraldehyde, but not in Formalin or in osmium tetroxide. One important factor in explaining these differences in preservation is that glutaraldehyde (but not Formalin or osmium tetroxide) can rapidly cross-link the amino groups of macromolecules in cells. It was also observed that osmium tetroxide resulted in a preferential breakdown of nascent ribonucleic acid. These results are interpreted as indicating that glutaraldehyde is able to stabilize the exponential-phase nucleoid before it assumes the more central appearance seen in osmium tetroxide- and Formalin-fixed cells. These results are discussed in terms of the proposed organization of the exponential-phase nucleoid in unfixed cells.
Bacillus subtilis deoxyribonuclease activity specific for single-stranded deoxyribonucleic acid: cellular site and variations during germination and sporulation
Authors: Cobianchi F , Attolini C , Falaschi A , Ciarrocchi G
Published: January 2020

The endonuclease of Bacillus subtilis specific for single-stranded deoxyribonucleic acid is absent in spores, appears during germination only after the start of deoxyribonucleic acid synthesis, and is located almost exclusively in the periplasm.